Hasani Baharanyi
Research Interests
RNAi in Plasmodium falciparum.
Lara Bethke
Research Interests
The protozoan parasites, which cause malaria are remarkably successful at evading both the human immune system and antimalarial drugs, due in large part to their genetic diversity. I am currently investigating the generation of sequence diversity in these members of the Plasmodium species. This research may contribute a better understanding of the complexity of the population structure for vaccine and drug design, and may suggest regions of high and low diversity that might make good targets of intervention. I am investigating two mechanisms by which the parasite may generate genetic diversity: recombination/gene conversion and inaccurate DNA repair. Specifically, I have focused on the acyl-CoA synthetase gene family, which appears to be subject to frequent recombination events, and the DNA mismatch repair system.
We began investigating acyl-CoA synthetase, an enzyme involved in fatty acid metabolism, because it had a high level of single-nucleotide polymorphisms in an oligonucleotide array analysis of the chromosome 2 genes of 5 Plasmodium falciparum isolates (Volkman et al., Science, 2002). We found 10 putative acyl-CoA synthetase paralogs, 8 of which are located in subtelomeric chromosomal regions, in the published P. falciparum genome sequence. One paralog, located on chromosome 12, was a hybrid form of the paralogs on chromosomes 13 and 14. We investigated the predicted chromosome 12 gene by PCR and Southern blot analysis, including direct sequence of the predicted crossover point, and confirmed the hybrid structure. This result implies that the gene on chromosome 12 was created by a recombination event that involved the subtelomeric regions of both chromosome 13 and 14. RT-PCR analysis demonstrates that all 10 of the paralogs are expressed in erythrocytic stages. Phylogenetic analysis suggests the subtelomeric paralogs are more closely related to each other than to the paralogs located at internal chromosomal sites.
We analyzed 4 additional P. falciparum isolates by Southern blot using probes specific for the chromosome 13 and 14 genes, and found evidence for alternate banding patterns in 3 of the 4 isolates. These results are consistent with alternate recombination or deletion events that may be a consequence of the subtelomeric locations. The presence of a new acyl-CoA synthetase gene created by a double gene conversion event and the evidence for alternate recombination events in the subtelomeric regions further imply that mechanisms of recombination/gene conversion may play a major role in the generation of sequence diversity in Plasmodium falciparum. The DNA mismatch repair pathway has been shown to be involved in point mutation-mediated drug resistance in many organisms, including yeast and bacteria. Our laboratory has previously demonstrated the presence of the post-replicative mismatch repair pathway in the human malaria parasite, P. falciparum, and in the rodent malaria species, P. berghei. We have shown that genes with significant sequence homology to MutS and MutL of S. cerevisiae are present in the P. falciparum genome, and that these genes are expressed in a cell cycle-dependent manner, suggesting that they are functional. Analysis of PfMutS and PfMutS2, two P. falciparum MutS homologues, by expression in bacterial cells indirectly indicates a role for the PfMutS2 gene in mismatch repair activity. My current research involves an investigation of the role of the MutS homologues in drug resistance of malaria parasites by development of MutS null mutants in the rodent malaria parasite P. berghei. Future work may involve further investigation of the DNA mismatch repair pathway in P. falciparum, in order to better understand the role of this pathway in parasite adaptation and survival.
Dr. Birnbaum is cofounder of Achillion Pharmaceuticals and has served as the company's Senior Vice President of Research since February 2000. He is an acknowledged industry leader for his successful management of an array of major drug discovery and development programs. Dr. Birnbaum most recently was the Senior Vice President for Strategic R&D Operations for Bristol-Myers Squibb Pharmaceutical Research Institute from 1998 to 2000. Previously, he served as the Senior Vice President of Pharmaceutical Development, the largest division of the BMS organization from 1990 to 1998. Dr. Birnbaum also served as the Executive Vice President for all therapeutic areas in the Bristol-Myers Pharmaceutical Research Division where he was responsible for a broad range of programs including infectious diseases, oncology, neurosciences, cardiovascular and dermatology. During this period he spearheaded the successful early development of ddI, d4T, cefepime and cefprozil. Prior to BMS, he was a Vice President in the Merck Research Laboratories for several years and was involved in the discovery of many important infectious disease therapies including cefoxitin, norfloxacin, imipenem and ivermectin.
Dr. Birnbaum has received numerous awards including the Selman A. Waksman Award for outstanding contributions to microbiology, the Merck Board of Directors Scientific Award for his leadership in the discovery and development of the avermectin family of antiparasitic drugs, and the Daniel Drake Medal from the University of Cincinnati College of Medicine for contributions to the development of ivermectin for both human and animal health. In recognition of his contributions to the discovery of clinically important microbial products and development of antimicrobial chemotherapeutic agents Dr. Birnbaum was elected Fellow in the American Academy of Microbiology in 2000.
In addition to his duties at Achillion Pharmaceuticals he serves on the Scientific Advisory Boards and Boards of Directors of several biotechnology companies. Dr. Birnbaum is a founding member of the Advisory Council of the Harvard University Malaria Initiative. He is a member of the Board of Trustees of the Robert Wood Johnson University Hospital Foundation in New Brunswick, NJ
Dr. Birnbaum holds doctoral and masters degrees in microbial physiology and genetics from the University of Cincinnati and an undergraduate degree from Brooklyn College of the City University of New York.
Mr. Buck has over two decades of business, advisory and transactional experience in the technology and life sciences industries and for over ten years has provided strategic advisory services to large and small companies in all major sectors. He has led and advised on major strategic initiatives for multinational pharmaceutical companies as well as providing implementation services in the development of strategic alliances, new business ventures, joint ventures, mergers, acquisitions and divestitures. As a result he has significant expertise in the areas of corporate, operations and business development, transaction origination and implementation, and pre and post merger processing.
He is particularly knowledgeable regarding advanced technologies and science in the biomedical arena and has founded and/or cofounded several companies in these fields, some of which are creating new industries in their own right. Mr. Buck has advised large corporations on the impact of new technology on their businesses and new organizational models to adapt to changing market, operational and investor requirements. He has also assisted companies in identifying, developing and financing new technologies and products as well as converting technologies for new commercial applications in the rapidly growing arena of innovation at the interface of the physical and biological sciences.
His career has demonstrated a unique capacity for creating strategic programs to exploit emerging or novel commercial opportunities and, more importantly, devising the mechanisms for their implementation which he has orchestrated through to successful commercial fruition. Mr. Buck's capacity for identifying often latent core assets and managing the implementation of plans for their exploitation has led to a notable track record of rapid growth and turn around successes for his client companies. His insights are often solicited by institutional investors and analysts, research-based and academic institutions and members of the trade and lay press.
Mr. Buck's industry experience includes that of Corporate Development Vice President of Bristol-Myers Squibb and Legal Vice President of Squibb Corporation where, in addition to conceiving, implementing and managing numerous strategic projects, he successfully structured global acquisition transactions, strategic alliances, technology transfers and venture investments, including the merger of Bristol-Myers Company and Squibb Corporation. Mr. Buck has served as Chief Executive Officer of a biotechnology company and has also served in executive positions in the defense, electronics and telecommunications industries. Earlier in his career he was associated with a major Wall Street Law firm as a transaction and financing specialist and business legal advisor.
During Mr. Buck's recent tenure as a partner in the Health Industries business of Arthur D. Little he was a key player in the development of the value creation model for the business on a global basis and the introduction of that new model to senior managements throughout the healthcare industry. Prior to ADL Mr. Buck headed the Health Industry Consulting practice of SRI (Stanford Research Institute) with which he had been heavily involved in the conversion of various defense technologies to commercial applications.
He has managed business and transaction projects, including market development, in countries around the globe including those in East Asia, particularly China and Japan, South America and Eastern Europe and Russia and has particular expertise regarding the healthcare systems and markets of Western Europe.
Mr. Buck graduated magna cum laude from Princeton University and received his Juris Doctor degree from Columbia Law School where he was Harlan Fiske Stone Scholar and Editor, Columbia Journal of Transnational Law. He also served as line officer in the U.S. Navy on the Sixth Fleet Flagship stationed in Italy.
Vice President, Scientific Affairs & Distinguished Lilly Research Scholar for Infectious Diseases Eli Lilly and Company Indianapolis, IN Dr. Cassell, a world-renowned infectious diseases researcher who helped establish Lilly's multi-drug resistant tuberculosis initiative, has been intimately involved in the establishment of science policy and legislation related to biomedical research and public health. She has served as an advisor on infectious diseases and indirect costs of research to the White House Office of Science & Technology Policy, and has been an invited participant in numerous congressional hearings and briefings related to infectious diseases, antimicrobial resistance and biomedical research. She joined Eli Lilly and Co. in 1997 as vice president of infectious disease research. Dr. Cassell is a member of the Institute of Medicine of the National Academy of Sciences, a member of the Director's Advisory Committee of the National Centers of Disease Control & Prevention, and vice president of the International Union of Microbiological Societies Executive Board. She is also a member of the board of directors for the Global Alliance for TB Drug Development. At HSPH, she is a member of the Leadership Council. Dr. Cassell's major research contribution to the field of microbiology in the recent past has been the establishment of Ureaplasma urealyticum as a significant cause of chorioamnionitis and disease in premature human infants. She has received several national research awards and published over 300 articles and book chapters. She is a longtime colleague and friend of Dean Bloom and has served on the Committee on National Needs for Biomedical & Behavioral Scientists with former dean of HSPH, Howard Hiatt. A graduate of the University of Alabama at Tuscaloosa, Dr. Cassell received an MS and a PhD in microbiology from the University of Alabama, Birmingham (UAB). She also holds an honorary degree from the Thomas Jefferson University Medical College. She began her research and teaching career at UAB in 1973 as an assistant professor in the department of comparative medicine. She was named the Charles H. McCauley professor of microbiology in 1994, served as chair of the department of microbiology from 1987 to 1997 and is now professor emerita in that UAB department, a department which ranked first in research funding from the National Institutes of Health during her leadership.
Dr. Clardy moved to the Harvard Medical School at the beginning of 2003 as a Professor in the Department of Biological Chemistry and Molecular Pharmacology. His research involves many aspects of biologically active small molecules, especially those known as natural products. He is closely affiliated with the Initiative in Chemical Genetics, an effort to broaden the range of small molecule therapeutic agents, and more generally moderators of all biological processes, through the screening of libraries of structurally diverse compounds in both ad hoc and systematic screens. In the area of malaria, Dr. Clardy's laboratory defined the structure of a crucial enzymatic target, P. falciparum's dihydroorotate dehydrogenase (DHODH), for antimalarial agents. His current activities in this program include finding new molecular templates for DHODH inhibitors and understanding the structural basis of its mechanism. His work in this area was funded by the Burroughs-Wellcome Fund. He is also engaged in forward chemical genetic screens to find new targets for antimalarial and antitrypanosomal therapy.
Dr. Clardy graduated Phi Beta Kappa from Yale University and received his Ph.D. from Harvard University, both in chemistry. He joined the chemistry faculty of Iowa State University and a few years later moved to Cornell University where he remained for over twenty years. He has received many awards for his research including fellowships from the Alfred P. Sloan Foundation, the Camille and Henry Dreyfus Foundation, a John Simon Guggenheim Foundation. He has also received the Ernest Guenther Award and an Arthur C. Cope Scholar Award from the American Chemical Society, and the Research Achievement Award from the American Society of Pharmacognosy. He is a Fellow of the American Academy of Arts and Sciences and the American Association for the Advancement of Science, and won Cornell's highest award for teaching in the College of Arts and Sciences.
Jan - Mar 2006 appointment
I am an Infectious Disease physician whose research interests in Plasmodium falciparum are mechanisms of drug resistance and molecular basis of host parasite interaction and how this affects disease presentation.
My previous work has been in the Plasmodium gallinaceum system where we developed the first transfection methods for expressing foreign genes into the parasite 1. More recently, my work has been to correlate putative chloroquine resistance polymorphisms with chloroquine in vivo and in vitro sensitivity in Plasmodium falciparum clinical isolates. This project has been developed through an ongoing collaboration with scientists at Cheikh Anta Diop University, in Dakar Senegal. We have established a clinical study to evaluate patients' response to chloroquine through observation of patient's clinical response and clearance of the parasite in their blood stream, determining IC 50 of each isolate and correlating known and putative mutations in the parasite genome to each of these outcomes. A well characterized parasite gene, pfcrt, an important gene in chloroquine resistance has been studied in this patient population in Dakar. Interestingly, the wild type form of this gene almost completely correlates with in vitro sensitivity as expected, however, the mutated form gives rise to both in vitro sensitive and resistant IC50s 2,3. This suggests that the pfcrt mutation is necessary but that other genetic mechanisms may be necessary for full resistance. Through the use of whole genomic techniques, we will identify other putative genetic correlates of resistance through this collaboration.
I am also very interested in host pathogen interaction, particularly in defining parasite molecular correlates of disease variation. The field has not yet characterized fully the biological processes that result in disease and why there is such a spectrum of disease severity, even in the non immune patient. This is likely due to the many host genetic factors that confer resistance to severe disease, but it may be due to variation in virulence between different parasites as well. Through this field site, we plan to evaluate individual parasite strains at the whole genomic level and explore variation in parasite diversity, host response and disease outcomes. Differentially expressed genes, or those that have different polymorphism that correlate to host outcomes may provide insight into the molecular basis of important host pathogen processes.
Karen P. Day, Ph.D.
Research Interests
Plasmodium falciparum diversity and the transmission dynamics of malaria
Malaria Research Group
Plasmodium falciparum causes the most virulent form of human malaria and is responsible for 200 to 300 million infections and 1 to 3 million deaths per annum. Genetic variability of this pathogen underlies its transmission success and thwarts efforts to control malarial disease.The Malaria Research Group, headed by Karen Day, has a 20 year history of combining laboratory, field and molecular genetic approaches to study the biology, epidemiology and control of malaria in the context of parasite diversity.
The research goals of the Malaria Research Group are broadly to define the genomic diversity of Plasmodium spp and explore the role of within species diversity in the transmission success of malaria. The role that the human immune response plays in selection for diversity is an integral part of this research. The malaria parasite has a fascinating life history that lends itself to the generation of diversity and adaptation to diverse environments presented by genetically variable human and mosquito hosts. Unlike viruses and bacteria, sex is an obligatory part of the malaria life cycle. Recombination between genetically distinct clones, is possible when the parasite passes successfully through the mosquito vector leading to the extraordinary genomic diversity we see in the field.
The academic disciplines of parasitology, genetics, ecology, evolution, immunology, cell biology and epidemiology underpin our research.
A large collection of parasite material facilitates the research of the group. Field research has been completed in Papua New Guinea, Thailand, Zimbabwe and Brazil with collaborators listed below. Longitudinal data collection is in progress in Papua New Guinea in association with the PNG Institute of Medical Research.
Excellent culture and insectary facilities have been custom built for the group to study phenotypic diversity in cytoadherence, gametocytogenesis and transmission characteristics of isolates of P. falciparum. Analysis of the genetic changes as a result of long term culture is also a focus of our research.
Genotypic methods to describe parasite diversity of the two major Plasmodium spp infecting humans i.e. P. falciparum and P. vivax have been developed. These include microsatellite typing, variation in antigen and drug resistance loci. More recently, we have begun to exploit the data emerging from the Malaria Genome Project to study genetic variation in housekeeping genes. High throughput sequencing has become the method of choice to generate variation data. State of the art sequencing facilities exist in the building to facilitate such research.
Tiffany DeSimone
Research Interests
Human infective strains of Plasmodium have exhibited much genomic variation over the ensuing years, contributing to widespread resistance of many first-line antimalarials. To combat the adaptability of these apicomplex parasites, i n vitro screens, such as the hypoxanthine assay, have been implemented that enable the rapid assessment of multiple, potential drug therapies. Using the hypoxanthine assay, I surveyed 31 compounds, some of which were previously shown to be inhibitory on Toxoplasma (also belonging to Phylum Apicomplexia), to determine their effects on the growth and invasive capabilities of P. falciparum.
Though the hypoxanthine assay has quantified the antimalarial efficacies of compounds with much fidelity, our laboratory has sought the development of an alternative, non-radioactive screen. That alternative lies in exploiting the light properties of the green fluorescent protein (GFP), a live reporter molecule that exists stably as an episome in P. falciparum. Though still in its preliminary stages, we believe that the successful delineation and introduction of a fluorescent-based in vitro screen for detecting Plasmodium growth is feasible.
Therese Dieng, Ph.D.
Research Interests
In vitro assessment of chloroquine sensitivity of wild senegalese isolates of Plasmodium falciparum compared with the research of molecular drug resistance markers :gene PfCRT mutation/allele K76T, gene Pf MDR1 mutation/allele N86Y, gene PfMDR1 mutation/allele D1246Y.
Assay of in vitro cultivation and maintaining culture of Plasmodium falciparum from wild senegalese isolates of Plasmodium falciparum in order to obtain local chloroqine sensitive strains and chloroquine resistant strains.
Matthew A. Dodge
Research Interests
Protozoan parasites remain major causes of disease in developing countries throughout the world, yet little is known about the biology or molecular biology of these organisms. The long term goal of my work is to understand basic molecular mechanisms in protozoan parasites with the goal of discovering and applying parasite specific interventions. The approach my research has taken is to examine the problem of drug resistance in both Leishmania and Plasmodium from independent but complimentary perspectives. A cell biological, biophysical, genetic, and bioinformatics approach was used; each aimed at elucidating the problem of chemotherapeutic failure. First the cellular localization of LeMDR1, an ABC-transporter involved in the transport of a broad spectrum of compounds including important chemotherapeutics, was examined. Novel localization of this transporter to a new organelle in L. enriettii , the MVT, using microscopy of GFP and HA tagged versions of the protein explains an initially contradictory drug resistance phenotype. This intracellular localization could have important ramifications for duel drug therapy regimes. Second, indirect evidence of LeMDR1 transport activity is provided by FACS and microscopy using several known MDR substrates, but in order to verify that LeMDR1 transports vinblastine I have begun a collaboration with the Woods Hole Molecular Biology Institute. We are going to directly measure LeMDR1 transport ability by either expressing the protein in Xenopous oocytes or by reconstituting the purified protein in liposomes. Both measurements will be accomplished with new highly sensitive amperometric detection using vinblastine specific probes.
I am also examining how drug resistance may develop in these parasites. I have identified a homologue of MutS in L. major , the gene responsible for the classic “mutator” phenotype, using a combination of bioinformatics and RT-PCR. Because attempts to reduce MutS expression using anti-sense RNA were unsuccessful, I am currently making a MutS gene disruption in Leishmania so that I may assay the phenotype. It is possible that, like in many other organisms, dysfunction in MutS could be allowing parasites to achieve drug resistance at a more rapid rate than normally achievable. In fact, evidence from my lab suggests that a single-point mutation in the LeMDR1 gene can drastically alter the drug resistance phenotype of Leishmania .
Finally, in consultation with the malaria team in my lab I used bioinformatics to identify regulatory sequences in the newly sequence genome of P. falciparum . Upstream regions of coregulated genes were examined and a sequence motif was found that was over represented in these regions. In vivo assays with this motif demonstrate that it actually is needed for full expression in a luciferase assay, the first example of this method being used to find a biological relevant motif without a priori knowledge. Further examination of genes involved in heat shock and chloroquine resistance are underway.
Matthew received a B.S. Microbiology and a B.S. Biology: Cell & Molecular from University of Washington in Seattle in 1997. His undergraduate research involved the study of secondary structure induced frameshifts in E. coli ribosomal elongation.
Matthew came to Dyann Wirth's laboratory in 1998 were he began his investigation of tropical parasites. He is expected to graduate with a Ph.D. in Microbiology & Molecular Genetics in 2003.
Kobina Dufu
Research Interests
The recent completion of the Plasmodium falciparum genome project has made high-throughput expression profiling also possible in this system. These in turn have allowed us to monitor global patterns of gene expression and their perturbations in response to various stimuli. In addition, analysis of the parasite’s transcriptome may reveal global controls that operate on transcript levels.
Very little is known about cis-regulatory elements in P.falciparum, and basal regulatory elements, such as the TATA-box, have yet to been discovered in this organism. Using an Affymetrix chip technology gene clusters with similar expression profiles were examined in order to identify potential regulatory sequence that was over-represented in the 5’ upstream sequence. Three different clustering methodologies yielded statistically significant motifs that are currently being tested for functional activity in transient transfection assays. The object of my research is to characterize these motifs by asking if they are able enhance reporter gene expression when they are placed in varying context upstream of a firefly luciferase reporter gene. Motifs that yield interesting results will be further characterized by gel shift assays to possibly isolate and identify proteins that they might be interacting with.
Manoj T. Duraisingh, Ph.D.
Research Interests
Our long-term aim is to focus the research of our laboratory towards elucidating the molecular basis of the mechanisms underlying the pathogenesis of Plasmodium falciparum malaria in the human host, with the end goal of devising vaccine and drug strategies for control of the disease. The approach we favor is to use recently developed molecular and cell biological tools for the functional analysis of parasite genes that may be involved in these processes. These technologies are emerging at the same time as the availability of the P. falciparum genome sequence and post-genomic technologies such as microarrays and proteomics. Specifically, we are interested in the:
I) The functional analysis of molecules involved in the invasion of human erythrocytes by P. falciparum. In particular we seek to elucidate the role of two families of genes that encode proteins which have been shown to bind erythrocytes with high affinity and may be involved in the invasion process. These molecules have potential as vaccine candidates. We are also developing field-based projects to determine the relevance of invasion molecules as targets of antibody-mediated immunity in the field.
II) Genetic basis of antigenic variation in P. falciparum. We have been studying the molecular basis for switching of expression of members of the var gene family, the mechanism by which the malaria parasite places clonally variant molecules on the surface of the infected erythrocyte. Expression of specific var genes is responsible for cytoadherence of P. falciparum-infected erythrocytes to host receptors, a pathogenic process.
III) We maintain a long-term interest in the molecular basis and epidemiology of drug-resistance in malaria. Increased mortality in P. falciparum has been associated with the spread of drug-resistance. Our work has involved several collaborative projects in the context of clinical drug trials in Africa and Southeast Asia, to determine the contribution of putative markers to drug-resistance in areas with different epidemiological profiles.
Julia Fisher
Biographical Sketch
Julia Fisher received a B.A. in Biological Sciences from Mount Holyoke College in 2000. Her undergraduate research focused on the possible genetic and immunogenic interactions responsible for spontaneous abortion in a rat model. Julia joined Dyann Wirth’s laboratory as a Ph.D. student in 2003. She has begun research on the malaria parasite, Plasmodium falciparum.
Todd Michael Gierahn
Research Interests
The goal of my project was to identify new sequences in the P. falciparum genome that regulate transcription. Before I entered the lab, a couple of experiments had been done with whole genome microarrays. This data was used to generate putative regulatory DNA sequences by looking for over-represented sequences upstream of genes that were expressed the same. Using different clustering techniques, 4 sequences were identified as possible regulatory sequences. My project involved testing whether these sequences could increase the expression of a reporter gene. The reporter gene used was firefly luciferase. It contained upstream of it a part of the promoter for HSP86 which gave only minimal expression. I helped create constructs that contained the putative regulatory elements upstream of this minimal promoter. The constructs were then transfected into P. falciparum and firefly luciferase activity was assayed to determine gene expression. It was found that one construct significantly increased expression of the reporter gene.
Win E. Gutteridge, M.A., Sc.D.
A biomedical scientist with a record of achievement internationally as a Biologist, R&D Manager and Communicator in the academic community, the pharmaceutical industry and international agencies.
Christian Happi, Ph.D.
Malaria Research Laboratories (MRL), College of Medicine, University of Ibadan
Parasite diversity and drug resistance studies are carried out at the MRL.
Dr. Christian Happi is a parasitologist who has trained in the molecular mechanisms of drug resistance in malaria with Professor Wirth.
Research Interests
Malaria remains a devastating disease which kills about 1.2 million people in the world. Ninety percent of the mortality attributed to malaria occurs in the sub-saharan Africa. In the absence of an effective vaccine, chemotherapy remains the mainstay for treatment and prevention of malaria. However, resistance to chloroquine, the most widely used, safest, well-tolerated and affordable antimalarial drug, has exacerbated mortality and morbidity caused by Plasmodium falciparum especially in African children. Significant effort has been devoted to elucidate the genetic and biochemical basis of chloroquine resistance in the parasite and the human host which could hopefully guide the development of novel therapeutics.
My research focuses primarily on investigating the molecular basis of P. falciparum resistance to aminoquinolines, and antifolate combination drugs (e.g. sulfadoxine-pyrimethamin). I am particularly interested in uncovering new molecular markers of P. falciparum linked to chloroquine and DHFR/DHPS resistance. Such markers would be useful in developing surveillance tools to monitor changes in the efficacy of antimalarial drugs over time, the spread of drug resistant parasites in Africa, and the efficacy of experimental malaria therapeutics.
I am committed to impart my knowledge onto colleagues and students in Nigeria and the Benin Republic, to instill their interest in malaria research, and to develop state of the art research capabilities closer to patients in order to lessen the impact of malaria on the African continent.
Daniel L. Hartl, Ph.D.
Hartl lab
Research Interests
Population genetic studies of the age of the most recent common ancestor of P. falciparum are conflicting. Some evidence suggests that today's population includes multiple ancient lineages pre-dating human speciation. Other evidence suggests that today's population derives from only one, or a small number, of these ancient lineages. Resolution of this issue is important in evaluating the long-term efficacy of drug and immunological control strategies. We are carrying out analyses of polymorphisms in introns and other noncoding DNA sequences in order to obtain a more precise and reliable estimate of the age of this major pathogen.
We have also used DNA hybridization with high-density oligonucleotide arrays to detect single-nucleotide polymorphisms (SNPs) across chromosome 2 in P. falciparum. This approach has proven rapid and effective in spite of the genome's exceptionally high AT content (82%). A disproportionate number of polymorphisms are found in genes encoding proteins associated with the cell membrane. Most of the variation is concentrated in the subtelomeric 100 kb at each end, regions that are known to be rich in repetitive sequences and prone to gene conversion and unequal crossing over. In the central region of the chromosome genetic variation is much reduced compared to the subtelomeric regions. The functional categories of polymorphic genes are dramatically nonrandom, with the most frequent polymorphisms being in known antigenic determinants and proteins associated with the cell membrane. Discounting hypothetical proteins and those of unknown function, membrane-associated proteins are queried by less than 40% of all probes but account for more than 85% of all detected polymorphisms. A number of hypothetical proteins are also highly polymorphic, suggesting that these genes may be under genetic selection pressures similar to antigenic and membrane-protein genes. These could represent genes that have important functions in parasite viability or virulence, and warrant further functional characterization.
BiographyDaniel L. Hartl is Higgins Professor of Biology and former Chair of the Department of Organismic and Evolutionary Biology at Harvard University. His laboratory studies genetics, genomics and molecular evolution. His Ph.D. was awarded by the University of Wisconsin, he did postdoctoral studies at the University of California in Berkeley, and he has been on the faculty of the University of Minnesota, Purdue University and Washington University Medical School in St. Louis. Hartl has been honored with the Samuel Weiner Outstanding Scholar Award and Medal, the Medal of the Stazione Zoologica Anton Dohrn, and is an elected member of the American Academy of Arts and Sciences. He is also a Past President of the Genetics Society of America and the Society for Molecular Biology and Evolution. He has served on the National Institutes of Health Genetics Study Section, the National Institutes of Health Genetic Basis of Disease Review Committee, the National Academy of Sciences Committee on Research Opportunities in Biology, the National Academy of Sciences Committee on the Biological Effects of Ionizing Radiation, and on the Editorial Boards of Genetics, Annual Review of Genetics, Molecular Biology and Evolution, and other journals. In addition to more than 300 scientific articles, Hartl has authored or coauthored 20 books including Genetics: Analysis of Genes and Genomes, Essential Genetics: A Genomics Perspective, Principles of Population Genetics and Primer of Population Genetics.
Research in the Hartl laboratory is at the interface of molecular genetics, genomics and evolutionary biology. The goal is to learn about the processes by which organisms evolve and new species come into being. The approach is guided by the philosophy that progress in molecular biology and progress in molecular evolution often go hand in hand. Studies of molecular evolution are usually enhanced when they take advantage of information about biological function and molecular mechanism. The research often takes advantage of model organisms (fruit flies, nematodes, yeast, bacteria), but more recently organisms of interest in public health have become an important focus, particularly the malaria parasite. The Hartl laboratory also make use of state of the art molecular and statistical approaches. In recent years these have included genomics and gene-expression profiling, cloning and DNA sequencing, correlations of sequence data with three-dimensional protein structures, and Bayesian analysis of population samples implemented through Markov chain Monte Carlo methods.
The Hartl laboratory's current interests in malaria include improving genetic methods for studying the malaria parasite as well as the history of the malaria parasite. In regard to genetic manipulation, novel methods for creating gene knockouts are being investigated to allow efficient identification and analysis of genetic targets for drugs or vaccines. In regard to malaria's history, hyperendemic malaria is thought to have originated in central Africa 5,000–10,000 years ago, coincident with the innovation of slash-and-burn agriculture and the diversification of the Anopheles complex of mosquito vectors. Population genetic studies of the parasite are conflicting Some evidence suggests that today's population includes multiple ancient lineages pre-dating human speciation. Other evidence suggests that today's population derives from only one, or a small number, of these ancient lineages. Resolution of this issue is important in evaluating the long-term efficacy of drug and immunological control strategies.
Cameron Jennings, Ph.D.
Research Interests
Characterisation of the Reticulocyte Binding Protein homologues in Plasmodium falciparum.
Reticulocyte binding proteins from Plasmodium vivax (PvRBPs) are located at the apical end of the merozoite prior to invasion. These proteins are believed to facilitate the apical orientation of the parasite on the reticulocyte surface, an event that is required for invasion of the reticulocyte. Recently, homologues of PvRBPs have been identified in Plasmodium falciparum (PfRh proteins) and these proteins are the focus of my post-doctoral project. I will be using a combination of protein chemistry, biochemistry and molecular genetics to elucidate the role of PfRh proteins in directing alternative erythrocyte invasion pathways.
Biography
Cameron completed his Bachelor of Science with First Class Honors in 1998 at La Trobe University, Melbourne Australia. His honors project, supervised by Associate Professor Marilyn Anderson in the Department of Biochemistry at La Trobe University and Professor David Craik from the Institute for Molecular Bioscience at The University of Queensland, centered on the molecular events involved in the biosynthesis of cyclotides, cyclic knotted proteins from plants. In 1999 Cameron received an Australia Postgraduate Award and commenced a PhD at La Trobe University under the joint supervision of Marilyn and David where he continued his research into the molecular events involved in protein cyclization. After submission of his PhD thesis in October 2002, Cameron accepted a post-doctoral position at the HSPH under the supervision of Dr Manoj Duraisingh.
Deepa Jethwaney, Ph.D.
Research Interests
Identification and characterization of hepatocyte molecules interacting thrombospondin-related adhesive protein (TRAP) of Plasmodum berghei.
The objective of this project is to elucidate the mechanisms of target cell invasion in Plasmodium sporozoites. Plasmodium parasites actively invade host hepatocytes however; the molecular mechanisms involved in invasion are largely unknown. We have shown previously that a sporozoite surface molecule, the thrombospondin-related adhesive protein (TRAP), is required for gliding motility and infection of hepatocytes (Sultan, A et al., Cell 1997). The objective of this project is to explore this role of TRAP in more detail.
Approaches:
a) Generate various TRAP recombinant proteins and characterize their ability to inhibit sporozoite invasion of hepatocytes
b) Identify and characterize hepatocyte molecules interacting with the adhesive domains of TRAP by
(i)Affinity chromatography,
(ii)Immunoprecipitation
(iii)Testing knockout mice or cell lines deficient in molecules that may act as potential TRAP receptors on hepatocytes.
Nadira D. Karunaweera, M.B.,B.S.,Ph.D.
Research Interests
Malaria is counted among the worst scourges of mankind due to the high morbidity and mortality it causes, which affects approximately 40 percent of the global population. P. vivax is the most prevalent causative species of human malaria outside tropical Africa. Most symptoms associated with malaria are due to host and parasite factors associated with the infection. Identification of these factors would enable better control of disease manifestations. As a Radcliffe Institute fellow during 2005/2006 academic year, Karunaweera plans to study the genetic diversity of P. vivax malaria parasites in Sri Lanka by characterizing the genetic structure of parasite isolates from local patients. She will conduct experiments to analyze the genetic diversity at different loci. With these studies, Karunaweera hopes to gain insight into the genetic structure and diversity of the parasites within and between geographical regions and to make use of this information to establish the probable time of origin of these parasites.
Biography
Karunaweera earned her medical degree and PhD at the University of Colombo, Sri Lanka. She joined the same university as a lecturer in the department of parasitology and was promoted to senior lecturer, head of department, professor and Chair. Her honors include fellowships from the World Health Organization and European Union, as well as awards for excellence in research from the University of Colombo, Sri Lanka Medical Association, Sri Lanka College of Microbiologists, and the Presidential Award for Science in Sri Lanka.
Jacob Matthew Kasper
Research Interests
Jacob Kasper’s studies in antisense-RNA synthesis have led to his current project, which investigates post-transcriptional regulatory mechanisms in P. falciparum.
Biography
Jacob Kasper received his BA from Bates College in 2000. While at Bates his education focused on ecology; he completed an honors thesis studying morphological variations in the intertidal snail Nucella lapillus. After graduating from college he spent two summers in Ecuador and the Galapagos Island teaching biology and geology. He also spent 9 months aboard a whale research vessel sailing across the Pacific and Indian oceans studying toxin accumulation in the sperm whale Physeter macrocephalus. Upon returning to his native home in Boston, MA he took up a position in the Hartl Laboratory studying genetic diversity in Plasmodium falciparum. While working with Dr. Hartl, Jacob applied to the Biological and Biomedical Science program at Harvard Medical School.
In the fall of 2002 Jacob started in the BBS program and eagerly anticipated his rotation in the Wirth Laboratory studying antisense-RNA transcription in P. falciparum. When he joined the lab in early 2004, Jacob continued his studies in antisense-RNA synthesis, which has led to his current project, which investigates post-transcriptional regulatory mechanisms in this organism.
Elena Lozovsky, Ph.D.
Research Interests
The biology and population history of the protozoan parasite P. falciparum is substantially more complex than was initially assumed. Some evidence suggests that the extant population of this species includes genetic material from numerous ancient ancestors. Other evidence suggests that the existing population is recently derived from a small number, or even only one, common ancestral lineage. It is important to resolve this issue in order to be able to devise long-term strategies for treatment and prevention of malaria. To address this matter, we are studying single-nucleotide polymorphisms (SNPs) in noncoding regions of the genome across several chromosomes. SNP variation is also being examined in recently collected samples from Africa, South America and Asia in order to determine the extent to which cultured isolates represent the full range of genetic variation in natural populations of P. falciparum. We are also examining the genetic differences between P. falciparum and its closest known relative, the chimpanzee parasite P. reichenowi. These studies will improve estimates of the mutation rate for synonymous sites and help to determine the mutation rates for different types of noncoding DNA. They will also address the key issue whether the mutation rate is elevated in microsatellite repeats. Comparisons of coding regions between the species will allow analyses of polymorphism and divergence to examine whether certain genes give evidence of selection.
Amanda Lukens
Research Interests
The project I am working on in the Wirth lab is aimed at identifying factors affecting Plasmodium falciparum pathogenicity. We have employed whole genome oligonucleotide arrays to identify genes that are differentially transcribed when the parasite is in the host environment. We have compared multiple field isolates to an in vitro maintained laboratory strain, 3D7. A number of targets are at least two-fold over-expressed in all field samples relative to the 3D7 laboratory strain. A number of these up-regulated transcripts are hypothetical gene products that have not been characterized to date. I have begun to characterize one of these hypothetical proteins using bioinformatic approaches as well as traditional molecular biology tools. Based on primary amino acid sequence alignment we have found at least nine paralogs to PF14_0752 in the Plasmodium falciparum genome. These related proteins form a new and uncharacterized gene family.
We are currently further characterizing these gene products to elucidate their function. First, we are analyzing sequences from field isolates and the 3D7 strain to see if polymorphisms exist in the coding regions of the family members. Initial SNP analysis indicates that some of the family members are highly polymorphic. We are also in the process of confirming their sub-cellular localization to aide in our understanding of the gene family’s function. Most of the family members have a signal sequence that predicts their export to the red blood cell membrane. Based on this information, we predict that this gene family represents a novel antigen family in Plasmodium falciparum. To determine if the proteins are antigenic, we also plan to see if serum antibodies exist for members of this gene family. If so, we will then further characterize the role of these proteins in the host immune response to the malaria parasite. Future experiments may also include over-expression and/or knock-own experiments to evaluate the affect of the family members on the parasite and host response.
Biography
Amanda received a B.A. in biochemistry from the University of Pennsylvania. As part of her undergraduate thesis research in Dr. Ronen Marmorstein’s laboratory, she solved the x-ray crystallographic structure of a yeast transcriptional activator, HAP1-PC7. She then continued her study of transcriptional regulation and crystallography while working with Dr. Aneel Aggarwal at Mount Sinai School of Medicine.
During her undergraduate career, Amanda developed an interest in infectious diseases and the host immune response to infection. This interest was further developed while studying Kiswahili language and culture in Zanzibar, Tanzania on a Fulbright-Hays fellowship.
Because of her educational background in chemistry and biophysics, Amanda took a position in Dr. Laurie Glimcher’s laboratory in order to expand her knowledge of immunology and public health. Here, she studied the immune response to pregnancy.
Amanda started her pre-doctoral training in the Biological and Biomedical Sciences program at Harvard Medical School in the Fall of 2003. After a series of research lab rotations, she decided to join Dr. Dyann Wirth’s lab in the Fall of 2004. Amanda’s interest in integrating public health, field research, and basic science research made joining Dr. Wirth’s lab an obvious choice for her graduate thesis study. She plans to explore host-parasite interactions during malaria infection in Dr. Wirth’s lab.
Jacob Matthew Kasper
Research Interests
Jacob Kasper’s studies in antisense-RNA synthesis have led to his current project, which investigates post-transcriptional regulatory mechanisms in P. falciparum.
Biography
Jacob Kasper received his BA from Bates College in 2000. While at Bates his education focused on ecology; he completed an honors thesis studying morphological variations in the intertidal snail Nucella lapillus. After graduating from college he spent two summers in Ecuador and the Galapagos Island teaching biology and geology. He also spent 9 months aboard a whale research vessel sailing across the Pacific and Indian oceans studying toxin accumulation in the sperm whale Physeter macrocephalus. Upon returning to his native home in Boston, MA he took up a position in the Hartl Laboratory studying genetic diversity in Plasmodium falciparum. While working with Dr. Hartl, Jacob applied to the Biological and Biomedical Science program at Harvard Medical School.
In the fall of 2002 Jacob started in the BBS program and eagerly anticipated his rotation in the Wirth Laboratory studying antisense-RNA transcription in P. falciparum. When he joined the lab in early 2004, Jacob continued his studies in antisense-RNA synthesis, which has led to his current project, which investigates post-transcriptional regulatory mechanisms in this organism.
Professor Mboup serves as head of virology and bacteriology laboratory and directs major research projects in infectious diseases with an emphasis on HIV and AIDS. He has long standing collaborations with Dr. Phyllis Kanki and Dr. Max Essex in the HSPH Department of Immunology and Infectious Diseases. He is medical director of the Senegal Armed Services and has access to military personnel living in endemic areas for appropriate clinical and field based studies. He has successfully used this resource for work in HIV, hepatitis, and most recently in malaria.
John McGoldrick is Executive Vice President and General Counsel of Bristol-Myers Squibb Company, a diversified worldwide health care company with year 2001 revenues of $19 billion, whose principal businesses are pharmaceuticals, medical devices, consumer medicines and nutritionals. He is Vice Chairman of the Company’s Executive Committee. Mr. McGoldrick is also responsible for Global Corporate Policy. He is a Director of the Bristol-Myers Squibb Foundation.
In addition to his responsibility for the legal function, Mr. McGoldrick is a member of Bristol-Myers Squibb’s Pension and Savings Committee, and is responsible for Government Affairs and Corporate Security. Previously Mr. McGoldrick was President of the Company’s Medical Devices Group responsible for the Company’s orthopedics, wound care, and ostomy businesses. Earlier, he was Senior Vice President for Law and Strategic Planning, with responsibility for overall Company strategy. In the latter role, he chaired the Company’s Strategy Council.
Mr. McGoldrick has responsibility for Bristol-Myers Squibb’s HIV/AIDS initiatives in Africa, including its groundbreaking $117 million Secure The Future programs in Southern and Francophone Africa, as well as the ACCESS program to make antiretroviral therapy more accessible in the developing world.
Previously, for many years Mr. McGoldrick was a trial and appellate lawyer and partner of the law firm of McCarter & English, where he sat on its Executive Committee. He is a Fellow of the American College of Trial Lawyers, a Member of the American Law Institute, a Fellow of the American Academy of Appellate Lawyers, and a Fellow of the American Bar Association. He is a member of The Association of General Counsel, the Council of Chief Legal Officers, and the Executive Committee of the CPR Institute for Dispute Resolution.
He has since its founding in 1979 served as a Director of the New Jersey Transit Corporation, the United States’ third largest passenger rail and bus company. He has served as Vice Chairman and is the senior member of the Board. He is also a Board member of New Jersey Network (New Jersey Public Television), and of Zimmer Holdings, Inc., the NYSE-listed manufacturer of artificial hips and knees, and other orthopedic products. He chairs the Compensation and Management Development Committee of the Zimmer Board. Until recently, he was a member of the Board of Directors of AdvaMed, the medical devices trade association.
He has served on governmental reform commissions in New Jersey and has been called upon to represent personally governors of New Jersey from both political parties. He is a Member of The Aspen Institute on the World Economy, of the Council on Foreign Relations, of the Council for the U.S. and Italy, and of the World Economic Forum (Davos). He is also a Director of the Regional Plan Association, a Trustee of Legal Services of New Jersey, a Trustee of the HealthCare Institute of New Jersey, and a Member of The Committee to Visit the College and The Committee to Visit the School of Public Health of the Harvard Board of Overseers.
He is a graduate of Harvard College and the Harvard Law School.
Dr. Mendis has 19 years of experience of working in malaria research and control (1980-1999), in national and international contexts. At a national level, Dr. Mendis worked closely with the National Malaria Control Programme, implementing malaria control activities in Sri Lanka, and chaired the Presidential Task Force on National Malaria Control (1996 onwards). She established and directed a multi-disciplinary programme on malaria research and control in Sri Lanka with international collaboration; the programme gained wide international recognition. The Ministry of Health and the Ministry of Higher Education of Sri Lanka jointly established this programme as the research and training arm of the national malaria control programme. This also led to the establishment of a strong functional link between the Research and Academic Institutions (Ministry of Higher Education) and the National disease control programmes (Ministry of Health) in Sri Lanka, and led to training of professional staff of the national malaria control programme. Dr. Mendis has experience working in the international context in malaria research and control, having served on several international boards on malaria, chaired expert committees (see following pages), and has two years of working experience in the World Health Organisation in the areas of health research, and in the formulation of the Roll Back Malaria Project.
Dr. Mendis has engaged in research on malaria in wide ranging fields. These included clinical studies, studies on pathogenesis and epidemiology, immunological and molecular aspects of disease including vaccine research; studies on drug-resistance, molecular genetics, socio- cultural and anthropological research, and on the health system in relation to disease control. Dr. Mendis is an authority on malaria transmission, pathogenesis, epidemiology and immunity.
Ellen Mignoni, senior vice president in APCO Worldwide’s Washington, D.C., office, helped to build APCO’s global corporate responsibility practice. She provides positioning, corporate responsibility and communication counsel for APCO’s corporate clients. She also assists private foundations and nonprofit organizations with strategic planning, positioning, program development and communication. Her corporate work focuses on helping clients advance their business goals, as well as meet their corporate social responsibility, government affairs and public relations objectives. Recent corporate initiatives have focused on global health, labor, education and environmental issues. For nonprofit clients, Ms. Mignoni’s work focuses primarily on strategic planning, fundraising and organizational development activities. Ms. Mignoni also works with APCO’s executive committee in developing and managing the company’s strategic initiatives. Prior to joining APCO in 1988, Ms. Mignoni designed, implemented, and evaluated state and community-based alcohol and drug abuse treatment and education programs. She worked as a therapist and trainer on issues related to substance abuse for a wide variety of community-based groups, including members of the business community, educators, law enforcement and parent groups. Ms. Mignoni holds her Master of Business Administration in Organizational Behavior and Development from George Washington University, a Master of Arts from Catholic University of America and a Bachelor of Arts from Trinity College.
Kevin Militello, Ph.D.
Research Interests
I am currently involved in two projects regarding novel aspects of gene reguation in P. falciparum. First, I am interested in elucidating regulatory elements in the genome of P. falciparum. Second, I am analyzing the function of antisense RNAs in the parasite.
Biography
2000-current: Postdoctoral Fellow in the Department of Immunology and Infectious Diseases, Harvard School of Public Health
2000: Ph.D in Microbiology, State University of New York at Buffalo
1995: B.S. in Biological Sciences, State University of New York at Buffalo
Christina Takoudes Morrison, M.B.A.
Christina T. Morrison is the Director of Strategic Planning, The Rouse Company – Columbia, MD. Currently establishing a strategic planning group for the first public REIT in the US. Responsible for integrating disparate company-wide functions under the strategic planning umbrella as well as implementing new standards for evaluation of acquisitions, expansions and divestitures.
Anusha Munasinghe, Ph.D.
Research Interests
Exploring the Malarial Transcriptome by the Application of Serial Analysis of Gene Expression to Plasmodium falciparum
Our work demonstrates the successful adaptation of the genome-wide profiling technique SAGE in P.falciparum, which has more importantly, provided insights into global controls that operate on transcript levels of asexual forms. Our high-throughput analysis has generated a number of predictions in this system that are amenable to further experimental testing, including the possible role of antisense in modulating sense transcript abundance.
The SAGE technique generates comprehensive transcript profiles by quantitatively and qualitatively analyzing thousands of cDNA tags from a given population at the same time. The short 10bp SAGE tag is derived from a defined position within a transcript, and contains sufficient information to uniquely identify that locus. As such the relative abundance of SAGE tags accurately reflect that of its corresponding transcript in the population. We demonstrated the feasibility of the SAGE methodology as applied to the asexual stages of the 3D7 strain despite the AT richness of P.falciparum genome sequence. In fact our experimental SAGE tags identified parasite transcripts from both mitochondrial and nuclear genomes. Blast analysis of the 187 most abundant tags from a 3D7 SAGE library found that 88% corresponded to the parasite genome, with 70% matching single loci. Thus despite the lowered complexity of parasite sequence, the majority of SAGE tags identified unique Plasmodium genes. Of these 30% were derived from unknown or hypothetical ORFs, demonstrating the use of open platform profiling techniques in genome annotation.
Highly abundant SAGE tags also matched to known genes involved in mitochondrial, DOXP, polyamine, and folate metabolism, as well as parasite specific surface antigens. Their robust expression may explain why these same pathways have also been excellent target for antimalarials. Thus relative expression levels as revealed by SAGE will be useful for determining which genes play important roles in parasite growth and hence should be selected for further study as chemotherapeutic targets.
The directional nature of SAGE led to the discovery of a novel phenomenon in the parasite, that of antisense transcription. Alternate methods such as strand-specific northern blots and strand-specific RT-PCR confirmed that highly abundant antisense SAGE tags actually do reflect transcription from the minus strand of a number of different loci.
We integrated our SAGE expression data with genome annotation information compiled in the Plasmodium falciparum Genome Database (The Plasmodium Genome Database Collaborative, 2001; www.PlasmoDB.org), in order to extensively annotate SAGE libraries of approximately 4606 and 12639 tags each. Transcripts extending over a ~350 fold expression range were analyzed. The sense transcriptome was enriched for membrane associated ORFs involved in invasion/adhesion and possibly transport. Carbohydrate and mitochondrial metabolism, as well as signal transduction pathways were also highly represented relative to other housekeeping functions, underscoring their unique roles in parasite growth.
The global representation of antisense transcription across all abundance and metabolic groups was also characterized. This phenomenon was virtually absent in the mitochondria, while 20% of all nuclear-encoded loci possessed antisense SAGE tags. Furthermore the inverse relationship between antisense and sense transcript abundance across the transcriptome, suggests a role for the former in modulation of gene expression.
Finally we observed the differential regulation of over a 100 unique genes in a chloroquine sensitive strain following exposure to the antimalarial. A few of these loci could be related to previous observations on mechanism of drug action or resistance. For example, PfMDR1, which is involved in modulating drug sensitivity, was significantly upregulated following drug treatment. Interestingly, the present analysis uncovered the differential regulation of a large number of unknown ORFs.
It is our hope that this work together with array based technologies will contribute significantly to the expansion of the field of malarial genomics. In fact we are currently utilizing Affymetrix malaria chips to study 3D7 responses to varying doses of chloroquine, after both a 30 min and 6 hour exposure. It will be interesting to test whether similar groups of genes detected here will be regulated by drug and whether early responsive genes can be clearly distinguished from those induced after longer time points.
Alissa Myrick
Research Interests
Analysis of Drug Resistance in isolates of Plasmodium falciparum in Dakar, Senegal.
The problem of drug resistance in malaria is one of the most serious public health crises today. Chloroquine, the cheapest and most effective antimalarial drug has been rendered ineffective in many countries because of the high levels of resistance among malaria parasites. Our laboratory is not only interested in defining the molecular mechanisms of resistance, but also utilizing molecular and epidemiological tools to study this phenomenon in parasite populations.
We have formed a collaboration with Cheikh Anta Diop University in Dakar, Senegal to study drug resistance in field isolates of P.falciparum. Chloroquine resistance is on the rise in Senegal. Since the first report in 1988, there has been a 5.5fold increase in the level of malaria mortality in children. The goal of this project is to test current and identify new molecular markers of drug resistance that will be predictive of clinical outcome from a P.falciparum infection. The establishment of this collaboration has also created an opportunity for active exchange of graduate students and Senegalese scientists in the lab.
Understanding Transcriptional Regulation in P.falciparum Genes: The case of pfmdr1.
Unlike many other organisms, the elements involved in regulation of P.falciparum gene expression have not yet been clearly defined. The A-T richness of P.falciparum noncoding regions precludes the model of “classic” eukaryotic promoters; and indeed, when TATA boxes have been eliminated from the promoters of P.falciparum genes, there has not been a significant effect on expression levels. A consensus cis-acting sequence has yet to be identified in this parasite. Our laboratory is utilizing numerous approaches to elucidate the mechanisms of regulation in P.falciparum.
One project in the lab is the study of the P.falciparum multidrug resistance gene, pfmdr1. This gene is a member of the ATP Binding Cassette (ABC) transporter family; and has been associated with drug resistance in the parasite. The noncoding region of pfmdr1 contains many of the features that make P.falciparum a unique organism to study: a 90% A-T rich upstream region characterized by long homopolymeric dA and dT tracts as well as groups of inverted repeats. The length of the 5’UTR is approximately 1.95kb. We are currently using expression analysis to identify regulatory elements in this gene. Finally, we have shown that expression of pfmdr1 is induced in a sensitive strain of the parasite treated with chloroquine. We are continuing to investigate the transcriptional response of the gene when parasites are exposed to different drugs.
Daouda Ndiaye, M.D.
Research Interests
Drug resistance in Plasmodium falciparum and Epidemiology of schistosomiasis, toxoplasmosis, intestinal parasites, malaria in Senegal
Omar Ndir, PharmD, PhD Biographical Sketch Born November 30, 1950 in Dakar (Senegal), I did my studies at the Faculty of Medicine and Pharmacy of the Cheikh Anta Diop University of Dakar and obtained my pharmacist diploma in 1977. After many training periods in France, I had my specialization certificate in parasitology and mycology in 1985. I got my aggregation in parasitology in 1988, before being a senior lecturer, then a professor of parasitology at the Faculty of Medicine and Pharmacy of the Cheikh Anta Diop University of Dakar. I am a member of many learned societies such as: * the West African Society of Parasitology * the French Medical Society of Medical Mycology * and the Black African Medical Society In the hospital field, I was an intern at the teaching hospitals of Le Dantec and Fann, and now, I am directing the Parasitology and Mycology laboratory of Le Dantec hospital. In the research field, I worked on many publications concerning: * Malaria * Bilharziosis * Filariasis * Amoebiasis * Intestinal worm diseases * Mycosis In the field of malaria, which is the main parasitic endemic in Senegal, I studied its prevalence and its vectors in many regions of the country where hydro-agricultural projects exist. Actually, I am interested in the in vitro and in vivo studies of antimalarial drug sensitivity of Plasmodium falciparum, and the molecular biology of this parasite and particularly in genetic markers of the drug resistance, in collaboration with the team of Pr Dyann Wirth at the department of Immunology and Infectious Diseases in the Department of Public Health of Boston in the U.S.
A native of Lagos, Nigeria, Dr. Olukotun is currently Chief Medical Officer and Senior Vice President of Clinical and Regulatory Affairs for Esperion Therapeutics, Inc. and also serves as Chief Executive Officer of CR Strategies, L.L.C. He began his career as associate director of the cardiac catheterization lab at the Geisinger Clinic. He also worked for Pfizer, Inc. and the Bristol-Myers Squibb Corporation. He served as vice president for two divisions of the Bristol-Myers Squibb Corporation. In 1996, he joined Mallinckrodt Inc. as Vice President, Medical and Regulatory Affairs and Chief Medical Officer.
Oyé earned his B.A. in Chemistry from the University of North Carolina, his M.D. degree from the Albert Einstein College of Medicine, and his M.P.H. from the Harvard University School of Public Health. He has held academic appointments at the Mayo Clinic, Hershey Medical School, and Yale University School of Medicine. He currently serves as a fellow of the Councils on Radiology, Thrombosis, & Vascular Diseases, the American Heart Association, and the American College of Cardiology. He is also a member of the American Medical Association, the American Academy of Pharmaceutical Physicians, and the Drug Information Association. He currently serves as Chair of the Advisory Council of the Harvard Malaria Initiative, serves on the Board of Directors of BioMedical Systems, Inc. and Global Biomedical Research, Inc., and is a member of the Overseers’ Committee to Visit the Harvard School of Public Health. He has authored over thirty publications in scientific journals.
Oyé and his wife, Judy, have three sons and live on a small farm outside of Princeton, New Jersey.
Swati Patankar, Ph.D.
Research Interests
Dr. Patankar’s broad interest is in understanding regulation of gene expression in the malarial parasite. While microarray experiments have revealed spectacular patterns of gene expression at different stages of parasite development, we still do not fully understand mechanisms that underlie these dramatic changes in transcription. Dr. Patankar’s laboratory uses molecular techniques and bioinformatics to understand the role of non-coding RNAs in regulating parasite gene expression. Additionally, new classes of non-coding RNAs are being investigated using in silico comparative genomics as well as sequencing of the genes that encode such RNAs from different laboratory strains and clinical samples from India. This analysis of sequence diversity of non-coding RNAs will reveal whether non-coding genes apart from 5’ and 3’ regulatory sequences and introns are subject to the selective pressures that have been observed for Plasmodium open reading frames. This work will make use of the availability of both P. falciparum as well as P. vivax samples in India.
Biography
Dr. Patankar is an assistant professor at Indian Institute of Technology Bombay (IIT Bombay). After completing her Ph.D. from Tufts University, Dr. Patankar did postdoctoral research in the laboratory of Dr. Dyann Wirth, setting up whole-genome transcriptional profiling for the malarial parasite. She then returned to India and spent a year and a half in an Indian pharmaceutical company, gaining valuable industrial experience before returning to academia at IIT Bombay. Dr. Patankar is a recipient of the World Health Organization Re-Entry grant for young scientists returning to developing countries to work on tropical disease research. She is a member of the Special Programme for Research and Training in Tropical Diseases (TDR) Working Group on Genomes to Drugs and Diagnostics.
Steven C. Phillips, M.D., M.P.H.
Dr. Steven C. Phillips is the Corporate Medical Director, Global Issues and Projects, Exxon Mobil Corporation.
Previous ExxonMobil assignments for Dr. Phillips include Medical Director, International Medicine and Occupational Health, since the merger of Exxon Corporation and Mobil Corporation in 1999 until 2003. Prior to the merger, from 1997-1999, Dr. Phillips served as Medical Director, International Medicine and Occupational Health, Exxon Corporation.
Dr. Phillips is a native of California and received his B.S. in Biophysics and M.D. from Stanford University. He did his post-graduate training in internal medicine at the University of California San Francisco and received a Master of Public Health from UCLA.
From 1979-1981, Dr. Phillips served in the U.S. Public Health Service and was assigned to the Centers for Disease Control in Atlanta to conduct epidemic investigations of infectious, tropical, and occupational diseases.
In 1981, he joined Exxon as Director of Environmental Health in the Research and Environmental Health Division of Exxon Corporation. Dr. Phillips served as Associate Medical Director in the Medicine and Environmental Health Department of Exxon Company, International from 1986-1997 and as Medical Director of Exxon Chemical Europe from April 1987-1997.
Dr. Phillips has specialty certifications in internal medicine and occupational medicine by the American Board of Internal Medicine and the American Board of Preventive Medicine. He is a member of the American College of Physicians and a Fellow of the American College of Epidemiology. He is also a member of several medical and scientific societies including the American College of Occupational and Environmental Medicine, American Public Health Association, and the American Industrial Hygiene Council.
Radha Rangarajan, Ph.D.
Research Interests
Molecular mechanisms of malaria transmission
The focus of my work is to understand the molecular basis for sexual differentiation of the malaria parasite, a process that is critical for the transmission of the disease. The malaria parasite, Plasmodium replicates asexually within erythrocytes and causes the debilitating symptoms of malaria. However, in response to as yet poorly understood stimuli, the parasite switches from an asexual to a sexual mode of differentiation. This allows the parasite to become a terminally differentiated gametocyte that is now capable of surviving in the mosquito host. In the mosquito midgut, the gametocyte becomes a gamete and undergoes fertilization. Subsequently, the zygote undergoes meiosis and mitosis leading to the development of sporozoites that can infect the vertebrate host and renew the life cycle. Thus the process of sexual differentiation is essential to the transmission of the disease.
Our goal is to identify genes that are necessary for the develoment of gametocytes. To this end, we have selected two gametocyte specific genes, crk-1 (cdc-2 related kinase-1 ) and map-2 (mitogen activated kinase-2)and are studying their function. crk-1 is hypothesized to be a negative regulator of the cell cycle based on its homology to vertebrate homologs. map-2 is a component of a classical signal transduction pathway that allows cells to respond to a variety of stimuli. We are creating targeted deletions in these loci and will study the phenotypes of the mutant parasites.
Michael Reich, Ph.D.
Research Interests
Dr. Reich's research program addresses the political dimensions of public health policy. He is particularly interested in health and population policies of poor countries, the politics of policy-making processes, and pharmaceutical policy.
A major area of Dr. Reich's research examines access to medicines in developing countries. He recently edited a book on public-private partnerships for public health (distributed by Harvard University Press). The volume includes case studies of partnerships involving specific diseases such as trachoma and river blindness, international organizations such as the World Health Organization, multinational pharmaceutical companies, and products such as medicines and vaccines. Individual chapters draw lessons from successful partnerships as well as troubled ones in order to help guide efforts to reduce global health disparities. In an article in Science (2000), he analyzed how public policies can be designed to address the global drug gap, the disparity in access to medicines between rich and poor countries.
One of his previous research projects examined factors that affected access to praziquantel, the drug of choice for treatment of schistosomiasis. The study showed how interactions among four actors (pharmaceutical producers, international agencies, non-governmental agencies, and national governments) affected praziquantel availability in poor countries.
Dr. Reich has conducted various studies on the political economy of health policy reform, in both developed and developing countries. He has developed an applied research tool (a Windows-based software program) for analyzing the political dimensions of public policy. This tool, called PolicyMaker, provides a computer-assisted guide for strategic thinking about policy reform. The software leads the user through a step-by-step analysis of the policy content, positions and power of major players, opportunities and obstacles to policy change, and strategies for change. The method can be used for health policy reform as well as other areas of public policy. A free version of the software is available on the internet (www.polimap.com).
Dr. Reich and collaborators have applied the method for analyzing health reform issues in more than ten countries, in collaboration with national governments and international agencies. The method is used in policy courses around the world, including the World Bank Flagship Course on Health Sector Reform and Sustainable Financing.
Recently, Dr. Reich has begun a major research project on road traffic injuries in developing countries. Road traffic accidents in these countries account for 85% of all vehicle-related fatalities in the world each year. He co-directed an international conference on this topic in April 2002, and published a paper (with Vin and Nantulya) in the British Medical Journal on this neglected epidemic.
Professor of Infectious Diseases at UCAD and at the Fann Teaching Hospital. Professor Sow has extensive and broad experience in infectious diseases and has access to large hospital based patient populations.
Charles Sanders was formerly President of Massachusetts General Hospital and then served as Vice Chairman of Squibb Corporation before retiring as CEO of Glaxco US.
Ousmane Sarr, M.D.
Research Interests
Biography
Research fellow in Malaria Program at the Pasteur Institute in Dakar. Dr. Sarr has been a Visiting Scholar in Professor Wirth’s laboratory in 2001, 2002, and 2003.
President of Scheer & Company, Inc., a firm founded in 1981, with activities in venture capital, corporate strategy, and transactional advisory services focused on the life sciences. In venture capital, Mr. Scheer has been involved in the founding and has been a member of the Board of Directors of ViroPharma, Inc., OraPharma, Inc., Esperion Therapeutics, Inc. (of which he was Chairman), Achillion Pharmaceuticals, Inc., and Sopherion Therapeutics, Inc (of which he is Chairman). He has led engagement teams providing corporate strategic advisory services to a broad range of companies including Agouron Pharmaceuticals (now a Division of Pfizer), American Cyanamid (now a Division of American Home Products), BF Goodrich, Pharmacia AB, Pharmacia & Upjohn, Hoffmann La-Roche, Eli Lilly, Johnson & Johnson, Bristol-Myers Squibb, and a range of smaller, publicly- and privately-held companies. Mr. Scheer has also led or played a significant role in a series of transactions involving corporate alliances, licensing arrangements, divestments, acquisitions and mergers in the life sciences. He received his A.B. cum laude from Harvard College, and an M.S. from Yale University.
Dennis M. Schmatz began his career working on the in vitro cultivation of malaria at The Rockefeller University, New York, NY prior to joining Merck Research Laboratories in 1979. After joining Merck, he went on to complete his PhD in Biochemistry/Cell Biology at Rutgers University, New Jersey in 1984. Dennis has been directly involved identifying several drug development candidates during his career at Merck including CANCIDAS, a novel agent for treating patients with life threatening systemic fungal infections which was launched in 2001. Dennis' team at MRL has identified a number of novel drug targets in protozoan parasites including histone deacetylase, the mannitol cycle and cGMP dependent protein kinases. He continues to serve on several international scientific advisory committees including the Expert Scientific Advisory Committee of the Medicines for Malaria Venture (MMV) and the World Health Organization's Drug Discovery Research (DDR) committee. Dennis is currently Vice President of Basic Research at Merck Research Laboratories in Rahway, NJ. His responsibilities include Infectious Disease Research, Ion Channel Research and Natural Products Drug Discovery.
Heather Surkala
Research Interests
Understanding the genetic diversity of P.falciparum is a primary goal of our laboratory. As part of an ongoing collaboration between Dan Hartl's lab, the Wirth Lab and Karen Day's lab at Oxford, we have been approaching the question of MRCA from various angles. I have performed exhaustive SNP and microsatellite analysis of both upstream and downstream flanking regions of selected genes such as EBA175, CSP and PfMDR1. This analysis involved multiple rounds of PCR and cloning to ensure that the polymorphisms identified in 6 geographically distinct lab isolates were real. Expansion of this project is being conducted by studying the genetic diversity of isolates collected from patients in Dakar, Senegal. The benefit of examining the genetic profiles of field samples is that it allows us to observe how genetic diversity can change in "real-time". In order to achieve this, we are establishing strict protocols for in vitro culturing of the collected field isolates in our lab. We are also adapting microsatellite typing techniques to ensure that our isolates collected from patients represent monoclonal infections. One goal in perfecting field isolate culturing is to establish a reference strain from a patient sample. Culturing of such a sample will allow us to conduct detailed studies of drug resistance as well as whole genome analysis using microarray technology. These studies will provide novel insights into the parasite's response to drugs such as chloroquine. Surveying the results over an entire genome will allow for identification of novel genes involved in drug resistance; and may provide clues as to virulence factors in the parasite.
Terrie E. Taylor, B.A., D.O.
Research Interests
Pediatric malaria research project in Malawi for COM/CHM medical students, COGMET family practice residents, and faculty from the University of Malawi College of Medicine. The research focus is described as severe and complicated malaria: pathogenesis, treatment, prevention.
Susan Thomas, S.D.
Research Interests
The DNA mismatch repair system is crucial for the maintenance of genomic stability. Defects in this repair pathway have been implicated in the generation of drug resistance phenotypes in yeast, bacteria, and human tumor cells. In an attempt to elucidate the role of this DNA repair pathway in the drug resistance phenotype of P. falciparum, we undertook an investigation of the mismatch repair pathway of the malaria parasite, Plasmodium falciparum. A MutL and two MutS homologues of P. falciparum have been identified, and these genes are expressed in a cell cycle-dependent manner in the parasite.
Sequence analysis of the genes amplified from laboratory and field strains of P. falciparum reveals the presence of several sequence variations, though none of the changes are associated with the drug resistance status of the parasites. Analysis of the repair pathway has subsequently been expanded to indirectly investigate the function of the two MutS homologues from P. falciparum. The results suggest a role for one homologue, PfMutS2, in mutation avoidance.
We have also extended our investigation of the drug resistance phenotype of P. falciparum to include an analysis of chloroquine resistance markers in field isolates from Senegal in order to gain a better understanding of chloroquine resistance in an area where resistance to the drug has emerged only recently. Our results indicate that the molecular markers, pfcrt and pfmdr1, may not serve as reliable markers of in vitro chloroquine resistance in Senegal.
Sarah K. Volkman, S.D.
Research Interests
My research interests include understanding the genetic diversity of Plasmodium falciparum and how the level of genetic diversity impacts the development of therapeutic interventions including drug therapy and vaccines. This research effort includes analysis of the ATP Binding Cassette or ABC gene family in P. falciparum, a class of transport molecules that are conserved throughout evolution that have been implicated in mechanisms of drug resistance.
Genetic variation in falciparum malaria underlies its transmission success and thwarts efforts to control disease. In P. falciparum, the issue is controversial—genetic variation in proteins for antigenic determinants, drug resistance and pathogenesis is abundant, whereas DNA variation at silent (synonymous) sites in coding sequences appears virtually absent. Nevertheless, sequence variation among small tandemly repeated sequences, called microsatellites (MS), within and among subpopulations is widespread. We began to address this apparent discrepancy by looking at the level of mutations within intron sequences from genes on chromosomes 2 and 3, which were published at the time of the initial study. From this first analysis, we found few single nucleotide polymorphisms (SNPs), but many MS polymorphisms. In fact, there was a significant enrichment in the number of SNPs within these MS regions, suggesting that the mechanisms that contribute to making microsatellite sequences polymorphic also introduce SNP mutations. When we discounted SNPs within MS because these mutations were not being maintained in a neutral manner, we came up with estimates for the most recent common ancestor (MRCA) in the range of 6,300 to 23,000 years ago. This estimate suggests that sometime around the time when agriculture expanded, a single or few parasites spread throughout the human population and that the progeny of these ancestral parasites are found in humans today.
Other studies have come up with different estimates for the age to MRCA, so we have extended our analysis to noncoding and coding regions across the whole genome. One strategy to identify SNPs across the genome is to use high-density oligonucleotide arrays, or “DNA Chips”. This is work done in collaboration with Dr. Elizabeth Winzeler at the Novartis Research Foundation and Scripps Research Institute in San Diego, CA. From a pilot study using sequences from chromosome 2, we were able to identify SNPs within genes in a population of geographically diverse parasites using this technology. This initial study also revealed that there is an enrichment of SNPs within genes predicted to be associated with the surface of the parasite environment and thus recognized by the host immune system. We also found a nonrandom distribution of SNPs along the chromosome, with an increase in mutations within genes localized to the subtelomeric regions of the chromosome. We are currently using this technology to address the distribution of SNPs among genes throughout the whole falciparum genome sequence.
This estimate of the age to MRCA has important implications for the development of clinical interventions. Such an intervention (drug or vaccine) would target certain proteins in the parasite. If these proteins were variable, the parasite could easily outwit the effects of the drug or vaccine. This would require different strategies than if the protein targets did not change very much. Understanding the level of variation at potentially important target sites is therefore important for designing effective drugs and vaccines. One prediction is that genes that are under selection may have an enrichment of SNPs relative to genes that are not under selection. To test this prediction, I have focused on the ABC transporters, which are know to be involved in the mediation of drug resistance in a variety of evolutionarily diverse organisms including P. falciparum. Initial analysis of this class of molecules identifies over 15 members in P. falciparum, some that contain SNPs. I am currently using this dataset to determine if some of the ABC transporters are selected genes, which would argue for their biological importance to the parasite. As a consequence, these important gene products may provide new targets for the development intervention strategies to help combat malaria.
Biography
Sarah Volkman is a Senior Research Scientist in the Wirth Laboratory who works on the Genetic Diversity, Drug Resistance, and Chemical Genomics projects. Sarah received her BA from University of California, San Diego in 1986 graduating Cum Laude. After working in Cancer Biology and traveling for a year, she entered the doctoral program at the Harvard School of Public Health, where she received her ScD in 1995 working on the “Expression and Functional Analysis of the pfmdr1 gene of Plasmodium falciparum”. She continued on as a postdoctoral fellow and research scientist in the laboratory where she currently works as a Senior Research Scientist. Sarah also is an Assistant Professor in the School for Health Studies at Simmons College in Boston, MA, where she teaches Biochemistry, Microbiology, Anatomy & Physiology and Human Pathophysiology. She also teaches at Harvard University in the Science B-23 course on the Human Organism.
Dyann F. Wirth, Ph.D.
Research Interests
Dr. Wirth's research interests include development of new methods for diagnosis of parasitic diseases; the use of molecular genetics to develop new chemotherapeutic agents and other infectious diseases, analysis of molecular mechanisms of drug resistance and interventions. Dr. Wirth has been a leader in the development of genetic engineering methods for leishmania and malaria parasites.
Biography
The Harvard Malaria Initiative is directed by Professor Dyann Wirth, an expert in tropical disease and molecular microbiology. Dr. Wirth has played a leadership role in raising awareness of the burgeoning malaria problem, particularly malaria drug resistance, both in the research community and the general public.
A recipient of the Burroughs Wellcome Award in Molecular Parasitology, Dr. Wirth is the past president of the American Society of Tropical Medicine and Hygiene, the premier professional organization in tropical medicine worldwide. She has also advised and consulted in an expert capacity such preeminent organizations as the National Institutes of Health, the Institute of Medicine, and the World Health Organization. Through her efforts, the importance of new drug development for malaria has now been recognized as a priority in the world health arena.
Dr. Wirth has assembled a group of highly qualified and motivated students and postdoctoral fellows who are committed to the Initiative’s research. Harvard attracts the top 1-2% of students and fellows from both the United States and internationally; the Initiative’s ability to draw on this exceptional resource ensures the highest level of investigation and training in the project.
Professor Wirth's research focuses on tropical disease, primarily malaria (which affects 200300 million people, mostly children, worldwide) and leishmaniasis (which affects 12 million people globally and produces serious skin ulcers). Dr. Wirth is an expert in molecular microbiology and developed many of the molecular genetic tools used in the investigation of malaria and leishmania. Her work centers on the mechanisms of drug resistance and her group was the first to discover multidrug- resistance mechanisms in these organisms‹her work now focuses on the development and testing of new antiparasitic drugs. She is particularly interested in new compounds against multidrug-resistant parasites. The problem of multidrug resistance in malaria is particularly urgent and is leading to a resurgence of this fatal disease worldwide
Dr. Wirth graduated Phi Beta Kappa from the University of Wisconsin, spent one year as a Fulbright Fellow, and then completed her Ph.D. in cell biology and virology at Massachusetts Institute of Technology. She was awarded a Helen Hay Whitney Fellowship for her postdoctoral work in molecular biology at Harvard. She joined the faculty of Harvard School of Public Health in 1982 and was promoted to full professor in 1990. She is the recipient of the Burroughs Wellcome Award in Molecular Parasitology, the Bailey K. Ashford Award from the American Society of Tropical Medicine and Hygiene, and was elected President of ASTMH from1998-1999. She has served on numerous expert committees, including those for the Institute of Medicine, the National Institutes of Health, and the World Health Organization. She is current chair of the WHO/UNDP/World Bank Tropical Disease Research Steering Committee on Drugs for Malaria.
Muhammad Zaman, Ph.D.
Research Interests
Characterization of the requirements for full drug resistance by the Leishmania Enriettii V-circle.
In vitro, L. enriettii responds to increasing vinblastine concentrations by amplification of a 10.5kB region carrying multiple drug resistance (Lemdr1) transcription unit, along with 30kB of flanking sequences. Each one of the multiple-copy extracellular amplicon, called the V-circle, carries a single Lemdr1 transcriptional unit and flanking sequences. Le cells carrying disruptions on both Lemdr1 alleles are vinblastine-hypersensitive, whereas Le cells are partially resistant when expressing Lemdr1 from an extrachromosomal vector, suggesting Lemdr1 is essential though not sufficient for high resistance. Consistent with this observation, we find that extrachromosomal expression of the entire V-circle-derived transcriptional unit confers full resistance. The chromosomal-derived homologue, by contrast, confers only partial resistance, suggesting that only V-circle-specific elements are required. We have functionally dissected and analyzed the requirements for full vinblastine resistance by the use of extrachromosomal expression vectors that carry various deletions in the Lemdr1 transcriptional units, or carry various substitutions between the V-circle and chromosomal homologues. While any increased resistance is dependent on Lemdr1 copy number, partial resistance additionally requires only the 3’UTR. Conversely full expression requires the 5’UTR, but not the 3’UTR. DNA analysis of the two homologues indicates the presence of two point mutations in the V-circle homologue, with one present in the coding region and the other in the 3’UTR. By analyzing constructs carrying only one of the two mutations, we confirmed that only the coding region mutation is active, whereas the 3’UTR mutation is silent, consistent with the lack of requirement of 3’UTR for full resistance. We have confirmed the importance of the coding-region mutation loci by isolating a null mutation carrying a different point mutation at the same loci.
Although cells carrying expression vector-based V-circle Lemdr1 transcriptional unit have full vinblastine resistance compared to the chromosomal transcriptional unit on the same expression vector, DNA quantitation and RNA analysis shows that the plasmid copy number, poly(A)+ RNA levels and the Lemdr1 polyadenylation site are unchanged between the two homologues, suggesting that the increased resistance is conferred at the protein level. The observation that the null mutant homologue also exhibits unchanged plasmid copy number or poly(A)+ RNA levels is consistent with this hypothesis.
Martine Zilversmit
Research Interests
My research concerns the evolution of Plasmodium falciparum, the parasite that causes falciparum malaria. I am interested in understanding the evolutionary origin of the both the organism and its unique and highly virulent parasitic strategy. On the population level, I am also interested in the evolution of high virulence phenotypes, and at looking for the signature of human-Plasmodium coevolution in the parasite genome. All of the questions are studied at the interface between medical research and evolutionary biology.
Until very recently, P. falciparum was thought to have evolved from bird malarias, by horizontal transfer. This conclusion was based on a molecular phylogeny, and appeared to fit with the lethal parasitic strategy, as extreme virulence is often associated with host switching. Recent developments in phylogenetics, however, indicate that this is not the case, and though P. falciparum falls within a mammal clade, it is a relatively orphaned taxon. Better taxon sampling examine the phylogenetics and molecular genetics of many poorly studied primate malarias will allow for a better understanding of the origin and evolution of P. falciparum.
I am also interested in using methods in comparative genomics and population genetics to search for the signatures of selection throughout the P. falciparum genome. I am particularly interested in finding, and exploring the evolution of, genes related to increased strain virulence and to adaptation by the parasite to host defenses. Understanding the manner in which the organism evolves to adapt to host defenses, or for increased exploitation of host resources, is important to understanding the management and treatment of a disease that is an increasing public health threat.