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BIOGRAPHY:
Dr. Ménard received his M.D. in 1990 from the
Université Paris V René Descartes. He earned his Ph.D. in
microbiology in 1995 from the Institut Pasteur in Paris. From 1995 to
1998 he conducted postdoctoral research in the Pathology Department of
the New York University School of Medicine, where in 1998 he was named
Assistant Professor, Department of Medical and Molecular Parasitology.
He is the recipient of several awards, among them the 1995 Prix Jacques
Pirraud en Maladies Infectieuses by the Fondation pour la Recherche
Médicale, the 1997 T.D.R. Program in Parasitology Award from the
World Health Organization, a five-year Career Award in Biomedical
Sciences from the Burroughs Wellcome Fund in 1977, the 2001 Prix
“Charles-Louis de Saulses de Freycinet” from the French
Academy of Sciences, and the 2001 Prix “Georges Zermati” from the Fondation de France. He currently heads the Malaria Biology
and Genetics Unit in the Department of Parasitology of the Institut
Pasteur. His HHMI project entails identifying genes expressed in
malaria parasites at different parasite stages.
RESEARCH ABSTRACT SUMMARY:
Conditional Mutagenesis Using Site-Specific Recombination in
Plasmodium berghei
Despite the development of gene-targeting technology in
Plasmodium, the parasite that causes malaria, there are still
major limitations to reverse genetics in this haploid protozoan. The
only stage of the parasite that can be genetically transformed is the
stage that multiplies inside red blood cells (RBC). Therefore, the
function of the proteins that play a role in parasite invasion and
multiplication in RBC cannot be characterized using molecular genetic
tools, because corresponding loss-of-function mutants are lethal.
Another limitation of the gene-targeting technology in
Plasmodium is that constitutive inactivation of genes that
perform multiple functions during the parasite life only reveals their
earlier role in the cycle.
Here, we describe conditional mutagenesis in Plasmodium
berghei, a plasmodial species that infects rodents, which can be
cycled routinely through mosquitoes, and whose genome can be
manipulated easily by homologous recombination. Conditional mutagenesis
is triggered by site-specific recombination (SSR) using the Flp/FRT system of yeast. By homologous recombination, a target
DNA is flanked by FRT sequences (flirted) in RBC stages and
deleted in mosquito stages of the parasite upon expression of the Flp
recombinase. Deletants are generated by parasite fertilization between
two clones, having either the flirted target or the Flp gene
under the control of a stage-specific promoter. The deletants are
recognized in the cross progeny by linking the SSR event to
fluorescence expression. This approach should permit one to address the
function of essential genes of the Plasmodium parasite at any
time of its life cycle.
Photo: Kent Kallberg, Kallberg Studios
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