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Orgebin-Crist, Marie-Claire |
Professor
Center for Reproductive Biology Research, Vanderbilt University School of Medicine, Medical Center North, Room C-3306, Nashville, Tennessee 37232-2633.
Tel: 615 322 7484 Fax: 615 343 7797
Email: m-c.orgebin-crist@mcmail.vanderbilt.edu |
Academic history
B.S., Baccalaureat Latin-Sciences, Paris, France
M.S., Sorbonne, University of Paris
Ph.D., Lyon University, Paris, France
Mailing Address
Department of OB/GYN R-1215 Medical Ctr. North, Dept. of OB/GYN(2521) 37232-2521
Research Specialty
Epididymal structure and function; development of fertilizing ability in spermatozoa
Research Description
Our work has been directed toward understanding the maturation of spermatozoa in the epididymis and the mechanisms of its regulation. We have shown that, in vivo, spermatozoa develop the capacity to bind to the zona pellucida and to fertilize in a specific segment of the epididymis. At present, we are studying protein secretion by the epididymis and the modification of the sperm surface by epididymal secretory proteins. We have identified and purified several of these proteins: CRISP 1 (cystein-rich secretory protein 1), E-RABP (retinoic acid binding protein), PEBP (phosphatidylethanolamine binding protein), and CRES (cystatin related epididymal protein). We also have identified several glycoprotein-modifying enzymes that either add (glycosyltransferase) or cleave (glycosidase) sugar residues from the sperm surface glycoproteins. We are currently studying the murine E-RABP (Lcn5). This protein belongs to the lipocalin family. Lipocalins are extracellular carrier proteins that bind lipophilic molecules. mE-RABP binds active retinoids (9 cis and all-trans retinoic acid) and is likely involved in the delivery and trafficking of retinoids within the epididymis. To identify the molecular mechanisms underlying the regulation of tissue- and region-specific gene expression in the epididymis, transgenic mice carrying different lengths of the 5' flanking region of the Lcn5 gene driving the CAT reporter gene were produced. We found that important cis-DNA regulatory elements required for the hormonal regulation and spatial expression of the Lcn5 gene reside within 1.8 kb of the 5' flanking region. Using transient transfection assays, we found that the androgen responsiveness of the Lcn5 gene was conferred by an androgen-specific response region located within the first 600-bp of the Lcn5 gene. The Lcn5 gene is localized on mouse chromosome 2. We found that six other related genes, Lcn8, Lcn9, Lcn10, Lcn11, Lcn12, and Lcn13, that evolved by in situ tandem duplication on the same locus form a cluster of epididymis-specific genes. However, each gene has a distinct spatial expression within the epididymis and different regulation. Analysis of the human genome sequence showed the presence of genes on chromosome 9 with genomic organization, chromosomal arrangement, and orientation similar to that of the corresponding murine genes, indicating that the epididymal cluster is evolutionary conserved. A phylogenetic analysis of the new epididymal proteins reveals their spread position in the lipocalin protein family tree. This suggests preservation of regulatory sequences, while protein sequences have greatly diverged, reflecting functional diversity and possibly multifunctionality. The candidate ancestor gene likely appeared in amniotes and the duplications generating the cluster occurred at least in the common ancestor of rodents and primates. The presence and conservation from lizard to man of a cluster of genes encoding epididymal lipocalins, differently regulated and regionalized in the epididymis, strongly suggests that these proteins may play an important role in epididymal function.
Publications
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