Understanding molecular mechanisms underlying puberty onset in male fish
My current research interests aim to better understand molecular mechanisms underlying the sexual maturation (puberty) in fish, particularly in male. The initiation of the male gametogenesis (spermatogenesis) is an important biological process that impacts puberty onset and ultimately fish fertility. Puberty onset depends on the activation of the gonadotrope axis (GnRHs) that ultimately control the release from the pituitary of two gonadotropins named FSH and LH. Both hormones control the two main testicular functions (spermatogeneis and steroidogenesis). Spermatogeneis relies on the balance between renewal and proliferation/differentiation of germ stem cells. The role of the sexual hormones (gonadotropins and gonadotropin induced sexual steroids) in the regulation of this balance remains poorly understood.
My research is aimed at:
- characterizing gonadal factors that may be involved in the regulation of germ stem cell fate and/or spermatogonial proliferation in teleost fish species
- understanding the molecular mechanisms underlying the distinct effects of the sexual hormones (steroids and gonadotropins) on the gonadal functions with a focus on the regulation of testicular factors that regulate the spermatogonial proliferation.
Complementary genomic approaches based on the analysis of transcriptome changes during the testicular maturation and hormonal treatment are conducted in trout (cDNA microarrays, SSH, Q-rtPCR, in situ hybridisation). In silicoanalyses of fish genomes and phylogenetic studies are combined to the transcriptome approaches to understand the conservation and evolutionary changes of the selected genes in different fish orders. We have developed molecular tools to targetin vivogene expression in different cell types of the germinal niche. These studies lead to the production of GFP expressing transgenic lines that will be used to characterize the somatic and the adult germ cell stem cells, to identify new paracrine factors, and to address, in vivo, the functional significance of the selected gonadal factors.
The motility and fertilizing ability of the spermatozoa requires their passage through successive and complex microenvironments provided by different segments of the epididymal duct. My initial research interest was directed towards the understanding of the molecular mechanisms underlying the androgen responsiveness and segment-restricted expression of genes encoding epididymal secretory proteins. Using transient transfection assays, site directed mutagenesis, and in vitro binding studies (EMSA), several functional cis DNA regulatory elements were characterized within the 5' flanking region of the GPX5 and lcn5 genes including androgen receptor responsive elements. In addition, using transgenic mice, we demonstrated that promoter fragments (about 1.8 kb) of the lcn8 and lcn5 genes contained all the information required for the endocrine control and expression of transgene to the proximal (lcn8) and distal caput epididymidis (lcn5) in vivo.
Ph.D.: Cellular and Molecular Biology, Blaise Pascal University, Clermont-Ferrand, France (1996)
Master: Cellular and Molecular Biology, Blaise Pascal University, Clermont-Ferrand, France (1992)
B.Sc.: Mathematics and Biology, Clermont-Ferrand, France (1986)
1998- present: Researcher, SCRIBE, Research Unit UR 1037 (SCRIBE), Fish Reproduction research group, Animal Physiology Department, French National Institute for Agricultural Research
1996-1998: Research Associate, Center for Reproductive Biology Research, Departemnt of Obstetrics & Gynecology, Vanderbilt University, Medical School
2005-present: Co-animator of the "Reproductive Physiology and Environment " working group of the BIOSIT federative research institute
2011: Head of the research team “Puberty and Testicular Physiology”
2007-present: Person in charge of organizing Master courses for the training of agronomist specialized in the management of marine resources
Publications: articles, ouvrages et chapitres d'ouvrage