Hormonal Regulations of Testicular Functions in fish(F Le Gac, E Sambroni, AS Goupil)
Gonadotropins and sex steroids regulate gonadal functions through mechanisms that are not well defined. We previously characterized these reproductive hormone synthesis, blood concentrations and gonadal receptivity over/during the whole reproductive cycle. Their specific roles in gonad recrudescence are studied through in vitro and in vivo approaches. More recent works focus on gene expression profiles during trout spermatogenesis; transcriptome regulations by T, 11KT, FSH and LH and involve cross species comparative studies. We identify genes which are probably of crucial relevance for qualitative and quantative regulation of spermatogenesis in fish. Functional analysis of new target genes through transgenesis is also undertaken in collaboration with JJ Lareyre. (ANR support “SpermGen” and EU project “LifeCycle”)
Mechanisms underlying puberty onset in fish
1- I study pubertal process- at testicular level- events involved in initiation of spermatogenesis in trout, in particular the regulation of Spermatogonial Stem Cell fate (SSC). My immediate objectives include the characterization of these stem cells / undifferenciated spermatogonia : specific markers; isolation ; behavior in culture ; ability to colonize the gonad and produce spermatozoa. We show the conservation of morphological, molecular and functional characteristics of SSCs between fish and phylogenetically distant vertebrate species. We also points out for the Gdnf/Gfralpha1 as a critical pathway possibly governing the regulation of trout spermatogonial stem cell renewal. (F Le Gac, J Bellaiche, JJ Lareyre)
2- In fish, timing of puberty is known to be linked to growth and metabolic status. We found that the occurrence of puberty and the kinetics of gametogenesis in trout is related to early body growth, nutritional status, muscle lipid content and we questioned the role of the metabolic hormonal status : GH, IGF, thyroid h., leptine (F Le Gac ,C Weil, AS Goupil).
Mastering the fertility and controlling early sexual maturation in fish species are significant stakes for the competitiveness of aquaculture. It is also necessary to prevent the reproduction of allochton species in the environment. Applied programs concern - the potential to control puberty through anti-gonadotropin receptor vaccinations; - the biotechnology of Spermatogonial Stem Cells, cryopreservation and potential for regeneration of individuals through embryo/oocyte transfert (Infrastructures d’Avenir “CRB ANIM” ; collaboration C. Labbé); - providing early and non- invasive markers for precocious puberty phenotype in a fish farming context (Aquaexcel EU project).
Testicular steroid production, including by germ cells, and regulation by LH (GTH2) ; FSH and LH synthesis, blood concentrations and gonad receptivity have been described all along the reproductive cycle - in relation to gonad maturation, steroid hormone concentrations, and steps of spermatogenesis. FSH and LH receptors have been cloned and characterized. Their specific roles in gonad recrudescence are studied through in vitro and in vivo approaches. Sex steroid binding globulin production and regulation in testis and liver. GH receptor and GH actions on trout gonads. IGF and IGF receptor expression and function in trout testis. Role and mechanism of action of estradiol in the male fish.
Ph.D.: Reproductive Physiology, Jussieu University Paris VI, France (1981)
Master: Reproductive Physiology, Jussieu University Paris VI, France (1978)
Licence: Animal Physiology, Tours University, Tours, France
Since 1990: Research Director in Reproductive Physiology in Fish, with special interest for the control of testicular maturation
1990-1984: Research assistant on fish testicular functions, INRA SCRIBE, Rennes, France
1993 (6 months): Set up of a research program on human sperm, CECOS de l'Ouest, Rennes, France
1982-1981: Sertoli cell desensitisation to FSH in rat, Oslo Rikshospitalet, Norway, V. Hansson laboratory
1981-1979: PhD Thesis work on inhibin and ABP productions by Sertoli cells and regulation by FSH in rat, Melbourne University, Australia, D. de Kretser laboratory
2001-2007: Group leader on "Testicular functions and puberty in male fish"
2002-2005: In charge of the SCRIBE team " Fish Reproduction"
1998-2003: Animation of the "trout AGENAE national research program"
2003-2006: Member of the Scientific Council of the network for genomic studies in the western part of France, "OUEST Genopole"
Publications: articles, ouvrages et chapitres d'ouvrage