Analyse de profils d'expression génique au cours de la différenciation gonadique chez le poulet. Etude fonctionnelle d'un cas particulier : BMP4 (bone morphogenetic protein)

Govoroun Marina (Co-encadrante) Diplôme : Dr. d'Universit

Analyse des profils d'expression génique au cours de la différenciation gonadique chez le poulet (étude fonctionnelle d'un cas particulier)

Chez le poulet, le déterminisme du sexe est génétique (ZZ/ZW) mais à la différence des mammifères le déterminant majeur du sexe n a pas été identifié. Néanmoins, un certain nombre d acteurs moléculaires impliqués en aval dans la différenciation du testicule (DMRT1, AMH, SOX9 ) ou de l ovaire (CYP19A1, FOXL2, RSPO1 ) ont été identifiés. D autre part, le modèle poulet présente deux particularités que sont l asymétrie du développement ovarien et la sensibilité aux stéroïdes donnant la possibilité d inversions du sexe par des hormones exogènes. Par une analyse par PCR en temps réel à moyen débit, nous avons identifié des gènes dont l expression est sexuellement dimorphique et/ou asymétrique au cours de la différenciation gonadique. Parmi ces gènes plusieurs membres de la famille des bone morphogenetic protein sont préférentiellement exprimés dans l ovaire en comparaison au testicule. L étude des effets de BMP4 sur la culture organotypique d ovaires ou de testicules a montré qu il était un inhibiteur de la stéroïdogénèse basale et induite par la FSH et d autre part qu il est un inhibiteur de l expression de l AMH. Résultats qui nous ont amené à émettre l hypothèse que BMP4 était un facteur anti-testiculaire .In chicken, sex is determined by a ZZ/ZW sex chromosome system, where the female is heterogametic (ZW). However, the mechanism involved in the sex determination is still unknown. Several genes involved in testicular (DMRT1, AMH, SOX9 ) or in ovarian (CYP19A1, FOXL2, RSPO1...) differentiation have been identified. Furthermore, gonadal development in chicken embryos presents two particularities which are the asymmetrical ovarian development and the sensitivity to exogenous hormones leading to sex reversal. By real-time PCR analysis, we have identified several genes whose expression is sexually dimorphic and/or asymmetric. In particularly, we showed that several members of bone morphogenetic protein family are preferentially expressed in the ovary compared to the testis. Using organotypic culture of embryonic ovaries and testes, we showed that BMP4 inhibits the basal and FSH induced steroidogenesis and is an inhibitor of AMH mRNA expression. These findings lead us to propose that BMP4 is an anti-testicular factor.TOURS-Bibl.électronique (372610011) / SudocSudocFranceF

Gene expression profiling reveals new potential players of gonad differentiation in the chicken embryo

Background : In birds as in mammals, a genetic switch determines whether the undifferentiated gonad develops into an ovary or a testis. However, understanding of the molecular pathway(s) involved in gonad differentiation is still incomplete. Methodology/Principal Findings : With the aim of improving characterization of the molecular pathway(s) involved in gonad differentiation in the chicken embryo, we developed a large scale real time reverse transcription polymerase chain reaction approach on 110 selected genes for evaluation of their expression profiles during chicken gonad differentiation between days 5.5 and 19 of incubation. Hierarchical clustering analysis of the resulting datasets discriminated gene clusters expressed preferentially in the ovary or the testis, and/or at early or later periods of embryonic gonad development. Fitting a linear model and testing the comparisons of interest allowed the identification of new potential actors of gonad differentiation, such as Z-linked ADAMTS12, LOC427192 (corresponding to NIM1 protein) and CFC1, that are upregulated in the developing testis, and BMP3 and Z-linked ADAMTSL1, that are preferentially expressed in the developing ovary. Interestingly, the expression patterns of several members of the transforming growth factor β family were sexually dimorphic, with inhibin subunits upregulated in the testis, and bone morphogenetic protein subfamily members including BMP2, BMP3, BMP4 and BMP7, upregulated in the ovary. This study also highlighted several genes displaying asymmetric expression profiles such as GREM1 and BMP3 that are potentially involved in different aspects of gonad left-right asymmetry. Conclusion/Significance : This study supports the overall conservation of vertebrate sex differentiation pathways but also reveals some particular feature of gene expression patterns during gonad development in the chicken. In particular, our study revealed new candidate genes which may be potential actors of chicken gonad differentiation and provides evidence of the preferential expression of BMPs in the developing ovary and Inhibin/Activin subunits in the developing testis

Gadd45 gamma and Map3k4 Interactions Regulate Mouse Testis Determination via p38 MAPK-Mediated Control of Sry Expression

SummaryLoss of the kinase MAP3K4 causes mouse embryonic gonadal sex reversal due to reduced expression of the testis-determining gene, Sry. However, because of widespread expression of MAP3K4, the cellular basis of this misregulation was unclear. Here, we show that mice lacking Gadd45γ also exhibit XY gonadal sex reversal caused by disruption to Sry expression. Gadd45γ is expressed in a dynamic fashion in somatic cells of the developing gonads from 10.5 days postcoitum (dpc) to 12.5 dpc. Gadd45γ and Map3k4 genetically interact during sex determination, and transgenic overexpression of Map3k4 rescues gonadal defects in Gadd45γ-deficient embryos. Sex reversal in both mutants is associated with reduced phosphorylation of p38 MAPK and GATA4. In addition, embryos lacking both p38α and p38β also exhibit XY gonadal sex reversal. Taken together, our data suggest a requirement for GADD45γ in promoting MAP3K4-mediated activation of p38 MAPK signaling in embryonic gonadal somatic cells for testis determination in the mouse