209. The absence of betaglycan affects Sox9 m RNA expression at the time of sex determination in a mouse model

Abstract

Betaglycan is a co-receptor that binds both TGF-β and inhibin, and thereby acts as a modulator of the activities of multiple members of the TGF-β superfamily. We have previously shown that the murine betaglycan gene is expressed in somatic cells within the interstitium of the fetal testis from 12.5 dpc-16.5 dpc. Betaglycan protein was predominantly localised to the interstitial cells surrounding the developing seminiferous cords which stained positive for Cyp11a (p450 Scc), a Leydig cell marker. In order to determine the impact of this receptor on fetal Leydig cell biology, RNA was extracted from two independently collected sets of betaglycan knockout and wildtype male and female gonads at 12.5 dpc and 13.5 dpc (n = 4 gonad pairs/set), and quantitative real time PCR was performed to determine changes in the expression levels of key genes involved in fetal Leydig cell differentiation and function. This analysis revealed that the levels of mRNA expression of SF1, Cyp11a and Cyp17a1 were downregulated between 12.5–13.5 dpc in the betaglycan knockout embryos compared with wildtype embryos immediately after the time of sex determination. Interestingly, the expression level of the key Sertoli cell marker SRY-(sex determining region Y)-box 9 (Sox9) was transiently decreased at 12.5 dpc by 50% in the knockout testis in comparison with that of the wildtype testis. No significant change was found one day later at 13.5 dpc. Our data show that betaglycan is predominantly expressed in the fetal Leydig cells of the murine testis and that the presence of this receptor is required for normal fetal Leydig cell differentiation. Furthermore, the transient downregulation of Sox9 expression in null testis suggests that Sertoli cell differentiation may also be affected in betaglycan knockout mice, and that this defect may precede the defect in Leydig cell development. Supported by: the NHMRC Australia (RegKeys 338516; 241000).