Neonatal expression of amh, sox9 and sf-1 mRNA in Caiman latirostris and effects of in ovo exposure to endocrine disrupting chemicals

Abstract

Caiman latirostris is a reptilian species that exhibits temperature-dependent sex determination (TSD). Male-to-female sex reversal can be achieved after in ovo estrogen/xenoestrogen exposure. This is known as hormone-dependent sex determination (HSD). The amh, sox9 and sf-1 genes are involved in sex determination, sex differentiation, and steroidogenesis. The aims of this study were: (a) to establish the expression patterns of amh, sox9 and sf-1 mRNA in the gonad-adrenal-mesonephros (GAM) complexes of neonatal TSD-male and TSD-female caimans, (b) to compare the expression of these genes between TSD-females and HSD-females (born from E2-exposed eggs incubated at the male-producing temperature) and (c) to evaluate whether in ovo exposure to a low dose of E2 or bisphenol A (BPA) or to a high dose of endosulfan (END) modifies amh, sox9 or sf-1 mRNA expressions in neonatal males. The mRNA expressions of amh, sox9 and sf-1 in GAM complexes from TSD-males and TSD-females and from HSD-females were quantitatively compared by RT-PCR. A sexually dimorphic pattern of amh and sox9 mRNA expression was found, with a higher expression in TSD-males than in TSD-females. sf-1 mRNA did not differ between TSD-males and TSD-females. HSD-females exhibited a higher expression of sox9 than TSD-females. In males, increased mRNA expression of sex-determining genes was observed after in ovo exposure to END. E2 decreased sox9 but increased sf-1 mRNA expression. Changes induced by BPA were evident although not significant. These results provide new insights into the potential mechanisms that lead to the gonadal histo-functional alterations observed in caimans exposed to contaminated environments.