High-Throughput Sequencing Analyses of XX Genital Ridges Lacking FOXL2 Reveal DMRT1 Up-Regulation Before SOX9 Expression During the Sex-Reversal Process in Goats1

Abstract

FOXL2 loss of function in goats leads to the early transdifferentiation of ovaries into testes, then to the full sex reversal of XX homozygous mutants. By contrast, Foxl2 loss of function in mice induces an arrest of follicle formation after birth, followed by complete female sterility. In order to understand the molecular role of FOXL2 during ovarian differentiation in the goat species, putative FOXL2 target genes were determined at the earliest stage of gonadal sex-specific differentiation by comparing the mRNA profiles of XX gonads expressing the FOXL2 protein or not. Of these 163 deregulated genes, around two-thirds corresponded to testicular genes that were up-regulated when FOXL2 was absent, and only 19 represented female-associated genes, down-regulated in the absence of FOXL2. FOXL2 should therefore be viewed as an antitestis gene rather than as a female-promoting gene. In particular, the key testis-determining gene DMRT1 was found to be up-regulated ahead of SOX9, thus suggesting in goats that SOX9 primary up-regulation may require DMRT1. Overall, our results equated to FOXL2 being an antitestis gene, allowing us to propose an alternative model for the sex-determination process in goats that differs slightly from that demonstrated in mice.

Female-to-male sex reversal in mice caused by transgenic overexpression of Dmrt1

“…Our marker analyses further suggest that it acts in this role upstream of Sox9, a conclusion that is supported by the recent observation that upregulation of DMRT1 precedes SOX9 expression during femaleto-male sex reversal of polled intersex goats (Elzaiat et al, 2014). Thus, despite the existence of a variety of sex-determining mechanisms in the animal kingdom, our results support a model in which Dmrt1 provides a common genetic thread among metazoans (Fig.…”

Foxl2 and Its Relatives Are Evolutionary Conserved Players in Gonadal Sex Differentiation

“…In goat, a complete sex reversal is observed, while in mouse this is only partial. This difference has been suggested to be in relation with an important role of FOXL2 as a key regulator of steroid synthesis, especially estrogen production [Pannetier et al, 2006;Wang et al, 2007;Elzaiat et al, 2014]. In non-mammalian vertebrates, like fish for instance, the aromatase enzyme (Cyp19a1a), needed for estrogen synthesis, is a key enzyme for gonadal sex differentiation, as the presence of estrogens is necessary for ovarian differentiation [Guiguen et al, 2010].…”

“…On the other hand, FOXL2 has been clearly linked to control steroid synthesis, especially estrogen production, representing a crucial event of sexual differentiation in non-mammalian vertebrates, where changing sex steroid hormones induces sexual fate change into one sense or the other [Pannetier et al, 2006;Wang et al, 2007;Elzaiat et al, 2014].…”

Sex Reversal in Non-Human Placental Mammals

“…This feature of the female pathway also has an impact on the male counterpart where DMRT1 seems required for SOX9 upregulation in goats , which contrasts with what is found in mice [Sekido and Lovell-Badge, 2008]. Moreover, in the goat species, SRY is predicted to be involved in testicular maintenance by repressing FOXL2 during life in the Sertoli cells in order to protect them from trans-differentiation [Montazer-Torbati et al, 2010;Elzaiat et al, 2014]. In summary, all results obtained in goats led us to propose a sex-determining model that differs from the model currently admitted for mice ( fig.…”