DMRT1 is Required For Sex Determination in Rabbits
Résumé
DMRT1 is a transcription factor containing a DNA-binding domain (DM domain) highly conserved across evolution. Although it is considered as the Testis Determining Factor in many non-mammalian species, Dmrt1 disruptions in mice have no impact on testicular differentiation during fetal development. Otherwise, DMRT1 expression was shown to precede SOX9 up-regulation in XX sex-reversed goats (FOXL2-/-). In order to test our hypothesis that DMRT1 would be involved in sex determination in non-murine species, by targeting SOX9 expression, we used CRISPR/Cas9 technology to generate DMRT1 mutant rabbits. We showed that the absence of DMRT1 leads to male-to-female sex reversal in XY homozygous mutants. At 20 days post-conception, few days after sex-determination, XY DMRT1-/- gonads were devoid of testis cords structures and presented a typical ovarian organization. Molecular studies confirmed the ovarian signature with an up-regulation of ovary-driving genes (RSPO1, WNT4, FOXL2 and CYP19A1) and downregulation of testis-specific genes (SOX9, SOX10 and DHH) in the developing XY DMRT1-/- gonads (bulk RNA-sequencing and RT-qPCR data). Our data highlight the role of DMRT1 as a key player in sex determination in rabbits. DMRT1 is required to SRY action on SOX9 expression and may also be necessary to SOX9 function on its own target genes.