Fig. 5

Model of early sex differentiation gene network. Temporal expression pattern of prominent driver genes of early sex differentiation in P. vitticeps. We propose a W-linked repressor of dmrt1 and/or WNT-antagonists. We assume sex independent early activators (similar to the activator of SRY in mammals) of dmrt1, amh, WNT inhibitors and foxl2 [54, 99, 100]. Interactions between genes are displayed by green arrows for a positive influence of expression and red blockage signs for a negative influence based on common and well-established relations in other species which our data did not oppose. In the absence of a W chromosome, dmrt1 will eventually supress foxl2 expression which leads to the establishment of extremely high amh expression levels in males. WNT signalling cannot be established, and the male trajectory can pursue. With a W chromosome present, foxl2 expression can be established which in turn activates cyp19a1 expression [55]. Further, WNT signalling will be strengthened owing to suppression of WNT inhibitors. Both, WNT signalling and foxl2, retain amh expression. High cyp19a1 expression might subsequently block SOX9 nuclear localisation via estrogen. The balance of the expression network tips towards the female trajectory