Fig. 5

Comparative analysis of sox5 and dmrt1bY expression dynamics during gonadal primordium formation. Expression of sox5 compared to dmrt1by in a double transgenic fluorescent reporter line. a–c During early gonadal formation, sox5 is first detected in the somatic tissues surrounding the germ cells at stages 26 to 28. At the same time, dmrt1bY is expressed in germ cells. d–i By stages 33 to 34, sox5 expression becomes restricted to the germ cells. dmrt1bY is also expressed in the germ cells at those specific stages of development. Variations within the respective levels of sox5 and dmrt1bY expression are clearly observable (d compared to e and f and g compared to h and i). j,k Around hatching (stages 38/39), the expression of sox5 strengthens in all germ cells while parallel dmrt1bY expression quickly switches from germ cells only to somatic germ-cell-surrounding cells only. l In vivo visualization of the dynamics of expression localization of sox5 and dmrt1bY during male gonadal primordium development. The expression of sox5 and dmrt1bY is highly dynamic during primordium gonadal formation, switching from somatic to germ cells and vice versa, respectively, from stage 26 until hatching. Being mutual repressors of each other, a seesaw of expression is observed, finally finely restricting dmrt1bY expression in the somatic part of the primordium gonad. Blue and red represent cellular expression localizations only and should not been interpreted as expression levels