Fig. 6.

Regulation of neurogenin, Xebf2, and NCAM expression by XDmrt4. (A–C) Real-time RT-PCR of animal explants isolated from embryos injected with various combinations of mRNA and morpholinos as indicated and collected when sibling embryos reached stages 14 or 22. (A) Injection of XDmrt4 induces Xeb2 and NCAM expression. This activity is inhibited by coinjection of XDmrt4ΔC. (B) XDmrt4 induces robust expression of neurogenin at stage 14 and to a lesser extend at stage 22. (C) Noggin-mediated activation of neurogenin, Xebf2, and NCAM expression is blocked in the context of XDmrt4-depeleted embryos (+XDmrt4-mo). (D) Based on these findings and other studies that have positioned Xebf2 downstream of neurogenin (29) we propose that XDmrt4 is an upstream regulator of neurogenin and Xebf2 in the molecular cascade, leading to neuronal differentiation in the olfactory system.