Fig. 8. Ngn1 promotes glutamatergic differentiation. (A) Ngn1 induces ectopic Brn3a⁺ neurons in the ventral Helt⁺ domains. In transgenic mouse embryos expressing Ngn1 under the control of the nestin enhancer, Brn3a⁺ neurons are generated at E11.5 despite the fact that Helt expression is not repressed (arrowheads). Note that most of the exogenous Ngn1-expressing neurons in the ML express Brn3a. (B) Ngn1 determines glutamatergic fate in the m1 domain. Shown are the dorsal m1 domains of wild-type control embryos and transgenic embryos expressing Ngn1 and IRES-controlled GFP under the control of the nestin enhancer at E12.5. Neurons generated from transgene-expressing progenitors are marked by GFP expression. Virtually all the GFP⁺ neurons express Brn3a and do not express Lim1.