Figure 7.
Coexpression of transcription factors regulating habenula development. Expression of Brn3a, Nurr1, and Etv1 were examined by immunofluorescence at E16.5 and E12.5. A, Diagram depicting the planes of section in subsequent views. B–E, Coexpression of Brn3a and Nurr1 in E16.5 embryos. D, Nearly all neurons that express Brn3a in the MH and LH also express Nurr1, although relative expression levels vary. E, Nurr1 is almost undetectable in the Pou4f1−/− habenula. F–I, Coexpression of Brn3a and Etv1 in E16.5 embryos. In the Pou4f1−/− habenula, a small residual population of Etv1+ neurons is noted near the ventricle. J–L, Brn3a and Nurr1 expression in early habenular neurons at E12.5. J, Expression of the tauLacZ transgene faithfully replicates the expression of Brn3a protein in the first habenular neurons to differentiate in Pou4f1tLacZ/+ embryos. K, L, All or nearly all of these neurons coexpress Nurr1 (K), and Nurr1 expression is not initiated in the absence of Brn3a (L). Scale bars: B–I, J–L, 100 μm.