Fig. 1. Expression of Brn3a and Brn3b during development of the mouse facial-stato-acoustic ganglion. (A-J) Whole-mount (A,B) and inner ear sections (C-J) from embryos at the indicated stages were immunostained with anti-Brn3a (A,C,E,G,I) and anti-Brn3b (B,D,F,H,J) antibodies. Prominent Brn3a expression is initially found in the facial-stato-acoustic ganglion (FSAG) by E9-E9.5, and persists at later embryonic stages in all the ganglia derived from it, including the vestibulocochlear ganglion (VCG), spiral ganglion (SG), vestibular ganglion (VG) and geniculate ganglion (GG). Brn3b exhibits a much more delayed temporal expression pattern than Brn3a with no expression in the FSAG at E9-E10.5, weak expression in some cells of the VCG and GG by E12.5-E14.5, and prominent expression in the SG, VG and GG starting only at E16.5. The location of the otic vesicle (OV) is indicated in A-D. (K) Schematic illustrating the derivation of inner ear and gustatory sensory ganglia during embryogenesis, and temporal expression patterns of Brn3a and Brn3b in these ganglia and their primordia. Scale bar: 25 µm in A-F,I,J; 100 µm in G,H.