Fig. 1. Expression of Insm1 in the developing peripheral nervous system. To analyze Insm1 expression, we took advantage of the Insm1^lacZ allele in which lacZ sequences replace the Insm1-coding sequence. Insm1^lacZ/+ animals were analyzed at the indicated developmental stages, using antibodies directed against the lacZ gene product β-galactosidase (A,C-E) or X-gal staining (B). (A) Immunohistochemical analysis using anti-β-galactosidase (green) and anti-p75 (red) antibodies demonstrates expression of β-galactosidase in the primary sympathetic ganglion chain located lateral of the dorsal aorta (arrowhead), in the spinal cord and in condensing dorsal root ganglia at E9.5. (B) At E10.5, X-gal staining is detected in the entire primary sympathetic ganglion chain (arrowhead), as well as in sensory ganglia and in the central nervous system. (C,D) Immunohistochemical analyses of the primary sympathetic ganglion chain using antibodies directed against β-galactosidase (green), Phox2b (red in C) and Mash1 (red in D) indicate that the majority of β-galactosidase+ cells lateral of the dorsal aorta co-express Phox2b, and some β-galactosidase+ cells also express Mash1. (E) Immunohistochemical analysis of the adrenal gland at E13.5 using anti-β-galactosidase (green) and anti-Th (red) antibodies demonstrates Insm1 expression in chromaffin cells of the adrenal medulla. Scale bars: 100 µm in A,C,E; 500 µm in B.