Fig. 2. Reduced proliferation of sympatho-adrenal precursor cells causes a smaller size of primary sympathetic ganglia in Insm1 mutant mice. Phox2b and β-galactosidase expression was analyzed in the sympathetic ganglion chain at E10.5 (A-F), E11.5 (G-J) and E12.5 (K-N) of Insm1^lacZ/+ and Insm1^lacZ/Insm1^lacZ mice by in situ hybridization or immunohistochemical analyses. (A,B,G,H,K,L) In situ hybridization using a Phox2b-specific probe. (C-F,I,J,M,N) Immunohistochemistry using antibodies against (C-F,I,J,M,N) β-galactosidase (green) and (E,F) Phox2b (red). The number of cells in the primary sympathetic ganglion chain is reduced in the mutant at E11.5 and E12.5. (O) Cell proliferation, as determined by BrdU injections at the indicated time points in the primary sympathetic ganglion chain of Insm1^lacZ/+ and Insm1^lacZ/Insm1^lacZ mice. Shown is the proportion (%) of β-galactosidase+ cells that had incorporated BrdU 2 hours after the injection. Double asterisks indicate P<0.01. Scale bars: 100 µm in A,G,K.