Fig. 4. Decrease in Th expression in the petrosal ganglion of Phox2b^lacZ/+ E16.5 embryos and normalization at P10. (A,B) In situ hybridization for Th expression shows that the heterozygous mutant glomus expresses normal levels of Th. (C,D) The subpopulation of petrosal ganglionic neurons, positioned ventrally, which expresses Th seen in the wild type in C is sparser in heterozygous mutants (D). The contour of the ganglion is outlined in red. (E) Quantification of Th-positive cells in the petrosal ganglion of E16.5 wild-type (n=6 ganglia) and heterozygous mutant (n=6 ganglia) embryos and P10 wild-type (n=4 ganglia) and heterozygous mutant (n=4 ganglia) pups. Values are means±s.e.m. (^**P<0.01).