Expression of EGR2 (KROX20), Hoxa3 , Hoxb4 , and Crabp1 is unaltered in the hindbrain of Nav2 homozygous mutant embryos. Whole-mount immunohistochemistry for EGR2 shows staining in presumptive rhombomeres r3 and r5 at 8s in both (A) wild-type (WT) and (B) Nav2-/- (HOM) embryos. (C,D) In situ hybridization analysis of Hoxa3 mRNA at E9.5 shows staining in the neuroepithelium caudal to the r4/5 border in both genotypes. Hoxb4 mRNA at E9.5 is expressed caudal to the r6/7 border in both (E) wild-type and (F) Nav2-/- embryos. (G-I) Crabp1 mRNA at E9.5 is expressed in the neural crest cells, including those contributing to the IXth and X cranial nerves (bracket) in both wild-type (G) and Nav2-/- (H-I) embryos. A total of ten 8s wild-type and Nav2-/- embryos each were studied for EGR2 staining; 8 and 19, and 7 and 12 wild-type and Nav2-/- embryos were examined for Hoxa3 and Hoxb4, respectively. Seven wild-type and 13 Nav2-/- embryos were studied for Crabp1 staining. ov, otic vesicle; t, tail. Scale bar: 200 μm.