A, B. Protein expression levels of Npn-1 and Npn-2 at E14, E16 and E18 in the developing brainstem. Consistent with the immunohistochemical results, the protein expression levels decrease as development progresses. C, D. Protein expression levels of Sema-3A and Sema-3F. In contrast to neuropilin expression, semaphorin protein expression increases as development progresses. Sema-3A expression is seen later in development than Sema-3F. GAPDH was used as a loading control. Numbers at left of bands are in kDa.