Fig. 5.

Nf1^nc mice live longer than Nf1^−/−embryos and develop tumors of neural-crest origin. a,b, Comparison of newborn wild-type (a) and Nf1^nc (b) littermates. c,d, Sagittal sections of newborn pups showed normal sympathetic ganglia in wild-type embryos (arrow, c) and massively enlarged ganglia in Nf1^nc embryos (arrows, d). e–h, Adrenal gland (ad) of wild-type (e,g) and Nf1^nc (f,h) embryos showed hyperplastic adrenal medullary cells reminiscent of pheochromocytoma in Nf1^nc pups. The cells formed a large mass extrinsic to the adrenal gland (yellow arrows, f). Immunohistochemistry showed medullary (m) cells positive for tyrosine hydroxylase surrounded by cortex (c) in wild-type embryos (g), whereas cells positive for tyrosine hydroxylase were seen invading the cortex and surrounding tissues in Nf1^nc embryos (yellow arrows, h).