Fig. 8. Expression of Ret mRNA as revealed by in situ hybridization is strongly enhanced in the adrenal medulla of Mash1 knockout mice at E16.5. Photomicrographs show cross-sections through the adrenals of wild-type (A,B) and Mash1^–/– mice (C,D). Arrows indicate sympathetic ganglia that are positive for Ret (A) and TH (D). Appropriate sense controls have been performed (not shown). am, adrenal medulla. Scale bar: 100 µm.