Hand2 and Mash1 gene expression was examined by in situ hybridization using digoxigenin-labeled anti-sense cRNAs. A: In situ hybridization of a 12.5 dpc mouse embryo with Hand2. Hand2 is expressed throughout the length of the sympathetic trunk, in the coalescing adrenal gland, and in the parasympathetic and enteric nervous systems. B–H: Comparison of Hand2 (C, E, G) and Mash1 (D, F, H) expression in the SNS of 10.5 dpc (C–F) and 14.5 dpc (G–H) mouse embryos by in situ hybridization using alternate 10 µm cryosections. The regions of the embryo where sections were obtained for plates C–F are shown in plate B. Hand2 and Mash1 are co-expressed during early SNS development (C–F) but Hand2 expression continues after down regulation of Mash1 at 14.5 dpc (G–H). ad: adrenal gland; da: dorsal aorta; en: enteric plexus; nt: neural tube; sa: sacral parasympathetic plexus; sp: sphenopalatine ganglia; st: sympathetic trunk.