Two discrete domains of Shh -lineage along the rostrocaudal hypothalamic axis. (A) Adult mouse brain in sagittal view showing the hypothalamus (shaded gray) and its four transverse subdivisions. (B) Schematic distribution of tyrosine hydroxylase (Th) expressing cells (green dots) on a sagittal view of the hypothalamus (with information from the Allen Brain Atlas ). (C-K) Brains of ShhCreER/+; R26lz/+mice. Tamoxifen (TM) was administered as indicated and sections or whole-mount brains were labeled to detect the Shh-lineage. (C, F, H, K) Sagittal sections of adult hypothalamus labeled for Shh lineage (β-gal, red) and Th (green), TM as indicated. Dashed line outlines the brain. (D, J) Right side of hemi-dissected adult brain labeled for Shh-lineage (X-gal reaction, blue), TM as indicated. (E, G, I) Sagittal sections through the E18.5 hypothalamus labeled for Shh lineage (X-gal reaction, blue), TM as indicated. (G) Only few fate-mapped cells are found in the preoptic area with TM9.5. The boxed area is shown in higher magnification. Asterisks indicate the optic chiasm.A13, dopaminergic cell group A13; ac, anterior commissure; AHA, anterior hypothalamic region; cc, corpus callosum; fx, fornix; MAM, mammillary region; Ox, optic chiasm; PH, posterior hypothalamus; PRO, preoptic region; SNC, substantia nigra pars compacta; TUB, tuberal region.