Fig. 8. Distribution of mesotelencephalic dopaminergic fibers is altered in the diencephalon of Nkx2-1 mutants. (A,C) Sections horizontal to the diencephalon of E18.5 wild-type (A) and Nkx2-1 mutant (C) fetuses showing immunohistochemistry against tyrosine hydroxylase (TH). Caudal is upwards and rostral is downwards in both panels. The arrow points to the region where TH-positive fibers abnormally converge towards the rostral midline. (B,D) The path followed by dopaminergic mesotelencephalic axons (green) in wild-type (B) and Nkx2-1 mutant mice (D). The pink domains indicate the territories patterned by Nkx2-1 function. a/b, alar/basal boundary; AEP, anterior entopeduncular region; Chr, chiasmatic region; Chr*, mutant chiasmatic region; cp, cerebral peduncle; DT, dorsal thalamus; ET, eminentia thalami; GP, globus pallidus; H, hippocampus; Hb, hindbrain; Hyp, hypothalamus; Hyp*, mutant hypothalamus; ic, internal capsule; M, mesencephalon; mfb, medial forebrain bundle; NCx, neocortex; POa, preoptic area; POa*, mutant preoptic area; PrH, peduncular region of the hypothalamus; p/sp, pallial/subpallial boundary; PT, pretectum; ob, olfactory bulb; os, optic stalk; SC, superior colliculus; Str, striatum; Str*, mutant striatum; V, layer 5 cortical neurons; VI, layer 6 cortical neurons; VT, ventral thalamus. Scale bar: 400 µm.