Figure 6

S ubsets of meso-diencephalic dopamine neurons express Sema7A and plexinC1. In situ hybridization for tyrosine hydroxlyase (TH), Sema7A and plexinC1 (A-F), and colocalization of TH protein and Sema7A (G) and of TH protein and plexinC1 (H) on coronal sections of the adult meso-diencephalic dopamine (mdDA) system. A, C and E show consecutive sections of the rostral part of mdDA system, B, D and F of its caudal part. Dorsal is to the top. (A, B) TH labels mdDA neurons in the subtantia nigra (SN) and ventral tegmental area (VTA). Arrows in A through F outline the position of the SN as visualized by TH labeling. Arrowheads in B, D and F indicate the central part of the VTA. (A-F) Note that whereas overlap in TH and Sema7A expression is largely confined to the lateral aspect of the SN (C, D), TH and plexinC1 predominantly overlap in the central part of the VTA (F, indicated by arrowhead). No plexinC1 expression is detected in the SN (E, F). Asterisk indicates the fasciculus retroflexus. (G, H) Colocalization of TH protein (brown) and Sema7A (G; purple) in the SN and of TH protein (brown) and plexinC1 (H; purple) in the VTA reveals Sema7A or plexinC1-positive mdDA neurons (red arrows in G, H), mdDA neurons that lack these transcripts (arrowheads in G, H), and non-mdDA neurons or cells that express Sema7A or plexinC1 (black arrows in G, H). 7A, Sema7A; C1, plexinC1; fr, fasciculus retroflexus; mt, mammillothalamic tract; pc, pars compacta; pr, pars reticulare. Scale bar 250 μm (A-F), and 65 μm (G, H).