Fig. 6

Knockdown of Isl1 leads to a reduction of prethalamic DA neurons. The analyses of th expression (A–F) and of TH protein distribution (G–I) show a significant reduction in the number of prethalamic group 1 DA neurons (arrows) in the morphant embryos (B, C, E, F, H, I) compared to the controls (A, D, G). Similarly, slc6a3/dat (J–M) and ddc (N–Q) display a reduction of their prethalamic expression domains in Isl1 morphants (arrows, compare J with L and K with M for slc6a3/dat; N with P and O with Q for ddc), arguing for a role of isl1 in the specification of group 1 DA neurons. In addition, ddc expression in the epiphysis is lost in the morphants (arrowheads, compare N with P). The embryos were analyzed at 96 hpf. R: Evaluation of the effect of Isl1 knockdown on th expression for each DA cluster. The groups of the isl1 morphant larvae were compared with those of control MO injected larvae, which all developed normally and are summarized here in the left-most lanes (ctr). A–C, J, L, N, P are lateral views; D–I, K, M, O, Q are dorsal views, anterior is to the left. Scale bars: 100 μm. Abbreviations are like in Fig. 5.