Insc and Numb affect DA neuronal specification.
(A–I) St16–17 embryos showing TH expression in green (all panels) and Per expression in white (B, E, and H). (B, E and H) represent magnified and merged frames of A, D, and G, respectively. (A–C) wt embryos. One H-cell can be seen (A, arrowheads) flanked by two paramedial cells (vertical arrows). Per expression is present in cells at the midline as well as outside of the midline (B, in white) but excluded from the H-cells. TH expression in the dorsal lateral cells near the lateral-most border of the CNS (C, horizontal arrows). In numb embryos (D–F), H-cells at the ventral midline (D, bracketed) as well as dorsal lateral cells (F, horizontal arrows) are mostly missing. The loss/reduction of H-cells is accompanied by the gain of Per expression (E, open arrowhead). The paramedial cells are generally undetectable in numb embryos. In insc embryos (G–I), H-cells are duplicated at high frequency (G, arrowheads) but the paramedial cells are generally unaffected (G, vertical arrows). The gain of H-cells is accompanied by the reduction of Per expression (H, open arrowhead). The dorsal lateral DA neurons are duplicated but at lower frequency than that of H-cells (I, horizontal arrows). Brackets (A, C, D, F, G and I) mark the approximate positions of the midline.