Fig. 8

sst1.1+ neurons require Ascl1 function for their proper development. (A-D′) Whole-mount in situ hybridization for sst1.1. Loss of Ascl1 function leads to a severe reduction of sst1.1+ neurons in the prethalamus (A-D′, black arrowheads). A lesser reduction is already detectable in single mutants. ascl1a and double mutants also have less sst1.1+ neurons in the thalamus and the TuD region of the hypothalamus (B,B′,D,D′, non-filled arrowheads). (E–H) Fluorescent sst1.1 in situ hybridization coupled with immunofluorescence for Th. The reduced sst1.1+ neurons (E-H, white arrowheads) do not express Th, but are adjacent to the prethalamic DA neurons, which are also reduced in double mutants. (I–L) Fluorescent in situ hybridization for gad1b/2 and sst1.1. Coexpression analysis with gad1b/2 (I–L) shows that the sst1.1+ neurons in the prethalamus are GABAergic (white arrowheads in L - magnification of the entangled box in K). (A–H) 96 hpf wildtype, single or double ascl1a and ascl1b mutant embryos. (A-D, E-L) Dorsal and (A′-D′) lateral views. (E–H) z-projections of confocal stacks. (I–L) Single confocal planes of a wildtype embryo. Anterior is to the left. For numbers of analyzed embryos see Supplemental Table S2. Abbreviations: Pth, prethalamus; Tel, telencephalon; TuD, tuberal domain, dorsal part. Scale bars: A-D’ - 100 μm, E-K - 50 μm (for scale of L see K).