Activated caspase3 and Islet1/2 immunohistochemistry and expression of vsx1 in wild type and mutant embryos. Lateral views of 24 h WT sibling and mutant embryos as indicated. Dashed lines mark ventral limit of spinal cord. Dorsal, top; anterior, left. Scale bar = 50 microns. (A–F) Immunohistochemistry for activated Caspase-3. Very few labeled cells are seen in WT or mutant embryos (0–3 cells in a 5 somite-length of spinal cord). (G,H,J,K,M,N) Immunohistochemistry for Islet-1 and Islet-2. The smaller labeled nuclei in the ventral spinal cord correspond to motoneurons. The larger more dorsal nuclei belong to Rohon-Beard cells. Mean numbers of Islet1/2 expressing motoneurons in WT and mutant embryos (I,L,O; see Supplementary Table 6 for P-values). Only ventral cells that correspond to motoneurons were counted. These also have smaller nuclei than more dorsally-located Rohon Beard cells. (P,Q,S,T,V,W) vsx1 expression in V2a neurons. Mean numbers of vsx1-expressing V2a neurons in WT and mutant embryos (R,U,X, see Supplementary Table 6 for P-values). None of the comparisons contained in this figure revealed statistically significant differences.
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