dlAdx2 mutant embryos develop excess early born neurons and fewer late-born cell types. (A, B) Dorsal views, anterior to left, of neural plate stage embryos probed for isl1 expression to reveal presumptive primary motor neurons (pmn) in medial neural plate and presumptive Rohon Beard sensory neurons (RB) in lateral neural plate. Excess primary motor neurons and Rohon Beard neurons developed in dlAdx2 mutant embryos. (C-L) Lateral views, anterior left, dorsal up. (C, D) Approximately 36 h embryos labeled with zn-8 antibody, which identifies secondary motor neuron cell bodies (bracket) and ventral nerve roots (arrows). The mutant embryo had fewer cell bodies and only two ventral nerve roots, which appear to be smaller than normal, were evident in this region of the embryo. (E, F)18 somite stage embryos probed to detect isl2 expression, which marks CaP and VaP motor neurons in ventral spinal cord (asterisks) and Rohon Beard neurons in dorsal neural tube. One or two cells per hemisegment expressed isl2 in ventral spinal cord of a wild-type embryo (E). Clusters of 3–5 cells per hemisegment expressed isl2 in ventral spinal cord of the mutant embryo (F). (G, H) Approximately 30 h embryos probed for lim1 RNA expression. The mutant embryo had many more cells that expressed lim1 relative to wild type. Note, also, the lack of neural-crest derived melanophores, which appear brown in wild-type, in the mutant embryos shown in H and J. (I, J) Approximately 30 h embryos probed for lim2 expression. More cells expressed lim2 in the mutant than in wild type. (K, L) Approximately 26 h embryos labeled with antibody specific to Pax2. The mutant embryo had more Pax2-expressing cells than the wild-type. (M, N) Transverse sections of approximately 36 h embryos labeled with zrf-1 antibody, which identifies radial glial fibers. The mutant embryo completely lacked zrf-1 labeling, except for occasional cells in the ventral neural tube, which may be remnants of floorplate (arrows). Note, again, the absence of black melanophores in the mutant embryo. Scale bar, A, B 60 μm, E-L 30 μm, M, N 40 μm.
Appel et al. BMC Developmental Biology 2001 1:13 doi:10.1186/1471-213X-1-13