Fig. 8

Cell-autonomous action of nrd as revealed by mosaic analysis. Results of cell transplantation experiments between wild-type and nrd embryos viewed by confocal microscopy (A,B,D-H; all images are anterior to the left, dorsal up. Some images were flipped horizontal to maintain consistant antero-posterior orientation.). Low (A) and high (B) magnification of wild-type cells (LRD-labeled red) transplanted into a mutant environment that are able to differentiate into RB neurons (as revealed by HNK-1 antibody staining, green; where HNK-1 epitope expression is present in the same cell that contains the lineage label, the cells appear yellow). (C) Nomarski image of a similar live embryo to illustrate the location of the labelled cells in the dorsal neural tube (square indicates approximate location of confocal optical section for all embryos shown). Mutant cells (D-F, red) transplanted into a wild-type environment have never been observed to be able to form RB neurons although they can form other neuronal cell types in or near the RB forming domain of the neural cord. (E,F) Higher magnification views of two different optical planes showing that mutant cells (red) located within the wild-type domain of HNK-1-expressing cells are able to form commissural neurons (see axonal processes in F). Low and high magnification view of a mutant cell (G,H; red) transplanted into a mutant environment that forms commissural neurons with correct pathfinding ability. This axon can be seen crossing the floorplate on the contralateral side and projecting along the DLF. D, dorsal spinal cord; FP, floor plate; SC, spinal cord; N, notochord.