Fig. 7

STAT3 inactivation does not induce cell death of primary motoneurons. (A–I) Uninjected embryos at indicated developmental time points were stained for apoptosis by TUNEL as well as for primary motoneurons using the ZNP1 monoclonal antibody. Up to 3 days p.f., there is little cell death in embryos. The region encompassing motoneuron soma is demarcated between dashed lines. In the spinal cord, almost all TUNEL-positive neurons are sensory Rohon-Beard neurons positioned in the dorsal spinal cord above the dashed lines (white arrows). Occasionally, an apoptotic neuron (one in eight hemisegments) was present in the region of motoneuron soma (red arrow). (J–R) STAT3 morpholino injected embryos stained as in panel A–I. There is no increased cell death associated with morpholino injection. The most ventral axon position of CaP motoneurons that failed to reach the ventral target is marked with a white arrowhead (J, M, P). Identical results were also obtained upon dominant negative DN-STAT3-GFP expression (not shown). In all images, rostral is to the left, and dorsal is up.