xav mutants exhibit reduced motor axon branching and neuromuscular synaptogenesis that are not caused by change of motor neuron number or viability. A. SV2 (green) and AChR (red) labeling showed that motor axon branching and neuromuscular synaptogenesis were reduced in xav mutants and etfdh morphants compared to WT embryos, at 56 hpf and most strikingly at 72 hpf. Scale bar = 20 μm. B. Motor neuron number, as assayed by in situ hybridization for islet-2, is similar between xav mutants and WT embryos at 48 hpf. Scale bar = 100 μm. C. No substantial apoptosis was seen in the pool of motor neurons in xav compared to WT at 48 hpf, as assayed by double staining for TUNEL and Zn5, which labels secondary motor neurons. N>10 embryos, 3 carrier pairs. Scale bar = 20 μm.
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