Smaller number of PNS neurons express 22C10 in homozygous embryos and PNS axons dispay severe defects in growth cone guidance and fasciculation. Most noticeable phenotype is splitting of the intersegmental nerve into two fascicles, the ISN 'loop' phenotype. Defects in the CNS are similar to those observed in the PNS. Numerous muscles are missing, displaced or exhibit aberrant shapes. Embryos also contain many mononucleate myoblasts that fail to fuse into muscle syncytia. Defects also in the visceral and cardiac musculature.