cdon and boc affect trunk neural crest cell migration through a non-cell autonomous reduction of hedgehog signaling in zebrafish slow-twitch muscle
The immunoglobin superfamily members cdon and boc are transmembrane proteins implicated in regulating hedgehog signaling during vertebrate development. Recent work showing roles for these genes in axon guidance and neural crest cell migration further suggest that cdon/boc may play additional functions in regulating directed cell movements during development. Here we use novel and existing mutants to investigate a role for cdon and boc in zebrafish neural crest cell migration. We find that single cdon or boc mutant embryos exhibit normal neural crest phenotypes, but that neural crest migration is strikingly disrupted in double cdon/boc mutant embryos. We further show that this neural crest migration phenotype is associated with defects to the differentiation of slow-twitch muscle cells, and that this slow-twitch muscle phenotype is a consequence of reduced hedgehog signaling in mutant fish. While neural crest migratory ability is not affected in double mutant embryos, neural crest directionality is severely affected. These data suggest that neural crest migration defects are likely to be secondary to defects in slow-twitch muscle differentiation. Combined, our data add to a growing literature showing that cdon and boc act synergistically to promote hedgehog signaling during vertebrate development, and provide a foundation for using zebrafish to further study the function of these hedgehog receptor paralogs.