Transcription factor Ap-2α is necessary for development of embryonic melanophores, autonomic neurons and pharyngeal skeleton in zebrafish

AbstractThe genes that control development of embryonic melanocytes are poorly defined. Although transcription factor Ap-2α is expressed in neural crest (NC) cells, its role in development of embryonic melanocytes and other neural crest derivatives is unclear because mouse Ap-2α mutants die before melanogenesis. We show that zebrafish embryos injected with morpholino antisense oligonucleotides complementary to ap-2α (ap-2α MO) complete early morphogenesis normally and have neural crest cells. Expression of c-kit, which encodes the receptor for the Steel ligand, is reduced in these embryos, and, similar to zebrafish c-kit mutant embryos, embryonic melanophores are reduced in number and migration. The effects of ap-2α MO injected into heterozygous and homozygous c-kit mutants support the notion that Ap-2α works through C-kit and additional target genes to mediate melanophore cell number and migration. In contrast to c-kit mutant embryos, in ap-2α MO-injected embryos, melanophores are small and under-pigmented, and unexpectedly, analysis of mosaic embryos suggests Ap-2α regulates melanophore differentiation through cell non-autonomous targets. In addition to melanophore phenotypes, we document reduction of other neural crest derivatives in ap-2α MO-injected embryos, including jaw cartilage, enteric neurons, and sympathetic neurons. These results reveal that Ap-2α regulates multiple steps of melanophore development, and is required for development of other neuronal and non-neuronal neural crest derivatives