During vertebrate craniofacial development,neural crest cells(NCCs)contribute to most of the craniofacial pharyngeal skeleton.Defects in NCC specification,migration and differentiation resulting in malformations in the craniofacial complex are associated with human craniofacial disorders including Treacher-Collins Syndrome,caused by mutations in Tcof1.It has been hypothesized that ribosome biogenesis defect induced p53 signaling is the main cause of NCC progenitor cell death in mouse Tcof1 mutants.However,the underlying mechanisms linking ribosome biogenesis and NCC development remain poorly understood.Here we report a new zebrafish mutant,fantome/ fan,characterized by early NCC developmental defects.fan affects the zebrafish wdr43 locus,the ortholog to yeast Utp5.Here we show that the C-terminus of Wdr43,which is absent in fan mutant protein,is both necessary and sufficient to mediate its nucleolar localization and protein interaction in metazoans.We demonstrate that Wdr43 functions in ribosome biogenesis,and that NCC defects observed in fan mutants are mediated by a p53 dependent pathway.Finally,we show that proper nucleolar localization of Tcof1 is dependent on that of Wdr43.Together,our findings provide new insight into roles for Wdr43 in ribosome biogenesis and craniofacial development,and also into ribosomopathy-induced craniofacial phenotypes including Treacher-Collins Syndrome.