Craniofacial abnormalities including craniosynostosis and cleft lip and/or palate are considered among the most common congenital defects, occurring in 1/700 live births. Genetic mutations are known to play important roles in these craniofacial defects, but we have yet to elucidate the complex molecular processes leading to normal and syndromic craniofacial development. Regulatory factors controlling development are highly conserved in vertebrates, and over the years the zebrafish has emerged as a powerful animal model for studying human development. In addition to structural similarities between zebrafish and mammalian craniofacial development, the expression and regulation of the major signaling transduction pathways are also highly conserved. These characteristics, combined with experimental advantages of the zebrafish model, make them very attractive model .Zebrafish are particularly well suited for forward genetic mutagenesis screens, which have been used to identify a variety of craniofacial mutants relevant to human development and disease. Similarly, we used this approach to identify a number of skeletal/craniofacial mutants, including the Tft9n mutant. Next generation sequencing was then used to identify ddx10 as a candidate gene. The human ddx10 DEAD (Asp-Glu-Ala-Asp) box polypeptide 10 is an RNA helicase that has been implicated in diverse cellular processes involving alteration of RNA secondary structure such as translation initiation, nuclear and mitochondrial splicing, and ribosome and spliceosome assembly. RNA helicases also contain ATPase activity, which helps to unwind secondary structures of mRNA. Previous studies showed that ddX10 plays complex roles in tumor development, mutations in ATP-dependent RNA helicases result in deregulated protein function. There are no known associations of ddx10 to craniofacial disorders at this time.The goals of this study are to define phenotypic abnormalities of Tft9n mutants and to validate the candidate gene, ddx10. Identified Tft9n heterozygous adults are being used to generate developmentally staged embryos for Immunohistochemical (IHC) analysis of Ddx10 protein expression, and to characterize wild-type and mutant ddx10 mRNA expression. Single cell injection of ddx10 mRNA is being performed to demonstrate rescue of the mutant phenotype. Preliminary analyses show that Ddx10 is expressed in muscle, cartilage and the neurocranium, consistent with the affected tissues in these mutants. These studies demonstrate, for the first time, roles for ddx10 in craniofacial development. These studies were supported by NIH/NIDCR R01DE018043 (PCY). .