Nubp2is required for cranial neural crest survival in the mouse

The N-ethyl-N-nitrosourea (ENU) forward genetic screen is a useful tool for the unbiased discovery of novel mechanisms regulating developmental processes. We recovered the dorothy mutation in such a screen designed to recover recessive mutations affecting craniofacial development in the mouse. Dorothy embryos die prenatally and exhibit many striking phenotypes commonly associated with ciliopathies, including a severe midfacial clefting phenotype. We used exome sequencing to discover a missense mutation in Nucleotide Binding Protein 2 ( Nubp2 ) to be causative. This finding was confirmed with a complementation analysis between the dorothy allele and a Nubp2 null allele ( Nubp2 Null ). We demonstrate that Nubp2 is indispensable for embryogenesis. NUBP2 is implicated in both the Cytosolic Iron/Sulfur cluster Assembly (CIA) pathway and in the negative regulation of ciliogenesis. Conditional ablation of Nubp2 in the neural crest lineage with Wnt1-cre recapitulates the dorothy craniofacial phenotype. Using this model, we found that the proportion of ciliated cells in the craniofacial mesenchyme was unchanged, and that markers of the Shh, Fgf, and Bmp signaling pathways are unaltered. Finally, we show that the phenotype results from a marked increase in apoptosis within the craniofacial mesenchyme. Summary Statement An ENU screen identifies a novel allele of Nubp2 which is then demonstrated to be required for cranial neural crest survival and proper midfacial development.