The Core Splicing Factors EFTUD2, SNRPB and TXNL4A Are Essential for Neural Crest and Craniofacial Development.

Mandibulofacial dysostosis (MFD) is a human congenital disorder characterized by hypoplastic neural-crest-derived craniofacial bones often associated with outer and middle ear defects. There is growing evidence that mutations in components of the spliceosome are a major cause for MFD. Genetic variants affecting the function of several core splicing factors, namely SF3B4 , SF3B2 , EFTUD2 , SNRPB and TXNL4A , are responsible for MFD in five related but distinct syndromes known as Nager and Rodriguez syndromes (NRS), craniofacial microsomia (CFM), mandibulofacial dysostosis with microcephaly (MFDM), cerebro-costo-mandibular syndrome (CCMS) and Burn-McKeown syndrome (BMKS), respectively. Animal models of NRS and MFDM indicate that MFD results from an early depletion of neural crest progenitors through a mechanism that involves apoptosis. Here we characterize the knockdown phenotype of Eftud2, Snrpb and Txnl4a in Xenopus embryos at different stages of neural crest and craniofacial development. Our results point to defects in cranial neural crest cell formation as the likely culprit for MFD associated with EFTUD2 , SNRPB and TXNL4A haploinsufficiency, and suggest a commonality in the etiology of these craniofacial spliceosomopathies.