Project 462378

Mutations in the splicing factor EFTUD2 and SF3B4 are responsible for mandibulofacial dysostosis with microcephaly (MFDM) and Nager Syndromes, respectively. Malformations in the craniofacial region are found in most MFDM and Nager syndrome patients, along with syndrome-specific extracranial and face defects. Our goal is to uncover the requirement for EFTUD2 and SF3B4 during head and face development. MFDM and Nager syndrome patients show smaller cheek bones, upper and lower jaws, and ears that are malformed or mis-positioned. In addition, MDFM patients have microcephaly and developmental delay. We generated mutant mouse lines carrying conditional mutations in Eftud2 or Sf3b4. We showed that deletion of Eftud2 or Sf3b4 in the precursor of the bones affected in head and face of patient results in craniofacial malformations. We used RNAseq analysis to show that head malformations in Eftud2 mutant embryos are preceded by abnormal splicing of the P53-regulator Mdm2, as well as FoxM1, a transcription factor. P53-activity is increased in Eftud2 and Sf3b4 mutant embryos, and FoxM1 targets are dysregulated in Eftud2 mutants. However, the role of Foxm1 during craniofacial development has not been investigated. Nor has P53-independent roles of MDM2 in head development been examined. Our hypothesis is that mutations of Eftud2 or Sf3b4 in neural crest cells lead to mis-splicing of a set of transcripts, including Foxm1 and Mdm2 that are important for craniofacial development. We Aim to: 1.Identify the earliest steps in NCC development that are disrupted by mutation of Sf3b4; 2.Identify neural crest cell specific splicing events/pathways regulated by EFTUD2 and SF3B4; and 3.Determine the contribution of mis-splicing of Mdm2 or FoxM1 to craniofacial defects in splicing mutants. Our work will uncover pathways shared with other craniofacial syndromes, and will help in the development of treatments that can prevent or reduce the incidence of these defects in the population.