Mis-splicing of Mdm2 leads to Increased P53-Activity and Craniofacial Defects in a MFDM Eftud2 Mutant Mouse Model

Purpose: EFTUD2, a GTPase and core component of the splicesome, is known to be mutated in patients with mandibulofacial dysostosis with microcephaly (MFDM). In this study, we examine the role of this gene in neural crest cells, the precursors of bones and cartilages affected in MFDM patients. Methods: We generated a mutant mouse line with conditional mutation in Eftud2 and used Wnt1-Cre2 to delete it in neural crest cells. Results: We show that homozygous deletion of Eftud2 leads to neural crest cell death and malformations in the brain and craniofacial region of embryos. RNAseq analysis of embryonic heads revealed a significant increase in exon skipping and retained introns in mutants and enriched levels of Mdm2 transcripts lacking exon 3. Mutants also had increased nuclear P53, higher expression of P53-target genes, and increased cell death. Craniofacial development was significantly improved when mutant embryos were treated with Pifithrin-alpha, an inihibitor of P53. Conclusion: We propose that craniofacial defects caused by mutations of EFTUD2 are a result of mis-splicing of Mdm2 and P53-associated cell death. Hence, drugs that reduce P53 activity may help prevent craniofacial defects associated with spliceosomopathies. Overall design: Neural crest cell-specific Eftud2 embryos mRNA profiles of E9.0 and E9.5 heterozygous (Eftud2+/-) and homozygous (Eftud2-/-) mice