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

ABSTRACT: 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.

ORGANISM(S): Mus musculus

PROVIDER: GSE157356 | GEO | 2021/09/03

REPOSITORIES: GEO

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Project description:Purpose: Heterozygous mutations in SNRPB, an essential core component of the five small ribonucleoprotein particles of the spliceosome, are responsible for craniofacial and rib defects in patients with Cerebrocostomandibular Syndrome (CCMS). However, why the mutations in SNRPB causes tissue specific CCMS abnormalities such as craniofacial defects are unknown. We hypothesize that splicing of tissue specific transcripts required for craniofacial development is disrupted due to SNRPB deficiency, during embryonic development. The purpose of the study was to identify those developmentally important transcripts that are dysregulated due to Snrpb mutation. Methods: We mated Snrpbloxp mice that we have developed with commercially available Wnt-1-Cre2 transgenic mice to remove one allele of Snrpb from neural crest cells. The mutant (Snrpb \ncc+/-) embryos showed craniofacial abnormalities at E9.5 and onward. We collected morphologically normal embryos at E9.0 for both Snrpb wildtype and Snrpbncc+/- mutants. We pooled two embryo heads of similar somites for each genotype and extracted the RNA for RNAseq. Results: We found that Snrpbncc+/- mutants show aberrant splicing that includes both increased exon skipping and intron retention. A strong tendency towards increased exon skipping and intron inclusion in the mutant samples were observed; there were more SE (273 in Het versus 83 in WT) and RI (191 in Het versus 21 in WT). We identified 13 transcripts required for craniofacial development or stem cell development with significant increases in exon skipping including Smad2, Rere and Pou2f1. From pathway analysis of differentially expressed genes, we found they were associated with the spliceosome and the P53-pathway. We also found an increase in splicing of two P53 regulator, Mdm2 and Mdm4. Conclusions: We propose that abnormal splicing underlies the defects found in Snrpbncc+/-mutant embryos. We confirmed differential splicing of the P53 regulators, Mdm2 and Mdm4 and identified several transcripts important for craniofacial development which were abnormally spliced in Snrpbncc+/- embryos.

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

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