Cecr2 Mutations Causing Exencephaly Trigger Misregulation of Mesenchymal/Ectodermal Transcription Factors

BACKGROUND: Over 200 mouse genes are associated with neural tube defects (NTDs), including Cecr2, the bromodomain-containing subunit of the CERF chromatin remodeling complex. METHODS: Gene-trap mutation Cecr2(Gt45Bic) results in 74% exencephaly (equivalent of human anencephaly) on the BALB/c strain. Gene expression altered during cranial neural tube closure by the Cecr2 mutation was identified through microarray analysis of 11-14 somites stage Cecr2(Gt45Bic) embryos. RESULTS: Analysis of Affymetrix Mouse 430 2 0 chips detected 60 transcripts up-regulated and 54 transcripts down-regulated in the Cecr2(Gt45Bic) embryos (fold > 1.5, p < 0.05). The Cecr2 transcript was reduced only similar to 7- to 14-fold from normal levels, suggesting the Cecr2(Gt45Bic) is a hypomorphic mutation. We therefore generated a novel Cecr2 null allele (Cecr2(tm1 1Hemc)) Resulting mutants displayed a stronger penetrance of exencephaly than Cecr2(Gt45Bic) in both BALB/c and FVB/N strains, in addition to midline facial clefts and forebrain encephalocele in the FVB/N strain. The Cecr2 transcript is reduced 260-fold in the Cecr2(tm1 1Hemc) line Subsequent qRT-PCR using Cecr2 (tm1 1Hemc) mutant heads confirmed downregulation of transcription factors Alx1/Cart1, Dlx5, Eya1, and Six1. CONCLUSIONS: As both Alx1/Cart1 and Dlx5 mouse mutations result in exencephaly, we hypothesize that changes in expression of these mesenchymal/ectodermal transcription factors may contribute to NTDs associated with Cecr2. Birth Defects Research (Part A) 88:619-625, 2010 (C) 2010 Wiley-Liss, Inc