m hypomethylation as a mechanism for non-syndromic cleft lip and palate.

Non-syndromic cleft lip with or without cleft palate (NSCLP), the most common human craniofacial malformation, is a complex disorder given its genetic heterogeneity and multifactorial component revealed by genetic, epidemiological, and epigenetic findings. Epigenetic variations associated with NSCLP have been identified; however, functional investigation has been limited. Here, we combined a reanalysis of NSCLP methylome data with genetic analysis and used both and approaches to dissect the functional effects of epigenetic changes. We found a region in that is frequently hypomethylated in NSCLP cohorts (21-26%), leading to overexpression. overexpression in human neural crest cells led to downregulation of spliceosomal, ribosomal, and adherens junction genes. analysis using zebrafish embryos revealed that upregulation leads to craniofacial cartilage impairment. Also, we suggest that zebrafish embryonic hypoxia leads to upregulation combined with hypomethylation and also analogous palatal alterations. We therefore propose that hypomethylation, potentially induced by hypoxia in early development, is a novel and frequent predisposing factor to NSCLP.