Breakthroughs in the genetics of orofacial clefting.

Nonsyndromic orofacial clefts have a multifactorial etiology, involving both genetic and environmental factors. Although linkage and candidate gene studies have attempted to elucidate the underlying genetic architecture, only the interferon regulatory factor 6 (IRF6) gene has been identified as causative. The recent introduction of high-throughput genotyping technologies has enabled researchers to perform genome-wide association studies (GWAS). Four GWAS of nonsyndromic cleft lip with or without cleft palate have been conducted, and these have identified five new chromosomal loci. One locus, located in an intergenic region of chromosome 8q24, has been implicated in all GWAS and constitutes a major susceptibility locus. This review describes the latest genetic findings for nonsyndromic orofacial clefts and discusses their biological and functional implications.