Gene/environment causes of cleft lip and/or palate.

Craniofacial anomalies, and in particular cleft lip and palate, are major human birth defects with a worldwide frequency of 1 in 700 and substantial clinical impact. A wide range of studies in developmental biology has contributed to a better knowledge of how both genes and environmental exposures impact head organogenesis. Specific causes have now been identified for some forms of cleft lip and palate, and we are at the beginning of a time in which the common nonsyndromic forms may also have specific etiologies identified. Mouse models have an especially important role in disclosing cleft etiologies and providing models for environmental cotriggers or interventions. An overview of the gene-environment contributions to nonsyndromic forms of clefting and their implications for developmental biology and clinical counseling is presented.