Massachusetts Institute of Technology Apr 17 2025 Cleft lip and cleft palate are among the most common birth defects, occurring in about one in 1,050 births in the United States. These defects, which appear when the tissues that form the lip or the roof of the mouth do not join completely, are believed to be caused by a mix of genetic and environmental factors. In a new study, MIT biologists have discovered how a genetic variant often found in people with these facial malformations leads to the