CDKN1C and Beckwith-Wiedemann syndrome: Importantly, loss of CDKN1C expression is a major cause of the overgrowth phenotype in BWS patients, and knockout of maternal Cdkn1c in mice causes similar fetal overgrowth, as well as cleft palate, abdominal wall defects and placental defects such as placentomegaly that approximate the BWS phenotype (Yan et al., 1997; Zhang et al., 1997; Tunster et al., 2011).