Imprinted disorders and growth.

Fetal growth is a complex process. Its restriction is associated with morbidity and long-term metabolic consequences. Imprinted genes have a critical role in mammalian fetal growth. Beckwith-Wiedemann syndrome (BWS) and Silver-Russell syndrome (SRS) are two imprinting disorders with opposite fetal growth disturbance. SRS is leading to severe fetal and postnatal growth retardation with severe feeding difficulties during early childhood and long-term metabolic consequences and BWS is an overgrowth syndrome with an enhanced risk of tumors during childhood. Epigenetic (abnormal methylation at the imprinting center regions) or genetic (mutations, duplications, uniparental disomy [UPD]) including defects of imprinted genes on chromosome 11 (BWS and SRS), 7 (SRS) and more recently 14 (SRS) have been identified in these two syndromes. In humans, the 11p15 region contains genes important for the regulation of fetal and postnatal growth. This region includes two imprinted domains: the IGF2/H19 domain regulated by imprinting center region 1 (ICR1 or H19/IGF2:IG-DMR) and the CDKN1C/KCNQ1OT1 domain regulated by ICR2 (or KCNQ1OT1: TSS DMR).