Epigenetic regulation of growth: lessons from Silver-Russell syndrome.

Human growth is a complex process and requires the appropriate interaction of many members. Central members in the growth axes are regulated epigenetically and thereby reflect the profound significance of imprinting for correct mammalian ontogenesis. A prominent imprinting disorder, Silver-Russell syndrome (SRS), is a congenital disease characterized by intrauterine and postnatal growth retardation and other features. SRS represents the first human disorder with imprinting dis-turbances affecting two different chromosomes: nearly one tenth of patients carry a maternal unipa-rental disomy of chromosome 7 and more than 38% show a hypomethylation in the imprinting control region 1 in 11p15. Interestingly, hypermethylation of the same region is associated with the overgrowth disease Beckwith-Wiedemann syndrome (BWS), thus SRS and BWS can be regarded as genetically (and clinically) opposite diseases. Because of the different imprinting regions involved, SRS is a suitable model to decipher the role of imprinting in growth and the functional interaction between imprinted genes in different genomic regions.