Genetics of Silver–Russell Syndrome

Abstract

Human growth is a complex process and requires the appropriate interaction of many factors. 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 associated with a disturbed imprinting is Silver–Russell syndrome (SRS), a congenital disease characterised by intrauterine and post‐natal growth retardation and further characteristic features. SRS is molecularly heterogenous: 7% of patients carry a maternal uniparental disomy of chromosome 7, >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. Key Concepts: Silver–Russell syndrome is a clinically heterogeneous syndrome and belongs to the group of congenital imprinting disorders. Congential imprinting disorders show a broad spectrum of epimutations and mutations in differentially methylated regions. Different chromosomal regions might be affected by molecular alterations in Silver–Russell syndrome, that is chromosomes 7 and 11p15. The functional significance of the observed molecular aberrations in SRS is currently unknown. Multilocus methylation defects are present in a considerable number of patients with imprinting disorders and indicate a general disturbance of the establishment and/or maintenance of imprinting marks. Deciphering the molecular and functional basis for the clinical course of SRS helps to generally understand epigenetic regulation.