Silver-Russell and Beckwith-Wiedemann syndromes: opposite (epi)mutations in 11p15 result in opposite clinical pictures.

Progress in the identification of the (epi)genetic basis of imprinting disorders has provided greater insight into the central role of imprinted genes in regular human growth. In addition to the well-known Prader-Willi, Angelman, and Beckwith-Wiedemann syndromes, imprinting disturbances have recently been identified in transient neonatal diabetes mellitus, uniparental disomy (14) syndromes and Silver- Russell syndrome (SRS). Among these diseases, the growth retardation disorder SRS is unique because it is the first human disorder associated with epigenetic mutations that affect two different chromosomes. In addition to maternal uniparental disomy of chromosome 7, hypomethylation of the imprinting control region 1 in 11p15 and maternal duplication of 11p15 have recently been described as major (epi)genetic disturbances in SRS. Interestingly, opposite (epi)- mutations are involved in the overgrowth disease Beckwith-Wiedemann syndrome (BWS). Thus SRS and BWS can be regarded as two genetically and clinically opposite clinical pictures. Although not yet completely understood, SRS and BWS can be used as models to decipher the functional link between the observed (epi)genetic mutations and the clinical features in individuals with disturbed growth. Future studies will clarify the complex basis of human growth and hopefully contribute to better-directed therapies.