Parental imprinting of human chromosome region 11p15.3-pter involved in the Beckwith-Wiedemann syndrome and various human neoplasia.

Cytogenetic and DNA analyses of patients with the Beckwith-Wiedemann syndrome (BWS) enabled us to refine the localization of the syndrome at 11p15.3-pter to two distinct regions. One chromosome region (BWSCR1) is near the insulin (INS) and insulin-like growth factor 2 (IGF2) genes. The other region (BWSCR2) is more proximal near two sequences with zinc-binding finger motifs and a number of known and putative genes. This latter region, at least, seems to be associated with the development of childhood tumors. Our results strongly support the proposed involvement of parental imprinting in the etiology of BWS since all balanced chromosomal abnormalities in these patients were maternally transmitted while the mothers were phenotypically normal. We demonstrate that such an autosomal balanced rearrangement can lead to a specific maternal hypomethylation of the INS/IGF2 genes localized distal to the breakpoint. This underlines the role of these genes in the etiology of the syndrome.