David Law

Beckwith-Wiedemann syndrome (BWS), characterized by multiorgan developmental abnormalities and predisposition to cancer, usually occurs sporadically, but small apparently dominant pedigrees have been described. Since rare patients show varying karyotypic abnormalities on the short arm of chromosome 11, it has been suggested that BWS may be related to the Wilms tumor gene on 11p13 or, alternatively, to growth factor genes on 11p15. We performed genetic linkage analysis on two BWS kindreds, using RFLPs for loci on 11p. BWS was linked to the insulin gene (11p15.5), with an overall maximum lod score of 3.60 (recombination fraction = .00). Linkage to D11S16 (11p13) could be excluded for recombination fractions less than or equal to .03. These results suggest that BWS defines a tumor-predisposition gene on 11p15.

The Wilms tumor locus on chromosome 11p13 has been mapped to a region defined by overlapping, tumor-specific deletions. Complementary DNA clones representing transcripts of 2.5 (WIT-1) and 3.5 kb (WIT-2) mapping to this region were isolated from a kidney complementary DNA library. Expression of WIT-1 and WIT-2 was restricted to kidney and spleen. RNase protection revealed divergent transcription of WIT-1 and WIT-2, originating from a DNA region of less than 600 bp. Both transcripts were present at high concentrations in fetal kidney and at much reduced amounts in 5-year-old and adult kidneys. Eleven of 12 Wilms tumors classified as histopathologically heterogeneous exhibited absent or reduced expression of WIT-2, whereas only 4 of 14 histopathologically homogeneous tumors showed reduced expression. These data demonstrate a molecular basis for the pathogenetic heterogeneity in Wilms tumorigenesis.