Methylation and imprinting

A third of human patients with Beckwith-Wiedemann syndrome (BWS) have lost maternal-specific methylation of the KvDMR1 (differential methylated region) locus, a putative imprinting control region found within the KCNQ1 gene. In an Advanced Online Publication in Nature Genetics, Fitzpatrick et al. provide clear evidence linking KvDMR1 to imprinted gene expression (Nature Genetics, 9 September 2002, DOI:10.1038/ng988). They generated mice in which KvDMR1 was deleted by gene-targeted homologous recombination. Paternal transmission of the deletion resulted in deregulated imprinting of the genomic locus and reactivation of genes both distal and proximal to KvDMR1. Paternal inheritance was also associated with reduced weight. Fitzpatrick et al. speculate that elevated levels of maternally expressed genes (such as Cdkn1c, encoding a cyclin-dependent kinase inhibitor) account for the growth defect.