Identification of differential methylation of the WT1 antisense regulatoryregion and relaxation of imprinting in Wilms' tumor

Wilms' tumor (WT) is associated with loss of heterozygosity at chromosome 1 1p13, the site of the Wilms' tumor suppressor gene, WT1. Although the prefe rential Loss of maternal alleles suggested that differential allelic expres sion of WT1 might occur, this has not been evident in normal fetal tissues or WTs, In this study, we show that the WT1 antisense regulatory region is differentially methylated, with Southern blot analysis of four loss of hete rozygosity-negative WTs and their corresponding normal kidneys indicating t hat allelic methylation is lost in WTs, Reverse transcription-PCR expressio n analysis correlates methylation with mono-allelic expression of the antis ense WT1 transcript (WT1-AS) in normal kidney. However, WTs display hypomet hylation and biallelic expression of WT1-AS, Our findings are consistent wi th imprinting of WT1-AS in normal kidney and the relaxation of imprinting i n Wilms' tumorigenesis, This identifies the WT1 antisense regulatory region in intron 1 as a primary site for epigenetic deregulation at chromosome 11 p13 in WTs.