WT1 and Wilms tumor: We focused on the CpG island in Intron 1, which surrounds a cryptic promoter that regulates the expression of an antisense-oriented transcript which shows monoallelic expression in the developing kidney (consistent with imprinting), and this region, termed the antisense regulatory region (ARR), is hypomethylated in Wilms’ tumors with biallelic WT1 expression [21].