CHROMOSOME 11P15.5 REGIONAL IMPRINTING - COMPARATIVE-ANALYSIS OF KIP2AND H19 IN HUMAN TISSUES AND WILMS-TUMORS

The imprinted H19 gene is frequently inactivated in Wilms' tumors (WTs ) either by chromosome 11p15.5 loss of heterozygosity (LOH) or by hype rmethylation of the maternal allele and it is possible that there migh t be coordinate disruption of imprinting of multiple 11p15.5 genes in these tumors. To test this we have characterized total and allele-spec ific mRNA expression levels and DNA methylation of the 11p15.5 KIP2 ge ne in normal human tissues, WTs and embryonal rhabdomyosarcoma (RMS). Both KIP2 alleles are expressed but there is a bias with the maternal allele contributing 70-90% of mRNA. Tumors with LOH show moderate to m arked reductions in KIP2 mRNA relative to control tissues and residual mRNA expression is from the imprinted paternal allele. Among WTs with out LOH most cases with H19 inactivation also have reduced KIP2 expres sion and most cases with persistent H19 expression have high levels of KIP2 mRNA. In contrast to the extensive hypermethylation of the impri nted H19 allele, both KIP2 alleles are hypomethylated and WTs with bia llelic H19 hypermethylation lack comparable hypermethylation of KIP2 D NA. 5-aza-2'-deoxycytidine (aza-C) increases H19 expression in RD RMS cells but does not activate KIP2 expression. These data indicate coord inately reduced expression of two linked paternally imprinted genes in most WTs and also suggest mechanistic differences in the maintenance of imprinting at these two loci.