A NOVEL L23-RELATED GENE 40 KB DOWNSTREAM OF THE IMPRINTED H19 GENE IS BIALLELICALLY EXPRESSED IN MID-FETAL AND ADULT HUMAN TISSUES

The closely linked IGF2 and H19 genes on human chromosome 11p15.5 are monoallelically expressed as a result of genomic imprinting and show a ltered expression in Wilms' tumors (WTs). To map regional imprinting w e have sought to isolate additional human genes close to IGF2/H19 and to characterize their allelic expression patterns. Here we report a no vel gene, provisionally named L23MRP [L23 (mitochondrial)-related prot ein], which is oriented 'tail-to-tail' with H19 and is transcribed to within 40 kb of the last H19 exon. L23MRP is expressed biallelically i n many mid-fetal and adult human tissues. This gene is also expressed at normal levels in WTs which have lost expression of H19 either via l oss of the maternal chromosome 11p15.5 or via an epigenetic pathway in volving site-specific DNA hypermethylation. These data indicate that, at least in postembryonic stages, L23MRP is functionally insulated fro m the IGF2/H19 imprinted domain.