Parental-origin-specific epigenetic modification of the mouse H19 gene

Abstract

The H19 gene produces an abundant developmentally regulated transcript of unknown function in normal embryos. In the mouse it lies on chromosome 7 and is subject to transcriptional regulation by parental imprinting, which results in the maternally inherited gene being expressed and the paternally inherited gene being repressed. Embryos carrying maternal duplication/paternal deficiency for distal chromosome 7 (MatDi7) therefore express a double dose of H19. Here we examine the parental-origin-specific epigenetic modifications that may be involved in this regulation by comparing CpG methylation and nuclease sensitivity of chromatin in MatDi7 embryos with normal littermates. We show that specific sites in the CpG island promoter and 5' portion of the gene are methylated only on the paternal allele. Furthermore, active maternal alleles in chromatin of MatDi7 embryos are more sensitive and accessible to nucleases. Therefore hypermethylation and chromatin compaction in the region of the H19 promoter is associated with repression of the paternally inherited copy of the gene. Most, but not all, of these sites are unmethylated in sperm, with methylation of the paternal promoter occurring after fertilization. These results contrast with our findings for the closely linked and reciprocally imprinted gene encoding insulin-like growth factor II (ref. 4).

Expression of p16INK4a/p16α and p19ARF/p16β is frequently altered in non-small cell lung cancer and correlates with p53 overexpression

“…We did not observe any association between methylation of exon 1a in NSCLC and the age of the patients, although an association of age and gene hypermethylation has been described (Issa et al, 1994). Methylation of CpG islands is generally restricted to genes located on the inactive X chromosome (Singer-Sam and Riggs, 1993), imprinted genes (Ferguson-Smith et al, 1993) or genes that undergo de novo methylation during di erentiation or cell line immortalization and tumorigenesis (Laird and Jaenisch, 1994). The results obtained with normal lungs and matched tumour pairs are therefore intriguing.…”

Silencing of the VHL tumor-suppressor gene by DNA methylation in renal carcinoma.

“…As mentioned previously, CpG island methylation plays an active role in maintaining silencing of parentally imprinted genes (14)(15)(16)(17) and also in silencing genes on the inactivated X chromosome (13). We thus examined the expression status of the VHL gene at the RNA level in cell lines with unmethylated and abnormally methylated VHL genes.…”

“…In normal cells, CpG islands on autosomal chromosomes remain unmethylated. However, many islands on the transcriptionally inactive X chromosome (13) or in selected genes silenced by parental imprinting (14)(15)(16) are extensively methylated. The active participation of this methylation in silencing imprinted genes has recently been shown (17).…”

Erasure of methylation imprint at the promoter and CTCF-binding site upstream of H19 in human testicular germ cell tumors of adolescents indicate their fetal germ cell origin

“…Maternally expressed H19 is one of the best-characterized imprinted genes. The 5 0 region of H19 is methylated only on the paternal allele in both mouse (Bartolomei et al, 1993;Ferguson-Smith et al, 1993) and human (Jinno et al, 1996). This region is regarded as a key domain in the control of imprinting at this locus (Thorvaldsen et al, 1998).…”