Epigenetic mechanisms underlying the imprinting of the mouse H19 gene.

Abstract

The expression of the H19 gene is governed by parental imprinting in mammals. H19, an unusual gene encoding an RNA with no known function, is exclusively expressed from the maternal chromosome. In mouse, it lies 90 kb downstream from the lgf2 gene, which encodes a fetal-specific growth factor, insulin-like growth factor II, and is expressed primarily from the paternally inherited chromosome. In this report we have utilized interspecific hybrid mice to identify male-specific DNA methylation of a 7-to 9-kb domain surrounding the 1-119 gene and its promoter. This allele-specific methylation could function as a mark to suppress transcription of the H19 paternal allele. Consistent with this proposal, the H19 promoter displayed an open chromatin conformation only on the relatively unmethylated active maternal allele. In contrast, a cell type-specific enhancer that lies outside the methylation domain is hypersensitive to restriction enzyme digestion in nuclei on both maternal and paternal chromosomes. That the allele-specific methylation domain, coupled to the two H19 enhancers, contains all the information necessary for its imprinting was tested by examining two transgenic lines containing an internally deleted H19 transgene. Both displayed paternal-specific methylation of the transgene and maternal-specific expression. Although neither line has been tested in an inbred genetic background, and therefore the action of complex modifiers cannot be formally excluded, the result suggests that the sequences necessary for the imprinting of H19 have been identified.

Ablation of de novo DNA methyltransferase Dnmt3a in the nervous system leads to neuromuscular defects and shortened lifespan

“…In addition, we examined methylation at the imprinted genes H19 (Bartolomei et al, 1993) and Snrpn (Sutcliffe et al, 1994). DNA from control and mutant cerebral cortex showed the expected monoallelic methylation pattern, with roughly half the sequences being heavily methylated (Fig.…”

Maternal-Specific Methylation of the HumanIGF2RGene Is Not Accompanied by Allele-Specific Transcription

“…The closely linked and reciprocally imprinted mouse H19 gene is methylated specifically on the repressed paternal chro mosome (Bartolomei et al, 1993;Ferguson-Smith et al, 1993;Brandeis et al, 1993;Feil et aL, 1994). In addi tion, tissue-specific méthylation, directly proportional to the transcriptional levels, was found (Feil et al, 1994).…”

“…At pres ent, the nature of the primary im print and the molecu lar basis by which genes are recognized as paternally or maternally derived are still unknown. First evidence that méthylation plays an important role in genomic im printing came from the observation that many transgenes become hypomethylated after passage through the male germline and hypermethylated after passage through the female germline (Surani et a l,, 1988), Analysis of four imprinted genes in the mouse, H19 (Bartolomei et al, 1993;Ferguson-Smith et a l, 1993;Brandeis et al, 1993;Feil et al, 1994), insulinlike growth factor II {Igf2) (Sasaki et a l, 1992;Bran deis et al, 1993;Feil et al, 1994), Igf2 receptor (Igf2r) (Stôger et a lv 1993), and U2afl-rsl (SP2) (Hatada et al, 1995), has revealed that regions within the gene or adjacent to it are methylated in a parent-specific manner, The mouse Igf2r gene is expressed exclusively from the maternally inherited chromosome in fetal and adult tissues (Barlow et al, 1991), with the exception of the head and the brain, where biallelic expression has been observed (Villar and Pedersen, 1994). During preimplantation development, both maternal and pa ternal Ig f2 r alleles are expressed (Latham et al, 1994;Szabô and Mann, 1995), indicating that silencing of the paternal allele is a secondary event.…”

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).…”