Identification and characterization of an imprinted antisense RNA (MESTIT1) in the human MEST locus on chromosome 7q32

Abstract

Imprinted gene(s) on human chromosome 7 are thought to be involved in Russell-Silver syndrome (RSS), based on the fact that approximately 10% of patients have maternal uniparental disomy of chromosome 7. However, involvement of the known imprinted genes (GRB10 at 7p12, PEG10 at 7q21.3 and MEST at 7q32) in RSS has yet to be established. To screen for new imprinted genes, we are initially using somatic cell hybrids containing a paternal or maternal human chromosome 7. Transcripts located between D7S530 and D7S649 (a 1.5 Mb interval encompassing MEST ) were subjected to RT-PCR analysis using somatic cell hybrids. One transcript named MESTIT1 (for MEST intronic transcript 1) reproducibly showed paternal-specific expression. Upon further analysis, we found MESTIT1 to be (1) paternally (and not maternally) expressed in all fetal tissues and fibroblasts examined, (2) to be located in an intron of one of the two isoforms of MEST but transcribed in the opposite direction, (3) to be composed of at least two exons without any significant open reading frame, and (4) to exist as a 4.2 kb transcript in many fetal and adult tissues. We could also identify two isoforms of the mouse Mest gene as observed in humans, but it is still unknown if a murine ortholog of MESTIT1 exists. We also examined the imprinting status of MEST isoforms as a first step in assessing whether MESTIT1 might influence the allelic expression pattern of the sense transcript. MEST isoform 1 was determined to be exclusively expressed from the paternal allele in all fetal tissues and cell lines examined, whereas MEST isoform 2 was only preferentially expressed from the paternal allele in a tissue/cell-type-specific manner. Our results suggest that MESTIT1 is a paternally expressed non-coding RNA that may be involved in the regulation of MEST expression during development. MESTIT1 (also known as PEG1-AS) is now the third independent transcript (with MEST and COPG2IT1) identified at human chromosome 7q32 demonstrating paternal chromosome-specific expression.

Frequent IGF2/H19 Domain Epigenetic Alterations and Elevated IGF2 Expression in Epithelial Ovarian Cancer

“…A role for noncoding RNAs is implicated in the regulation of imprinted genes due to the preponderance of these transcribed sequences located in imprinted domains and empirical data suggesting their importance (26,27,(31)(32)(33)(34)(35)(36)(37)(38)(39)(40)(41)(42). For example, the genes Delta, Drosophila homologue-like 1 (DLK1) and maternally expressed gene 3 (MEG3) in the imprinted domain on human chromosome 14 bear remarkable similarity to the IGF2/H19 domain in terms of the genomic organization and putative regulatory features (43)(44)(45).…”

CXC Chemokine Ligand 13 and CC Chemokine Ligand 19 Cooperatively Render Resistance to Apoptosis in B Cell Lineage Acute and Chronic Lymphocytic Leukemia CD23+CD5+ B Cells

“…PEG10 is identified on human chromosome 7q21 (21,53). Mouse homolog PEG10 has recently been located in a large imprinted gene cluster on mouse proximal chromosome 6 and has been confirmed to be imprinted (54).…”

Variable imprinting of the MEST gene in human preimplantation embryos

“…13,16,37,47 Isoform 2 has been observed to be preferentially paternally expressed in foetal placenta in other studies, and also in kidney and fibroblast lines, with polymorphic imprinting observed between different fibroblast lines. 48 Variable imprinting of MEST, including that of isoform 2, has also been reported between humanembryonic stem cell (hESCs) lines, raising concerns of the epigenetic stability of these cells. 40,49,50 In view of the observations of aberrant MEST methylation and imprinting with disease, 13,14,16 we considered it important to further characterise expression at the MEST locus in the embryos with expression arising from both alleles.…”