Identification and characterization of an imprinted antisense RNA (MESTIT1) in the human MEST locus on chromosome 7q32.
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.
Nakabayashi
Kazuhiko
K
Department of Genetics, The Hospital for Sick Children, and Department of Molecular and Medical Genetics, University of Toronto, Toronto, ON, Canada.
Bentley
Louise
L
Hitchins
Megan P
MP
Mitsuya
Kohzoh
K
Meguro
Makiko
M
Minagawa
Sachi
S
Bamforth
John S
JS
Stanier
Philip
P
Preece
Michael
M
Weksberg
Rosanna
R
Oshimura
Mitsuo
M
Moore
Gudrun E
GE
Scherer
Stephen W
SW
D015152:Blotting, Northern; D002460:Cell Line; D002897:Chromosomes, Human, Pair 7; D018076:DNA, Complementary; D005347:Fibroblasts; D018392:Genomic Imprinting; D006801:Humans; D008969:Molecular Sequence Data; D020033:Protein Isoforms; D011506:Proteins / Q000235:genetics*; D016372:RNA, Antisense; D017422:Sequence Analysis, DNA
D018076:DNA, Complementary; D020033:Protein Isoforms; D011506:Proteins; D016372:RNA, Antisense; C103637:mesoderm specific transcript protein