title: Recent acquisition of imprinting at the rodent Sfmbt2 locus correlates with insertion of a large block of miRNAs.
abstract: BACKGROUND
  The proximal region of murine Chr 2 has long been known to harbour one or more imprinted genes from classic genetic studies involving reciprocal translocations. No imprinted gene had been identified from this region until our study demonstrated that the PcG gene Sfmbt2 is expressed from the paternally inherited allele in early embryos and extraembryonic tissues. Imprinted genes generally reside in clusters near elements termed Imprinting Control Regions (ICRs), suggesting that Sfmbt2 might represent an anchor for a new imprinted domain.
  
  
  RESULTS
  We analyzed allelic expression of approximately 20 genes within a 3.9 Mb domain and found that Sfmbt2 and an overlapping non-coding antisense transcript are the only imprinted genes in this region. These transcripts represent a very narrow imprinted gene locus. We also demonstrate that rat Sfmbt2 is imprinted in extraembryonic tissues. An interesting feature of both mouse and rat Sfmbt2 genes is the presence of a large block of miRNAs in intron 10. Other mammals, including the bovine, lack this block of miRNAs. Consistent with this association, we show that human and bovine Sfmbt2 are biallelic. Other evidence indicates that pig Sfmbt2 is also not imprinted. Further strengthening the argument for recent evolution of Sfmbt2 is our demonstration that a more distant muroid rodent, Peromyscus also lacks imprinting and the block of miRNAs.
  
  
  CONCLUSIONS
  These observations are consistent with the hypothesis that the block of miRNAs are driving imprinting at this locus. Our results are discussed in the context of ncRNAs at other imprinted loci. Accession numbers for Peromyscus cDNA and intron 10 genomic DNA are [Genbank:HQ416417 and Genbank:HQ416418], respectively.
authors.affiliation: Department of Cell and Systems Biology, University of Toronto, Ontario, Canada.
authors.forename: Qianwei
authors.initials: Q
authors.lastname: Wang
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Chow
authors.forename: Jenny
authors.initials: J
authors.lastname: Hong
authors.forename: Anne Ferguson
authors.initials: AF
authors.lastname: Smith
authors.forename: Carol
authors.initials: C
authors.lastname: Moreno
authors.forename: Peter
authors.initials: P
authors.lastname: Seaby
authors.forename: Paul
authors.initials: P
authors.lastname: Vrana
authors.forename: Kamelia
authors.initials: K
authors.lastname: Miri
authors.forename: Joon
authors.initials: J
authors.lastname: Tak
authors.forename: Eu Ddeum
authors.initials: ED
authors.lastname: Chung
authors.forename: Gabriela
authors.initials: G
authors.lastname: Mastromonaco
authors.forename: Isabella
authors.initials: I
authors.lastname: Caniggia
authors.forename: Susannah
authors.initials: S
authors.lastname: Varmuza
mesh_terms: D000483:Alleles; D000818:Animals; D001483:Base Sequence; D002417:Cattle; D019175:DNA Methylation; D005260:Female; D056426:Genetic Loci / Q000235:genetics*; D018392:Genomic Imprinting; D006801:Humans; D007438:Introns / Q000235:genetics; D051379:Mice; D035683:MicroRNAs / Q000235:genetics*; D008969:Molecular Sequence Data; D009865:Oocytes / Q000378:metabolism; D010542:Peromyscus / Q000235:genetics; D011247:Pregnancy; D051381:Rats; D012097:Repressor Proteins; D013045:Species Specificity; D014157:Transcription Factors / Q000235:genetics*
chemical_list: D035683:MicroRNAs; D012097:Repressor Proteins; C527638:Sfmbt2 protein, mouse; D014157:Transcription Factors