title: Imprinting of opossum Igf2r in the absence of differential methylation and air.
abstract: Phylogenetic comparison of extant mammals with divergent imprint status is a powerful method for identifying critical components of imprint regulation at individual loci. The entire genomic region of Igf2r in the imprinted marsupials, Didelphis virginiana and Monodelphis domestica, and the non-imprinted monotreme, Ornithorhynchus anatinus, was isolated and sequenced. Genetic and epigenetic comparisons of over 160 kb of sequence were then performed in five distinct mammalian species. Surprisingly, opossum Igf2r is imprinted and maternally expressed despite the absence of the intron 2 CpG island (CpG2), antisense Igf2r RNA (Air) and differential methylation of the promoter (CpG1) required for imprinting of this gene in mice. These findings demonstrate that the genomic elements necessary for imprinted Igf2r expression in eutherians are not required for imprinting of this locus in metatherians. Thus, the regulatory mechanisms of Igf2r imprinting did not evolve convergently within the Therian subclass of mammals.
authors.affiliation: Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina 27710, USA.
authors.forename: Jennifer R
authors.initials: JR
authors.lastname: Weidman
authors.forename: Dana C
authors.initials: DC
authors.lastname: Dolinoy
authors.forename: Kristin A
authors.initials: KA
authors.lastname: Maloney
authors.forename: Jan-Fang
authors.initials: JF
authors.lastname: Cheng
authors.forename: Randy L
authors.initials: RL
authors.lastname: Jirtle
mesh_terms: D000818:Animals; D001483:Base Sequence; D018899:CpG Islands; D019175:DNA Methylation; D044127:Epigenesis, Genetic; D018392:Genomic Imprinting; D007438:Introns; D051379:Mice; D009893:Opossums; D010802:Phylogeny; D011401:Promoter Regions, Genetic; D016372:RNA, Antisense; D017527:Receptor, IGF Type 2 / Q000235:genetics*; D016415:Sequence Alignment; D013045:Species Specificity
chemical_list: D016372:RNA, Antisense; D017527:Receptor, IGF Type 2