title: M6P/IGF2R imprinting evolution in mammals.
abstract: Imprinted gene identification in animals has been limited to eutherian mammals, suggesting a significant role for intrauterine fetal development in the evolution of imprinting. We report herein that M6P/IGF2R is not imprinted in monotremes and does not encode for a receptor that binds IGF2. In contrast, M6P/IGF2R is imprinted in a didelphid marsupial, the opossum, but it strikingly lacks the differentially methylated CpG island in intron 2 postulated to be involved in imprint control. Thus, invasive placentation and gestational fetal growth are not required for imprinted genes to evolve. Unless there was convergent evolution of M6P/ IGF2R imprinting and receptor IGF2 binding in marsupials and eutherians, our results also demonstrate that these two functions evolved in a mammalian clade exclusive of monotremes.
authors.affiliation: Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina 27710, USA.
authors.forename: J K
authors.initials: JK
authors.lastname: Killian
authors.forename: J C
authors.initials: JC
authors.lastname: Byrd
authors.forename: J V
authors.initials: JV
authors.lastname: Jirtle
authors.forename: B L
authors.initials: BL
authors.lastname: Munday
authors.forename: M K
authors.initials: MK
authors.lastname: Stoskopf
authors.forename: R G
authors.initials: RG
authors.lastname: MacDonald
authors.forename: R L
authors.initials: RL
authors.lastname: Jirtle
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D005075:Biological Evolution; D002352:Carrier Proteins / Q000235:genetics*; D018076:DNA, Complementary / Q000235:genetics; D018392:Genomic Imprinting; D007335:Insulin-Like Growth Factor II / Q000378:metabolism*; D007438:Introns; D008297:Male; D008322:Mammals / Q000235:genetics*; D008969:Molecular Sequence Data; D009893:Opossums / Q000235:genetics; D010987:Platypus / Q000235:genetics; D017527:Receptor, IGF Type 2 / Q000235:genetics*; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D004442:Tachyglossidae / Q000235:genetics
chemical_list: D002352:Carrier Proteins; D018076:DNA, Complementary; D017527:Receptor, IGF Type 2; D007335:Insulin-Like Growth Factor II