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Research Paper
Imprinting of Opossum Igf2r in the Absence of Differential Methylation and Air
Jennifer R. Weidman, Dana C. Dolinoy, Kristin A. Maloney, Jan-Fang Cheng and Randy L. Jirtle
volume 1 | issue 1
january/february/march 2006Pages: 49 - 54
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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 nonimprinted 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.
We now provide open access to journal articles published online for one year or more. This article may be downloaded at the following link:
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