Igf2r is maternally expressed in the American opossum (Killian
JK et al, 2000). It is not imprinted in platypus and echidna (monotremes).
Wiedman JR et al (Wiedman JR et al, 2006) reported
the absence of the intron 2 CpG
island (CpG2) and absence of differential methylation of the promoter (CpG1) in Didelphis virginiana
(American opossum) and
Monodelphis domestica (gray short-tailed opossum). Absence of an antisense Igf2r RNA (Air) was
reported for the American oppossum.