IGF2 (insulin-like growth factor 2) and M6P / IGF2R (mannose 6-phosphate/insulin-like growth factor 2 receptor) are imprinted in marsupials and eutherians but not in birds. These results along with the absence of M6P / IGF2R imprinting in the egg-laying monotremes indicate that the parental imprinting of fetal growth-regulatory genes may be unique to viviparous mammals. In this investigation, we have cloned IGF2 from two monotreme mammals, the platypus and echidna, to further investigate the origin of imprinting. We report herein that like M6P / IGF2R, IGF2 is not imprinted in monotremes. Thus, although IGF2 encodes for a highly conserved growth factor in chordates, it is only imprinted in therian mammals. These findings support a concurrent origin of IGF2 and M6P / IGF2R imprinting in the late Jurassic/early Cretaceous period. The absence of imprinting in monotremes, despite apparent interparental conflicts over maternal - offspring exchange, argues that a fortuitous congruency of genetic and epigenetic events may have limited the phylogenetic breadth of genomic imprinting to therian mammals. © 2001 Wiley-Liss, Inc.

Item Type:	Refereed Article
Research Division:	Biological Sciences
Research Group:	Genetics
Research Field:	Genetics not elsewhere classified
Objective Division:	Environmental Management
Objective Group:	Other environmental management
Objective Field:	Other environmental management not elsewhere classified
UTAS Author:	Stewart, NJ (Dr Niall Stewart)
UTAS Author:	Munday, BL (Dr Barry Munday)
UTAS Author:	Andersen, NA (Dr Niels Andersen)
UTAS Author:	Nicol, SC (Associate Professor Stewart Nicol)
ID Code:	22581
Year Published:	2001
Web of Science® Times Cited:	108
Deposited By:	Health Sciences A
Deposited On:	2001-08-01
Last Modified:	2011-08-03
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