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Vertebrate reproductive science and technology
RESEARCH ARTICLE (Open Access)

The origins of genomic imprinting in mammals

Carol A. Edwards https://orcid.org/0000-0002-1887-1280 A B , Nozomi Takahashi A , Jennifer A. Corish A and Anne C. Ferguson-Smith A
+ Author Affiliations
- Author Affiliations

A Department of Genetics, University of Cambridge, Downing Street, Cambridge CB2 3EH, UK.

B Corresponding author. Email: cae28@cam.ac.uk

Reproduction, Fertility and Development 31(7) 1203-1218 https://doi.org/10.1071/RD18176
Submitted: 10 May 2018  Accepted: 1 October 2018   Published: 8 January 2019

Journal Compilation © CSIRO 2019 Open Access CC BY

Abstract

Genomic imprinting is a process that causes genes to be expressed according to their parental origin. Imprinting appears to have evolved gradually in two of the three mammalian subclasses, with no imprinted genes yet identified in prototheria and only six found to be imprinted in marsupials to date. By interrogating the genomes of eutherian suborders, we determine that imprinting evolved at the majority of eutherian specific genes before the eutherian radiation. Theories considering the evolution of imprinting often relate to resource allocation and recently consider maternal–offspring interactions more generally, which, in marsupials, places a greater emphasis on lactation. In eutherians, the imprint memory is retained at least in part by zinc finger protein 57 (ZFP57), a Kruppel associated box (KRAB) zinc finger protein that binds specifically to methylated imprinting control regions. Some imprints are less dependent on ZFP57 in vivo and it may be no coincidence that these are the imprints that are found in marsupials. Because marsupials lack ZFP57, this suggests another more ancestral protein evolved to regulate imprints in non-eutherian subclasses, and contributes to imprinting control in eutherians. Hence, understanding the mechanisms acting at imprinting control regions across mammals has the potential to provide valuable insights into our understanding of the origins and evolution of genomic imprinting.

Additional keywords : epigenetics, evolution, marsupials.


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