Patterns of hybrid loss of imprinting reveal tissue- and cluster-specific regulation.
BACKGROUND
Crosses between natural populations of two species of deer mice, Peromyscus maniculatus (BW), and P. polionotus (PO), produce parent-of-origin effects on growth and development. BW females mated to PO males (bwxpo) produce growth-retarded but otherwise healthy offspring. In contrast, PO females mated to BW males (POxBW) produce overgrown and severely defective offspring. The hybrid phenotypes are pronounced in the placenta and include POxBW conceptuses which lack embryonic structures. Evidence to date links variation in control of genomic imprinting with the hybrid defects, particularly in the POxBW offspring. Establishment of genomic imprinting is typically mediated by gametic DNA methylation at sites known as gDMRs. However, imprinted gene clusters vary in their regulation by gDMR sequences.


RESULTS
Here we further assess imprinted gene expression and DNA methylation at different cluster types in order to discern patterns. These data reveal POxBW misexpression at the Kcnq1ot1 and Peg3 clusters, both of which lose ICR methylation in placental tissues. In contrast, some embryonic transcripts (Peg10, Kcnq1ot1) reactivated the silenced allele with little or no loss of DNA methylation. Hybrid brains also display different patterns of imprinting perturbations. Several cluster pairs thought to use analogous regulatory mechanisms are differentially affected in the hybrids.


CONCLUSIONS
These data reinforce the hypothesis that placental and somatic gene regulation differs significantly, as does that between imprinted gene clusters and between species. That such epigenetic regulatory variation exists in recently diverged species suggests a role in reproductive isolation, and that this variation is likely to be adaptive.
Wiley
Christopher D
CD
Department of Biological Chemistry, School of Medicine, University of California Irvine, Irvine, California, USA.
Matundan
Harry H
HH
Duselis
Amanda R
AR
Isaacs
Alison T
AT
Vrana
Paul B
PB
D000818:Animals; D002678:Chimera / Q000235:genetics*; D003433:Crosses, Genetic; D019175:DNA Methylation / Q000502:physiology; D004622:Embryo, Mammalian; D010450:Endopeptidases / Q000235:genetics / Q000378:metabolism; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D018392:Genomic Imprinting / Q000502:physiology*; D051741:Kruppel-Like Transcription Factors / Q000235:genetics / Q000378:metabolism; D008297:Male; D008954:Models, Biological; D005810:Multigene Family; D009928:Organ Specificity / Q000235:genetics*; D010542:Peromyscus / Q000235:genetics; D062085:RNA, Long Noncoding; D023121:RNA, Messenger, Stored / Q000235:genetics; D022661:RNA, Untranslated / Q000235:genetics / Q000378:metabolism; D014018:Tissue Distribution / Q000235:genetics; D064570:Ubiquitin-Specific Proteases
C449939:KCNQ1OT1 RNA; D051741:Kruppel-Like Transcription Factors; D062085:RNA, Long Noncoding; D023121:RNA, Messenger, Stored; D022661:RNA, Untranslated; D010450:Endopeptidases; D064570:Ubiquitin-Specific Proteases