Lessons from comparative analysis of species-specific imprinted genes

Okamura, Koji; Ito, Takashi

doi:10.1159/000090828

Cited by 19 publications

(16 citation statements)

References 98 publications

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“…We focused on six known imprinted genes in mouse that also had a high level of genomic sequence conservation in eutherians, namely MEST [8,30], COPG2 [31], HTR2A [32], L3MBTL [33], IMPACT [34,35] and PLAGL1 [36] . …”

Section: Resultsmentioning

confidence: 99%

Convergent and divergent evolution of genomic imprinting in the marsupial Monodelphis domestica

et al. 2012

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BackgroundGenomic imprinting is an epigenetic phenomenon resulting in parent-of-origin specific monoallelic gene expression. It is postulated to have evolved in placental mammals to modulate intrauterine resource allocation to the offspring. In this study, we determined the imprint status of metatherian orthologues of eutherian imprinted genes.ResultsL3MBTL and HTR2A were shown to be imprinted in Monodelphis domestica (the gray short-tailed opossum). MEST expressed a monoallelic and a biallelic transcript, as in eutherians. In contrast, IMPACT, COPG2, and PLAGL1 were not imprinted in the opossum. Differentially methylated regions (DMRs) involved in regulating imprinting in eutherians were not found at any of the new imprinted loci in the opossum. Interestingly, a novel DMR was identified in intron 11 of the imprinted IGF2R gene, but this was not conserved in eutherians. The promoter regions of the imprinted genes in the opossum were enriched for the activating histone modification H3 Lysine 4 dimethylation.ConclusionsThe phenomenon of genomic imprinting is conserved in Therians, but the marked difference in the number and location of imprinted genes and DMRs between metatherians and eutherians indicates that imprinting is not fully conserved between the two Therian infra-classes. The identification of a novel DMR at a non-conserved location as well as the first demonstration of histone modifications at imprinted loci in the opossum suggest that genomic imprinting may have evolved in a common ancestor of these two Therian infra-classes with subsequent divergence of regulatory mechanisms in the two lineages.

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Section: Resultsmentioning

confidence: 99%

Convergent and divergent evolution of genomic imprinting in the marsupial Monodelphis domestica

et al. 2012

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“…However, imprinting-like phenomena exist outside the mammalian lineage, for example in plants and insects. It is also known that different species can have species-specific imprinted genes (Okamura and Ito, 2006) and that some genes appear to have a polymorphic imprinting status, i.e. they are imprinted in some individuals but not others (Spencer, 2000).…”

Section: Discussionmentioning

confidence: 99%

Parent-of-origin specific QTL – a possibility towards understanding reciprocal effects in chicken and the origin of imprinting

Tuiskula-Haavisto¹,

Vilkki²

2007

Cytogenet Genome Res

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Reciprocal effects for sexual maturity, egg production, egg quality traits and viability are well known in poultry crosses. They have been used in an optimal way to form profitable production hybrids. These effects have been hypothesized to originate from sex-linked genes, maternal effects or a combination of both. However, these may not be the only explanations for reciprocal effects. Recent mapping of quantitative trait loci (QTL) has revealed autosomal areas with parent-of-origin specific effects in the chicken. In mammals, parental imprinting, i.e. the specifically regulated expression of either maternal or paternal allele in the offspring, is the main cause of such effects. The most commonly accepted hypothesis for the origin of imprinting, the conflict hypothesis, assumes a genetic conflict of interest between the maternal and paternal genomes regarding the allocation of resources to the offspring. It also intrinsically implies that imprinting should not occur in oviparous taxa. However, new molecular genetic information has raised a need to review the possible involvement of imprinting or some related phenomena as a putative cause of reciprocal effects in poultry. Comparative mapping provides strong evidence for the conservation of orthologous imprinted gene clusters on chicken macrochromosomes. Furthermore, these gene clusters exhibit asynchronous DNA replication, an epigenetic mark specific for all imprinted regions. It has been proposed that these intrinsic chromosomal properties have been important for the evolution of imprinted gene expression in the mammalian lineage. Many of the mapped parent-of-origin specific QTL effects in chicken locate in or close to these conserved regions that show some of the basic features involved in monoallelic expression. If monoallelic expression in these regions would be observed in birds, the actual mechanism and cause may be different from the imprinting that evolved later in the mammalian lineage. In this review we discuss recent molecular genetic results that may provide tools for understanding of reciprocal differences in poultry breeding and the evolution of imprinting.

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“…This is true for more ancient vertebrate genes such as Igf2 and Impact, which performed important roles in ancestral vertebrates before acquiring imprinting specifically in the mammalian lineage [106,107]. It is thought that two rounds of whole genome duplication occurred early in vertebrate evolution [108], and it is likely that the Igf2 gene originated from one of these large-scale events [109].…”

Section: Imprinting Of Duplicated Genesmentioning

confidence: 99%

Genomic Imprinting in Mammals: Emerging Themes and Established Theories

Wood¹,

Oakey²

2006

PLoS Genet

206

151

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The epigenetic events that occur during the development of the mammalian embryo are essential for correct gene expression and cell-lineage determination. Imprinted genes are expressed from only one parental allele due to differential epigenetic marks that are established during gametogenesis. Several theories have been proposed to explain the role that genomic imprinting has played over the course of mammalian evolution, but at present it is not clear if a single hypothesis can fully account for the diversity of roles that imprinted genes play. In this review, we discuss efforts to define the extent of imprinting in the mouse genome, and suggest that different imprinted loci may have been wrought by distinct evolutionary forces. We focus on a group of small imprinted domains, which consist of paternally expressed genes embedded within introns of multiexonic transcripts, to discuss the evolution of imprinting at these loci.

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Lessons from comparative analysis of species-specific imprinted genes

Cited by 19 publications

References 98 publications

Convergent and divergent evolution of genomic imprinting in the marsupial Monodelphis domestica

Convergent and divergent evolution of genomic imprinting in the marsupial Monodelphis domestica

Parent-of-origin specific QTL – a possibility towards understanding reciprocal effects in chicken and the origin of imprinting

Genomic Imprinting in Mammals: Emerging Themes and Established Theories

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