Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, Tennessee 37996, USA.
Evolution. 2011 Feb;65(2):462-75. doi: 10.1111/j.1558-5646.2010.01115.x. Epub 2010 Sep 29.
Genomic imprinting refers to genes that are silenced when inherited via sperm or via egg. The silencing of genes conditional upon their parental origin requires an evolutionary explanation. The most widely accepted theory for the evolution of genomic imprinting-the kinship theory-argues that conflict between maternally inherited and paternally inherited genes over phenotypes with asymmetric effects on matrilineal and patrilineal kin results in self-imposed silencing of one of the copies. This theory has been applied to imprinting of genes expressed in the placenta, and infant brain determining the allocation of parental resources being the source of conflict parental promiscuity. However, there is growing evidence that imprinted genes are expressed in the postinfant brain where parental promiscuity per se is no longer a source of conflict. Here, we advance the kinship theory by developing an evolutionary model of genomic imprinting in adults, driven by intragenomic conflict over allocation to parental versus communal care. We consider the role of sex differences in dispersal and variance in reproductive success as sources of conflict. We predict that, in hominids and birds, parental care will be expressed by maternally inherited genes. In nonhominid mammals, we predict more diversity, with some mammals showing the same pattern and other showing the reverse. We use the model to interpret experimental data on imprinted genes in the house mouse: specifically, paternally expressed Peg1 and Peg3 genes, underlying maternal care, and maternally expressed Gnas and paternally expressed Gnasxl genes, underlying communal care. We also use the model to relate ancestral demography to contemporary imprinting disorders of adults, in humans and other taxa.
基因组印记是指当基因通过精子或卵子遗传时会被沉默。基因的沉默取决于其亲源，这需要一个进化解释。基因组印记进化的最广泛接受的理论——亲缘关系理论——认为，母系和父系遗传的基因之间在具有不对称影响母系和父系亲属的表型上存在冲突，导致其中一个拷贝自我沉默。该理论已被应用于胎盘表达的基因的印记，以及决定父母资源分配的婴儿大脑，其冲突源是父母滥交。然而，越来越多的证据表明，印记基因在婴儿后的大脑中表达，而父母滥交本身不再是冲突的来源。在这里，我们通过开发一个关于基因组印记在成人中的进化模型来推进亲缘关系理论，该模型由基因组内分配给父母和公共照顾的冲突驱动。我们考虑了性别差异在分散和繁殖成功率方差中的作用作为冲突的来源。我们预测，在人类和鸟类中，亲代照顾将由母系遗传的基因表达。在非人类哺乳动物中，我们预测会有更多的多样性，一些哺乳动物表现出相同的模式，而其他哺乳动物则表现出相反的模式。我们使用该模型来解释关于家鼠中印记基因的实验数据：具体来说，父系表达的 Peg1 和 Peg3 基因，其基础是母系照顾，以及母系表达的 Gnas 和父系表达的 Gnasxl 基因，其基础是公共照顾。我们还使用该模型将祖先人口统计学与人类和其他分类群中成年人的当代印记障碍联系起来。
