Kobayashi Hisato
Department of Embryology, Nara Medical University, Kashihara, Japan.
Front Cell Dev Biol. 2021 Aug 5;9:713878. doi: 10.3389/fcell.2021.713878. eCollection 2021.
Genomic imprinting is an epigenetic phenomenon that results in unequal expression of homologous maternal and paternal alleles. This process is initiated in the germline, and the parental epigenetic memories can be maintained following fertilization and induce further allele-specific transcription and chromatin modifications of single or multiple neighboring genes, known as imprinted genes. To date, more than 260 imprinted genes have been identified in the mouse genome, most of which are controlled by imprinted germline differentially methylated regions (gDMRs) that exhibit parent-of-origin specific DNA methylation, which is considered primary imprint. Recent studies provide evidence that a subset of gDMR-less, placenta-specific imprinted genes is controlled by maternal-derived histone modifications. To further understand DNA methylation-dependent (canonical) and -independent (non-canonical) imprints, this review summarizes the loci under the control of each type of imprinting in the mouse and compares them with the respective homologs in other rodents. Understanding epigenetic systems that differ among loci or species may provide new models for exploring genetic regulation and evolutionary divergence.
基因组印记是一种表观遗传现象,它导致同源的母本和父本等位基因表达不均等。这个过程在生殖系中启动,并且亲代的表观遗传记忆在受精后能够得以维持,并诱导单个或多个相邻基因(即印记基因)发生进一步的等位基因特异性转录和染色质修饰。迄今为止,在小鼠基因组中已鉴定出260多个印记基因,其中大多数由印记生殖系差异甲基化区域(gDMRs)控制,这些区域表现出亲源特异性DNA甲基化,这被认为是初级印记。最近的研究提供了证据,表明一部分无gDMR的、胎盘特异性的印记基因受母源组蛋白修饰的控制。为了进一步理解DNA甲基化依赖型(经典)和非依赖型(非经典)印记,本综述总结了小鼠中每种印记类型控制下的基因座,并将它们与其他啮齿动物中的相应同源物进行比较。了解基因座或物种间不同的表观遗传系统可能为探索遗传调控和进化分歧提供新的模型。