Abstract：
Imprinted genes provide an attractive paradigm to unravel links between transcription and genome architecture. The parental allele-specific expression of these essential genes - which are clustered in chromosomal domains - is mediated by parental methylation imprints at key regulatory DNA sequences. Recent chromatin conformation capture (3C)-based studies show differential organization of topologically associating domains between the parental chromosomes at imprinted domains, in embryonic stem and differentiated cells. At several imprinted domains, differentially methylated regions show allelic binding of the insulator protein CTCF, and linked focal retention of cohesin, at the non-methylated allele only. This generates differential patterns of chromatin looping between the parental chromosomes, already in the early embryo, and thereby facilitates the allelic gene expression. Recent research evokes also the opposite scenario, in which allelic transcription contributes to the differential genome organization, similarly as reported for imprinted X chromosome inactivation. This may occur through epigenetic effects on CTCF binding, through structural effects of RNA Polymerase II, or through imprinted long non-coding RNAs that have chromatin repressive functions. The emerging picture is that epigenetically-controlled differential genome architecture precedes and facilitates imprinted gene expression during development, and that at some domains, conversely, the mono-allelic gene expression also influences genome architecture.
摘要：
印记基因提供了一个有吸引力的范例来解开转录和基因组结构之间的联系。这些聚集在染色体结构域中的必需基因的亲本等位基因特异性表达是由关键调节DNA序列上的亲本甲基化印记介导的。最近基于染色质构象捕获（3C）的研究表明，在印迹域上，亲本染色体之间拓扑关联域的差异组织。胚胎干细胞和分化细胞。在几个印记域，差异甲基化区域显示绝缘子蛋白CTCF的等位基因结合，和粘着素的焦点保留，仅在非甲基化等位基因上。这会在亲本染色体之间产生染色质循环的差异模式，已经在早期胚胎中，从而促进等位基因表达。最近的研究也唤起了相反的情况，其中等位基因转录有助于差异基因组组织，类似于印迹X染色体失活的报道。这可能是通过对CTCF结合的表观遗传效应发生的，通过RNA聚合酶II的结构效应，或通过印迹具有染色质抑制功能的长非编码RNA。新出现的情况是，表观遗传控制的差异基因组结构在发育过程中先于并促进印迹基因表达，在某些领域，相反,单等位基因基因表达也影响基因组结构。
