Ainscough J F, John R M, Surani M A
Wellcome/CRC Institute of Cancer and Developmental Biology, University of Cambridge, UK.
Genet Res. 1998 Dec;72(3):237-45. doi: 10.1017/s0016672398003565.
Genomic imprinting is an epigenetic mode of gene regulation that results in expression of the autosomal 'imprinted' genes from only a single allele, determined exclusively by parental origin. To date over 20 imprinted genes have been identified in mouse and man and these appear to lie in clusters in restricted regions on a subset of chromosomes. This may be a critical feature of imprinting suggesting a domain-type mode of regulation. Imprinted domains are replicated asynchronously, show sex-specific meiotic recombination frequencies and have CpG-rich regions that are differentially methylated, often associated with the imprinted genes themselves. Mouse distal chromosome 7 is one such domain, containing at least nine imprinted genes spanning over 1 Mb of DNA. For the maternally expressed p57Kip2 gene, passage through the female germline is essential to generate the active state, whereas passage through the male germline is needed to force the maternally expressed H19 gene into an inactive state. It is therefore possible that the mouse distal chromosome 7 imprinted domain is actually composed of two or more independently regulated subdomains.
基因组印记是一种表观遗传的基因调控模式，它导致常染色体上的“印记”基因仅从单个等位基因表达，这完全由亲本来源决定。到目前为止，在小鼠和人类中已鉴定出20多个印记基因，这些基因似乎成簇位于一部分染色体的受限区域。这可能是印记的一个关键特征，提示一种结构域类型的调控模式。印记结构域异步复制，显示性别特异性减数分裂重组频率，并且具有富含CpG的区域，这些区域存在差异甲基化，通常与印记基因本身相关。小鼠7号染色体远端就是这样一个结构域，包含至少9个跨越超过1 Mb DNA的印记基因。对于母源表达的p57Kip2基因，通过雌性生殖系对于产生活性状态至关重要，而通过雄性生殖系则是使母源表达的H19基因进入非活性状态所必需的。因此，小鼠7号染色体远端印记结构域实际上可能由两个或更多个独立调控的亚结构域组成。
