哺乳动物印记基因的研究进展

Progress on Imprinted Genes in Mammals

哺乳动物印记基因是指只表达亲本一方的遗传信息 ,而另一方处于关闭状态的一类基因。约 80 %的印记基因呈串出现在染色体上 ;在哺乳动物品种之间 ,印记基因具有较高的保守性 ;印记基因的复制通常表现为不同时性 ;一些印记基因具有印记遗传的时空性 ;少数印记基因只转录为mRNA而不翻译成蛋白质 ;印记基因的反意链通常表达 ,表达产生具有调节印记基因的作用。哺乳动物印记基因的调控序列的DNA甲基化、组蛋白乙酰酸化和组蛋白甲基化等引起其印记表达 ,其中DNA分子的甲基化是关键 ,它在生命周期中可被清除 ,也可被标记。印记基因之间的调控表达通常是相互作用的。克隆动物作为印记基因研究的实验动物模型 ,已获得许多有意义的研究结果。

Imprinted genes are only expressed from one parental allele in eutherian mammals (monoallelic expression).The common features of imprinted genes are,clustering of multiple imprinted genes in one chromosomal region (around 80%),conservation of imprinting among eutherian mammals,asynchrony of DNA replication of imprinted genes,temporal and spatial regulation of expression of imprinted genes,coding for untranslated RNAs as well as proteins,antisense transcripts may regulate expression of imprinted genes.Once established,the imprinting pattern is stably transmitted through cell division but reset in germ cells of the fetal gonads. Therefore,imprinting is not inherited across generations (epigenetics). DNA methylation and histone acetylation are important regulatory mechanisms of expression of the imprinted genes in mammals.Both mechanisms can be erased and reestablished in the life cycle.There are expression competitions in some imprinted genes.Somatic cloning by nuclear transfer bypasses the gonads and therefore is a good model to study imprinting regulations. \;