Essential role for de novo DNA methyltransferase Dnmt3a in paternal and maternal imprinting
Essential role for de novo DNA methyltransferase Dnmt3a in paternal and maternal imprinting
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DOI：
10.1038/nature02633
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发表时间：
2004-06-24
期刊：
影响因子：
64.8
通讯作者：
Sasaki, H
中科院分区：
文献类型：
--
作者：
Kaneda, M;Okano, M;Sasaki, H
印记基因在配子体形成过程中被表观遗传标记，因此它们在后代中只由父本或母本等位基因表达(1)。在哺乳动物中，印记阻止孤雌生殖，并且在先天性畸形综合征、肿瘤和克隆动物中经常被破坏(1)。尽管Dnmt3家族的新生DNA甲基转移酶与母体印迹有关(2)，但Dnmt3a和Dnmt3b敲除小鼠的致病性(3)阻碍了进一步的研究。我们在这里报道了通过条件敲除技术破坏生殖细胞中的Dnmt3a和Dnmt3b，并将其保存在体细胞中(4)。Dnmt3a条件突变雌性的后代在子宫内死亡，并且在所检查的所有母体印迹位点缺乏甲基化和等位基因特异性表达。Dnmt3a条件突变雄性显示精子发生受损，在精原细胞中检查的三个父亲印记位点中有两个缺乏甲基化。相比之下，Dnmt3b条件突变体及其后代没有明显的表型。除了一个位点的甲基化差异外，Dnmt3a条件突变体的表型与Dnmt3L基因敲除小鼠的表型没有区别2,5。这些结果表明，Dnmt3a和Dnmt3L都是生殖细胞中大多数印迹位点甲基化所必需的，但也表明其他因素的参与。
Imprinted genes are epigenetically marked during gametogenesis so that they are exclusively expressed from either the paternal or the maternal allele in offspring(1). Imprinting prevents parthenogenesis in mammals and is often disrupted in congenital malformation syndromes, tumours and cloned animals(1). Although de novo DNA methyltransferases of the Dnmt3 family are implicated in maternal imprinting(2), the lethality of Dnmt3a and Dnmt3b knockout mice(3) has precluded further studies. We here report the disruption of Dnmt3a and Dnmt3b in germ cells, with their preservation in somatic cells, by conditional knockout technology(4). Offspring from Dnmt3a conditional mutant females die in utero and lack methylation and allele-specific expression at all maternally imprinted loci examined. Dnmt3a conditional mutant males show impaired spermatogenesis and lack methylation at two of three paternally imprinted loci examined in spermatogonia. By contrast, Dnmt3b conditional mutants and their offspring show no apparent phenotype. The phenotype of Dnmt3a conditional mutants is indistinguishable from that of Dnmt3L knockout mice2,5, except for the discrepancy in methylation at one locus. These results indicate that both Dnmt3a and Dnmt3L are required for methylation of most imprinted loci in germ cells, but also suggest the involvement of other factors.