Ding Feng, Patel Carol, Ratnam Sarayu, McCarrey John R, Chaillet J Richard
Genesis. 2003 Aug;36(4):209-13. doi: 10.1002/gene.10215.
Imprinted genes have been identified in both eutherian mammals and in marsupials. In eutherian species, there is a conservation of the imprinting process, both in terms of the genes imprinted and the epigenetic inheritance mechanism. In the mouse, the inheritance of gametic methylation patterns depends on an oocyte-derived isoform of the Dnmt1 (cytosine-5)-methyltransferase protein, Dnmt1o, which functions during preimplantation development to maintain methylation patterns on imprinted alleles. To determine if this component of genomic imprinting is also found in marsupials, Dnmt1 isoforms were examined in somatic cells and germ cells of the South American opossum Monodelphis domestica. There is a Dnmt1o protein in Monodelphis oocytes that is synthesized, as in the mouse, from a different transcript than the somatic Dnmt1 protein. Thus, an essential component of imprinting in eutherian mammals is found in a marsupial species, suggesting that marsupials and eutherian mammals imprint their genes with the same methylation-dependent mechanism.
印记基因已在有胎盘类哺乳动物和有袋类动物中被鉴定出来。在有胎盘类物种中，无论是在被印记的基因方面还是在表观遗传遗传机制方面，印记过程都具有保守性。在小鼠中，配子甲基化模式的遗传依赖于Dnmt1（胞嘧啶-5）-甲基转移酶蛋白的一种卵母细胞衍生同工型Dnmt1o，它在植入前发育过程中发挥作用，以维持印记等位基因上的甲基化模式。为了确定基因组印记的这一组成部分是否也存在于有袋类动物中，研究人员在南美负鼠（Monodelphis domestica）的体细胞和生殖细胞中检测了Dnmt1同工型。在Monodelphis的卵母细胞中存在一种Dnmt1o蛋白，与小鼠一样，它是由与体细胞Dnmt1蛋白不同的转录本合成的。因此，在有袋类物种中发现了有胎盘类哺乳动物印记的一个重要组成部分，这表明有袋类动物和有胎盘类哺乳动物以相同的甲基化依赖机制印记它们的基因。
