Identification of the essential factor(s) to establish the genome imprinting in mammals.

为了了解基因组印迹的机制，我们试图确定印迹建立所需的因子、染色质的表观遗传修饰和高阶染色质结构。我们发现，尽管在禽类杂交细胞中，人类H19基因位点的DNA甲基化状态和组蛋白修饰与哺乳动物细胞中的相同，但禽类杂交细胞中人类H19基因位点的高阶染色质环结构与哺乳动物细胞中的不同。这一结果提示了一种可能性，即由一种未知因素介导的高阶染色质结构的形成可能是重要的，这种未知因素不在鸟类细胞中，而在哺乳动物细胞中。

In order to understand the mechanism of the genome imprinting, we tried to identify the factor(s), epigenetic modifications of chromatin, and higher order chromatin structures requiring for the establishment of the imprinting. We demonstrated that higher order chromatin loop structures at human H19 gene locus in the avian cell hybrids are different from those in mammalian cells, although DNA methylation status and histone modifications at the locus in the hybrids are maintained to those in the mammalian cells. This result suggested a possibility that it may be important to being formed the proper higher order chromatin structures mediated by an unknown factor that is not in the avian cells, but is in the mammalian cells.