Mechanisms of Genomic Imprinting

描述(申请人提供)：印迹基因表现出体细胞亲本特异性的单等位基因表达。印记基因表达的表观遗传决定因素尚不完全清楚，也不能完全基于CpG甲基化来解释--尚不清楚是什么机制启动了印记控制区的DNA甲基化。印记基因上的染色质差异，如等位基因特异性的蛋白质因子结合和/或组蛋白共价修饰，与体细胞中的许多印记基因有关，并构成了一层细胞记忆，但体内没有证据表明这种差异或它们在男性或女性生殖细胞印记控制区的作用。这些差异可能在性腺特异性DNA甲基化之前就存在了，因此可能是印迹建立所必需的。只有在获得甲基化印迹的时间窗口对生殖细胞进行分析，才能揭示染色质组成中先前存在的“初级染色质差异”。我们的研究将检验这一假设，即男性和女性生殖细胞之间存在“初级染色质差异”，并且可能是在印迹控制区建立DNA甲基化印记所必需的。我们将分析正常和突变的体细胞以及男性和女性生殖细胞发育过程中H19/lgf2印记控制区的染色质结构，以揭示“初级染色质差异(S)”，并确认这些“初级染色质差异”在印记形成中的作用。这些研究与人类健康有关，因为基因组印记是许多人类疾病的基础，如Beckwith-Wiedemann综合征和Wilm‘s瘤。在基础水平上对基因组印记的定义将进一步揭示与印记失败相关的人类疾病的遗传学和表观遗传学基础。

DESCRIPTION (provided by applicant): Imprinted genes exhibit somatic parental specific monoallelic expression. The epigenetic determinants of imprinted gene expression are not fully understood and cannot be solely explained based on CpG methylation-it is not known what mechanism initiates DNA methylation at the imprinting control regions. Chromatin differences at imprinted genes, such as allele-specific \n vivo protein factor binding and/or histone covalent modifications are associated with-and constitute a layer of-cell memory for a number of imprinted genes in somatic cells, but no in vivo evidence exists of such differences or their role at the imprinting control regions in male or female germ-cells. These differences may exist before gonad-specific DNA methylation, and may, therefore, be required for imprint establishment. Such preexisting "primary chromatin differences" in chromatin composition can only be revealed by the analysis of germ cells at the window of time when methylation imprints are attained. Our studies will test the hypothesis, that "primary chromatin differences" between male and female germ cells exist and may be required for DNA methylation imprint establishment at the imprinting control regions. We will analyze the chromatin structure of the H19/lgf2 imprinting control region in normal and mutant somatic cells and also during male and female germ cell development in order to reveal the "primary chromatin difference(s) and confirm the role of these "primary chromatin differences" in imprint establishment. These studies are related to human health in that genomic imprinting underlies a number of human diseases, such as Beckwith-Wiedemann syndrome and Wilm's tumor. Definition of genomic imprinting at a fundamental level should shed further light on the genetic and epigenetic basis of human diseases associated with imprinting failure.