MARSUPIAL X INACTIVATION

有袋类 X 失活

• 批准号: 6387264
• 负责人: Christine M. Disteche
• 金额: $ 29.38万
• 依托单位: UNIVERSITY OF WASHINGTON
• 依托单位国家: 美国
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-09-01 至 2003-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6387264
• 关键词: DNA methylation; Marsupialia; animal genetic material tag; female; fluorescent in situ hybridization; gene dosage; gene expression; gene induction /repression; genetic library; genetic regulation; genetically modified animals; genomic imprinting; laboratory mouse; molecular cloning; nucleic acid sequence; sex chromosomes; southern blotting

X chromosome inactivation is a form of chromosome-wide gene regulation which results in the silencing of one of the two X chromosomes in female mammals, thereby restoring equal dosage of gene expression between males and females. There are significant differences in this inactivation process between mammal groups, which probably reflects its evolution. One of the most striking difference is that in metatherian mammals (marsupials) only the paternal X chromosome is inactivated, whereas eutherian (placental) mammals show random inactivation in most tissues. X inactivation is initiated at the XIST locus in eutherians, but no homologous locus has yet been demonstrated in marsupials. X inactivation is less stable in marsupials than in eutherians, and is incomplete and tissue-specific. The molecular basis, too may be different. Although differences in histone acetylation have been demonstrated between active and inactive X chromosomes in marsupials as well as eutherians, DNA methylation of the promoter region of inactive genes have not, perhaps accounting for the less stable inactivation in this mammalian group. These differences between the X inactivation processes in marsupials and eutherian mammals suggest that marsupials may have retained a less complex and more primitive form of X inactivation. The differences between the groups offer a unique opportunity to dissect out the layers of the process of gene silencing at a chromosome level. Our goal is to investigate these differences by a series of molecular approaches. We plan first to isolate the XIST locus from marsupials, based on our preliminary finding of a female-specific RNA signal using a probe enriched in marsupial X chromosome DNA. We will compare eutherian and metatherian XIST sequence and methylation status to examine possible XIST imprinting in marsupials. Secondly, we will investigate the stability of X inactivation of marsupial genes in comparison to mouse by measuring expression from the active and inactive X chromosomes in individual cells. Thirdly, we will insert a marsupial gene into the mouse X chromosome to determine whether the gene is susceptible or resistant in vivo to epigenetic changes which characterize eutherian genes.

X染色体灭活是一种全染色体基因调节的一种形式，它导致在女性哺乳动物中的两个X染色体之一沉默，从而恢复雄性和女性之间基因表达相等的剂量。哺乳动物组之间的这种失活过程存在显着差异，这可能反映了其演变。最引人注目的差异之一是，在元中哺乳动物（有袋动物）中，只有父亲X染色体被灭活，而在大多数组织中，Eutherian（胎盘）哺乳动物在大多数组织中都会随机失活。 X在Eutherians的Xist基因座开始，但在有袋动物中尚未证明同源基因座。 X在有袋动物中的失活不如Eutherians稳定，并且不完整且特定于组织。分子基础也可能不同。尽管在有袋动物的活性和非活性X染色体之间以及尤特尔人之间已经证明了组蛋白乙酰化的差异，但无活性基因的启动子区域的DNA甲基化尚未考虑到该哺乳动物组中较不稳定的失活。有袋动物和Eutherian哺乳动物的X失活过程之间的这些差异表明，有袋动物可能保留了X失活的较复杂和更原始的形式。两组之间的差异提供了一个独特的机会，可以在染色体水平上剖析基因沉默过程的层次。我们的目标是通过一系列分子方法研究这些差异。我们计划使用富含有袋动物X染色体DNA的探针对女性特异性RNA信号的初步发现，首先将XIST基因座与有袋动物分离。我们将比较Eutherian和Metatherian Xist序列和甲基化状态，以检查有袋动物中可能的XIST烙印。其次，我们将通过测量各个细胞中的活性和无活性X染色体的表达来研究与小鼠相比，与小鼠相比，我们将研究X失活的稳定性。第三，我们将在小鼠X染色体中插入一个小袋中的基因，以确定该基因在体内对表观遗传变化的敏感还是抗性，这些变化是表观遗传变化的，这些变化是表观遗传学的。