CONTROL OF GENOMIC IMPRINTING BY A MOUSE IMPRINTOR LOCUS

通过小鼠印记基因座控制基因组印记

• 批准号: 2186639
• 负责人: LEE M SILVER
• 金额: $ 31.35万
• 依托单位: PRINCETON UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1993
• 资助国家: 美国
• 起止时间: 1993-05-01 至 1997-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2186639
• 关键词: RNase protection assay; alleles; artificial chromosomes; chromosome walking; computer assisted sequence analysis; developmental genetics; gene expression; genetic library; genetic mapping; genetic markers; genomic imprinting; molecular cloning; phenotype; polymerase chain reaction; protein structure function; regulatory gene; restriction fragment length polymorphism; spermatogenesis

Over the last decade, genomic imprinting has captured the interest and imagination of many mammalian geneticists because of its clear violation of classical Mendelian assumptions concerning equality of gametes and F(1) genotypes. Although genetic studies implicate the existence of imprinting at a multiplicity of loci throughout the mouse genome, to date, only three naturally-imprinted genes have been cloned -- Igf2, Igf2r, and H19 -- and the molecular mechanism of imprinting at even these loci remains elusive. Recently, two independent examples of genetic variation that appear to cause a loss of imprinting at the paternal allele of the Tme locus have been discovered. (Although the mutationally-defined Tme locus was assumed previously to be identical to the Igf2r gene, these new results suggest that this may not be the case.) One form of variation has led to the first genetic identification of a candidate Imprintor locus (named Imp-1) that may act within the male germ line prior to fertilization, and may be at least partially responsible for the trans-acting machinery that "marks" the Tme locus. The second variant suggests that the "imprinting maintenance machinery" may be transferable between homologs in somatic cells. It is proposed to take advantage of these new systems to further investigate the genetic basis of imprinting. The rationale behind this proposal is that an understanding of these variant systems will provide a better understanding of the mechanisms responsible for normal imprinting. The five overall goals can be summarized in the form of the following questions: (1) Where does the Imp-1 locus map, and does the map position provide an entry to its function? (2) Does the Imp-1 locus have a more general role in the control of imprinting at multiple loci? This question will be approached by determining whether the "non-marking" Imp-1 allele allows paternal expression of the normally imprinted H19 locus. (3) Does the Imp-1 locus function during the haploid phase of spermatogenesis? Results will provide information on the time at which the initial imprint is marked. (4) Is the expression of developmentally abnormal phenotypes attributed previously to the "somatic transfer of imprinting machinery" eliminated in conjunction with the removal of paternal imprinting at the Tme locus? Results could validate or refute the idea of a transferable imprinting machinery. (5) What is the nature of the Imp-1 gene product? A complete understanding of the Imp-1 gene and its role in imprinting can only be attained with a cloned copy of the gene "in- hand". This will be accomplished by combining a high resolution genetic map with limited YAC library walking and candidate gene identification.

在过去的十年中，基因组印记引起了人们的兴趣并 许多哺乳动物遗传学家的想象力因其清晰的 违反了关于平等的经典孟德尔假设 配子和 F(1) 基因型。 尽管遗传学研究表明 整个小鼠的多个位点存在印记 迄今为止，基因组中仅克隆了三个自然印记基因 -- Igf2、Igf2r 和 H19 -- 以及印记的分子机制 甚至这些位点仍然难以捉摸。 最近，两个独立的例子 遗传变异似乎会导致印记丢失 Tme 基因座的父系等位基因已被发现。 （虽然 之前假设突变定义的 Tme 位点是相同的 对于 Igf2r 基因，这些新结果表明这可能不是 案例。）一种形式的变异导致了第一个遗传 候选印记基因座（名为 Imp-1）的识别 在受精前在雄性种系内起作用，并且可能在 对“标记”的交易机制至少负有部分责任 Tme 轨迹。 第二种变体表明“印记 维护机制”可能在体细胞同源物之间转移 细胞。 建议利用这些新系统 进一步研究印记的遗传基础。 理由 这个提议的背后是对这些变体系统的理解 将有助于更好地理解负责的机制 正常印记。 五个总体目标可概括为 以下问题的形式：（1）Imp-1 基因座在哪里作图， 地图位置是否提供了其功能的入口？ (2) 是否 Imp-1 基因座在印记控制中具有更普遍的作用 在多个位点？ 这个问题将通过确定 “非标记”Imp-1 等位基因是否允许父系表达 通常印记的 H19 基因座。 (3) Imp-1位点是否发挥作用 在精子发生的单倍体阶段？ 结果将提供 有关标记初始印记的时间的信息。 (4) 发育异常表型的表达是否归因于 此前已被“印记机械体细胞转移”淘汰 结合在时间上去除父系印记 轨迹？ 结果可以验证或反驳可转让的想法 压印机械。 (5)Imp-1基因的本质是什么 产品？ 全面了解 Imp-1 基因及其在 印记只能通过基因“in-”的克隆副本来实现 手”。这将通过结合高分辨率来完成 具有有限YAC文库行走和候选基因的遗传图谱 鉴别。