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: 3308437
• 负责人: LEE M SILVER
• 金额: $ 31.45万
• 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/3308437
• 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.

在过去的十年里，基因组印记已经引起了人们的兴趣， 许多哺乳动物遗传学家的想象力，因为它清楚地 违反了经典的孟德尔假设， 配子和F（1）基因型。 尽管基因研究表明 在整个小鼠的多个位点存在印记 基因组，迄今为止，仅克隆了三个自然印记基因 --Igf 2、Igf 2 r和H19 --以及印迹的分子机制 在这些位点上的基因定位仍然是难以捉摸的。 最近，两个独立的例子 基因变异的结果，似乎会导致印记的丧失， 已经发现了Tme基因座的父系等位基因。 （虽然 先前假定突变定义的Tme基因座是相同的 Igf 2 r基因，这些新的结果表明，这可能不是 case.） 一种变异形式导致了第一个基因 鉴定候选印记基因座（命名为Imp-1），其可 在受精前作用于雄性生殖系内， 至少部分地负责“标记”的交易机制， Tme基因座 第二种说法认为， 维持机制”可能是可转移的同源体之间的体细胞 细胞 建议利用这些新系统， 进一步研究印记的遗传基础。 的理由 这个提议背后的原因是， 将提供一个更好的了解机制负责 正常的印记 这五个总体目标可归纳为 以下问题的形式：（1）Imp-1基因座定位在哪里， 地图位置是否提供了其功能的入口？ (2)并 Imp-1基因座在印迹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本表达 正常印记的H19基因座 (3)Imp-1基因座是否起作用 在精子发生的单倍体阶段？ 结果将提供 标记初始印记的时间信息。 （四） 发育异常表型的表达是否归因于 以前的“体细胞转移的印记机器”消除 同时在Tme阶段去除父亲的印记 轨迹？ 结果可以验证或反驳可转移的想法， 压印机械 (5)Imp-1基因的本质是什么 产品？ 完整了解Imp-1基因及其在 印记只能通过基因的克隆拷贝来实现，“在- 手”。 这将通过结合高分辨率 具有有限YAC文库步移和候选基因的遗传图谱 识别.