Chromatin Diminution in Ascaris

蛔虫染色质减少

基本信息

批准号：
8320495
负责人：
RICHARD E. DAVIS
金额：
$ 23.04万
依托单位：
UNIVERSITY OF COLORADO DENVER
依托单位国家：
美国
项目类别：
财政年份：
2012
资助国家：
美国
起止时间：
2012-02-15 至 2014-01-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/8320495
关键词：
Address Affect Antibodies Area Ascaris Ascaris suum Biology Caenorhabditis elegans Cell division Cell-Free System Cells Centromere ChIP-seq Chromatin Chromosomal Breaks Chromosome Breakage Chromosome Segregation Chromosomes Complex DNA DNA Sequence DNA Sequence Rearrangement Development Embryo Employee Strikes Epigenetic Process Gene Expression Gene Expression Profile Gene Silencing Generations Genes Genome Human Human Biology Indirect Immunofluorescence Individual Kinetochores Length Location Maintenance Metaphase Plate Methods Mitosis Molecular Nematoda Organism Parasites Parasitic nematode Play Process Proteins Public Health RNA Role Site Small RNA Specific qualifier value Staging Surveys System Testing Time Tissues Transfection chromatin modification chromosome loss comparative daughter cell genome sequencing histone modification insight male new technology novel strategies pathogen prevent programs role model segregation socioeconomics tool

项目摘要

DESCRIPTION (provided by applicant): Genome maintenance and stability are essential, and an organism's genome rarely changes. In striking contrast, chromatin diminution is a programmed process that eliminates specific DNA sequences from the genome. In the parasitic nematode, Ascaris, 25% of the genome is eliminated in the somatic lineages during the 3rd through 5th cleavage (4 to 16 cell stage), while the germline genome remains intact. Both repetitive and unique sequences (genes) are lost during chromatin diminution. The elimination results in chromosome breakage and the loss of chromosome termini as well as the generation of new chromosomes. This process is thought to be a form of gene silencing necessary for development and germline establishment, yet how this programmed elimination contributes to the germline to somatic transition in early Ascaris development remains a mystery more than 100 years after it was discovered. Furthermore, the mechanisms for how chromosomal regions are targeted for elimination, where the sites of chromosomal breakage are located, how DNA breaks are made, what sequences are lost, and how specific sequences are selected to be lost or retained remain unknown. New technologies and approaches will be leveraged to exploit the unique biology and tools in Ascaris to examine chromatin diminution and define eliminated and re-arranged sequences, to examine chromatin modifications associated with diminution, to test a new hypothesis for how eliminated DNA is not segregated during cell division, and to gain additional insight into the potential role of small RNAs in chromatin diminution. We propose that a comprehensive comparison of the somatic and germline genome in Ascaris will permit us to address for the first time a number of central questions regarding diminution including: What rearrangements occur? What genes are lost? Are there common features among the breakpoints that provide insight into how the breakpoints are defined? Are the chromosomal breakpoints at the same approximate location in all individuals or do they vary in different individuals? Furthermore, we propose that epigenetic chromatin changes are associated with the process of diminution and that Ascaris 22G endo-siRNAs and the associated Argonaute CSR-1 RISC complex contribute to chromatin diminution by marking regions of Ascaris chromosomes for retention or elimination. Ascaris is an important human pathogen as it infects over a billion people. Understanding gene maintenance, alterations, and the role of alterations in gene expression in Ascaris is important in understanding the biology of this human parasite. Furthermore, understanding the molecular regulators, mechanism, and consequences of diminution will not only provide insight into DNA elimination and its importance in nematodes, but is likely to increase our understanding of this phenomenon and germline, chromosome, and genome biology in general. PUBLIC HEALTH RELEVANCE: Parasitic nematodes remain a significant public health problem in many parts of the world. Ascaris alone infects upwards of 1 billion people and hinders socioeconomic development in endemic areas. We will carry out studies on an unusual form of programmed DNA elimination in Ascaris, chromatin diminution, important in the biology of the organism.

描述（由申请人提供）：基因组维持和稳定性至关重要，生物体的基因组很少发生变化。与此形成鲜明对比的是，染色质减少是一个从基因组中消除特定 DNA 序列的程序化过程。在寄生线虫蛔虫中，在第 3 至 5 次卵裂（4 至 16 细胞阶段）期间，25% 的基因组在体细胞谱系中被消除，而种系基因组保持完整。在染色质减少过程中，重复序列和独特序列（基因）都会丢失。消除导致染色体断裂和染色体末端丢失以及新染色体的产生。这一过程被认为是发育和种系建立所必需的基因沉默的一种形式，然而，这种程序性消除如何促进早期蛔虫发育中种系向体细胞的转变，在其被发现一百多年后仍然是一个谜。此外，如何靶向消除染色体区域、染色体断裂位点位于何处、DNA断裂如何发生、丢失哪些序列以及如何选择丢失或保留特定序列的机制仍然未知。将利用新技术和方法来利用蛔虫中独特的生物学和工具来检查染色质减少并定义消除和重新排列的序列，检查与减少相关的染色质修饰，测试关于消除的DNA如何在过程中不分离的新假设。细胞分裂，并进一步了解小 RNA 在染色质减少中的潜在作用。我们建议，对蛔虫体细胞和种系基因组进行全面比较将使我们能够首次解决有关减少的一些核心问题，包括：发生了哪些重排？哪些基因丢失了？断点之间是否存在共同特征，可以让您深入了解断点的定义方式？所有个体的染色体断点都位于相同的大致位置，还是不同个体的染色体断点有所不同？此外，我们提出表观遗传染色质变化与减少过程相关，并且蛔虫 22G 内切 siRNA 和相关的 Argonaute CSR-1 RISC 复合物通过标记蛔虫染色体区域以保留或消除，从而有助于染色质减少。蛔虫是一种重要的人类病原体，它感染超过十亿人。了解蛔虫的基因维持、改变以及基因表达改变的作用对于了解这种人类寄生虫的生物学非常重要。此外，了解减少的分子调节因子、机制和后果不仅可以深入了解 DNA 消除及其在线虫中的重要性，而且可能会增加我们对这种现象以及种系、染色体和基因组生物学的理解。公共卫生相关性：寄生线虫在世界许多地区仍然是一个重大的公共卫生问题。仅蛔虫就感染了超过 10 亿人，并阻碍了流行地区的社会经济发展。我们将研究蛔虫中一种不寻常的程序性 DNA 消除形式，即染色质减少，这在生物体生物学中很重要。