Dissecting the genetic basis of selfish sex chromosomes

剖析自私性染色体的遗传基础

• 批准号: 10327780
• 负责人: Spencer A Koury
• 金额: $ 6.53万
• 依托单位: STOWERS INSTITUTE FOR MEDICAL RESEARCH
• 依托单位国家: 美国
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-03-15 至 2022-03-14
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10327780
• 关键词: Dissecting; genetic; basis; selfish; sex

Sex-Ratio (SR) chromosomes are X chromosome variants that subvert the transmission of Y chromosomes, distort the sex ratio of progeny and gain an evolutionary advantage at a cost to organismal fitness. SR chromosomes initiate intense genetic conflict between X-linked distorters, Y-linked targets, and an array of autosomal suppressors. This evolutionary arms race provides a powerful explanation of meiotic sex chromosome inactivation, turnover of sex chromosomes, and evolution of sex determination systems. SR chromosomes are thought to target satellite repeats and heterochromatic regions found on degenerate Y chromosomes, yet very little is known about the specific genetic basis or molecular mechanisms of distortion. This is because SR systems are primarily known from non-model organisms and are often bound up in complex genomic rearrangements. Without characterizing the underlying genetic basis and molecular mechanisms it remains impossible to directly connect the arms race initiated by selfish elements to broader phenomena in the evolution of meiosis and sex chromosome systems. I develop two independent methods to circumvent the confounding effects of chromosomal inversions and dissect the genetic basis underlying this selfish behavior in closely related Drosophila species. Specific Aim 1: Developing a mutagenesis approach to identify the genes causing Sex-Ratio distortion in D. pseudoobscura. Through saturation mutagenesis of SR chromosomes, I identify X-linked of genes contributing to distortion by screening for reduced transmission. To date, >5,000 lines have been screened (95% saturation), with 33 lines exhibiting reduced distortion. Using CRISPR-Cas9 genome editing, I propose to test the necessary and sufficient conditions of resulting candidate loci and place them into a functional pathway for SR distortion. Specific Aim 2: Engineering a synthetic chromosomal inversion to allow recombination mapping of Sex-Ratio distortion in D. persimilis. This approach adapts the Flp/FRT site-specific recombination tools to generate a perfectly collinear non-driving chromosome to allow free recombination in the region containing all necessary and sufficient genes for SR distortion. Once candidate genes are mapped, validated, and organized into a functional pathway for D. persimilis, a comparative analysis of these two systems will test whether SR mechanisms are unique or shared. Together, these two methods will provide the most complete genetic architecture of sex-linked segregation distorters to date, open the door to understanding the molecular mechanisms of distortion in two species, and for the first time explicitly test both the evolutionary conservation hypothesis and the population genetic hypothesis that Sex-Ratio distortion is determined by epistatically interacting X-linked genes bound together by chromosomal inversions. The proposed research provides training opportunities in both genomic analyses and genetic engineering, and establishes a strong basis for my continuing research program dissecting the evolutionary and cellular basis of selfish sex chromosomes.

性别比 (SR) 染色体是 X 染色体变体，可破坏 Y 染色体的传递， 扭曲后代的性别比例并以牺牲有机体适应性为代价获得进化优势。 SR 染色体在 X 连锁扭曲者、Y 连锁目标和一系列 常染色体抑制因子。这种进化军备竞赛为减数分裂性染色体提供了有力的解释 失活、性染色体的更新和性别决定系统的进化。 SR 染色体是 被认为针对简并 Y 染色体上发现的卫星重复序列和异染色质区域，但非常 对于扭曲的具体遗传基础或分子机制知之甚少。这是因为SR 系统主要来自非模型生物体，并且通常与复杂的基因组结合在一起 重新安排。如果没有描述潜在的遗传基础和分子机制，它仍然存在 不可能将自私因素引发的军备竞赛与更广泛的进化现象直接联系起来 减数分裂和性染色体系统。我开发了两种独立的方法来规避 染色体倒位的混杂效应并剖析这种自私背后的遗传基础 密切相关的果蝇物种的行为。 具体目标 1：开发诱变方法来识别导致性别比例扭曲的基因 在 D.pseudoobscura 中。通过SR染色体的饱和诱变，我识别出X连锁基因 通过筛选减少传输而导致失真。迄今为止，已筛选了超过 5,000 个品系（95% 饱和度），其中 33 条线表现出减少的失真。我建议使用 CRISPR-Cas9 基因组编辑来测试 产生候选基因座的必要和充分条件，并将它们放入功能途径中 SR 失真。具体目标 2：设计合成染色体倒位以实现重组 D. persimilis 性别比例扭曲的绘图。该方法适应 Flp/FRT 特定站点 重组工具可生成完美共线的非驱动染色体，从而允许在 包含 SR 畸变所有必要和充分基因的区域。一旦候选基因被定位， 验证并组织成 D. persimilis 的功能途径，对这两个系统进行比较分析 将测试 SR 机制是唯一的还是共享的。这两种方法结合在一起将提供最大的 迄今为止，与性别相关的隔离扭曲者的完整遗传结构，为了解 两个物种扭曲的分子机制，并首次明确测试了进化论 保护假说和人口遗传假说，性别比扭曲由以下因素决定 通过染色体倒位结合在一起的上位相互作用的 X 连锁基因。拟议的研究 提供基因组分析和基因工程方面的培训机会，并奠定坚实的基础 表彰我的持续研究计划，剖析自私性染色体的进化和细胞基础。

项目成果

Mitotic exchange in female germline stem cells is the major source of Sex Ratio chromosome recombination in Drosophila pseudoobscura.

• DOI: 10.1093/g3journal/jkac264
• 发表时间: 2022-12-01
• 期刊: G3 (Bethesda, Md.)