Tracking the Rapid Evolution of Sex Chromosome Palindromes and Their Genes

摘要 在许多物种中，与男性生育有关的基因和基因组区域进化迅速。哺乳动物的性行为 染色体被丰富，因为快速进化的大回文序列含有睾丸特有的基因。 然而，驱动X-和Y-回文及其相关基因快速进化的机制尚不清楚 明白了。我认为回文内部的基因转换--从一个回文中复制序列 通过重组臂到另一臂-是推动X和Y回文进化的主要机制。这个 这一建议的前提是基于我最近在MICE和之前发表的研究结果中的观察 在灵长类动物中，X回文和Y回文分别进行正在进行的回文内基因转换。 为了解决X和Y回文序列的快速进化，我将首先确定选择压力 (即正选择或纯化选择)影响小鼠X-和Y-回文序列的进化。这将是 是第一个对单个物种内X和Y回文序列进化的系统分析 理解支配它们进化的选择压力。我还将开发一种新的分析方法来解决， 首次测定了X-和Y-回文基因在体内的转化频率。了解进化过程 X回文和Y回文以及回文内基因转换的体内频率将提供有价值的 对对男性生育能力至关重要的基因组区域的快速进化的洞察。

ABSTRACT In many species, genes and genomic regions involved in male fertility evolve rapidly. Mammalian sex chromosomes are enriched for rapidly evolving large palindromic sequences harboring testis-specific genes. However, the mechanism driving rapid evolution of X- and Y- palindromes and their associated genes is poorly understood. I propose that intra-palindrome gene conversion – the “copying” of sequence from one palindrome arm to the other via recombination – is the primary mechanism driving X- and Y- palindrome evolution. The premise of this proposal is based upon observations from my recently published findings in mouse and previous studies in primates that X- and Y-palindromes, respectively, undergo on-going intra-palindrome gene conversion. To address the rapid evolution of X- and Y-palindromic sequences, I will first identify whether selective pressures (i.e. positive or purifying selection) influence the sequence evolution of X- and Y- palindromes in mice. This will be the first systematic analysis of both X- and Y-palindrome sequence evolution within a single species to understand the selective pressures governing their evolution. I will also develop a novel assay to address, for the first time, the in vivo frequencies of X- and Y- intra-palindrome gene conversion. Understanding the evolution of X- and Y- palindromes and in vivo frequencies of intra-palindrome gene conversion will provide valuable insights into the rapid evolution of genomic regions important for male fertility.