Tracking the Rapid Evolution of Sex Chromosome Palindromes and Their Genes

摘要 在许多物种中，涉及雄性生育力的基因和基因组区域迅速进化。哺乳动物性别 染色体富集了快速进化的含有睾丸特异性基因的大回文序列。 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， 明白我认为回文内基因转换--从一个回文中“复制”序列 是驱动X和Y回文序列进化的主要机制。的 这个建议的前提是基于我最近发表的对小鼠和以前的研究结果的观察。 在灵长类动物中的研究表明，X-和Y-回文序列分别经历持续的回文序列内基因转换。 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是否 (i.e.正选择或纯化选择）影响小鼠中X-和Y-回文序列的进化。这将 是第一个系统分析X-和Y-回文序列进化在一个单一的物种， 理解控制它们进化的选择压力。我还将开发一种新的测定方法来解决， 第一次，在体内频率的X-和Y-内回文基因转换。理解进化 的X-和Y-回文和体内频率的回文内基因转换将提供有价值的 深入了解对男性生育力重要的基因组区域的快速进化。

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.