The molecular basis of meiotic crossover distribution

我的实验室已经确定了一个基因的分子基础，该基因负责确定秀丽线虫减数分裂中交叉事件的分布。这是一个重要的结果，因为rec-1表型是独一无二的，因为它改变了所测量的交叉事件的位置，而不会对重组频率、繁殖力或发育过程产生任何其他可测量的影响。rec-1基因的一个显著特征是，它在初级序列水平上与其他物种的保守性很差，尽管迄今为止所有物种都表现出减数分裂模式，这是另一种说法，即交叉分布在染色体上并不均匀。对于这一明显的悖论，有很多种解释；然而，这里要测试的假设是，rec-1是减数分裂特有功能的一个例子，它在功能上是保守的，但不是在其主要序列中。这个提议的基本原理是，对于一个物种来说，使用物种特有的分子来执行减数分裂的基本生物学功能所涉及的过程，以保护其减数分裂功能不受跨物种的影响，是有选择地有利的。这是所有有性繁殖个体广泛使用的过程。*为了检验这一假说，建议的口述将在关系密切的物种中确定。这将通过检查保守的rec-1两侧的基因来实现。在使用这些侧翼基因来寻找线虫中rec-1所在的同步区时，我们将在我们预期的位置寻找编码区。我们已经做了一些初步的实验，发现在预期的位置有一个编码区，但与rec-1在序列上不是高度保守的。为了确认该编码区对应于rec-1基因，我们将在关系密切的物种中对其进行鉴定。利用CRISPR系统对该基因进行突变(敲除)。然后对该突变株和野生型菌株进行沿着同源染色体的交叉分布的鉴定。布里吉萨线虫中存在突变株，它们鉴定出与线虫的同源基因，野生型菌株已经测序并鉴定了与线虫的同源性。因此，可以使用基本工具来解决所提出的直系基因在这两个物种中是否具有相同功能的问题。此外，我们将通过确定与REC-1蛋白的相互作用伙伴来研究减数分裂模式是如何建立的。为了做到这一点，我们将采取两种遗传方法，研究基因与已知的减数分裂功能的相互作用，以及识别蛋白质相互作用的分子方法。用这种方法描述一种现象的分子基础，该现象一直是生物学中一个长期悬而未决的问题的目标。

My laboratory has identified the molecular basis of a gene responsible for establishing the distribution of crossover events in meiosis of Caenorhabditis elegans.  This is a significant result because the phenotype o rec-1 is unique in that it alters the position of the measured crossover event without any other measurable effects on frequency of recombination, fecundity or developmental processes.  A notable feature of the rec-1 gene is that it is poorly conserved at the level of primary sequence with other species, even though all species characterized to date show a meiotic pattern, which is another way of saying that the distribution of crossing over is not uniform along a chromosome.  There are a number of explanations for this apparent paradox; however the hypothesis that will be tested here is that rec-1 is an example of a***meiosis-specific function that is conserved functionally, but not in its primary sequence.  The rationale for this proposal is that it is selectively advantageous for a species to protect its meiotic functions from cross-speciation using species-specific molecules to perform the processes involved in the basic biological function of meiosis.  A process widely used by all sexually reproducing individuals.******In order to test this hypothesis, the proposed orothologs will be identified in closely related species. This will be achieved by examining the genes flanking rec-1, which are conserved.  Using these flanking genes to find the syntenic region where rec-1 is situated in C. elegans, we will look for a coding region in the position where we expect rec-1 to be.  We have done some preliminary experiments and found that there is a coding region in the expected location, but one that is not highly conserved sequence-wise with rec-1. To confirm that the coding region corresponds to the rec-1 gene, we will characterize it in the closely related species, C. briggsae.  The gene in C. briggsae will be mutated (knocked out) using the CRISPR system.  The C. briggsae mutant knock-out and the wild-type strain will be characterized with regard to the distribution of crossing over along an orthologous chromosome. There are mutant strains in C. briggsae that identify orthologous genes to those in C. elegans and the wild-type strain has been sequenced and characterized with regard to synteny with C. elegans.  So the basic tools are available to address the question of whether or not the proposed ortholog performs the same function in the two species.  ******In addition, we will investigate how the meiotic pattern is established by identifying interacting partners with the REC-1 protein.  To do this we will take both a genetic approach, examining gene interactions with known meiotic functions along with a molecular approach to identify protein interactions.  In this way characterize the molecular basis responsible for a phenomenon that has been the object of a long-standing, out-standing question in biology.****** *****