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，该基因负责建立秀丽隐杆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的表型是独特的，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，它与其他物种在初级序列水平上的保守性很差，尽管迄今为止表征的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。对于这个明显的悖论，有很多解释；然而，这里要验证的假设是，rec-1是减数分裂特异性功能的一个例子，它在功能上是保守的，但不是在其主序列中。这一建议的基本原理是，使用物种特异性分子来执行减数分裂基本生物学功能的过程，对物种保护其减数分裂功能免受跨物种形成是选择性有利的。一种被所有有性繁殖的个体广泛使用的过程。******为了验证这一假设，将在密切相关的物种中确定所提出的人种。这将通过检查rec-1两侧的保守基因来实现。利用这些侧翼基因来寻找秀丽隐杆线虫中rec-1所在的共胞区，我们将在rec-1所在的位置寻找一个编码区。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，但是一个与rec-1序列不高度保守的编码区。为了确认该编码区与rec-1基因相对应，我们将在密切相关的物种C. briggsae中对其进行表征。使用CRISPR系统，C. briggsae中的基因将发生突变（被敲除）。briggsae突变型敲除菌株和野生型菌株将在沿同源染色体交叉分布方面具有特征。在C. briggsae中存在与秀丽隐杆线虫同源基因的突变菌株，野生型菌株已被测序并与秀丽隐杆线虫同源性鉴定。因此，基本的工具是可用的，以解决问题，是否提出的直系同源在两个物种中执行相同的功能。******此外，我们将研究如何通过识别与REC-1蛋白相互作用的伙伴来建立减数分裂模式。为了做到这一点，我们将采用遗传方法，检查基因与已知减数分裂功能的相互作用，以及分子方法来识别蛋白质相互作用。以这种方式描述导致一种现象的分子基础，这种现象一直是生物学中一个长期存在的突出问题的对象。****** *****

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.****** *****