Characterization of the Synapis Checkpoint in C. elegans Meiosis

描述（由申请人提供）：减数分裂从二倍体细胞产生单倍体配子，使二倍体基因组在受精后恢复。减数分裂过程中染色体的正确分离取决于减数分裂前期的事件，如同源染色体的配对和突触以及交叉重组。染色体分离错误通常对受精卵是致命的，但也可能导致癌症易感性或严重的发育障碍。我已经确定了一个减数分裂检查点，它对同源突触中的缺陷作出反应，独立于DNA损伤/重组检查点，并激活细胞凋亡以避免非整倍体配子的产生。并不是所有的非突触序列都有能力触发这个检查点；相反，这条通路是由非突触配对中心（PCs）特异性激活的，这是线虫中促进突触的染色体位点。此外，检查点需要秀丽隐杆线虫的PCH-2同源物，PCH-2是一种出芽酵母pachytene检查点基因，这表明检测突触失败的分子机制是广泛保守的。

DESCRIPTION (provided by applicant): Meiosis generates haploid gametes from a diploid cell such that a diploid genome is restored upon fertilization. The proper segregation of chromosomes during the meiotic divisions depends on events in meiotic prophase, such as the pairing and synapsis of homologous chromosomes and crossover recombination. Errors in chromosome segregation are usually fatal to the fertilized zygote but can also result in cancer predisposition or serious developmental disorders. I have identified a meiotic checkpoint that responds to defects in homolog synapsis, independent of a DNA damage/recombination checkpoint, and activates apoptosis to avoid the generation of aneuploid gametes. Not all unsynapsed sequences have the capacity to trigger this checkpoint; rather, this pathway is specifically activated by unsynapsed pairing centers (PCs), chromosome sites that promote synapsis in C. elegans. Furthermore, the checkpoint requires the C. elegans homolog of PCH-2, a budding yeast pachytene checkpoint gene, suggesting that the molecular mechanism that detects synaptic failure is widely conserved. I plan to further characterize this synapsis checkpoint. I am particularly interested in the PC's contribution to synapsis checkpoint activation. The identification and characterization of proteins that interact with factors required for PC function will provide insight into how this locus activates the checkpoint when unsynapsed. Studies that address the regulation of heterochromatin on unsynapsed chromosomes and how the PC may inhibit the DNA damage checkpoint will also be undertaken. I will determine the role of the synaptonemal complex (SC) in the synapsis checkpoint by characterizing two genes that interact with the SC and appear to be required for the checkpoint by preliminary RNA inteferference (RNAi) experiments. I will investigate the function and regulation of the known checkpoint component, pch-2; a GFP-PCH-2 fusion protein will be localized in a variety of genetic backgrounds and a reagent will be provided to identify interacting proteins biochemically. Furthermore, I will identify additional components of the checkpoint by undertaking an RNAi screen that will focus on candidate genes that fulfill specific expression and phenotypic profile criteria. These complementary approaches will enable me to gain a molecular and mechanistic understanding of how homolog synapsis is monitored and how an unsynapsed or inappropriately synapsed homolog generates a checkpoint signal that is ultimately translated into an apoptotic response. Meiosis produces gametes, such as eggs and sperm. Checkpoints monitor meiotic events to ensure that gametes have the correct number of chromosomes. If a gamete has an incorrect number of chromosomes, the embryo that results from fertilization is often inviable. Occasionally, an embryo inherits an extra chromosome that is not lethal but can cause cancer predisposition or serious developmental defects.