| 研究実績の概要 |
Meiosis is the cell division that produces sperm and eggs by reducing the chromosome number in half. Since around 15% of couples have some degree of infertility, finding the mechanisms of proper sperm and egg production by meiosis is a pressing need. In the current research term, we have analyzed the conserved protein HIM-3, which we have shown receives phosphorylation during meiosis but is dephosphorylated at a particular chromosome segment before cell division occurs. Homologs of HIM-3 are found in every sexually-reproducing organism, and are important for formation of the chromosome axis and ensuring correct chromosome structure in meiosis. To understand its role, we performed immunostaining and high-resolution three-dimensional fluorescence imaging of HIM-3 in mutants in which HIM-3 cannot be phosphorylated. We found that HIM-3 phosphorylation is important for proper localization of several proteins that are essential for determining which regions of chromosomes separate and which remain connected in the first meiotic division. Further, by analyzing mutants which fail to make sufficient numbers of DNA double-strand breaks, leading to reduced crossover recombination, we found that proper localization of phosphorylated HIM-3 on chromosomes depends on the total number of crossover events, implying a global nucleus-wide feedback between genetic recombination and the localization of chromosome-binding proteins. From these results, we conclude that phosphoregulation of HIM-3 plays an important role in establishing the proper structure of chromosomes in meiosis.
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