Elucidation of mechanisms ensuring optimal double-strand break number in meiotic cells

本年度继续研究通过DSB-1蛋白的磷酸化调节来控制减数分裂双链断裂（DSB）的机制，发现即使在DSB-2蛋白缺失的情况下，将DSB-1中的一个丝氨酸残基S186突变为丙氨酸，也会导致DSB的过度形成。DSB-2的丢失通常会导致由于DSB丢失而导致的高胚胎不存活率。由于DSB-2的丢失可以很容易地被挽救，我们推断它可能是长期基因组稳定所必需的。因此，我们对DSB-1不可磷酸化突变株系进行了全基因组长读段测序，这些突变株系经历了超过50代的高DSB水平。虽然对该序列信息的分析仍在进行中，但已分离出具有自发突变和自发四倍化的个体突变动物。由于在野生型动物中从未观察到自发的四倍化，所以在不可磷酸化的DSB-1突变动物中基因组变得不太稳定是合理的。然而，我们现在已经完成了FLAG标记的DSB-1等位基因的构建，其具有完全的活力，在蛋白质印迹上非常干净;该试剂将极大地帮助我们进一步表征DSB-1。

We have continued to address the mechanisms of meiotic double-strand break (DSB) control by phosphoregulation of the protein DSB-1 in this fiscal year.We found that mutating a single serine residue in DSB-1, S186, to alanine, leads to hyperactive DSB formation, even in the absence of the protein DSB-2. Loss of DSB-2 norally leads to high embryonic inviability due to loss of DSBs. Since loss of DSB-2 can be rescued so easily, we reasoned that it might be required for long-term genome stability. We therefore have performed whole-genome long-read sequencing on DSB-1 non-phosphorylatable mutant lines that have been experiencing high DSB levels for over 50 generations. While analysis of this sequence information is still in progress, individual mutant animals have been isolated with spontaneous mutations and spontaneous tetraploidization. Since spontaneous tetraploidization is never observed in wild-type animals, it is plausible that the genome has become less stable in the non-phosphorylatable DSB-1 mutant animals.Our attempts to directly demonstrate phosphorylation of DSB-1 by phosphospecific antibody production or mass spectrometry have not yet been successful; however, we have now completed construction of a FLAG-tagged DSB-1 allele with full viability that is very clean on a western blot; this reagent should greatly aid in our further efforts to characterize DSB-1.