Study of Meiotic Kinetochore Regulation

我们之前的研究表明，MEIKIN与分裂酵母中的moa1一样，在I期后期维持着丝粒内聚是必需的。我们已经证明，小鼠减数分裂中着丝粒粘聚蛋白的保护因子Shugoshin-2 （Sgo2）的着丝粒定位减少，这可能解释了MEIKIN KO（基因敲除）中姐妹染色单体在I期后期分离过早的原因。为了研究Meikin-/-精母细胞中SGO2定位减少的原因，我们检测了已知的调节SGO2定位的Bub1。由于在减数分裂中Plk1的富集很大程度上依赖于MEIKIN，这些结果提出了Plk1活性可能是小鼠减数分裂中Bub1在着丝点定位所必需的。在Plk1被抑制的野生型精母细胞中，BI 2536处理后，着丝粒Bub1信号在I中期减少，这与MEIKIN KO一致，而在糖尿病中没有明显的影响。接下来，我们研究了Mps1对野生型精母细胞中Bub1定位的调控，这些精母细胞用Mps1抑制剂Reversine处理。事实上，Mps1在糖尿病过程中特异性调节Bub1，并且在I中期表现出比Plk1抑制更温和的作用。最后，Plk1和Mps1的同时抑制不仅降低了前期的Bub1水平，也降低了中期的Bub1水平。我们得出结论，MEIKIN依赖性Plk1可能在减数分裂I中将Bub1招募到着丝点，从而调节着丝粒上SGO2的定位。此外，Plk1和Mps1在减数分裂I中冗余调控Bub1。

Our previous study suggests that MEIKIN is required for maintenance of centromeric cohesion in anaphase I like moa1 in fission yeast. We have shown that centromeric localization of Shugoshin-2 (Sgo2), the protector of centromeric cohesin in mouse meiosis, is diminished and it may explain precocious sister chromatids separation during anaphase I in MEIKIN KO (knockout). To investigate the cause of SGO2 localization decrease in Meikin-/- spermatocytes, we examined Bub1 which are known to regulate SGO2 localization.Since kinetochore enrichment of Plk1 largely depends on MEIKIN in meiosis, these results raised the possibility that Plk1 activity might be required for Bub1 localization at kinetochore in mouse meiosis. In Plk1 inhibited wild-type spermatocytes by BI 2536 treatment, centromeric Bub1 signals are diminished in metaphase I which coincide with MEIKIN KO whereas no significant effects could be seen in diakinesis.Next we examined that Mps1 regulation for Bub1 localization in wild-type spermatocytes which are treated with the Mps1 inhibitor Reversine. Indeed, Mps1 specifically regulated Bub1 in diakinesis and showed milder effect in metaphase I than Plk1 inhibition. Finally, simultaneous inhibition of both Plk1 and Mps1 reduced additional levels of Bub1 not only in diakinesis but also metaphase I. We conclude that MEIKIN dependent Plk1 may recruit Bub1 to the kinetochore in meiosis I that regulates SGO2 localization on centromere. Furthermore, Plk1 and Mps1 redundantly regulate Bub1 in meiosis I.