Miao Yilong, Zhou Changyin, Cui Zhaokang, Dai Xiaoxin, Zhang Mianqun, Lu Yajuan, Xiong Bo
a College of Animal Science and Technology, Nanjing Agricultural University , Nanjing , China.
Cell Cycle. 2017 Mar 19;16(6):536-544. doi: 10.1080/15384101.2017.1282583. Epub 2017 Jan 24.
Smc1β is a meiosis-specific cohesin subunit that is essential for sister chromatid cohesion and DNA recombination. Previous studies have shown that Smc1β-deficient mice in both sexes are sterile. Ablation of Smc1β during male meiosis leads to the blockage of spermatogenesis in pachytene stage, and ablation of Smc1β during female meiosis generates a highly error-prone oocyte although it could develop to metaphase II stage. However, the underlying mechanisms regarding how Smc1β maintains the correct meiotic progression in mouse oocytes have not been clearly defined. Here, we find that GFP-fused Smc1β is expressed and localized to the chromosomes from GV to MII stages during mouse oocyte meiotic maturation. Knockdown of Smc1β by microinjection of gene-specific morpholino causes the impaired spindle apparatus and chromosome alignment which are highly correlated with the defective kinetochore-microtubule attachments, consequently resulting in a prominently higher incidence of aneuploid eggs. In addition, the premature extrusion of polar bodies and escape of metaphase I arrest induced by low dose of nocodazole treatment in Smc1β-depleted oocytes indicates that Smc1β is essential for activation of spindle assembly checkpoint (SAC) activity. Collectively, we identify a novel function of Smc1β as a SAC participant beyond its role in chromosome cohesion during mouse oocyte meiosis.
Smc1β是一种减数分裂特异性黏连蛋白亚基，对姐妹染色单体黏连和DNA重组至关重要。先前的研究表明，雌雄两性的Smc1β基因敲除小鼠均不育。雄性减数分裂期间Smc1β的缺失会导致粗线期精子发生受阻，而雌性减数分裂期间Smc1β的缺失会产生极易出错的卵母细胞，尽管它可以发育到减数第二次分裂中期。然而，关于Smc1β如何维持小鼠卵母细胞减数分裂正确进程的潜在机制尚未明确。在此，我们发现绿色荧光蛋白融合的Smc1β在小鼠卵母细胞减数分裂成熟过程中从生发泡期到减数第二次分裂中期均有表达并定位于染色体上。通过显微注射基因特异性吗啉代寡核苷酸敲低Smc1β会导致纺锤体装置受损和染色体排列紊乱，这与动粒-微管附着缺陷高度相关，从而导致非整倍体卵的发生率显著升高。此外，在Smc1β缺失的卵母细胞中，低剂量诺考达唑处理诱导的极体过早挤出和减数第一次分裂中期阻滞的逃逸表明，Smc1β对于纺锤体组装检查点（SAC）活性的激活至关重要。总之，我们确定了Smc1β在小鼠卵母细胞减数分裂过程中作为SAC参与者的新功能，这超越了其在染色体黏连中的作用。
