Flynn Jonathan R, McNally Francis J
Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA 95616.
Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA 95616
Mol Biol Cell. 2017 Sep 1;28(18):2410-2419. doi: 10.1091/mbc.E17-01-0056. Epub 2017 Jul 12.
During female meiosis, haploid eggs are generated from diploid oocytes. This reduction in chromosome number occurs through two highly asymmetric cell divisions, resulting in one large egg and two small polar bodies. Unlike mitosis, where an actomyosin contractile ring forms between the sets of segregating chromosomes, the meiotic contractile ring forms on the cortex adjacent to one spindle pole, then ingresses down the length of the spindle to position itself at the exact midpoint between the two sets of segregating chromosomes. Depletion of casein kinase 1 gamma (CSNK-1) in led to the formation of large polar bodies that contain all maternal DNA, because the contractile ring ingressed past the spindle midpoint. Depletion of CSNK-1 also resulted in the formation of deep membrane invaginations during meiosis, suggesting an effect on cortical myosin. Both myosin and anillin assemble into dynamic rho-dependent cortical patches that rapidly disassemble in wild-type embryos. CSNK-1 was required for disassembly of both myosin patches and anillin patches. Disassembly of anillin patches was myosin independent, suggesting that CSNK-1 prevents expulsion of the entire meiotic spindle into a polar body by negatively regulating the rho pathway rather than through direct inhibition of myosin.
在雌性减数分裂过程中，单倍体卵子由二倍体卵母细胞产生。染色体数量的这种减少通过两次高度不对称的细胞分裂发生，产生一个大的卵子和两个小的极体。与有丝分裂不同，有丝分裂中肌动球蛋白收缩环在分离的染色体组之间形成，减数分裂收缩环在靠近一个纺锤极的皮质上形成，然后沿着纺锤体的长度向内凹陷，将自身定位在两组分离染色体之间的确切中点。酪蛋白激酶1γ（CSNK-1）的缺失导致形成包含所有母源DNA的大极体，因为收缩环越过纺锤体中点向内凹陷。CSNK-1的缺失还导致减数分裂期间形成深的膜内陷，表明对皮质肌球蛋白有影响。肌球蛋白和膜收缩蛋白都组装成动态的rho依赖性皮质斑块，在野生型胚胎中迅速解体。CSNK-1是肌球蛋白斑块和膜收缩蛋白斑块解体所必需的。膜收缩蛋白斑块的解体不依赖于肌球蛋白，这表明CSNK-1通过负调节rho途径而不是通过直接抑制肌球蛋白来防止整个减数分裂纺锤体被排出到极体中。
