核型,由染色体组成,必须通过有丝分裂纺锤体准确划分,以获得最佳的细胞健康。然而,目前还不清楚核型的潜在特征,如染色体数量和大小,控制有丝分裂纺锤体的缩放,以确保准确的染色体分离和细胞增殖。我们利用染色体较少的出芽酵母菌株,包括两个巨型染色体,“研究主轴尺寸和功能如何响应,并按比例缩放,核型。我们确定纺锤体相关基因的缺失和过表达不利于具有两条染色体的菌株的生长,这表明巨型染色体对纺锤体有改变的需求。使用共聚焦显微镜,我们证明了染色体较少但较长的细胞具有较小的纺锤体,较少的微管,和更长的主轴。此外,使用电子层析成像和共聚焦成像,我们观察到细长的,在具有大型染色体的菌株中,弯曲的后期纺锤体具有较少的核心微管。带有巨型染色体的细胞生长得更慢,有丝分裂延迟,一个子集正在努力完成染色体分离。我们认为细胞的核型决定了微管的数量,type,主轴杆体尺寸,和主轴长度,随后影响有丝分裂的动力学,如主轴伸长率和极分离速度。一起来看,我们的结果表明,有丝分裂纺锤体是高度可塑性的超微结构,可以适应和适应各种核型,甚至在一个物种内。
Karyotypes, composed of chromosomes, must be accurately partitioned by the mitotic spindle for optimal cell health. However, it is unknown how underlying characteristics of karyotypes, such as chromosome number and size, govern the scaling of the mitotic spindle to ensure accurate chromosome segregation and cell proliferation. We utilize budding yeast strains engineered with fewer chromosomes, including just two \"mega chromosomes,\" to study how spindle size and function are responsive to, and scaled by, karyotype. We determined that deletion and overexpression of spindle-related genes are detrimental to the growth of strains with two chromosomes, suggesting that mega chromosomes exert altered demands on the spindle. Using confocal microscopy, we demonstrate that cells with fewer but longer chromosomes have smaller spindle pole bodies, fewer microtubules, and longer spindles. Moreover, using electron tomography and confocal imaging, we observe elongated, bent anaphase spindles with fewer core microtubules in strains with mega chromosomes. Cells harboring mega chromosomes grow more slowly, are delayed in mitosis, and a subset struggle to complete chromosome segregation. We propose that the karyotype of the cell dictates the
microtubule number, type, spindle pole body size, and spindle length, subsequently influencing the dynamics of mitosis, such as the rate of spindle elongation and the velocity of pole separation. Taken together, our results suggest that mitotic spindles are highly plastic ultrastructures that can accommodate and adjust to a variety of karyotypes, even within a species.