改变教科书！哺乳动物胚胎首次细胞分裂是两个纺锤体让亲本染色体保持分开！根据经典细胞生物学教材中的描述，胚胎第一次细胞分裂过程中是由一个纺锤体负责将胚胎中的染色体分离到两个细胞中。而实际是什么样子的？

最近，Science期刊发表了标题为“Dual-spindle formation in zygotes keeps parental genomes apart in early mammalian embryos”的文章，该文借助于光片层扫描显微镜观察彻底否定了胚胎第一次分裂是由单个纺锤体牵引的观点，而是存在两个纺锤体分别执行牵引父本染色体和母本染色体的分离(图片引自学术经纬对科学杂志的视频截图)，该研究结果改变了传统观念中关于胚胎第一次细胞分裂的经典描述，是不是可以说精卵真正融合是在第一次分裂之后？哈哈。具体细节见原文报道：http://science.sciencemag.org/content/361/6398/189/tab-pdf。

论文摘要：At the beginning of mammalian life, the genetic material from each parent meets when the fertilized egg divides. It was previously thought that a single microtubule spindle is responsible for spatially combining the two genomes and then segregating them to create the two-cell embryo. We used light-sheet microscopy to show that two bipolar spindles form in the zygote and then independently congress the maternal and paternal genomes. These two spindles aligned their poles before anaphase but kept the parental genomes apart during the first cleavage. This spindle assembly mechanism provides a potential rationale for erroneous divisions into more than two blastomeric nuclei observed in mammalian zygotes and reveals the mechanism behind the observation that parental genomes occupy separate nuclear compartments in the two-cell embryo.