It takes two to tango Fusion of egg and sperm combines the genetic material of both parents in one cell. In mammals, including humans, each parental genome is initially confined in a separate pronucleus. For the new organism to develop, the two genomes must be spatially coordinated so that the first embryonic division can create two cells that combine both genomes in one nucleus. Reichmann et al. found that at the beginning of the first division, two microtubule spindles organize the maternal and paternal chromosomes and subsequently align to segregate the parental genomes in parallel (see the Perspective by Zielinska and Schuh). Failure of spindle alignment led to two-celled embryos with more than one nucleus per cell. Dual-spindle assembly in the zygote thus offers a potential mechanistic explanation for division errors frequently observed in human embryos in the fertility clinic. Science, this issue p. 189; see also p. 128 After fertilization, two spindles form around pronuclei in mammalian zygotes and keep the parental genomes apart. 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.

中文翻译：

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受精卵中的双轴形成使早期哺乳动物胚胎中的亲本基因组分开

探戈需要两个人进行卵子和精子的融合，将父母双方的遗传物质结合在一个细胞中。在包括人类在内的哺乳动物中，每个亲本基因组最初都被限制在一个单独的原核中。为了开发新的生物体，两个基因组必须在空间上协调，以便第一次胚胎分裂可以创建两个细胞，将两个基因组结合在一个细胞核中。赖希曼等人。发现在第一次分裂开始时，两个微管纺锤体组织母本和父本染色体，随后对齐以平行分离亲本基因组（参见 Zielinska 和 Schuh 的观点）。纺锤体对齐失败导致双细胞胚胎每个细胞有一个以上的细胞核。因此，受精卵中的双轴组装为生育诊所中人类胚胎中经常观察到的分裂错误提供了潜在的机械解释。科学，这个问题 p。189; 另见第。128 受精后，哺乳动物受精卵的原核周围会形成两个纺锤体，并使亲本基因组分开。在哺乳动物生命的开始，当受精卵分裂时，来自父母双方的遗传物质相遇。以前认为单个微管纺锤体负责在空间上组合两个基因组，然后将它们分离以创建双细胞胚胎。我们使用光片显微镜显示受精卵中形成了两个双极纺锤体，然后独立地将母本和父本基因组集中起来。这两个纺锤体在后期之前对齐它们的极点，但在第一次切割期间将亲本基因组分开。这种纺锤体组装机制为在哺乳动物受精卵中观察到的错误分裂成两个以上的卵裂球核提供了潜在的基本原理，并揭示了亲本基因组在双细胞胚胎中占据单独的核区室这一观察结果背后的机制。