Department of Histology and Embryology, Faculty of Medicine, Masaryk University, Brno, Czech Republic.
Reprofit International, Clinic of Reproductive Medicine, Brno, Czech Republic.
Nat Commun. 2024 Jul 29;15(1):6369. doi: 10.1038/s41467-024-50732-z.
The first embryonic division represents a starting point for the development of a new individual. In many species, tight control over the first embryonic division ensures its accuracy. However, the first division in humans is often erroneous and can impair embryo development. To delineate the spatiotemporal organization of the first mitotic division typical for normal human embryo development, we systematically analyzed a unique timelapse dataset of 300 IVF embryos that developed into healthy newborns. The zygotic division pattern of these best-quality embryos was compared to their siblings that failed to implant or arrested during cleavage stage. We show that division at the right angle to the juxtaposed pronuclei is preferential and supports faithful zygotic division. Alternative configurations of the first mitosis are associated with reduced clustering of nucleoli and multinucleation at the 2-cell stage, which are more common in women of advanced age. Collectively, these data imply that orientation of the first division predisposes human embryos to genetic (in)stability and may contribute to aneuploidy and age-related infertility.
第一次卵裂代表着新个体发育的起点。在许多物种中，对第一次卵裂的严格控制确保了其准确性。然而，人类的第一次分裂往往是错误的，会损害胚胎的发育。为了描绘正常人类胚胎发育中第一次有丝分裂的时空组织，我们系统地分析了 300 个体外受精胚胎的独特延时数据集，这些胚胎发育成了健康的新生儿。将这些最佳质量胚胎的卵裂模式与未能着床或在卵裂期停滞的胚胎进行比较。我们发现，与毗邻原核成直角的分裂是首选的，并且支持合子的准确分裂。第一次有丝分裂的替代构型与核仁聚集减少和 2 细胞期的多核化有关，这些在高龄妇女中更为常见。总的来说，这些数据表明第一次分裂的方向使人类胚胎容易发生遗传（不）稳定性，并可能导致非整倍体和与年龄相关的不孕。
