Large Cytoplasm Is Linked to the Error-Prone Nature of Oocytes

Publication date: 8 May 2017
Source:Developmental Cell, Volume 41, Issue 3
Author(s): Hirohisa Kyogoku, Tomoya S. Kitajima
Chromosome segregation during meiosis in oocytes is error prone. The uniquely large cytoplasmic size of oocytes, which provides support for embryogenesis after fertilization, might be a predisposing factor for meiotic errors. However, this hypothesis remains unproven. Here, we show that cytoplasmic size affects the functionality of the acentrosomal spindle. Artificially decreasing the cytoplasmic size in mouse oocytes allows the acentrosomal spindle poles to have a better-focused distribution of microtubule-organizing centers and to biorient chromosomes more efficiently, whereas enlargement of the cytoplasmic size has the opposite effects. Moreover, we found that the cytoplasmic size-dependent dilution of nuclear factors, including anaphase inhibitors that are preformed at the nuclear membrane, limits the spindle's capacity to prevent anaphase entry with misaligned chromosomes. The present study defines a large cytoplasmic volume as a cell-intrinsic feature linked to the error-prone nature of oocytes. This may represent a trade-off between meiotic fidelity and post-fertilization developmental competence.

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Teaser

Kyogoku and Kitajima show that cytoplasmic size affects the functionality of the acentrosomal spindle and the stringency of the spindle checkpoint in mouse oocytes, thus providing evidence that the large cytoplasmic size of oocytes is linked to error-prone chromosome segregation during female meiosis, which is a leading cause of aneuploidy.


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