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24 November 2018 Mouse oocytes connect with granulosa cells by fusing with cell membranes and form a large complex during follicle development
Kouji Komatsu, Satoru Masubuchi
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Proper development and maturation of oocytes requires interaction with granulosa cells. Previous reports have indicated that mammalian oocytes connect with cumulus cells through gap junctions at the tip of transzonal projections that extend from the cells. Although the gap junctions between oocytes and transzonal projections provide a pathway through which small molecules (<1 kDa) can travel, it is unclear how molecules >1 kDa are transported between the oocytes and cumulus cells. In this study, we presented new connections between oocytes and granulosa cells. The green fluorescein protein Aequorea coerulescens green fluorescein protein (AcGFP1) localizing in oocyte cell membrane, 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanine perchlorate and dextran conjugates (10,000 MW) injected into the oocytes, which were unable to pass through gap junctions, were diffused from the oocytes into the surrounding granulosa cells through these connections. These connect an oocyte to the surrounding cumulus and granulosa cells by fusing with the cell membranes and forming a large complex during follicle development. Furthermore, we show two characteristics of these connections during follicle development—the localization of growth and differentiation factor-9 within the connections and the dynamics of the connections at ovulation. This article presents for the first time that mammalian oocytes directly connect to granulosa cells by fusing with the cell membrane, similar to that in Drosophila.

Summary Sentence

An oocyte connects with surrounding granulosa cells by fusing with cell membranes. These connections are important for transportation between the oocyte and granulosa cells and for ovulation.

© The Author(s) 2018. Published by Oxford University Press on behalf of Society for the Study of Reproduction. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (, which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact
Kouji Komatsu and Satoru Masubuchi "Mouse oocytes connect with granulosa cells by fusing with cell membranes and form a large complex during follicle development," Biology of Reproduction 99(3), 527-535, (24 November 2018).
Received: 19 November 2017; Accepted: 23 March 2018; Published: 24 November 2018
cumulus cell
follicular development
granulosa cell
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