Cortical Granule Distribution and Expression Pattern of Genes Regulating Cellular Component Size, Morphogenesis, and Potential to Differentiation are Related to Oocyte Developmental Competence and Maturational Capacity In Vivo and In Vitro.

Magdalena Kulus,Małgorzata Józkowiak,Mariusz T Skowroński,Lisa Moncrieff,Ievgeniia Kocherova,Piotr Celichowski,Bartosz Kempisty,Paul Mozdziak,Jakub Kulus,Aneta Konwerska,Paweł Antosik,Sylwia Ciesiółka,Dorota Bukowska,Wiesława Kranc,Maria Wieczorkiewicz,J M Jaśkowski ,Patrycja Sujka‐Kordowska ,Hanna Piotrowska‐Kempisty ,Šárka Hanuláková ,Marie Machatková ,Michal Ješeta

doi:10.3390/genes11070815

Abstract

Polyspermia is an adverse phenomenon during mammalian fertilization when more than one sperm fuses with a single oocyte. The egg cell is prepared to prevent polyspermia by, among other ways, producing cortical granules (CGs), which are specialized intracellular structures containing enzymes that aim to harden the zona pellucida and block the fusion of subsequent sperm. This work focused on exploring the expression profile of genes that may be associated with cortical reactions, and evaluated the distribution of CGs in immature oocytes and the peripheral density of CGs in mature oocytes. Oocytes were isolated and then processed for in vitro maturation (IVM). Transcriptomic analysis of genes belonging to five ontological groups has been conducted. Six genes showed increased expression after IVM (ARHGEF2, MAP1B, CXCL12, FN1, DAB2, and SOX9), while the majority of genes decreased expression after IVM. Using CG distribution analysis in immature oocytes, movement towards the cortical zone of the oocyte during meiotic competence acquisition was observed. CGs peripheral density decreased with the rise in meiotic competence during the IVM process. The current results reveal important new insights into the in vitro maturation of oocytes. Our results may serve as a basis for further studies to investigate the cortical reaction of oocytes.

Highlights

Knowledge of molecular mechanisms that protect oocytes against polyspermia is important both in basic research and in the future of human medicine, as well as to improve the efficiency of in vitro production (IVP) in animals
index of cortical granules distribution (Icgd) in oocytes with lower meiotic competence (1.48 ± 0.31) shows a tendency of oocytes with higher meiotic competence the peripheral concentration of cortical granules (CGs) was more than two-fold central orientation of CGs in the cytoplasm of oocytes derived from SF (Figure 1)
We have evaluated the distribution of CGs in immature oocytes, both from small and medium follicles

Summary

Introduction

Knowledge of molecular mechanisms that protect oocytes against polyspermia is important both in basic research and in the future of human medicine, as well as to improve the efficiency of in vitro production (IVP) in animals. It is known that there are two mechanisms that prevent more than one sperm from entering the oocyte [1]. The first barrier works at the level of the plasma membrane of the oocyte, which is depolarized after sperm fusion and excretion of the egg’s sperm receptor Folr. The cortical reaction itself is a well-known phenomenon, but its molecular background is not fully explained. There have been reports related to the transport of CGs from the cytoplasmic center to the periphery of the cell [5,6], docking to the plasma membrane [6] or resulting in exocytosis of CGs [7,8,9], but not fully illustrating these processes. It is very significant to know the expression profile of the genes involved in the cortical reaction, which, in turn, will expand the possibilities of detailed research

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