Current hypothesis of oocyte activation in mammals —Another oocyte activation factor or activation mechanism strikes back?—

JMOR, 41(2) 53-67, 2024

Shunsuke Takarabe¹# Hibiki Sugita¹# Atsuko Kageyama² Yui Kawata² Junya Ito^1,2* Naomi Kashiwazaki^1,2

¹Laboratory of Animal Reproduction, Graduate School of Veterinary Medicine, Azabu University, 1-17-71 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252-5201, Japan, ²School of Veterinary Medicine, Azabu University, 1-17-71 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252-5201, Japan

When sperm penetrates into the oocyte during mammalian fertilization, there are repetitive increases in calcium ions (called calcium oscillations). Since these calcium oscillations are only observed during mammalian fertilization, including in humans and mice, they are considered to be important in oocyte activation and subsequent embryonic development. It has been revealed that sperm-specific phospholipase C (PLC), known as PLC zeta (PLCζ), functions as an oocyte activation factor, controlling calcium oscillations and oocyte activation. However, there are still unresolved aspects, such as the fact that Plcz1 gene-deficient male mice do not show the phenotype of infertility. In this review, based on previous literature, we outline the role of PLCζ in calcium oscillations and oocyte activation and discuss the possibility of the existence of other oocyte activation factors and mechanisms besides PLCζ as well as their potential applications to human reproductive medicine.

Keywords: Fertilization Calcium oscillations Oocyte activation Phospholipase C ζ

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Vol.41 No.2