Nat Commun 2016 Jul 15;7:121982016/07/15

The cellular fusion of sperm and egg is the critical step in mammalian fertilization, and requires the interaction between IZUMO1 on the sperm plasma membrane and JUNO on the egg plasma membrane. However, the molecular mechanism by which JUNO specifically recognizes IZUMO1 and participates in the sperm-egg adhesion step remains to be fully understood.
Drs Ikawa, Satouh et al. have determined the essential region of the JUNO protein for the interaction with the IZUMO1 protein by structure-based prediction of an interactive surface with the IZUMO1 protein and a novel complementation assay using JUNO deleted eggs and supplementation of mutated JUNOs. In this study, a collaborative project with Drs Nureki’s group (Department of Biological Sciences, Graduate School of Science, The University of Tokyo), the mouse JUNO protein was crystallized, and the X-ray crystal structure of JUNO was determined at 2.3 Å resolution.
The newly established complementation system using CRISPR/Cas9-based gene-deletion is expected to be a framework in future studies for the elucidation of the general mechanisms of the sperm-egg interaction, and the result presented in this study improves a fundamental understanding of the mechanism of mammalian fertilization.

Press Release from Osaka University(PDF, Japanese)

Nat Commun web site