Development and analysis of gene-manipulated mouse lines as infertility animal model Construction of rat genetic maps and rat-mouse-human comparative genetic maps

Institute of Laboratory Animals, Graduate School of Medicine, Kyoto University Many factors have been reported to be critical in the mechanism of fertilization. However, recent gene knockout approaches have revealed that many of these factors were largely dispensable in gene-manipulated animals. However, some factors emerged as essential factors from gene-manipulated animals [1]. By identifying an antigen, recognize by a monoclonal antibody, we found a novel immunoglobulin superfamily protein as a mouse fusion related protein on spermatozoa. We produced Izumo1-/mouse line and found the mice were healthy but males were sterile. They produced normal-looking spermatozoa that bound to and penetrated the zona pellucida but were incapable of fusing with eggs [2]. CD9 on egg was also found essential for fusion serendipitously. IZUMO1 is hidden under the plasma membrane and is transferred to sperm surface by acrosome reaction. We generated a transgenic mouse line and the dynamic movement of a fusion-related protein IZUMO1 upon acrosome reaction and during sperm-egg fusion was revealed [3].