Tetraspanin-interacting protein IGSF8 is dispensable for mouse fertility

ObjectiveTo determine the physiological role of IGSF8 for fertility.DesignExperimental prospective study.SettingAcademic basic research laboratory.Animal(s)C57BL/6J and hybrid B6D2F1 mice, as well as Cd9 and Igsf8 knockout mice (C57BL/6J and 129/SvJ mix background), were used for this study.Intervention(s)None.Main Outcome Measure(s)In vitro and in vivo fertility tests of Igsf8 knockout mice.Result(s)Tetraspanin family member CD9 plays an important role in sperm-egg fusion. Recently, some researchers have reported that CD9 tightly associates with the immunoglobulin superfamily member IGSF8 on the egg surface and that IGSF8 is undetectable on the surface of Cd9-deficient eggs. This led us to hypothesize that IGSF8 participates in sperm-egg fusion together with CD9. To examine the physiological role of IGSF8 in vivo, we generated Igsf8-deficient mice by homologous recombination and examined the fertility of the females.Conclusion(s)The Igsf8-deficient female mice showed no fertilization defect in vitro or in vivo. We observed that Igsf8-deficient eggs retained the normal level and localization of CD9, resulting in normal microvilli formation, which indicates that IGSF8 is dispensable in fertility.