Reduced fertilization after ICSI and abnormal phospholipase C zeta presence in spermatozoa from the wobbler mouse

Failed fertilization after intracytoplasmic sperm injection (ICSI) can be due to a reduced oocyte-activation capacity caused by reduced concentrations and abnormal localization of the oocyte-activation factor phospholipase C (PLC) zeta. Patients with this condition can be helped to conceive by artificial activation of oocytes after ICSI with calcium ionophore (assisted oocyte activation; AOA). However some concern still exists about this approach. Mouse models could help to identify potential oocyte-activation strategies and evaluate their safety. In this study, the fertilizing capacity of wobbler sperm cells was tested and the efficiency of AOA with two exposures to ionomycin to restore fertilization and embryo development was studied. The quality of the obtained blastocysts was assessed and embryo transfer was performed to evaluate post-implantation development. The presence of PLCzeta in the spermatozoa and testis of the wobbler mouse was evaluated by PLCzeta immunostaining and quantitative reverse-transcription polymerase chain reaction. Sperm cells from wobbler mice had reduced fertilizing capacity and abnormalities in PLCzeta localization, but not in its expression. Artificially activating the oocytes restored fertilization and embryo development. Therefore, the wobbler mouse can be a model for failed fertilization after ICSI to study PLCzeta dynamics and aid in optimization of the AOA method.A small percentage of patients experience failed fertilization after intracytoplasmic sperm injection (ICSI), which is mainly caused by insufficient oocyte activation. Men with a rare disorder, globozoospermia often face failed fertilization due to a reduced oocyte-activating capacity of the sperm cells caused by decreased concentrations of the oocyte-activating factor phospholipase C zeta (PLCζ). Patients can be helped to conceive by artificially activating the oocytes after ICSI with calcium ionophore (assisted oocyte activation; AOA). However, concerns exist about this approach. Therefore optimization of AOA would be of great benefit, in addition to a proper evaluation of preimplantation, but more importantly post-implantation development. Mouse models could help to identify potential oocyte activation strategies and allow evaluation of the safety of such methods. This study focused on the wobbler mouse, which suffers from motor neuron disease and male infertility. Fertilizing capacity of wobbler sperm cells was tested and efficiency of AOA with two exposures to ionomycin to restore fertilization and embryo development was studied. Quality of obtained blastocysts was assessed and embryo transfer was performed to evaluate post-implantation development. The presence of PLCζ in the spermatozoa and testis of the wobbler mouse was evaluated by PLCζ immunostaining and quantitative reverse-transcription polymerase chain reaction. Sperm cells from wobbler mice had reduced fertilizing capacity and abnormalities in presence of PLCζ. Artificially activating the oocytes restored fertilization and blastocysts could be obtained. These findings suggest the wobbler mouse could be used as a model to study failed fertilization after ICSI and to optimize the AOA method.