1. 1Department of Cell Biology, Faculty of Medicine and Nursing, University of the Basque Country, Leioa, Bizkaia, Spain
2. 2Department of Physiology, Faculty of Medicine and Nursing, University of the Basque Country, Leioa, Bizkaia, Spain
3. 3Human Reproduction Unit, Cruces Hospital, Biocruces, University of the Basque Country, Leioa, Bizkaia, Spain
4. 4IVI (Instituto Valenciano de Infertilidad), Bilbao, Bizkaia, Spain