PLCζ sequence, protein levels, and distribution in human sperm do not correlate with semen characteristics and fertilization rates after ICSI

International audiencePurpose Sperm-borne PLCζ protein induces Ca 2+ oscillations in the oocyte and is believed to play a major role during oocyte activation. However, its implication in fertilization failure following ICSI is still debated. We analyzed PLCζ gene sequence, protein expression level, and localization in both patients with previous failed fertilization by ICSI and sperm donors with proven fertility in order to assess the association of PLCζ with both sperm characteristics and ability to fertilize. Methods Semen from 15 patients and 13 sperm donors with proven fertility was included in the study. Analysis of the PLCζ gene sequence, protein expression through Western blot, and protein localization by immunofluorescence were performed. Results Two patients with total fertilization failure presented mutations in heterozygosis in the PLCζ gene. Comparison with donor sample sequences displayed comparable SNP al-lele frequency. Distribution pattern of PLCζ did not vary significantly between donor and patient samples. Levels of PLCζ protein in sperm cells showed an interindividual variability both in patient and donor samples. Several SNPs previously reported in infertile patients were also present in fertile men. Conclusion Failed fertilization occurs even when levels and distribution of PLCζ protein are within normal range. PLCζ seems to be a necessary but not sufficient factor in determining the molecular pathway involved in oocyte activation

PLCζ disruption with complete fertilization failure in normozoospermia

Purpose: Intracytoplasmic sperm injection (ICSI) is widely used to achieve fertilization in the presence of severe male factor, resulting in high fertilization rates. Nevertheless, 1–3 % of couples experience complete fertilization failure after ICSI.When a male factor is identified, assisted oocyte activation (AOA) can help overcome fertilization failures. The objective of this study is to describe a case of repeated complete fertilization failures after ICSI with donor oocytes, and to investigate the molecular and functional aspects of phospholipase C zeta (PLCζ) protein in the patient semen. Methods: The patient was a normozoospermic male who had previously fathered, through natural conception, four children by a different partner. Molecular and functional analysis of sperm-specific PLCζ in the patient and control samples by means of gene sequencing, immunocytochemistry, Western blot, mouse oocyte activation test (MOAT), and mouse oocyte calcium analysis (MOCA) were used. Results: PLCζ expression levels and distribution were significantly disrupted, although MOAT and MOCA did not indicate a decrease in activation ability. Conclusions: Normozoospermic males can have disrupted expression and distribution of PLCζ, and reduced activation ability after ICSI in human oocytes, despite their normal activation potential in functional testing using mouse oocytes. Discrepancy among molecular and functional data might exist, as mutations in the gene sequence may not be the only cause of alteration in PLCζ protein related to activation failures