Effect of protamine-2 deficiency on ICSI outcome

During spermiogenesis, histones are replaced by protamines (P1 and P2), resulting in sperm chromatin condensation followed by a halt to gene expression in haploid spermatids and spermatozoa. As a consequence, protamine deficiency and aberrant P1/P2 ratio have a profound effect on both fertilization and embryo development. However, reports on the effect of the P1/P2 ratio on fertilization and embryo development after intracytoplasmic sperm injection (ICSI) are contradictory between human and animal studies. The question that still remains to be elucidated is which type of protamine deficiency is most common among protamine deficient samples. The present study has a direct bearing on this issue investigating the correlation of the P1/P2 ratio with protamine deficiency, fertilization, embryo quality and embryo development in ICSI patients. This study was carried out on 71 patients. Chromomycin A3 (CMA3) staining was used to determine protamine deficiency. Since this procedure does not indicate the type of protamine deficiency, the P1/P2 ratio was evaluated by nuclear protein extraction, acetic acid urea polyacrylamide gel electrophoresis and analysis of protein bands with software. Polyclonal anti-P1 and anti-P2 antibodies were used to confirm P1 and P2 presence. Results show a negative significant correlation of fertilization rate with protamine deficiency and P1/P2 ratio. No significant correlation was observed between protamine deficiency and P1/P2 ratio. Therefore, it can be concluded that altered P1/P2 ratio effects fertilization rate and embryo quality which subsequently may affect implantation and pregnancy outcome.