Detection of P2 Precursors in the Sperm Cells of Infertile Patients Who Have Reduced Protamine P2 Levels

Objective: To determine whether the reduction in the protamine P2 content (increased P1/P2 ratio) reported in some infertile patients could result from incomplete processing of protamine P2 precursors.

Design: Analysis of samples with a marked reduction in the protamine P2 content using polyacrylamide gel electrophoresis and subsequent detection of protamine P2 precursors through Western blot analysis.

Setting: University departments and laboratories.

Patient(s): One hundred eighty-four men undergoing an evaluation for infertility.

Main Outcome Measure(s): Comparative Western blot analysis of nuclear sperm proteins using specific antibodies to protamine P1 and protamine P2.

Result(s): After selection of the samples with a marked reduction of the protamine P2 content and subsequent analysis by Western blot, a small proportion of putative P2 precursors was detected in most samples, whereas a significant increase was detected in two of them.

Conclusion(s): In some infertile men, a reduction in the protamine P2 content relative to protamine P1 (increased P1/P2 ratio) is detected concomitant with an increase in the amount of putative P2 precursors. This could represent the first report of incomplete processing of a nuclear sperm protein in humans.