The clinical utility of the protamine 1/protamine 2 ratio in sperm

During spermiogenesis,human sperm undergo a dramatic reorganization of the chromatin in which canonical histones are replaced by two types of protamines,protamine 1 (p1) and protamine (p2). p1 and p2 are expressed approximately at a 1:1 ratio in healthy men. alteration of this ratio is associated with male infertility. patients with an abnormal p1/p2 ratio generally exhibit diminished semen quality,lower fertilization ability,and lower pregnancy rates when undergoing in vitro fertilization. many studies have reported an elevated incidence of abnormal p1/p2 ratios in infertile men compared to fertile controls,and have evaluated the relationship between infertility and abnormal protamination; however,no prospective study has investigated the normal range of the p1/p2 ratio in men from the general population. here,we report a p1/p2 reference range of 0.54 to 1.43 in a fertile,normozoospermic population. this rather wide normal range of p1/p2 led us to the conclusion that abnormal protamination is more likely indicative of other perturbations during spermatogenesis than the underlying mechanism to cause infertility. alternatively,protamine expression may act as a checkpoint mechanism and thus be indirectly related to semen quality. © 2011 bentham science publishers ltd.