Changes in protamine 1 distribution in human sperm nucleus during in vitro sperm-oocyte interaction: an immunoelectron microscopic study.
OBJECTIVE: To determine whether the process of sperm nuclear destabilization would begin before sperm-oocyte fusion in humans. DESIGN: Changes in the distribution of human protamine 1 were investigated in human spermatozoa from the ejaculate, in spermatozoa selected by swim-up or Percoll techniques, and in spermatozoa bound to zona pellucida (ZP) from oocytes that failed to fertilize in an IVF program. SETTING: Center for Infertility and Assisted Reproductive Technology, and university departments. PATIENT(S): Fifteen couples undergoing an IVF program. INTERVENTION(S): Women underwent a similar superovulation induction protocol that consisted of GnRH agonist associated with hMG. MAIN OUTCOME MEASURE(S): Comparative immunoelectron microscopic study of sperm nucleus labeling with an anti-human protamine 1 specific protamine monoclonal antibody. RESULT(S): After selection by swim-up or by Percoll, spermatozoa show a significantly lower nuclear labeling than in the ejaculate. After binding to the ZP, labeling increases, more in spermatozoa selected by swim-up than by Percoll, but, after Percoll selection, labeling in zona-bound spermatozoa is lower than in the ejaculate. CONCLUSION(S): In humans sperm binding to the ZP induces differences in the accessibility of the anti-human protamine 1 antibody, which are consistent with structural rearrangements of the DNA-nucleoproteins complex. These modifications must be a prelude to sperm decondensation, protamines replacement by histones, and subsequent reactivation of the sperm genome in the oocyte.