Sperm antigen MSH27 participates in sperm-egg membrane fusion

A monoclonal antibody (mAb), MSH27 has been selected from an mAb library wh ich has been prepared with separated mouse sperm heads as antigens. Three a spects of evidence indicated that the MSH27 antigen was involved in the pro cess of sperm-egg membrane fusion. After the acrosome reaction, the antigen was located at sperm equatorial segment and in postacrosomal area, where, it was widely accepted, the sperm-egg membrane fusion initially occurred. I n in vitro fertilization, the MSH27 antibody could decrease the index of sp erm-egg membrane fusion, but made no effects on sperm approaching and bindi ng to the plasma membrane of eggs. The inhibition showed an antibody concen tration-dependent manner, with a rate decrease of 90% at 600 mu g/mL immuno -globulin IgM, Furthermore, the antigen was able to affect the sperm-egg me mbrane fusion directly. The fusion index was obviously reduced after the zo na-free eggs were exposed to the antigen purified by immune-affinity chroma tography. These, all together, demonstrated that the MSH27 antigen played a n important role in sperm-egg membrane fusion.