The failure of human hamster fusion in the presence of anti-human izumo antibody clearly showed that Human izumo protein is essential for fertilization.

This study however has raised some new questions. The difference in fertilization capacities between wild type and Izumo +/- type was not clearly discussed. Also, the fact that ICSI of izumo -/- produces twice as many litters as did the izumo +/- type implicates the possible role of other proteins, the expression of which is affected by the allele. That is to say that the mutant knockout sperm might have up-regulated or down regulated the expression of this unknown protein which may have aided the fertilization process as indicated by the statistics. [Katie Winter] contraceptive vaccine targeting the sperm is very much in prospect but much work is yet to be accomplished. A CD46 gene knockout as tried by the author in an earlier study did not...
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