TEAMS of French and Japanese researchers have independently found that a cell
surface protein called CD9 is essential for normal sperm and egg fusion. The
researchers were originally interested in CD9 because it plays a role in cell
adhesion, and tumours with low amounts of the protein seem more likely to
spread.
So both Claude Boucheix of INSERM in Villejuif, France, and Eisuke Mekada at
the National Institute of Infectious Diseases in Tokyo bred mice that lacked the
gene for CD9 (Science, vol 287, p 319). The mice appeared normal but
had reduced fertility, and further studies showed that the sperm and egg had not
fused. 鈥淲e had no idea that the CD9 knockout might affect fertility,鈥� says
Boucheix.