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Clusterin is a protein encoded by the CLU gene and it is expressed in most human tissue types, especially when under stress, where it helps protects cells.
A team of Egyptian researchers led by Taymour Mostafa of the Andrology and Sexology Department at Cairo University found that the expression of CLU is much higher in the spermatozoa of infertile men.
Mostafa and his colleagues examined semen samples from 124 men, some of whom had reduced sperm motility, abnormally shaped sperm cells or low sperm counts.
They found significantly elevated levels of clusterin protein and its mRNA precursor in men with dysfunctional sperm compared to men with healthy spermatozoa. They also found that clusterin levels were closely correlated with sperm quality, such that the higher the expression of CLU, the lower the sperm count and less motile the cells.
Increased clusterin expression was also associated with increased DNA fragmentation in the spermatozoa of infertile men.
Clusterin normally prevents proteins from precipitating inside sperm cells and stops abnormal sperm cells from clumping together. The new findings suggest that increased expression of the protein may be indicative of spermatozoa under stress, and could be a useful marker for low quality sperm.
Mostafa says he and his colleagues have completed a study on the effect of cell phone usage on clusterin expression in spermatozoa, which they have just submitted for publication.