Researchers until now have studied only the Y chromosome in the search for the genetic underpinnings of low sperm counts. The study was published in the journal Nature Genetics. By default, we've traditionally thought of the X chromosome as sexually neutral or as a specialist in female characteristics. Our findings indicate that the X chromosome has a specialty in sperm production, much like the Y chromosome does. Males have one X and one Y sex chromosome.
Females have two X chromosomes, only one of which is active.
Unlike other stem cells, such as blood stem cells, which have been closely studied, sperm stem cells have remained largely unexplored. The researchers searched for genes that are active exclusively in sperm stem cells in mice. They came up with 25 genes, including 19 new ones, that were expressed exclusively in the sperm stem cells of mice. But they were stunned by the fact that only three of them were associated with the Y chromosome and 10 were linked to the X chromosome. Page said the finding had major implications for future research.