February 11th, 2014
The Y chromosome has long been considered a genetic marker for the male sex. But there might be more to learn about the chromosome. According to a new study published in the Science Journal (Article Link), only two genes on the chromosome are needed males–at least, male mice–to fertilize an egg.
It is an important finding as it can point to ways that otherwise infertile men may have children, revealed researchers. For example, men with azoospermia, a condition preventing healthy sperm production, could ultimately benefit from treatment based on these findings.
“We’re not trying to eliminate Y chromosomes with our work – or men, for that matter,” Monika Ward, a reproductive biologist at the University of Hawaii, told LiveScience.
She continued, “we’re just trying to understand how much of the Y chromosome is needed, and for what.”
Still, since the research was done on mice, it is still unclear how applicable to results will be for male infertility treatments.
Past research showed that when a gene called Sry was inserted into mouse embryos that are genetically female, it changed the gender fate of the mice.
“Even though they had two X chromosomes they developed into males,” explained Ward.
These mice developed testicles and produced sperm precursor cells known as spermatogonia; however, these cells did not develop into sperm cells.
In the new work, the researchers added other Y chromosome genes into such mice. The trial-and-error process eventually revealed a gene called Eif2s3y helped spermatogonia occasionally develop into spermatids, or immature sperm.
Revealing that although mice with Sry and Eif2s3y are male and can generate sex cells, they cannot normally have offspring.
To see if males with this pair of Y genes could reproduce with a little help, Ward and her colleagues injected these spermatids directly into egg cells. They found they could successfully fertilize the eggs with this method, resulting in viable offspring.
However, researchers ultimately emphasized that this does not mean that the rest of the Y chromosome is useless. The entire chromosome is probably needed for normal reproduction.
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