Chuck Bednar for redOrbit.com – @BednarChuck
A team of Japanese scientists have discovered the genetic switch that determines whether the reproductive precursor cells known as germ cells go on to develop into sperm or eggs, according to new research published last week in the journal Science.
As part of their study, Dr. Toshiya Nishimura and Minoru Tanaka from the National Institute for Basic Biology’s Laboratory of Molecular Genetics for Reproduction and their colleagues studied a small fish known as the medaka or Japanese rice fish, the Press Trust of India (PTI) said.
They discovered that the gene known as foxl3 is responsible for determining the type of reproductive cell a germ cell will become in females, Reuters added. When a female fish does not have functional foxl3 genes, its body appearance will remain completely female, but it will produce higher quantities of sperm cells and fewer eggs in the ovaries.
A similar mechanism may also be present in humans
The foxl3 gene is primarily active in a female’s germ cells to prevent them from becoming sperm cells instead of egg cells in the ovaries, the study authors explained. When they inactivated the gene in female fish, it caused germ cells to become sperm cells instead of egg cells.
Those sperm cells functioned normally, they added, successfully fertilizing eggs and producing healthy offspring. While the research team noted that people do not possess this particular gene, they believe it is likely that a similar genetic switch mechanism also exists in humans.
“Our result indicates that once the decision is made, the germ cells have the ability to go all the way to the end. I believe it is of very large significance that this mechanism has been found,” Tanaka told PTI. “While germ cells can become either sperm or eggs, nobody knew that in vertebrates the germ cells have a switch mechanism to decide their own sperm or egg fate.”
“In spite of the environment surrounding the germ cells being female, the fact that functional sperm has been made surprised me greatly,” added Dr. Nishimura, a reproductive biologist at the National Institute for Basic Biology. “That this sexual switch present in the germ cells is independent of the body’s sex is an entirely new finding.”
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