Scientists have identified a "genetic switch" that determines if a germ cell becomes sperm or eggs.
The gene, dubbed foxl3, was pinpointed in small medaka fish, the National Institutes of Natural Sciences reported. Without the functionality of this gene, medaka females produce sperm in their ovaries. These sperm function normally, and produce healthy offspring. The researchers found the foxl3 gene works in the germ cells of females to "suppress differentiation of sperm."
"In spite of the environment surrounding the germ cells being female, the fact that functional sperm has been made surprised me greatly. That this sexual switch present in the Germ Cells is independent of the body's sex is an entirely new finding," said researcher Toshiya Nishimura.
Females that lack functional foxl3 genes appear completely female, but a large number of sperm can be found in the ovaries along with a smaller number of eggs. The recent study found females lacking the function of foxl3 functional sperm are easier to obtain that functioning males, which could have implications for aquaculture.
"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. 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," said associate Professor Minoru Tanaka.
The findings were published in a recent edition of the journal Science Express.
