Scientists find first sex-determining “gene switch” in vertebrates

Scientists. Image source timeshighereducation

Scientists. Image source timeshighereducation

Japanese researchers on Friday in Tokyo confirmed that they have found, for the first time in vertebrates, a genetic switch that determines whether germ cells become sperm or eggs.

Toshiya Nishimura, the first author of the National Institute for Basic Biology, said the gene was named foxl3, and had been identified using a small fish called medaka or Japanese rice fish.

He said the finding had been reported in the U.S. Journal Science.

Nishimur said in medaka fish lacking functional foxl3 genes, a large number of sperm were found to form in the ovaries of females and they were functional and could produce normal offspring.

He said only a small number of eggs were formed at the same time.

“foxl3 gene works in a way that suppresses differentiation into sperm in the germ cells of females.

“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,’’ he said.
Nishimur said the study also showed that in these females lacking the function of foxl3, functional sperm could be obtained in a shorter period of time than in normal wild-type males.

Minoru Tanaka, Associate Professor of the National Institute for Basic Biology, who led the study, said an applied research into uses for aquaculture was already underway.

He said the results were believed to help researchers learn more about how the sexual fate of germ cells was determined during vertebrate development.

“While germ cells can become either sperm or eggs, nobody knows that in vertebrates, the germ cells have a switch mechanism to decide their own sperm or egg fate.

Tanaka said the result indicated that once the decision was made the germ cells have the ability to go all the way to the end.

He said it was of very large significance that the mechanism had been found.

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