foxl3 gene decides sperm-egg fate in medaka fish, says study

Germ cells can turn into either sperm or eggs in the body. Now, a new study conducted on fish has given researchers reasons to believe that there’s a genetic switch that determines the fate of germ cells. The findings of the said study might give scientists the opportunity of establishing how a similar process works even in the humans.

During the study, researchers examined Oryzias latipes or Medaka, a fish species more commonly referred to as the Japanese rice fish. They found that the reproductive systems of this fish required a gene called foxl3 for functioning properly.

Researchers removed the foxl3 gene from some female fish and found that those creatures stopped developing eggs in their ovaries; instead, they had sperm cells. Surprisingly, those sperm cells, according to the scientists, were normal and potent enough to produce offspring. In spite of producing sperm cells within their ovaries, the female fish looked normal from the exterior; the appearance of their genitalia also didn’t change.

Minoru Tanaka, a representative of Japan’s National Institute of Natural Sciences, said that while it was a known fact that germ cells could either become eggs or sperm, it was not known that germs cells showcase a switch mechanism in vertebrates that decide whether they will turn into eggs or sperm.

According to Tanaka, this new study reveals that once the choice is made, germ cells are capable of going “all the way”. He added that the discovery of this mechanism marks a very significant episode.

Both females and males have germ cells in their body; Normally, these cells either form sperm cells or eggs in one’s body. To date, no one knew about any genetic switch that is capable of transforming germ cells’ fate. Before the discovery of this mechanism, biologists thought germs cells are passive in nature and are strictly regulated by other somatic cells.

Reproductive biologist Toshiya Nishimura, a member of the research team conducting the study, said that he has been greatly surprised to find that formation of sperm cell is possible in the same environment that enables formation of eggs. He added that it was never thought that sexual switch present in germ cells can be independent of the sex of the body they belong to. The entire study can be read on Science Express, the online version of the widely read journal Science.