Daily Yomiuri Online reports that the team led by Asato Kuroiwa, an associate professor at the university specializing in studies of the sex-determining mechanism and sex chromosome evolution in mammals, announced its findings in an electronic edition of the journal Proceedings of the National Academy of Sciences of the United States of America, earlier this month.

In mammals, a gene called hemogen plays a role in the development of cells that later produce blood. The researchers found that cHEMGN, the chicken homologue of hemogen, also plays a role in making an embryonic chicken's gonads develop into testes.

The team used a retrovirus to increase the presence of cHEMGN in a chromosomally female egg, and found that the gonads, which were set to develop into ovaries, instead became testes. Using the method, the team turned 33 genetically female eggs into genetically male eggs.

If a way can be found to do the reverse - turning a male egg into a female egg by suspending the activity of the gene - it could contribute to an improvement in the productivity of chicken egg farms, according to the team.

"The research will help promote research on sex differentiation, not only of birds, but also of mammals and so on," Tsutomu Ogata, professor at Hamamatsu University School of Medicine, said.