The (UK) Telegraph reports:

"The simple procedure causes the modified mice to reject the advances of their male counterparts and attempt to mate with fellow females.

"Researchers found that disabling the FucM gene – which influences the levels of oestrogen to which the brain is exposed – caused the mice to behave as if they were male as they grew up.

[Skip]

"By deleting the enzyme-producing gene, the scientists believe that they caused the female mice to be exposed to extra oestrogen, by preventing their brains from filtering out the hormone.

"While oestrogen masculinises the brain in mice, it does not have the same effect on humans.

"Professor Park now hopes to investigate whether the enzyme produced by the gene – fucose mutarotase – has any influence on human sexuality, but conceded that it may be 'very difficult' to find willing volunteers."

The New Scientist explains in slightly more detail:

"Female mice lacking the gene avoided the advances of males, stopped sniffing male urine and attempted to mate with other females, though their ability to have pups was unaffected. (BMC Genetics, DOI: 10.1186/1471-2156-11-62)."

The report notes that the "hormone masculinises the brain in mice – though not in people."