Prince Henry's Institute - Male to female sex reversal








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Media Release

10 June 2003

Scientists discover clue to male to female sex reversal

Scientists at Prince Henry’s Institute and Monash University have discovered how the male SRY gene fails to work in some patients with Swyer Syndrome, a socially traumatic intersex condition.

“We have no scientific explanation about the molecular basis of most intersex conditions. Our research, in collaboration with Professor David Jans at Monash University, not only helps to better understand the molecular basis of sex determination but also how things change in children with Swyer Syndrome,” Associate Professor Vincent Harley from Prince Henry’s Institute said.

“This research has the potential to improve the quality of life for people with Swyer Syndrome, whose risk of gonadal cancer is extremely high," said Tony Briffa, President of the Androgen Insensitivity Syndrome Support Group Australia .

Usually, boys’ sex chromosomes are XY and girls are XX. Intersex children are born with reproductive organs/genitalia that do not match their sex chromosomes - it affects about one in 4,000 Australians. In Swyer syndrome, individuals with male chromosomes develop as females, assisted by oestrogen treatment.

In a typical male, SRY needs to be transported into the nucleus of the cell where it switches on other genes required to make a testis. Dr Harley and colleagues showed that SRY from several Swyer patients did not move to its proper site of action within the cell. This failure may prove to be a common feature of Swyer Syndrome.

“If access to the nucleus is blocked by alterations in SRY, this can also result directly in an XY female,” Professor David Jans of Monash University said.

Importantly, this research published today in the US journal Proceedings of the National Academy of Sciences represents the first example of a human genetic variation arising from a gene change that restricts the movement of a protein, in this case SRY, into the nucleus of a cell.

In previous work published in the journal Science, Dr Harley showed that to switch genes on, DNA binding by SRY is essential for sex determination. “The current work builds on this research showing that efficient transport of SRY into the nucleus is also required for sex determination”, Dr Harley said.

For further information contact: Ian Muchamore (03) 9594 4049