XX Chromosome found in Male Mice

(Sutton, 2007)

This article was taken of the ABC News website and was posted Tuesday august 21 2007.

A south Australian research team looking at the effect the Sox3 gene has one mouse has stumbled across a peculiar discovery: male mice with two X chromosomes. Characteristically, a mouse will have a single X chromosome and then either a single Y chromosome indicating it is a male, or an additional X chromosome indicating it is a female.  But now South Australian researchers have discovered a way of changing a single gene to create male mice without a Y-chromosome. The so-called "pseudo-male" mice look and act like other males, but they have two X-chromosomes, which is previously described as the normal female pattern. The litter of mice doctor Edwina Sutton, from the University of Adelaide, was working on were 80% male. However many of these had two X chromosomes, yet could not be told apart from those with a Y chromosome.

"What we know is that some of them are XX with extra copies of the brain gene, so they are the sex-reversed animals, and there are some that are actually XY," Dr Sutton said. She began experimenting with the mice to examine a brain gene known as Sox3. Differing levels of that gene in humans has been known to cause mental retardation. "We created a mouse that has increased amounts of this particular brain gene to try and then look really closely at the brain and work out what's occurring differently during their development," she said. "So they were chromosomally female, but they had extra amounts of this brain gene which had caused them to switch from being female to male." These mice however were unable to reproduce, which is a common outcome of abnormal breeding.  Dr Sutton believes she may have uncovered a link between the brain gene and the gene that determines whether an animal is male or female.

 What is believed to have been found is the original version of the maleness gene on the y chromosome.  This research may be able to help assist in the research into why 1 in 500 Australians are born with a genital defect.  An aspect that Dr Sutton has yet to pursue is whether the brain of the XX males is ‘hardwired’ to be male or female.

 

 

Sutton, D. E. (2007, August). Chromosome study reveals new insight into sexual genetics. ABC News , 2.