In 2002, a girl was born with a very peculiar quality. Despite physiologically being a healthy female, she is in possession of a Y chromosome. Pre-natal tests showed a healthy baby with 46 chromosomes, and the assumption was safely made that it would be a boy. Usually in females with the XY karyotype, the gonads are underdeveloped. So how does such a person develop to be a healthy female? A team led by Anna Biason-Lauber believes they have the answer.
In a report published by the team, they suggest that mutations in the gene CBX2 cause the switching off of a second gene, SRY, known to be critical in male sex development. This mutation would subsequently inhibit development of male sex organs, allowing for the healthy development of female ones, expressing a female phenotype.
As for further implications of this mutation, the team are reserving judgement. Studies on mice lacking the CBX2 gene have shown they are sterile, however Biason-Lauber and other researchers say it is too early to ascertain whether their patient will be fertile or not. This case is yet another example of how a single gene mutation can have profound effects on a person’s phenotype.
By Ryan Pickels
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Biason-Lauber, A et. al. Ovaries and Female Phenotype in a Girl with 46,XY Karyotype and Mutations in the Cbx2 Gene. American Journal of Human Genetics, 2009 April 8 [Epub ahead of print]
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BBC News (2005) Female chromosome has X factor – Available from: http://news.bbc.co.uk/1/hi/sci/tech/4355355.stm [14 April 2009]
BBC News (2005) Female chromosome has X factor – Available from: http://news.bbc.co.uk/1/hi/sci/tech/4355355.stm [14 April 2009]
