Scientists have identified a gene which may play a role in a common defect affecting the genitalia of baby boys.
Hypospadias, which affects one in every 375 boys, is the result of incomplete development in the womb.
The latest research, in the journal Nature Genetics, found a gene which, when mutated, more than doubled the risk of the condition.
A UK researcher said it may help explain why hypospadias runs in families.
In boys who have the malformation, the opening of the urethral tube is not at the tip of the penis, but either further down the penis, at its base, or even further back, in the scrotum.
The normal solution is surgery at a young age, but even when corrected in this way, there can be long-term medical, psychological and sexual consequences.
The problem starts during the development of the sexual organs in the womb, and while there have been suggestions that exposure to environmental chemicals early in pregnancy may contribute, evidence to support this is not conclusive.
The only reliable clue has been the fact that the condition is more likely if a male relative has suffered it - pointing, at least in part, to a genetic origin.
Scientists had already found a gene playing a significant role in a more severe form of hypospadias, but the genetic mutations contributing to the more common, less severe version, have proved elusive.
Environmental factors 'trigger'
Researchers from King's College London, and Radboud University Njimegen Medical Centre in the Netherlands joined forces to carry out a large scale genome study.
This compared the genetic code of hundreds of boys, with and without the condition, to uncover genetic mutations which appeared more commonly in those with hypospadias.
They found that boys with a mutated version of the DGKK gene were 2.5 times more likely to be born with hypospadias.
Dr Jo Knight, from King's College London, said that this gene was found on the X-chromosome, which in boys can only be inherited from the mother.
She said: "We still don't know exactly how this causes the condition, so there is more research to be done to look at other genes and environmental factors that might trigger the malformation."
Professor Ieuan Hughes, a specialist in paediatrics at Cambridge University, said that it was likely that a number of genes acting together would be responsible for the condition.
He said: "People have been struggling for years to find out what the genes are that cause the common form of hypospadias, so this is an important study.
"However, it is certainly not clear how this gene might be creating the problem, and further work will be needed to confirm its involvement."
He said that although it had been suggested that environmental factors were contributing to hypospadias, he was "not quite convinced" that this was the case.
The normal solution is surgery at a young age, but even when corrected in this way, there can be long-term medical, psychological and sexual consequences.
The problem starts during the development of the sexual organs in the womb, and while there have been suggestions that exposure to environmental chemicals early in pregnancy may contribute, evidence to support this is not conclusive.
The only reliable clue has been the fact that the condition is more likely if a male relative has suffered it - pointing, at least in part, to a genetic origin.
Scientists had already found a gene playing a significant role in a more severe form of hypospadias, but the genetic mutations contributing to the more common, less severe version, have proved elusive.
Environmental factors 'trigger'
Researchers from King's College London, and Radboud University Njimegen Medical Centre in the Netherlands joined forces to carry out a large scale genome study.
This compared the genetic code of hundreds of boys, with and without the condition, to uncover genetic mutations which appeared more commonly in those with hypospadias.
They found that boys with a mutated version of the DGKK gene were 2.5 times more likely to be born with hypospadias.
Dr Jo Knight, from King's College London, said that this gene was found on the X-chromosome, which in boys can only be inherited from the mother.
She said: "We still don't know exactly how this causes the condition, so there is more research to be done to look at other genes and environmental factors that might trigger the malformation."
Professor Ieuan Hughes, a specialist in paediatrics at Cambridge University, said that it was likely that a number of genes acting together would be responsible for the condition.
He said: "People have been struggling for years to find out what the genes are that cause the common form of hypospadias, so this is an important study.
"However, it is certainly not clear how this gene might be creating the problem, and further work will be needed to confirm its involvement."
He said that although it had been suggested that environmental factors were contributing to hypospadias, he was "not quite convinced" that this was the case.
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