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[KARACHI] An international team of researchers has identified three genes that are linked to stammering or stuttering, a speech defect that affects millions worldwide.

The three genes lie in a single chromosome, researchers from the Centre for Excellence in Molecular Biology (CEMB), University of Punjab, Lahore, and the National Institute on Deafness and Other Communication Disorders (NIDCD) under the US National Institutes of Health (NIH) report in the New England Journal of Medicine this month (10 February).

NIH says the cause of stuttering, which affects one per cent of adults worldwide, has baffled scientists for hundreds of years and its study is the first to pinpoint the genetic links. Current therapies focus on reducing anxiety, regulating breathing and rate of speech, and using electronic devices to help improve fluency.

The study on 219 volunteers from Pakistan and 546 from the US and UK first identified a gene on one of the chromosomes — 46 tiny, thread-like structures inside a cell's nucleus that carry genetic information — linked to stuttering. This gene, involved in daily break-down and recycling of cell wastes, contained four mutations in stutterers and the team identified these mutations or changes that are linked to stuttering.

They next identified two more genes which were also linked to the speech defect.

Two of the three genes have already been linked to disorders of joints, skeleton, heart, liver, and brain development due to changes in cell functioning.

With the discovery of mutations in the third gene, which is closely related to the other two, "we have understood the genetic basis of stuttering; and also pinpointed its biochemical pathway", Sheikh Riazuddin, professor at CEMB and one of the authors of the paper, told SciDev.Net.

The researchers have estimated that about nine per cent of stammers around the world may have mutations in at least one of these three genes.

The long-term goal of the researchers is to look for a potential drug for patients who cannot be treated with existing psychological therapies, says Dennis Drayna, the lead author of the study and a geneticist at NIDCD.


New England Journal of Medicine doi 10.1056/NEJMoa0902630 (2010)

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