Disrupted gene causes severe mental retardation

May 11th, 2009 - 12:01 pm ICT by IANS  

Washington, May 11 (IANS) A disrupted gene triggers severe mental retardation known as the Angelman Syndrome, according to a new study.
The syndrome is one of a small family of single gene, autism-related, neuro-developmental disorders.

The study by Duke University Medical Centre (DUMC) and University of North Carolina (UNC) researchers identified the gene as UBE3A in mice, which helps neurons form and connect with other neurons for storing sensory information.

Angelman Syndrome develops typically when children are between one and two years old. This is the period when the cortex, the sheet of convoluted folds at the brain surface, undergoes profound rearrangements driven by sensory experiences.

The experience of seeing reorganises the visual cortex, for example, during the same period when symptoms are becoming obvious in Angelman Syndrome.

“We wanted to look at an animal model to learn if this experience-dependent reorganisation of the cortex was abnormal in animals that were missing the gene,” said Michael Ehlers, Duke professor of neurobiology and co-senior author of the study.

The authors found that brains cells in Angelman Syndrome mice lacked the ability to appropriately strengthen or weaken in the cortex, an area of the brain important for cognitive abilities, said a DUMC release.

“By strengthening and weakening appropriate connections between brain cells, a process termed synaptic plasticity, we are able to constantly learn and adapt to an ever-changing environment.” Ben Philpot, UNC professor in Cell and Molecular Physiology and co-senior author of the study.

Afflicted children appear to respond normally to stimuli during their first year but around 12-18 months, they start missing milestones of cognitive development and language, typically learning only a two to three words over their lifetime.

These findings were published in Nature Neuroscience.

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