Novel gene variants behind autism and mental retardation discovered

May 26th, 2010 - 3:39 pm ICT by ANI  

London, May 26 (ANI): Previously unknown mutations in the SHANK2 gene-partially responsible for linking nerve cells-could cause autism and mental impairment, researchers have found.

However, researchers working with Professor Gudrun Rappold, Director of the Department of Molecular Human Genetics at Heidelberg University Hospital, said that a single gene mutation is not always enough to trigger the illness.

In some cases, a certain threshold of mutation must be exceeded.

The researchers concluded that a correct inner structure of the nerve cell synapses is necessary to enable the normal development of language, social competence, and cognitive capacity.

Essential for the success of the project were the studies by the Heidelberg research team with the doctoral student Simone Berkel and collaboration with a Canadian research team headed by Steve Scherer.

The researchers focused their studies on the SHANK2 gene, which encodes a structural protein at the nerve cell synapses.

It is responsible for the mesh structure of the basic substance in the postsynapse.

Only when the postsynapse is properly structured can nerve impulses be correctly transmitted.

The researchers analysed the genetic material of a total of 396 patients with autism and 184 patients with mental retardation.

They found that different mutations in their SHANK2 genes in the area of individual base pairs, but also variants in the number of gene copies.

The mutations led to varying degrees of symptoms. None of the observed gene variants occurred in healthy control persons.

“Apparently an intact postsynaptic structure is especially important for the development of cognitive functions, language, and social competence,” Nature quoted Rappold as saying.

Some of the genetic mutations identified were new occurrences of mutations that were not inherited from the parents, but some of the mutations were also found in one parent.

Since there are also healthy carriers of gene variants, we must assume that a certain threshold of gene mutations must be exceeded for the disease to appear.

“Moreover, the same mutation can be present in an autistic patient with normal intelligence and in a mentally impaired patient,” said Rappold.

There is some overlap in the clinical symptoms of mental retardation and autism, which can now be explained by a common genetic cause.

The study has been published online in ‘Nature Genetics’. (ANI)

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