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Autism and Mental Impairment Genetically Conditioned
New discovered gene mutations
seem to be responsible for autism
and mental impairment; © SXC
Researchers have discovered previously unknown mutations in autistic and mentally impaired patients in what is known as the SHANK2 gene, a gene that is partially responsible for linking nerve cells.
The researchers working with Gudrun Rappold, Director of the Department of Molecular Human Genetics at Heidelberg University Hospital, conclude from their results that a correct inner structure of the nerve cell synapses is necessary to enable the normal development of language, social competence, and cognitive capacity.
Autism and mental retardation can occur together but also independently of one another and are determined to a great extent by hereditary factors. Some of the responsible genes have already been identified but the precise genetic mechanisms have not yet been explained.
Rappold and her team 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 analyzed the genetic material of a total of 396 patients with autism and 184 patients with mental retardation.
They found 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," explained Rappold.
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.
REHACARE.de; Source: University Hospital Heidelberg
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( Source: REHACARE.de )