Scientists Decode Molecular Details Of Genetic Defect That Causes Autism

Using an animal model, brain researchers in Göttingen have examined the effects of mutations that cause autism in humans. These are mutations in the genes which carry the building instructions for proteins in the neuroligin family. The study published in the scientific journal Neuron (September 21, 2006) shows that neuroligins ensure that signal transmission between nerve cells functions. In the brain of genetically altered mice without neuroligins, the contact points at which the nerve cells communicate, the synapses, do not mature. The researchers assume that similar malfunctions are experienced by autistic patients.

Autism is one of the most common psychiatric illnesses. Around 0.5 percent of all young children have a syndrome belonging to the "autistic spectrum". The main symptoms of this developmental malfunction are delayed language development or no language development at all, disturbed social behaviour and repetitive behaviour patterns. In many patients, the disease is accompanied by mental disability. Autistic individuals exhibiting high intelligence or outstanding skills in a particular area, called "savants", such as the main character in the film "Rain Man", are rare.

Even up to the middle of the last century, exceptionally cold emotional behaviour on the part of the mother was given as the cause for autism. However, the "refrigerator mom" theory has now been refuted. The belief widely held in the 1990s that the measles, mumps and rubella vaccine could cause autism in small children has no scientific basis at all. Today, it is clear that genetic factors are the major cause of the illness. Studies of identical twins have been particularly convincing in demonstrating this fact - the probability that the identical twin of an autistic person will also be autistic lies between 80 and 95 percent.

In 2003, French geneticist Thomas Bourgeron showed in an investigation of families with several autistic children that mutations in the two genes NLGN3 and NLGN4X had lead to a complete loss of function in the genes and triggered autism in affected patients. Bourgeron’s work sent a shock wave through neuro-scientific institutes worldwide, as the a NLGN genes were not unknown. They are responsible for the creation of two proteins, neuroligin-3 and neuroligin-4, which are considered to play an important part in the structure of nerve cell contacts.

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Scientists Decode Molecular Details Of Genetic Defect That Causes Autism