Autism is known to be highly heritable. Research done by some institutions seek to find a way for early and more accurate detection of autism similar to Rett syndrome. Instead of searching for one particular gene as the cause for autism, many of the studies tend to search for complex interactions between a number of genes.
A 2005 study done by the Duke Center for Human Genetics at Duke University finds some evidence that complex interactions between GABA (gamma aminobutyric acid) receptor genes might be part of the cause of autism. One of the functions of the GABA genes is to inhibit the nerve system from firing. The theory is that somehow GABA genes suffer damage of some kind, leading to an overwhelmed sensory system causing the characteristics or symptoms of autism.