Researchers have identified nearly 4,000 genetic regions that may be critical for brain function, and harbor mutations involved in disorders such as autism, they reported 25 May in Nature Genetics.

A repeated sequence within the gene mutated in fragile X syndrome forms unusual loops of genetic material, reports a study published 17 April in PLoS Genetics. The loops may trigger a cascade of genetic changes that push a precursor mutation into one that causes the disorder.

People with autism tend to carry mutations that duplicate or delete several genes at once, according to a large study published 1 May in the American Journal of Human Genetics.

The protein underlying Rett syndrome exists in two different forms that differ in their distribution throughout the brain, reports a study published 3 March in PLoS One.

A large study of autism in Swedish families suggests that about half of the risk for autism comes from genetics and the other half from environmental factors, researchers reported 7 May in The Journal of the American Medical Association. However, the mathematical model the study used may not be appropriate for evaluating autism risk, experts say.

Having one too many copies of MeCP2, the Rett syndrome gene, may block the growth of neuronal branches by interfering with the production of small pieces of RNA, according to a study published 10 March in Developmental Cell.

A Swedish twin study plans to search for the shared genetic and environmental origins of autism and attention deficit hyperactivity disorder, which are often mistaken for each other.

The symptom severity of three girls with fragile X syndrome tracks with how much the levels of the fragile X protein in their blood differs from that of their unaffected mothers. If the results, published 29 January in Molecular Syndromology, are confirmed in a larger study, they may help doctors predict how the disorder will manifest in girls.

Children with autism are about four times more likely to experience gastrointestinal distress than are their typically developing peers, reports a large review published 28 April in Pediatrics.

A new computational model predicts the sites in the brain of 64 types of neurons, researchers reported 8 April in Proceedings of the National Academy of Sciences.