Three new studies analyzing genetic data from families in which just one child has autism have found the strongest evidence yet that rare new mutations contribute to the disorder.

Deletions on a segment of chromosome 11 are associated with autism, attention problems and obesity, according to a study published in the June issue of the American Journal of Medical Genetics Part A.

What’s known about the genetics of autism supports the ‘snowflake’ hypothesis — that the molecular underpinnings of disease are essentially unique from individual to individual — says human geneticist Brett Abrahams.

Mice with a mutation in SHANK3, a leading autism candidate gene, show moderate social defects, including less-than-normal interest in other mice. The findings, published 27 May in Cell, suggest that mutations in different sites on the gene can lead to different behaviors. This paper was retracted on 17 January 2013. Associate director of research Alan Packer discusses the implications of the retraction here.

Autism is diagnosed based on the severity and variety of its symptoms. This makes it very difficult to diagnose and easy to confuse with other disorders, such as language delay and intellectual disability, cautions Isabelle Rapin.

Genetic screening of children with autism is critical to designing more effective interventions and treatment, says a pediatrician.

Good mouse models of autism, and accurate tests to assay their phenotypes, are key to both narrowing down a cause and developing effective treatments, argues expert Jacqueline Crawley.

Two rare, unlikely and inherited mutations in the same gene may together have contributed to a case of autism, according to a study published 23 March in Molecular Psychiatry. The results suggest that the gene, DIAPH3, is a new candidate for autism risk.

Identical twins can be genetically different, which could explain why they do not always share disorders such as schizophrenia or autism, according to a study published in March in PLoS One.

Small duplications or deletions of DNA regions — called micro-copy number variations — may not lead directly to disease, but could raise the risk of autism when combined with other mutations, according to a study published in March in the American Journal of Medical Genetics Part B: Neuropsychiatric Genetics.