The three genetic research papers on Autism Spectrum Disorder (ASD) in 2012, with links below, summarize that no single gene or gene complex candidate has yet been discovered to be the cause.
1) Dr Sanders and others showing the new mutations that are associated with Autism but not causal.
2) Dr Brian O’Roak and others show that for 70% of ASD cases with no previous cases in the family there is no known genetic cause. Researching the coding regions of genes they find that:
a) Parental age contributes to new mutations – risk of older father;
b) 39% of disruptive genes affect the beta-catenin/chromatin protein network resulting in the most severe autism;
c) CHD8 and NTNG1 were recurrent protein altering genes with new mutations.
3) Dr Benjamin Neale and others sequenced the coding region of the genes of ASD patients and their parents to show that new mutations in a polygenic model that affect a complex of protein pathways such as CHD8 and KATNAL2 are genuine risk factors for ASD.