Some small fragments of RNA are expressed differently in people with autism than in controls, according to two new studies. The findings unveil another layer of complexity in the genetics of autism.These pieces of single-stranded RNA ― dubbed microRNAs or miRNAs ― have wide-ranging, subtle effects on the production of many different proteins without affecting a cell's underlying DNA code.That may account for some of the widespread variation among people with autism, and even among family members who share genes, experts say.“It's possible that microRNAs can have some kind of regulatory role over multiple targets and affect them a little bit differently in different people,” says Kenneth Kosik, co-director of the Neuroscience Research Institute at the University of California, Santa Barbara.Read more at...SFARI, November 2008.