A study at the University of California, San Diego School of Medicine identified genetic mechanisms involved in abnormal early brain development and overgrowth in young autism patients. Using whole-genome analysis of mRNA levels from 33 autistic and control postmortem brain samples, the researchers found the genetic mechanisms that normally regulate the amount of cortical neurons to be abnormal. The genes did not have the normal functional expression. There were also abnormal numbers and patterns of brain cells, possibly leading to too many brain cells in some locations and too few in other regions. Also, the study discovered a shutting down of the genetic mechanisms responsible for detecting DNA defects and correcting affected cells during periods of prenatal development.