Studies suggest that autism spectrum disorder (ASD) has a genetic and neuron-developmental basis. Evidence suggests that the brain's cerebellum is structurally abnormal in ASD. It has reduced numbers of "Purkinje" cells. Additionally, it is active in tasks, such as language and attention, which are abnormal in people with ASD. Two different DNA variants within the human gene called "ENGRAILED 2" (EN2) are often inherited in people with ASD, suggesting to the researchers that variants of this gene may confer susceptibility to ASD. The researchers have studied mice with the EN2 gene and found the mice to display autistic-like anatomical, neurochemical and behavioral defects, establishing it as a genetically relevant mouse model for ASD. They hypothesize that stem cells can reverse the damage created by autism-related variants of the EN2 gene in mice, replacing cerebellar cells lost to ASD, and can be used to treat some of the ASD symptoms. The researchers will first identify the stem cell source that has the greatest likelihood of being effective, and then determine the experimental conditions that will result in the most significant incorporation and differentiation of stem cells into brain cells affected by ASD. Thereafter, they will introduce these stem cells in the ASD mouse model, and determine their actions. Significance: this animal model stem cell research is anticipated to identify the source for stem cells that have the most likelihood of success in reversing ASD brain cell damage, and to provide initial evidence of whether stem cell therapy may be feasible in humans with ASD.