ASH1L and Down syndrome: Interestingly, FOXG1 syndrome and ASH1L mutations-induced ASD/ID have highly overlapping clinical manifestations26, suggesting that ASH1L might function as a master epigenetic regulator to facilitate the expression of FOXG1 and other critical genes for normal brain development, while mutations of ASH1L lead to mis-regulation of gene expression, disturbance of the normal brain developmental program, and brain functional abnormalities of ASD/ID.