ARX and developmental and epileptic encephalopathy, 1: Variants in ARX have been associated with several X-linked intellectual disability (XLID) syndromes, including XL lissencephaly, developmental and epileptic encephalopathy type 1 (DEE1) and Partington syndrome [96], reflecting the central role of this member of the homeobox gene family of TFs in controlling the formation of many brain structures during early embryonic development.