ACTR2 and Down syndrome: ACTR2 encodes a component of the ARP2/3 complex, a reduction of which may cause abnormal neuronal and glial migration and impaired neurite extension.42 One independent case (SLI-146_3, Table 3) was found to have two de novo events; a deletion in CSNK1A1, which has been related to dopamine signalling and ADHD43 and a duplication within the region typically duplicated in 22q11.2 microduplication syndrome.