WDR6 (WD repeat domain 6) is broadly expressed in the brain, particularly the hypothalamus. Its protein product is involved in cell growth arrest54, and recent studies have implicated it in anorexia nervosa55 and Parkinson’s disease56. DALRD3 (DALR anticodon binding domain containing 3) is located on chromosome 3 in the same region as WDR6. DALRD3, when fully disrupted, is implicated in a form of epileptic encephalopathy with associated developmental delay57. Finally, a third gene in the 3p21 locus, CELSR3 (cadherin EGF LAG seven-pass G-type receptor 3), encodes a protocadherin that is highly expressed in the developing basal ganglia58. Multiple loss-of-function mutations in CELSR3 have been associated with Tourette syndrome59,60, which cooccurs with OCD in 10–20% of patients.
