DOCK3, a presenilin-binding protein, belongs to the DOCK180 family of proteins and is highly expressed in the neurons (Kashiwa et al., 2000; Cote and Vuori, 2002; Namekata et al., 2002). There is additional supporting evidence for the 3p21 region and DOCK3 as AD/HD candidates. A genome-wide association study for bipolar disorder (BPD) identified two SNPs within DOCK3 that were significantly associated with BPD in two independent populations (Baum et al., 2008). This is of interest because BPD and AD/HD share some overlapping characteristics and sometimes co-occur. In addition, a previous study described an individual with a 3p21.31 duplication who exhibited many AD/HD-like characteristics, such as hyperactive-impulsive behaviors, attention deficits, and poor school performance (Stuart et al., 2007).
