Role of SNAP‐25 MnlI variant in impaired working memory and brain functions in attention deficit/hyperactivity disorder

INTRODUCTION: Attention deficit/hyperactivity disorder (ADHD) is a hereditary neurodevelopmental disorder characterized by working memory (WM) deficits. The MnlI variant (rs3746544) of the synaptosomal‐associated protein 25 (SNAP‐25) gene is associated with ADHD. In this study, we investigated the role and underlying mechanism of SNAP‐25 MnlI variant in cognitive impairment and brain functions in boys with ADHD. METHOD: We performed WM capacity tests using the fourth version of the Wechsler Intelligence Scale for Children (WISC‐IV) and regional homogeneity (ReHo) analysis for the resting‐state functional magnetic resonance imaging data of 56 boys with ADHD divided into two genotypic groups (TT homozygotes and G‐allele carriers). Next, Spearman's rank correlation analysis between the obtained ReHo values and the WM index (WMI) calculated for each participant. RESULTS: Compared with G‐allele carrier group, there were higher ReHo values for the left medial prefrontal cortex (mPFC) and higher WM capacity in TT homozygote group. Contrary to TT homozygote group, the WM capacity was negatively correlated with the peak ReHo value for the left mPFC in G‐allele carrier group. CONCLUSION: These findings suggest that SNAP‐25 MnlI variant may underlie cognitive and brain function impairments in boys with ADHD, thus suggesting its potential as a new target for ADHD treatment.