SLCO5A1 and synaptic assembly genes contribute to impulsivity in juvenile myoclonic epilepsy

Elevated impulsivity is a key component of attention-deficit hyperactivity disorder (ADHD), bipolar disorder and juvenile myoclonic epilepsy (JME). We performed a genome-wide association, colocalization, polygenic risk score, and pathway analysis of impulsivity in JME ( n = 381). Results were followed up with functional characterisation using a drosophila model. We identified genome-wide associated SNPs at 8q13.3 ( P = 7.5 × 10 −9 ) and 10p11.21 ( P = 3.6 × 10 −8 ). The 8q13.3 locus colocalizes with SLCO5A1 expression quantitative trait loci in cerebral cortex ( P = 9.5 × 10 −3 ). SLCO5A1 codes for an organic anion transporter and upregulates synapse assembly/organisation genes. Pathway analysis demonstrates 12.7-fold enrichment for presynaptic membrane assembly genes ( P = 0.0005) and 14.3-fold enrichment for presynaptic organisation genes ( P = 0.0005) including NLGN1 and PTPRD . RNAi knockdown of Oatp30B , the Drosophila polypeptide with the highest homology to SLCO5A1 , causes over-reactive startling behaviour ( P = 8.7 × 10 −3 ) and increased seizure-like events ( P = 6.8 × 10 −7 ). Polygenic risk score for ADHD genetically correlates with impulsivity scores in JME ( P = 1.60 × 10 −3 ). SLCO5A1 loss-of-function represents an impulsivity and seizure mechanism. Synaptic assembly genes may inform the aetiology of impulsivity in health and disease.