Polymorphism in the DBH Promoter Region Shown to Exert Cell-Specific Effect on Transcription

Background: Autism is an early onset neurodevelopmental disorder affecting three core areas of behaviour – communication, social behaviour and restricted/repetitive behaviour. Pathophysiological studies have implicated dysfunctions in the catecholamine neurotransmitter system in the aetiology of autism. Dopamine-B-Hydroxylase (DBH) catalyses the conversion of dopamine to noradrenaline in the catecholamine pathway.  Previous studies have shown altered DBH activity in individuals with autism.  rs1611115, located in the DBH promoter region, has previously been shown to explain approximately 52% of the variance in DBH activity levels. 

Objectives: This study investigated the effect of rs1611115 on DBH promoter function using a reporter assay system. 

Methods: Inserts representing each allele at rs1611115 were inserted into the pGL3 basic reporter vector (,).  Each construct was then transfected into two cell lines – CHO K1 and SH SY-5Y.  Differences in promoter activity between alleles was then determined using a luciferase reporter assay system (, ). 

Results:

In the non-neuronal CHO K1 cell line, neither reporter construct increased relative expression levels of the luciferase reporter gene.  In the neuronal SH SY-5Y cell line, both constructs increased gene expression beyond background levels.  Additionally, significant allelelic differences in relative expression levels were observed (p=0.0049). 

Conclusions:

This finding confirms at the molecular level previous reports that variation at rs1611115 affects DBH promoter efficiency.