The potential impact of COMT gene variants on dopamine regulation and phenotypic traits of ASD patients

Catechol-O-methyltransferase (COMT) enzyme has a major role in the adjustment of catechol-dependent functions, for example, cognition, cardiac function, and pain processing. The pathogenesis of autism may be related to dysfunction in the midbrain dopaminergic system. Therefore, we aimed to clarify how COMT gene variants affect dopamine level, and its potential impact on phenotype traits of autistic patients. 52 autistic patients were subjected to comprehensive clinical investigation, sequencing of exon 4 of the COMT gene by direct Sanger Sequencing, and measuring of dopamine levels. The clinical presentations of autistic subjects were correlated with detected COMT variants and dopamine level. Our molecular results revealed that three COMT variants were found: rs8192488 [C > T], rs4680 (Val158Met) and rs4818 [C > G]. Within autistic subjects, Val158Met rs4680 carriers were significantly distributed (71.2% P = 0.014) accompanied with abnormal dopamine, abnormal Electroencephalogram (EEG) and increasing the severity of autistic behaviour. As regards the haplotypes, CC/VM/CG block was significantly distributed among the autistic subjects (30.8%) presented with low mean dopamine level (15.8 ± 4.7 pg/ml, p = 0.05), while CC/MM/CC were presented with high mean level (77.8 ± 8.6 pg/ml, p = 0.05). Evidence is currently limited and preliminary, further studies are necessary in order to set up a coherent dopaminergic model of Autism Spectrum Disorder (ASD), which would further pave the way for an adequate treatment.