Dopaminergic signalling and behavioural alterations by Comt-Dtnbp1 genetic interaction and their clinical relevance

Background and PurposeCognitive and motor functions are modulated by dopaminergic signalling, which is shaped by several genetic factors. The biological effects of single genetic variants might differ depending on epistatic interactions that can be functionally multi-directional and non-linear. Experimental ApproachWe performed behavioural and neurochemical assessments in genetically modified mice and behavioural assessments and genetic screening in human patients with 22q11.2 deletion syndrome (22q11.2DS). Key ResultsHere, we confirm a genetic interaction between the Comt (catechol-O-methyltransferase, human orthologue: COMT) and Dtnbp1 (dystrobrevin binding protein 1, alias dysbindin, human orthologue: DTNBP1) genes that modulate cortical and striatal dopaminergic signalling in a manner not predictable by the effects of each single gene. In mice, Comt-by-Dtnbp1 concomitant reduction leads to a hypoactive mesocortical and a hyperactive mesostriatal dopamine pathway, associated with specific cognitive abnormalities. Like mice, in subjects with the 22q11.2DS (characterized by COMT hemideletion and dopamine alterations), COMT-by-DTNBP1 concomitant reduction was associated with analogous cognitive disturbances. We then developed an easy and inexpensive colourimetric kit for the genetic screening of common COMT and DTNBP1 functional genetic variants for clinical application. Conclusions and ImplicationsThese findings illustrate an epistatic interaction of two dopamine-related genes and their functional effects, supporting the need to address genetic interaction mechanisms at the base of complex behavioural traits.