Dopamine 2-hydroxylase (DBH) catalyzes synthesis of the neurotransmitter norepinephrine (NE) from dopamine (DA), and thereby regulates levels of both molecules. DBH is detectable in human serum, where its activity largely reflects sequence variation at the structural locus DBH. We identified a single nucleotide polymorphism (SNP) 970 bp upstream of the transcriptional start site (-970C>T) that accounts for 30-50% of the total variance in serum DBH activity, with the """"""""T"""""""" allele being associated with lower activity than the """"""""C"""""""" allele, in a co-dominant pattern. Our work on a population-genetic level, and molecular experiments from another laboratory provide strong evidence that -970C>T is a true regulatory variant, affecting transcription of DBH. However, the molecular experiments suggested that the low-serum-DBH T allele associates with greater transcription. Thus, how -970C>T regulates DBH expression in vivo is not clear. The present project proposes to use BAC transgenesis, followed by crossing with Dbh -/- mice lacking endogenous DBH expression, to investigate DBH expression in brain, adrenal medulla and serum, associated with either the T or C allele in an otherwise identical human-sequence context of ~170 kb. This project will inform multiple areas of public health research, including studies of psychosis, mood disorders, drug addiction, neuro-degenerative disorders, and disorders of human blood pressure, as variation in serum DBH and/or -970C>T associates with important aspects of human phenotypes related to all of those disorders. The proposed work will produce a valuable and innovative animal model for investigation of many aspects of genetic variation in NE-mediated neurotransmission.
Project Narrative: Dopamine 2-hydroxylase (DBH) is an enzyme that synthesizes the neural signaling molecule norepinephrine (NE), which is in turn involved in human psychiatric, neurological and blood-pressure related disorders. A sequence variant (polymorphism) in the human DBH gene strongly regulates levels of DBH, and influences all of the foregoing human disorders. This project will put the two versions (alleles) of the human DBH gene into mice that lack their own Dbh. This will allow functional study of this important human polymorphism in a mouse model.