AZI23’UTR Is a New SLC6A3 Downregulator Associated with an Epistatic Protection Against Substance Use Disorders

Abstract

Regulated activity of SLC6A3, which encodes the human dopamine transporter (DAT), contributes to diseases such as substance abuse disorders (SUDs); however, the exact transcription mechanism remains poorly understood. Here, we used a common genetic variant of the gene, intron 1 DNP1B sequence, as bait to screen and clone a new transcriptional activity, 3'UTR, for SLC6A3.3'UTR is a 3' untranslated region (3'UTR) of the human 5-Azacytidine Induced 2 gene (AZI2) but appeared to be transcribed independently of AZI2. Found to be present in both human cell nuclei and dopamine neurons, this RNA was shown to downregulate promoter activity through a variant-dependent mechanism in vitro. Both reduced RNA density ratio of 3'UTR/AZI2 and increased DAT mRNA levels were found in ethanol-naive alcohol-preferring rats. Secondary analysis of dbGaP GWAS datasets (Genome-Wide Association Studies based on the database of Genotypes and Phenotypes) revealed significant interactions between regions upstream of3'UTR and SLC6A3 in SUDs. Jointly, our data suggest that 3'UTR confers variant-dependent transcriptional regulation of SLC6A3, a potential risk factor for SUDs.

Dopamine Genetics: Substance Use Disorders vs. Parkinson’s Disease

“…Specifically data from four SUD [12] cohorts were obtained from the three datasets: Collaborative Study on the Genetics of Alcoholism (COGA, dbGaP accession#: phs000125.v1.p1), Study of Addiction: Genetics and Environment (SAGE, polysubstance abuse but mainly with cigarette smoking, dbGaP accession#: phs000092.v1.p1), and the Australian twin-family study of alcohol use disorder (OZALC, dbGaP accession#: phs000181.v1.p1). After COGA data quality control (QC), data from the US Caucasians of European (EA) descent and African Americans (AA) were split into these 2 separate ethnic cohorts.…”

“…Determine whether these neuropsychiatric disorders have common risks in DA-associated genes, including DA synthesis (2 genes), metabolism (2 genes), receptors (DRs, 5 genes), monoamine transporters (5 genes), an uptake modulator (alpha-synuclein: SNCA), and transcription factors (7 genes) [11,12].…”

Functional validation of a finding from a mouse genome-wide association study demonstrates that a mutant allele ofAzi2alters sensitivity to methamphetamine

“…The Azi2 3'UTR on exon 8 that we amplified using qRT-PCR is homologous to the 3'UTR amplified in the rat alcohol model (Liu et al, 2018) and is only present in two of the four full-length Azi2 transcripts, ENSMUST0000044454.11 and ENSMUST00000133580.7.…”

“…One possible mechanism by which Azi2 could influence the response to methamphetamine was proposed by another group after the publication of Parker et al (2016) (20). Liu et al (2018) identified the second half of 3' UTR of Azi2 mRNA ( AZI2 3'UTR) as a regulator of Slc6a3 (Liu et al, 2018), which encodes the dopamine transporter (DAT), a critical regulator of the neurotransmitter dopamine concentrations in the synaptic cleft. Importantly, DAT is the molecular target of methamphetamine (28), providing a plausible mechanism by which Azi2 might influence sensitivity to methamphetamine.…”

“…Importantly, DAT is the molecular target of methamphetamine (28), providing a plausible mechanism by which Azi2 might influence sensitivity to methamphetamine. In addition to a number of cellular assays, Liu et al (2018) also showed that rats that had been bi-directionally selected for alcohol preference showed differential AZI2 3'UTR expression and differential expression of Slc6a3 expression in the ventral tegmental area (VTA) (Liu et al, 2018).…”