Genetic Variation in the Vesicular Monoamine Transporter 1 (VMAT1/SLC18A1) Gene and Alcohol Withdrawal Severity

Multi-ancestry Whole-exome Sequencing Study of Alcohol Use Disorder in Two Cohorts

Alcohol use disorder (AUD) is a leading cause of death and disability worldwide. There has been substantial progress in identifying genetic variants underlying AUD. However, there are few whole-exome sequencing (WES) studies of AUD. We analyzed WES of 4,530 samples from the Yale-Penn cohort and 469,835 samples from the UK Biobank (UKB). After quality control, 1,420 AUD cases and 619 controls of European ancestry (EUR) and 1,142 cases and 608 controls of African ancestry (AFR) from Yale-Penn were retained for subsequent analyses. WES data from 415,617 EUR samples (12,861 cases), 6,142 AFR samples (130 cases) and 4,607 South Asian (SAS) samples (130 cases) from UKB were also analyzed. Single-variant association analysis identified the well-known functional variant rs1229984 in ADH1B ( P =4.88×10 -31 ) and several other common variants in ADH1C . Gene-based tests identified ADH1B ( P =1.00×10 -31 ), ADH1C ( P =5.23×10 -7 ), CNST ( P =1.19×10 -6 ), and IFIT5 (3.74×10 -6 ). This study extends our understanding of the genetic basis of AUD.

Genetic and Pharmacological Manipulations of Glyoxalase 1 Mediate Ethanol Withdrawal Seizure Susceptibility in Mice

Central nervous system (CNS) hyperexcitability is a clinically significant feature of acute ethanol withdrawal. There is evidence for a genetic contribution to withdrawal severity, but specific genetic risk factors have not been identified. The gene glyoxalase 1 (Glo1) has been previously implicated in ethanol consumption in mice, and GLO1 inhibition can attenuate drinking in mice and rats. Here, we investigated whether genetic and pharmacological manipulations of GLO1 activity can also mediate ethanol withdrawal seizure severity in mice. Mice from two transgenic lines overexpressing Glo1 on different genetic backgrounds (C57BL/6J (B6) and FVB/NJ (FVB)) were tested for handling-induced convulsions (HICs) as a measure of acute ethanol withdrawal. Following an injection of 4 g/kg alcohol, both B6 and FVB mice overexpressing Glo1 showed increases in HICs compared to wild-type littermates, though only the FVB line showed a statistically significant difference. We also administered daily ethanol injections (2 g/kg + 9 mg/kg 4-methylpyrazole) to wild-type B6 mice for 10 days and tested them for HICs on the 10th day following treatment with either a vehicle or a GLO1 inhibitor (S-bromobenzylglutathione cyclopentyl diester (pBBG)). Treatment with pBBG reduced HICs, although this effect was only statistically significant following two 10-day cycles of ethanol exposure and withdrawal. These results provide converging genetic and pharmacological evidence that GLO1 can mediate ethanol withdrawal seizure susceptibility.

Flying Together: Drosophila as a Tool to Understand the Genetics of Human Alcoholism

Alcohol use disorder (AUD) exacts an immense toll on individuals, families, and society. Genetic factors determine up to 60% of an individual's risk of developing problematic alcohol habits. Effective AUD prevention and treatment requires knowledge of the genes that predispose people to alcoholism, play a role in alcohol responses, and/or contribute to the development of addiction. As a highly tractable and translatable genetic and behavioral model organism, Drosophila melanogaster has proven valuable to uncover important genes and mechanistic pathways that have obvious orthologs in humans and that help explain the complexities of addiction. Vinegar flies exhibit remarkably strong face and mechanistic validity as a model for AUDs, permitting many advancements in the quest to understand human genetic involvement in this disease. These advancements occur via approaches that essentially fall into one of two categories: (1) discovering candidate genes via human genome-wide association studies (GWAS), transcriptomics on post-mortem tissue from AUD patients, or relevant physiological connections, then using reverse genetics in flies to validate candidate genes' roles and investigate their molecular function in the context of alcohol. (2) Utilizing flies to discover candidate genes through unbiased screens, GWAS, quantitative trait locus analyses, transcriptomics, or single-gene studies, then validating their translational role in human genetic surveys. In this review, we highlight the utility of Drosophila as a model for alcoholism by surveying recent advances in our understanding of human AUDs that resulted from these various approaches. We summarize the genes that are conserved in alcohol-related function between humans and flies. We also provide insight into some advantages and limitations of these approaches. Overall, this review demonstrates how Drosophila have and can be used to answer important genetic questions about alcohol addiction.

Lipid profile dysregulation predicts alcohol withdrawal symptom severity in individuals with alcohol use disorder

Alcohol withdrawal syndrome (AWS) is a serious medical condition of high variability in alcohol use disorder (AUD) after drinking cessation. Identification of clinical biomarkers capable of detecting severe AWS is needed. While alcohol consumption and withdrawal are linked with lipid profile dysregulation, the relationship between lipid levels (high-density lipoprotein cholesterol [HDL-C], low-density lipoprotein cholesterol [LDL-C], and triglycerides) and AWS is unknown. Therefore, this study investigated whether HDL-C, LDL-C, and triglycerides conferred risk for moderate-to-severe AWS symptoms in treatment-seeking individuals (n = 732) admitted to the National Institute on Alcohol Abuse and Alcoholism (NIAAA) alcohol treatment program. Lipid levels were measured upon admission, and the Clinical Institute Withdrawal Assessment of Alcohol Scale, Revised (CIWA-Ar) assessed AWS severity for generating a three-level AWS typology (none-to-mild, moderate, and severe). Multivariable multinomial logistic regression examined whether lipid levels were associated with risk for moderate-to-severe AWS. We found significant predictive relationships between AWS and HDL-C, LDL-C, and triglycerides. While extremely high HDL-C (≥100 mg/dL) conferred the highest odds for moderate (4.405, 95% CI, 2.572-7.546, p < 0.001) and severe AWS (5.494, 95% CI, 3.541-8.523, p < 0.001), the lowest odds ratios for moderate AWS (0.493, 95% CI, 0.248-0.981, p = 0.044) and severe AWS (0.303, 95% CI, 0.223-0.411, p < 0.001) were associated with high LDL-C (≥160 mg/dL). The present study demonstrates that altered lipid levels, measured upon admission for inpatient AUD treatment, may help to predict which individuals are at risk for medically relevant moderate-to-severe AWS. This suggests that further research into the role of lipid biomarkers in AWS may be beneficial for identifying biologically determined risk profiles in AUD.

Human-specific mutations in VMAT1 confer functional changes and multi-directional evolution in the regulation of monoamine circuits

BACKGROUND

Neurochemicals like serotonin and dopamine play crucial roles in human cognitive and emotional functions. Vesicular monoamine transporter 1 (VMAT1) transports monoamine neurotransmitters, and its variant (136Thr) is associated with various psychopathological symptoms and reduced monoamine uptake relative to 136Ile. We previously showed that two human-specific amino acid substitutions (Glu130Gly and Asn136Thr/Ile) of VMAT1 were subject to positive natural selection. However, the potential functional alterations caused by these substitutions (Glu130Gly and Asn136Thr) remain unclear. To assess functional changes in VMAT1 from an evolutionary perspective, we reconstructed ancestral residues and examined the role of these substitutions in monoamine uptake in vitro using fluorescent false neurotransmitters (FFN), which are newly developed substances used to quantitatively assay VMATs.

RESULTS

Immunoblotting confirmed that all the transfected YFP-VMAT1 variants are properly expressed in HEK293T cells at comparable levels, and no significant difference was seen in the density and the size of vesicles among them. Our fluorescent assays revealed a significant difference in FFN206 uptake among VMAT1 variants: 130Glu/136Asn, 130Glu/136Thr, and 130Gly/136Ile showed significantly higher levels of FFN206 uptake than 130Gly/136Asn and 130Gly/136Thr, indicating that both 130Glu and 136Ile led to increased neurotransmitter uptake, for which 136Thr and 136Asn were comparable by contrast.

CONCLUSIONS

These findings suggest that monoamine uptake by VMAT1 initially declined (from 130Glu/136Asn to 130Gly/136Thr) in human evolution, possibly resulting in higher susceptibility to the external environment of our ancestors.

Deletion of the vesicular monoamine transporter 1 (vmat1/slc18a1) gene affects dopamine signaling

The vesicular monoamine transporter is involved in presynaptic catecholamine storage and neurotransmission. Two isoforms of the transporter exist, VMAT1 and VMAT2, and both are expressed in the brain, though VMAT2 expression is more robust and has been more widely studied. In this study we investigated the role of VMAT1 KO on markers of dopaminergic function and neurotransmission, and dopamine-related behaviors. Null-mutant VMAT1 mice were studied behaviorally using the tail suspension test, elevated zero maze and locomotor activity assessments. Tissue monoamines were measured both ex vivo and by using in vivo microdialysis. Protein expression of tyrosine hydroxylase and D2 dopamine receptors was measured using western blot analysis. Results show that VMAT1 KO mice have decreased dopamine levels in the frontal cortex, increased postsynaptic D2 expression, and lower frontal cortex tyrosine hydroxylase expression compared to WT mice. VMAT1 KO mice also show an exaggerated behavioral locomotor response to acute amphetamine treatment. We conclude that dopaminergic signaling is robustly altered in the frontal cortex of VMAT1 null-mutant mice and suggest that VMAT1 may be relevant to the pathogenesis and/or treatment of psychiatric illnesses including schizophrenia and bipolar disease.

WFSBP * and IAWMH ** Guidelines for the treatment of alcohol use disorders in pregnant women

OBJECTIVES

These practice guidelines for the treatment of alcohol use disorders during pregnancy were developed by members of the International Task Force of the World Federation of Societies of Biological Psychiatry and the International Association for Women's Mental Health.

METHODS

We performed a systematic review of all available publications and extracted data from national and international guidelines. The Task Force evaluated the data with respect to the strength of evidence for the efficacy and safety of each medication.

RESULTS AND DISCUSSION

There is no safe level of alcohol use during pregnancy. Abstinence is recommended. Ideally, women should stop alcohol use when pregnancy is planned and, in any case, as soon as pregnancy is known. Detecting patterns of alcohol maternal drinking should be systematically conducted at first antenatal visit and throughout pregnancy. Brief interventions are recommended in the case of low or moderate risk of alcohol use. Low doses of benzodiazepines, for the shortest duration, may be used to prevent alcohol withdrawal symptoms when high and chronic alcohol intake is stopped and hospitalisation is recommended. Due to the low level of evidence and/or to low benefit/risk ratio, pharmacological treatment for maintenance of abstinence should not be used during pregnancy. At birth, foetal alcohol spectrum disorders must be searched for, and alcohol metabolites should be measured in meconium of neonates in any doubt of foetal alcohol exposure.

Expression of the Vesicular Monoamine Transporter Gene Solute Carrier Family 18 Member 1 (SLC18A1) in Lung Cancer

BACKGROUND

One aspect of smoking and lung cancer that has not been closely examined, is that regarding genes that may predispose to tobacco dependence. Smoking and mental illness are tightly linked, apparently the result of smokers using cigarettes to self-medicate for mental problems. The gene for solute carrier family 18 member A1 (vesicular monoamine transporter; SLC18A1) is of particular interest in this regard because of its association with schizophrenia, autism and bipolar illness as well as with cancer. In the current study, the relationship of SLC18A1 expression with smoking and lung cancer was analyzed.

MATERIALS AND METHODS

The association between smoking, SLC18A1 expression and overall survival in the lung cancer dataset in The Cancer Genome Atlas was evaluated using the Genomic Data Commons Data Portal (https://portal.gdc.cancer.gov), as well as CbioPortal for Cancer Genomics (http://www.cbioportal.org) and the University of California Santa Cruz Xena browser (https://xenabrowser.net).

RESULTS

Increased expression of SLC18A1 was found to be associated with a significantly increased survival in patients with adenocarcinoma (p=0.0058), but not those with squamous carcinoma (p=0.96). Lifelong never-smokers had the highest SLC18A1 expression. In the Pan Cancer Atlas, increased expression of SLC18A1 places such a tumor in group C5, among immunologically-quiet tumors.

CONCLUSION

Most never-smokers with lung cancer do not respond to immune checkpoint inhibitors (ICIs). But for unknown reasons, a small proportion do show clinical benefit from the ICI pembrolizumab. Because of the good response of this group, it may be worthwhile assessing their SLC18A1 expression pre-treatment as a marker for potential clinical benefit. If SLC18A1 expression is low, a never-smoker may respond well to ICIs. High levels of expression would indicate a C5 tumor less likely to respond to ICIs. SLC18A1 might complement other biomarkers currently under study in relation to programmed cell death protein 1/programmed cell death protein ligand 1 inhibition.

Association study of the vesicular monoamine transporter 1 (VMAT1) gene with autism in an Iranian population

Autism Spectrum Disorders (ASD) (MIM 209850) are a group of neurodevelopmental disorders distinguished by destructed social interaction and communication abilities along with peculiar repetitive behavior. Several genetic loci have been linked to this disorder. Vesicular monoamine transporter 1 (VMAT1/SLC18A1) is an attractive candidate gene for psychiatric disorders because of its participation in regulation monoamines. In the present case-control study, we evaluated the link between three non-synonymous single nucleotide polymorphisms (SNPs) (rs2270641 [Pro4Thr], rs2270637 [Thr98Ser] and rs1390938 [Thr136Ile]) and one intronic SNP (rs2279709) across the VMAT1 gene and ASD in a group of Iranian patients. Allele frequency analyses showed significant over-presentation of rs1390938-G allele in cases compared with controls (P<0.001). The analysis under different genetic models showed that the AA genotype of the rs1390938 was protective against ASD under dominant and recessive models. The rs2270641 SNP was associated with ASD risk only in over-dominant model. Other SNPs showed no significant difference in allele or genotype frequencies between two groups. Haplotype analysis revealed that C A T T and C A T G haplotypes (rs2270637, rs1390938, rs2279709 and rs2270641 respectively) have a protective effect against ASD. Consequently, the functional rs1390938 SNP in VMAT1 is associated with ASD in Iranian population. Considering the role of VMAT1 in regulation of monoamines, the dysregulated expression of this protein during early stages of brain development might be implicated in ASD.

Genetic Correlates of Spirituality/Religion and Depression: A Study in Offspring and Grandchildren at High and Low Familial Risk for Depression

RATIONALE

Possible genetic correlates of spirituality and depression have been identified in community samples. We investigate some of the previously identified candidates in a sample of families at both high and low-risk for depression.

METHOD

Offspring and grandchildren of individuals at high and low-risk for depression, participating in a multi-wave thirty-year longitudinal study, were assessed for seven SNPS drawn from four single gene candidates associated with systems implicated in both depression and spirituality: Serotonin (5-HT1B and 5-HT2A), Dopamine (DRD2), Oxytocin (OT) and Monoamine Vesicular Transporter (VMAT1).

RESULTS

Dopamine (DRD2) Serotonin (5-HT1B), their Transporter (VMAT1) and Oxytocin (OXTR) were positively associated with a high level of importance of spirituality or religion (S/R) in the group at low familial risk for depression. DRD2 minor allele was associated with both lifetime major depressive disorder (MDD) and spirituality in the low-risk group for depression. No SNPs were related to S/R in the group at high familial risk for depression. OXTR was associated with lifetime MDD in the full sample.

CONCLUSION

Genes for dopamine, serotonin, their vesicular transporter, and oxytocin may be associated with S/R in people at low familial risk for depression. Genes for dopamine may be associated both with S/R and increased risk for depression in people at low-risk for depression, suggesting a common pathway or physiology to mild to moderate depression. MDD is associated with oxytocin across risk groups. In the high-risk group, phenotypic expression of S/R may be suppressed.

IMPLICATIONS

The shared association of DRD2 by S/R and depression, generally found to be inversely related, calls for further research on their common physiological pathways, and the phenotypic expression of these pathways based upon use and environment. Prevention for offspring at high familial risk for depression might include support for the development of child spirituality.