BDNF (Val66Met) genetic polymorphism is associated with vulnerability for methamphetamine dependence

Enhanced methamphetamine sensitisation in a rat model of the brain-derived neurotrophic factor Val66Met variant: Sex differences and dopamine receptor gene expression

Brain-derived neurotrophic factor (BDNF) and the Val66Met polymorphism may play a role in the development of psychosis and schizophrenia. The aim of this study was to investigate long-term effects of methamphetamine (Meth) on psychosis-like behaviour and dopamine receptor and dopamine transporter gene expression in a novel rat model of the BDNF Val66Met polymorphism. At the end of a 7-day subchronic Meth treatment, female rats with the Met/Met genotype selectively showed locomotor hyperactivity sensitisation to the acute effect of Meth. Male rats showed tolerance to Meth irrespective of Val66Met genotype. Two weeks later, female Met/Met rats showed increased locomotor activity following both saline treatment or a low dose of Meth, a hyperactivity which was not observed in other genotypes or in males. Baseline PPI did not differ between the groups but the disruption of PPI by acute treatment with apomorphine was absent in Meth-pretreated Met/Met rats. Female Met/Met rats selectively showed down-regulation of dopamine D2 receptor gene expression in striatum. Behavioural effects of MK-801 or its locomotor sensitisation by prior Meth pretreatment were not influenced by genotype. These data suggest a selective vulnerability of female Met/Met rats to short-term and long-term effects of Meth, which could model increased vulnerability to psychosis development associated with the BDNF Val66Met polymorphism.

Consequences of the rs6265 (Val66Met) polymorphism in the BDNF gene in selected mental disorders and sport

Introduction: Brain-derived neurotrophic factor (BDNF) is a polypeptide of 247 amino acid residues and is widely distributed throughout the central nervous system of the CNS. It plays an important role in the survival, differentiation, growth, and development of neurons in the central nervous system. The human BDNF gene is located on chromosome 11 in the p13-14 region and covers approximately 70 kb. The gene has a complex structure as it consists of 11 exons (I-IX, plus Vh and VIIIh) and nine functional promoters. BDNF expression in the brain is relatively low but it is found in most major regions of the brain.

Material and methods: The gene encoding the brain-derived neurotrophic factor BDNF has many polymorphisms, but one of them mainly attracts the attention of researchers. This is a common, non-conservative polymorphism - rs6265 - a single nucleotide SNP polymorphism that results in an amino acid change – valine (Val) to methionine (Met) - at codon 66.

Results: Polymorphism rs6265 is associated with many neuropsychiatric disorders, including depression or a higher risk of addiction, but it also determines other features, such as e.g. sports performance. Few studies are investigating the relationship between rs6265 polymorphism and predisposition to play sports.

Conclusions: The results on the effect of rs6265 BDNF polymorphic variants on the risk of depression and addition are inconsistent, indicating a significant association in some studies and none in others. Therefore, more studies are needed to determine how rs6265 affects gene expression and function.

Chronic methamphetamine interacts with BDNF Val66Met to remodel psychosis pathways in the mesocorticolimbic proteome

Methamphetamine (Meth) abuse has reached epidemic proportions in many countries and can induce psychotic episodes mimicking the clinical profile of schizophrenia. Brain-derived neurotrophic factor (BDNF) is implicated in both Meth effects and schizophrenia. We therefore studied the long-term effects of chronic Meth exposure in transgenic mice engineered to harbor the human BDNF^Val66Met polymorphism expressed via endogenous mouse promoters. These mice were chronically treated with an escalating Meth regime during late adolescence. At least 4 weeks later, all hBDNF^Val66Met Meth-treated mice exhibited sensitization confirming persistent behavioral effects of Meth. We used high-resolution quantitative mass spectrometry-based proteomics to biochemically map the long-term effects of Meth within the brain, resulting in the unbiased detection of 4808 proteins across the mesocorticolimbic circuitry. Meth differentially altered dopamine signaling markers (e.g., Dat, Comt, and Th) between hBDNF^Val/Val and hBDNF^Met/Met mice, implicating involvement of BDNF in Meth-induced reprogramming of the mesolimbic proteome. Targeted analysis of 336 schizophrenia-risk genes, as well as 82 growth factor cascade markers, similarly revealed that hBDNF^Val66Met genotype gated the recruitment of these factors by Meth in a region-specific manner. Cumulatively, these data represent the first comprehensive analysis of the long-term effects of chronic Meth exposure within the mesocorticolimbic circuitry. In addition, these data reveal that long-term Meth-induced brain changes are strongly dependent upon BDNF genetic variation, illustrating how drug-induced psychosis may be modulated at the molecular level by a single genetic locus.

Changes of BDNF exon IV DNA methylation are associated with methamphetamine dependence

Aim: We investigated DNA methylation of BDNF in methamphetamine (METH) dependence in humans and an animal model. Materials & methods: BDNF methylation at exon IV was determined by pyrosequencing of blood DNA from METH-dependent and control subjects, and from rat brain following an escalating dose of METH or vehicle. Bdnf expression was determined in rat brain. Results: BDNF methylation was increased in human METH dependence, greatest in subjects with psychosis and in prefrontal cortex of METH-administered rats; rat hippocampus showed reduced Bdnf methylation and increased gene expression. Conclusion: BDNF methylation is abnormal in human METH dependence, especially METH-dependent psychosis, and in METH-administered rats. This may influence BDNF expression and contribute to the neurotoxic effects of METH exposure.

Association of PICK1 and BDNF variations with increased risk of methamphetamine dependence among Iranian population: a case-control study

BACKGROUND

Genetic factors play an important role in susceptibility to methamphetamine dependency. In this line, protein that interact with C-kinase-1 (PICK1) and brain-derived neurotrophic factor (BDNF) genes are linked to methamphetamine dependence (substance use disorder). Thus, in a case-control study, we investigated the association between polymorphisms of PICK1 and BDNF genes and methamphetamine dependence in an Iranian population.

METHODS

Total of 235 cases and 204 controls were recruited in a period between 2015 to 2018. The PICK1-rs713729, -rs2076369 and BDNF-rs6265 genotypes were determined via ARMS-PCR assay. Statistical analysis was performed, using SPSS 20.0, PHASE 2.1.1 program as well as SNP Analyzer 2.0.

RESULTS

In the present study, two polymorphisms including PICK1-rs713729 (OR 1.38 (CI 1.08-1.52; P-value 0.004) in multiplicative and dominant models, and PICK1-rs2076369 (OR 1.31 (CI 1.10-1.56; P-value 0.002) in multiplicative, dominant and co-dominant models were associated with the risk of methamphetamine abuse. Moreover, haplotype analysis showed a significant association of haplotype AG (OR 2.50 (CI 1.50-4.16; P-value 0.0002) in dominant, recessive and co-dominant models, and haplotype TT (OR 0.67 (CI 0.50-0.91; P-value 0.009) in dominant and co-dominant models with the risk of methamphetamine abuse. None of the polymorphisms in this study had a high level of linkage disequilibrium.

CONCLUSION

Our findings indicate that the PICK1 gene polymorphism might affect the risk of methamphetamine dependency in our population.

Genetics of methamphetamine use disorder: A systematic review and meta-analyses of gene association studies

Genetic susceptibility to methamphetamine use disorder is poorly understood. No twin or adequately powered genome-wide association studies (GWASs) have been conducted. However, there are a large number of hypothesis-driven candidate gene association studies, which were systematically reviewed herein. Seventy-six studies were identified, investigating markers of 75 different genes. Allele frequencies, odds ratios, 95 % confidence intervals and power were calculated. Risk of bias was also assessed as a quality measure. Meta-analyses were conducted for gene markers if three or more studies were available. Eleven markers from adequately powered studies were significantly associated with methamphetamine use disorder, with Fatty Acid Amide Hydrolase (FAAH) and Brain Derived Neurotrophic Factor (BDNF) representing promising targets. Limitations of these studies include unclear rationale for candidate gene selection, low power and high risk of bias. Future research should include replications to enable more meta-analyses, well-powered GWASs or whole exome or genome sequencing, as well as twin and family studies to further complement the findings of this review to uncover genetic contributions toward methamphetamine use disorder.

A breeding strategy to identify modifiers of high genetic risk for methamphetamine intake

Trace amine-associated receptor 1 (Taar1) impacts methamphetamine (MA) intake. A mutant allele (Taar1^m1J ) derived from the DBA/2J mouse strain codes for a non-functional receptor, and Taar1^m1J/m1J mice consume more MA than mice possessing the reference Taar1⁺ allele. To study the impact of this mutation in a genetically diverse population, heterogeneous stock-collaborative cross (HS-CC) mice, the product of an eight-way cross of standard and wild-derived strains, were tested for MA intake. HS-CC had low MA intake, so an HS-CC by DBA/2J strain F2 intercross was created to transfer the mutant allele onto the diverse background, and used for selective breeding. To study residual variation in MA intake existing in Taar1^m1J/m1J mice, selective breeding for higher (MAH) vs lower (MAL) MA intake was initiated from Taar1^m1J/m1J F2 individuals; a control line of Taar1^+/+ individuals (MAC) was retained. The lines were also examined for MA-induced locomotor and thermal responses, and fluid and tastant consumption. Taar1^m1J/m1J F2 mice consumed significantly more MA than Taar1^+/+ F2 mice. Response to selection was significant by generation 2 and there were corresponding differences in fluid consumed. Fluid consumption was not different in non-MA drinking studies. Taar1^m1J/m1J genotype (MAL or MAH vs MAC mice) was associated with heighted MA locomotor and reduced hypothermic responses. MAL mice exhibited greater sensitization than MAH mice, but the selected lines did not consistently differ for thermal or tastant phenotypes. Residual variation among high-risk Taar1^m1J/m1J mice appears to involve mechanisms associated with neuroadaptation to MA, but not sensitivity to hypothermic effects of MA.

Pharmacogenetics of drug dependence: Polymorphisms of genes involved in glutamate neurotransmission

Multiple studies provide evidence to support dysfunction of glutamate neurotransmission in the pathogenesis of drug dependence. Pharmacogenetic investigation of glutamate-related genes has provided further support for the involvement of this neurotransmitter in the risk of, and consequences of, drug abuse and dependence. This paper aims to provide a brief review of these association studies. Findings involving single nucleotide polymorphisms (SNPs) in glutamate receptor genes (GRIN, GRIA) and glutamate transporter genes (SLC1A, SLC17A) are reviewed as potential risk factors. As yet a clear perspective of the functional consequences and interactions of the various reported findings is lacking.

Neuropharmacological and Neurogenetic Correlates of Opioid Use Disorder (OUD) As a Function of Ethnicity: Relevance to Precision Addiction Medicine

BACKGROUND

Over 100 people die daily from opioid overdose and $78.5B per year is spent on treatment efforts, however, the real societal cost is multifold greater. Alternative strategies to eradicate/manage drug misuse and addiction need consideration. The perception of opioid addiction as a social/criminal problem has evolved to evidence-based considerations of them as clinical disorders with a genetic basis. We present evaluations of the genetics of addiction with ancestryspecific risk profiles for consideration.

OBJECTIVE

Studies of gene variants associated with predisposition to substance use disorders (SUDs) are monolithic, and exclude many ethnic groups, especially Hispanics and African Americans. We evaluate gene polymorphisms that impact brain reward and predispose individuals to opioid addictions, with a focus on the disparity of research which includes individuals of African and Hispanic descent.

METHODOLOGY

PubMed and Google Scholar were searched for: Opioid Use Disorder (OUD), Genome- wide association studies (GWAS); genetic variants; polymorphisms, restriction fragment length polymorphisms (RFLP); genomics, epigenetics, race, ethnic group, ethnicity, ancestry, Caucasian/ White, African American/Black, Hispanic, Asian, addictive behaviors, reward deficiency syndrome (RDS), mutation, insertion/deletion, and promotor region.

RESULTS

Many studies exclude non-White individuals. Studies that include diverse populations report ethnicity-specific frequencies of risk genes, with certain polymorphisms specifically associated with Caucasian and not African-American or Hispanic susceptibility to OUD or SUDs, and vice versa.

CONCLUSION

To adapt precision medicine-based addiction management in a blended society, we propose that ethnicity/ancestry-informed genetic variations must be analyzed to provide real precision- guided therapeutics with the intent to attenuate this uncontrollable fatal epidemic.

Association Between Brain-Derived Neurotrophic Factor Val66Met Polymorphism and Methamphetamine Use Disorder: A Meta-Analysis

Background: Several studies had examined the association between brain-derived neurotrophic factor (BDNF) Val66Met polymorphism and methamphetamine (METH) use disorder, whereas the results were conflicting. The aim of this study was to conduct a meta-analysis to achieve a pooled effect size of the association between BDNF Val66Met polymorphism and METH use disorder. Methods: Literature searches were conducted in PubMed, EMBASE, and Cochrane Library up to July, 2020. All relevant studies on the relationship of BDNF Val66Met polymorphism and METH addiction were retrieved. Pooled odds ratios (ORs) with 95% confidence intervals (95% CIs) were calculated in the dominant, recessive, co-dominant, and allele model to appraise the association. Results: Seven case-control studies with a total of 2,204 subjects (956 METH-dependent cases and 1,248 healthy controls) were included in this meta-analysis. The results showed a significant correlation between BDNF Val66Met polymorphism and METH dependence in overall population under different genetic models. However, subgroup analysis indicated that the association only existed in Han Chinese but not in other Asian populations. Conclusion: Although the current data indicate that BDNF Val66Met polymorphism might be a potential genetic factor for METH use disorder, more researches are needed to prove its role in different populations.

Riluzole for treatment of men with methamphetamine dependence: A randomized, double-blind, placebo-controlled clinical trial

BACKGROUND

Riluzole is a glutamate regulator and effective in treatment of neuropsychiatric conditions.

AIMS

We assessed riluzole for treatment of methamphetamine dependence.

METHODS

In this randomized, double-blind, placebo-controlled clinical trial, male outpatients with methamphetamine dependence who were 18-65 years old received either 50 mg riluzole ( n=34) or placebo ( n=54) twice daily for 12 weeks. Patients were excluded in case of comorbid serious medical conditions or neurologic disorders, comorbid psychiatric disorders other than methamphetamine dependence requiring specific treatment interventions, simultaneous positive urine test result for substances of abuse other than methamphetamine, smoking >3 days per week, simultaneous consumption of medications which are contraindicated or have interaction with riluzole.

RESULTS

Concerning primary outcomes, the cumulative mean number of attended weekly visits was higher in the riluzole arm compared with the placebo arm approaching a statistically significant difference (riluzole, median (range)=13.00 (2.00-13.00); placebo=4.00 (2.00-13.00); Mann-Whitney U=505.00, p-value=0.073), and the weekly measured rate of positive methamphetamine urine test results was significantly lower in the riluzole arm by the end of the study (riluzole=1 (5.00%), placebo=9 (45.00%), p-value=0.004). Patients in the riluzole arm experienced significantly greater improvement on all the craving, withdrawal, and depression measures regarding mean score changes from baseline to endpoint. No significant difference was detected between the two arms in terms of incidence of adverse events.

CONCLUSION

Future randomized clinical trials are needed to investigate proper dosing strategy in a more inclusive sample.

Functional rs6265 polymorphism in the brain-derived neurotrophic factor gene confers protection against neurocognitive dysfunction in posttraumatic stress disorder among Chinese patients with hepatocellular carcinoma

Posttraumatic stress disorder (PTSD) is a psychiatric disorder that plagues trauma survivors. Evidence shows that brain-derived neurotrophic factor (BDNF) may be involved in the occurrence and development of PTSD. Here we tried to demonstrate whether BDNF gene polymorphisms are correlated with neurocognitive function following PTSD in patients with hepatocellular carcinoma (HCC). This study included 102 patients with HCC complicated with PTSD, 146 HCC patients, and 152 healthy volunteers. Initially, we evaluated the neurocognitive function of the study subjects. Next, we measured BDNF G11757C and rs6265 polymorphisms by polymerase chain reaction-restriction fragment length polymorphism. The correlation of BDNF polymorphisms and BDNF level with HCC complicated with PTSD was evaluated. The results revealed that HCC complicated with PTSD showed decreased serum BDNF level and Mini-mental state examination (MMSE) score. Serum BDNF level of HCC and HCC complicated with PTSD was positively correlated with MMSE score. GA + AA allele and A allele of rs6265 increased the risk of PTSD among patients with HCC. GA and AA genotypes of rs6265 were correlated with the decreased MMSE score of HCC complicated with PTSD. Haplotype GA of rs6265 and G11757C increased the risk of PTSD for HCC, while haplotype CG decreased this risk. Lastly, the logistic regression analysis suggested that low BDNF level was a contributor to HCC complicated with PTSD, while GG genotype of rs6265 served as a protective factor. Collectively, this study defines the GG genotype of BDNF rs6265 polymorphism as a protector to HCC complicated with PTSD. In addition, these results provided a promising target for PTSD prevention in patients with HCC.

Association study of the functional Catechol-O-Methyltranferase (COMT) Val158Met polymorphism on executive cognitive function in a Thai sample

Catechol-O-Methyltranferase (COMT) plays a crucial role in the removal of cortical dopamine and is strongly implicated in human executive function. Numerous studies have reported associations of the COMT Val158Met (rs4680) polymorphism with executive function in healthy subjects. However, little work has investigated this in the Thai population and the relationship of age and education with this association remains unclear. Therefore, this study was designed to investigate the association of this polymorphism of the COMT gene with executive cognitive brain function in healthy subjects and the relationship with age and education. The Wisconsin Card Sorting Test (WCST) was performed to assess executive function in 254 healthy Thai subjects (aged 20-72 years). The results showed a significant association of rs4680 with executive function, in which Val/Met heterozygotes demonstrated better cognitive set shifting performance. Moreover, Met allele carriers showed a significantly stronger effect in the categories completed score than did Val homozygotes. Furthermore, age and education also showed a significant association with COMT genotype and WCST. These results revealed that executive cognitive function is associated with COMT genotype and influenced by age and/or education level in a Thai sample.

Genetic variation of GRIA3 gene is associated with vulnerability to methamphetamine dependence and its associated psychosis

Methamphetamine (METH) is an addictive psychostimulant drug commonly leading to schizophrenia-like psychotic symptoms. Disturbances in glutamatergic neurotransmission have been proposed as neurobiological mechanisms and the α-amino-3 hydroxy-5 methyl-4 isoxazole propionic acid (AMPA) glutamate receptor has been implicated in these processes. Moreover, genetic variants in GRIAs, genes encoding AMPA receptor subunits, have been observed in association with both drug dependence and psychosis. We hypothesized that variation of GRIA genes may be associated with METH dependence and METH-induced psychosis. Genotyping of GRIA1 rs1428920, GRIA2 rs3813296, GRIA3 rs3761554, rs502434 and rs989638 was performed in 102 male Thai controls and 100 METH-dependent subjects (53 with METH-dependent psychosis). We observed no evidence of association with METH dependence and METH-dependent psychosis in the GRIA1 and GRIA2 polymorphisms, nor with single polymorphisms rs3761554 and rs989638 in GRIA3. An association of GRIA3 rs502434 was identified with both METH dependence and METH-dependent psychosis, although this did not withstand correction for multiple testing. Combining the analysis of this site with the previously-demonstrated association with BDNF rs6265 resulted in a highly significant effect. These preliminary findings indicate that genetic variability in GRIA3 may interact with a functional BDNF polymorphism to provide a strong risk factor for the development of METH dependence in the Thai population.

Verification of a genetic locus for methamphetamine intake and the impact of morphine

A quantitative trait locus (QTL) on proximal chromosome (Chr) 10 accounts for > 50% of the genetic variance in methamphetamine (MA) intake in mice selectively bred for high (MAHDR) and low (MALDR) voluntary MA drinking. The µ-opioid receptor (MOP-r) gene, Oprm1, resides at the proximal end of Chr 10, and buprenorphine reduces MA intake in MAHDR mice. However, this drug has only partial agonist effects at MOP-r. We investigated the impact of a full MOP-r agonist, morphine, on MA intake and saccharin intake, measured MOP-r density and affinity in several brain regions of the MA drinking lines and their C57BL/6J (B6) and DBA/2J (D2) progenitor strains, and measured MA intake in two congenic strains of mice to verify the QTL and reduce the QTL interval. Morphine reduced MA intake in the MAHDR line, but also reduced saccharin and total fluid intake. MOP-r density was lower in the medial prefrontal cortex of MAHDR, compared to MALDR, mice, but not in the nucleus accumbens or ventral midbrain; there were no MOP-r affinity differences. No significant differences in MOP-r density or affinity were found between the progenitor strains. Finally, Chr 10 congenic results were consistent with previous data suggesting that Oprm1 is not a quantitative trait gene, but is impacted by the gene network underlying MA intake. Stimulation of opioid pathways by a full agonist can reduce MA intake, but may also non-specifically affect consummatory behavior; thus, a partial agonist may be a better pharmacotherapeutic.

Association of polymorphisms in GAD1 and GAD2 genes with methamphetamine dependence

AIM

Association between polymorphisms in GAD genes and methamphetamine (METH) dependence was investigated in the Thai population.

MATERIALS & METHODS

Genotypes of rs769404 and rs701492 in GAD1 and rs2236418 in GAD2 polymorphisms were determined in 100 METH-dependent male subjects and 102 matched controls.

RESULTS

The genotype and allele frequencies of rs2236418 (GAD2) were associated with METH dependence and METH with psychosis, in which the G allele was related to increased risk. The presence of the rs769404-rs701492 (GAD1) C-C haplotype was associated with METH psychosis.

CONCLUSION

This study indicates that genetic variability in GAD1 and GAD2 contributes to risk of METH dependence and METH psychosis in the Thai population and indicates the role of the GABAergic system in these disorders.

Effect of the sonic hedgehog receptor smoothened on the survival and function of dopaminergic neurons

OBJECTIVE

To determine the influence of the sonic hedgehog (shh) pathway and its receptor smoothened (smo), on the survival and functionality of dopaminergic (DA) neurons.

BACKGROUND

During early development, shh induces the differentiation of DA neurons. However, it is unknown whether shh signaling is required in the maturation or maintenance of DA neurons during later development and adulthood due to the lethality of traditional shh knockout models.

METHODS

We utilized the cre-loxP system to achieve late developmental stage and cell type-specific deletion of the shh receptor, smo, in DA neurons by crossing DATcre (dopamine transporter) mice with Smo(loxP/loxP) mice. We assessed for differences between knockout (ko) and wildtype (wt) mice using combined histochemistry, gene expression analysis, and behavioral evaluation. Number and size of DA neurons in ventral midbrain and the DA neural terminal density in striatum were measured using unbiased stereological quantification. The survival of DA neurons under neurotoxin challenge was examined in the unilateral 6-hydroxydopamine (6-OHDA) Parkinson's disease animal model and the more subtle function under challenge of the dopaminergic system was examined by methamphetamine single- and repeated challenge in wt and ko mice.

RESULTS

Tyrosine hydroxylase (TH) positive neuronal counts and neuronal size in substantia nigra (SN) and ventral tegmental area (VTA) showed no difference between wt and DAT-Smo ko mice in young (5months) or aged (22months) mice. There was also no difference in the striatal DA projections between wt and ko mice in both age groups. In unilateral striatal 6-OHDA lesions modeling Parkinson's disease, using stereotaxic injection of 6-OHDA intrastriatally led to loss of dopaminergic neurons in SN and diminished TH positive projections in striatum. However, there was no differences in survival of DA neurons between wt and ko mice. DAT-Smo ko mice demonstrated hyperactivity compared to wt mice at 5months, but showed no difference in activity at 22months. When injected with a one-time bolus of methamphetamine (METH), despite the higher basal locomotion activity, DAT-Smo ko mice showed a diminished response to a single METH challenge. In METH sensitization testing, ko mice showed decreased sensitization compared to wt mice without evidence of a delayed shift in dynamics of sensitization. Gene expression analysis showed decreased gene expression of smo, Gli 1 (known target gene of smo) and BDNF (brain-derived neurotrophic factor) in the SN. Gene expression was not altered in striatum for the genes examined in this study including dopamine receptor genes, neurotropic genes such as Glial cell line-derived neurotrophic factor (GDNF), and bone morphogenetic protein 7 (BMP7).

CONCLUSION

Our study showed the smo receptor function is not required for the maturation and survival of DA neurons during late development, aging or under stress challenge. However, smo function has an influence on behavior in young adult mice and in responses of mice to a drug that modulates DA neurochemistry through regulation of gene expression in DA neurons. Since young adult DAT-smo ko mice show hyperactivity and altered response to a psychostimulant drug (METH), this may indicate the involvement of the shh pathway in the development of functional changes that manifest as alterations in DA pathway dynamics.

Identification of Treatment Targets in a Genetic Mouse Model of Voluntary Methamphetamine Drinking

Methamphetamine has powerful stimulant and euphoric effects that are experienced as rewarding and encourage use. Methamphetamine addiction is associated with debilitating illnesses, destroyed relationships, child neglect, violence, and crime; but after many years of research, broadly effective medications have not been identified. Individual differences that may impact not only risk for developing a methamphetamine use disorder but also affect treatment response have not been fully considered. Human studies have identified candidate genes that may be relevant, but lack of control over drug history, the common use or coabuse of multiple addictive drugs, and restrictions on the types of data that can be collected in humans are barriers to progress. To overcome some of these issues, a genetic animal model comprised of lines of mice selectively bred for high and low voluntary methamphetamine intake was developed to identify risk and protective alleles for methamphetamine consumption, and identify therapeutic targets. The mu opioid receptor gene was supported as a target for genes within a top-ranked transcription factor network associated with level of methamphetamine intake. In addition, mice that consume high levels of methamphetamine were found to possess a nonfunctional form of the trace amine-associated receptor 1 (TAAR1). The Taar1 gene is within a mouse chromosome 10 quantitative trait locus for methamphetamine consumption, and TAAR1 function determines sensitivity to aversive effects of methamphetamine that may curb intake. The genes, gene interaction partners, and protein products identified in this genetic mouse model represent treatment target candidates for methamphetamine addiction.