{"gene":"CHRNA6","run_date":"2026-04-28T17:28:52","timeline":{"discoveries":[{"year":2020,"finding":"A de novo missense mutation in CHRNA6 (encoding the α6 subunit of neuronal nicotinic receptors) disrupts acetylcholine receptor structure and function, as demonstrated by in silico modeling, in vitro expression in Xenopus oocytes and GH4C1 cells, and in vivo studies in C. elegans; the α6 subunit is involved in cholinergic modulation of dopamine release in the striatum.","method":"In silico structural modeling, in vitro electrophysiology in Xenopus oocytes, cell-based assay in GH4C1 cells, and in vivo C. elegans functional studies","journal":"Parkinsonism & related disorders","confidence":"Medium","confidence_rationale":"Tier 1–2 — multiple orthogonal methods in a single study; functional disruption validated in vitro and in vivo","pmids":["32120303"],"is_preprint":false},{"year":2016,"finding":"α6-containing nAChRs (α6*-nAChRs), located in the ventral tegmental area (VTA), are required for nicotine self-administration; selective re-expression of the α6 subunit in the VTA of α6-knockout mice via lentiviral vector restores the reinforcing properties of nicotine.","method":"Genetic knockout mouse model with lentiviral rescue of α6 expression in the VTA; nicotine self-administration behavioral assay","journal":"Translational psychiatry","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis (knockout + region-specific rescue) with defined behavioral readout, consistent with broader literature on α6 nAChRs","pmids":["27327258"],"is_preprint":false},{"year":2016,"finding":"Substitution of Leu with Ser at the 9' residue in the M2 domain (pore-lining transmembrane segment) of the α6 subunit produces nicotine-hypersensitive knock-in mice with enhanced dopamine release, establishing that this residue is critical for α6-mediated channel function and dopaminergic reward signaling.","method":"Knock-in mouse (α6 L9'S gain-of-function mutation); nicotine-induced behavior and dopamine release measurements","journal":"Translational psychiatry","confidence":"High","confidence_rationale":"Tier 1–2 — active-site mutagenesis via knock-in with defined physiological readout (dopamine release), replicated across multiple labs as cited in review","pmids":["27327258"],"is_preprint":false},{"year":2022,"finding":"The human CHRNA6 3'-UTR SNP (rs2304297) is functional in vivo: knock-in rats with the G allele show genotype- and sex-specific enhancement of nicotine-induced locomotion and anxiolytic behavior after 4-day nicotine pretreatment, but no effect on baseline food reinforcement or locomotion.","method":"CRISPR-Cas9 knock-in rat model; behavioral assays (open-field locomotion, anxiety tests, food self-administration)","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2 — direct genetic manipulation with defined behavioral phenotype; single lab","pmids":["35328565"],"is_preprint":false},{"year":2023,"finding":"The human CHRNA6 3'-UTR SNP (rs2304297) sex-dependently enhances nicotine + cue-primed reinstatement of nicotine-seeking in adolescent male rats (α6GG > α6CC), but not cue-only or nicotine-only reinstatement, and has no effect on natural food reward or nicotine self-administration acquisition.","method":"CRISPR-Cas9 knock-in rat model; intravenous nicotine self-administration, extinction, and reinstatement paradigm","journal":"Frontiers in psychiatry","confidence":"Medium","confidence_rationale":"Tier 2 — direct genetic manipulation with defined behavioral phenotype; single lab","pmids":["36704741"],"is_preprint":false},{"year":2024,"finding":"The CHRNA6 3'-UTR SNP (rs2304297) sex- and genotype-dependently modulates dopamine (DA) and norepinephrine (NE) tissue levels in limbic reward regions (including nucleus accumbens) during development and after nicotine + cue reinstatement, with male α6GG rats showing suppressed NAc DA levels post-reinstatement.","method":"CRISPR-Cas9 knock-in rat model; HPLC-based tissue neurochemistry for DA, NE, and metabolites across brain regions","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2 — direct genetic manipulation with neurochemical readout; single lab","pmids":["38612487"],"is_preprint":false},{"year":2024,"finding":"The CHRNA6 3'-UTR SNP (rs2304297) sex- and genotype-dependently enhances nicotine-induced methamphetamine self-administration and modulates nicotine/METH-induced dopamine overflow in the nucleus accumbens shell of adolescent rats, measured by in vivo microdialysis.","method":"CRISPR-Cas9 knock-in rat model; intravenous METH self-administration; in vivo microdialysis with HPLC-ECD for DA overflow in NAc shell","journal":"Frontiers in pharmacology","confidence":"Medium","confidence_rationale":"Tier 2 — direct genetic manipulation with orthogonal in vivo neurochemical and behavioral readouts; single lab","pmids":["39206256"],"is_preprint":false},{"year":2026,"finding":"The CHRNA6 3'-UTR SNP (rs2304297) produces age-, sex-, and genotype-dependent differences in nicotine-induced locomotor activity and tyrosine hydroxylase (dopamine synthesis marker) levels in the VTA; adolescent male α6GG rats have higher TH levels in the VTA than α6CC rats independent of drug exposure.","method":"CRISPR-Cas9 knock-in rat model; locomotor behavioral assay; western blot or immunohistochemistry for tyrosine hydroxylase in VTA and NAc","journal":"Nicotine & tobacco research","confidence":"Medium","confidence_rationale":"Tier 2 — direct genetic manipulation with protein expression and behavioral readouts; single lab","pmids":["40736212"],"is_preprint":false},{"year":2012,"finding":"Chrna6 is preferentially expressed by retinal ganglion cells (RGCs) in the mouse retina, as confirmed by immunofluorescence; Chrna6 expression decreases progressively with RGC death in glaucomatous DBA/2J mice and after optic nerve crush injury, and is expressed by RGCs independently of photoreceptor-derived stimuli.","method":"Immunofluorescence, gene expression arrays, RT-PCR in mouse retina; genetic model (DBA/2J glaucoma), optic nerve crush model, C3H/HeJ photoreceptor-less retinas","journal":"Current eye research","confidence":"Medium","confidence_rationale":"Tier 2 — direct protein localization confirmed by immunofluorescence with functional correlation in disease model; single lab","pmids":["23002780"],"is_preprint":false},{"year":2022,"finding":"Inhibition of CHRNA6 (using the antagonist BPiDl) ameliorates depression-like behavior in a chronic unpredictable mild stress rat model and alters dopamine levels in the brain, suggesting CHRNA6 channel activity contributes to dopaminergic regulation relevant to mood.","method":"Pharmacological inhibition with BPiDl in CUMS rat model; behavioral tests; ELISA for neurotransmitters; qRT-PCR for gene expression and miRNAs","journal":"Behavioural brain research","confidence":"Low","confidence_rationale":"Tier 3 — pharmacological inhibition in vivo with behavioral readout but limited mechanistic resolution for CHRNA6 specifically","pmids":["35063497"],"is_preprint":false}],"current_model":"CHRNA6 encodes the α6 subunit of neuronal nicotinic acetylcholine receptors (nAChRs), which are ligand-gated ion channels; α6-containing receptors in the ventral tegmental area are required for nicotine self-administration and dopamine release (demonstrated by knockout/rescue in mice), the M2 domain 9' leucine residue is critical for channel gating (gain-of-function knock-in mice show enhanced dopamine release and nicotine hypersensitivity), a functional 3'-UTR SNP (rs2304297) sex- and genotype-dependently modulates nicotine-induced dopaminergic activity and reward behaviors in adolescent rats, and a missense mutation disrupts receptor structure and function as shown in Xenopus oocytes and C. elegans."},"narrative":{"teleology":[{"year":2012,"claim":"Establishing that Chrna6 is not exclusively a midbrain dopaminergic gene, this study showed preferential expression in retinal ganglion cells and its progressive loss accompanying RGC death, broadening the known expression map of α6 nAChR subunits.","evidence":"Immunofluorescence and gene expression arrays in mouse retina, DBA/2J glaucoma model, and optic nerve crush model","pmids":["23002780"],"confidence":"Medium","gaps":["Functional role of α6-containing nAChRs in retinal ganglion cell physiology or survival not established","No electrophysiological characterization of α6 currents in RGCs"]},{"year":2016,"claim":"Two critical mechanistic questions were answered simultaneously: α6-containing nAChRs in the VTA are necessary and sufficient for nicotine reinforcement (knockout/rescue), and the M2 9' leucine is a key gating determinant whose mutation produces hypersensitive channels and enhanced dopamine release (gain-of-function knock-in).","evidence":"α6-knockout mice with lentiviral VTA rescue; α6 L9'S gain-of-function knock-in mice; nicotine self-administration and dopamine release assays","pmids":["27327258"],"confidence":"High","gaps":["Subunit stoichiometry of native α6-containing receptors mediating reinforcement not defined","Whether α6 acts in VTA cell bodies versus terminals for dopamine release not resolved","No structural data for the α6 M2 domain pore region"]},{"year":2020,"claim":"A de novo missense mutation demonstrated that single amino acid changes in the α6 subunit can disrupt receptor assembly and function, providing the first human genetic variant with validated loss-of-function mechanism.","evidence":"In silico modeling, Xenopus oocyte electrophysiology, GH4C1 cell expression, and C. elegans in vivo functional assays","pmids":["32120303"],"confidence":"Medium","gaps":["Single patient/variant; broader genotype-phenotype spectrum for CHRNA6 coding mutations unknown","Mechanism of disruption (assembly vs. trafficking vs. gating) not fully dissected","No mammalian in vivo validation of this specific mutation"]},{"year":2022,"claim":"The CHRNA6 3'-UTR SNP rs2304297 was shown to be functional in vivo by CRISPR knock-in, producing genotype- and sex-specific differences in nicotine-induced locomotion and anxiety, establishing that non-coding variation at CHRNA6 directly modulates nicotine behavioral pharmacology.","evidence":"CRISPR-Cas9 knock-in rat model with behavioral assays for locomotion, anxiety, and food self-administration","pmids":["35328565"],"confidence":"Medium","gaps":["Molecular mechanism by which the G allele alters α6 mRNA or protein levels not determined","Effects observed in a single lab; independent replication pending"]},{"year":2023,"claim":"Extending the functional characterization of rs2304297, the G allele was shown to selectively enhance nicotine + cue-primed reinstatement of drug-seeking in adolescent males, dissociating relapse vulnerability from acquisition of self-administration.","evidence":"CRISPR knock-in rats; intravenous nicotine self-administration with extinction and reinstatement paradigm","pmids":["36704741"],"confidence":"Medium","gaps":["Neural circuit through which the SNP modulates reinstatement not mapped","Whether the SNP affects α6 protein expression in the VTA/NAc not directly measured"]},{"year":2024,"claim":"The neurochemical basis of the rs2304297 behavioral phenotype was identified: the G allele sex-dependently modulates dopamine and norepinephrine tissue levels in reward regions and alters nicotine-induced dopamine overflow in the nucleus accumbens shell, directly linking the SNP to mesolimbic catecholamine signaling.","evidence":"CRISPR knock-in rats; HPLC tissue neurochemistry and in vivo microdialysis in NAc shell","pmids":["38612487","39206256"],"confidence":"Medium","gaps":["Whether altered dopamine levels reflect changes in α6 receptor density, affinity, or downstream signaling unknown","All rs2304297 studies from a single laboratory","Post-translational or trafficking effects of the 3'-UTR variant not examined"]},{"year":null,"claim":"The molecular mechanism by which rs2304297 alters α6 subunit expression or receptor function remains undefined, and the subunit stoichiometry and interacting partners of native α6-containing nAChRs in specific circuits are incompletely characterized.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No direct measurement of how rs2304297 affects mRNA stability, translation, or miRNA binding in native neurons","Crystal or cryo-EM structure of α6-containing nAChR not available","Role of α6 nAChRs in non-dopaminergic circuits (e.g., retinal, cortical) functionally unexplored"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005215","term_label":"transporter activity","supporting_discovery_ids":[0,1,2]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,1,2,8]}],"pathway":[{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[1,2,5,6]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[1,2,3,5]}],"complexes":["neuronal nicotinic acetylcholine receptor (α6-containing)"],"partners":[],"other_free_text":[]},"mechanistic_narrative":"CHRNA6 encodes the α6 subunit of neuronal nicotinic acetylcholine receptors (nAChRs), a ligand-gated ion channel subunit that is critical for dopaminergic neurotransmission and nicotine reward signaling in the mesolimbic system. α6-containing nAChRs in the ventral tegmental area are required for nicotine self-administration, as demonstrated by knockout/lentiviral rescue experiments, and the M2 domain 9' leucine residue is essential for channel gating and dopamine release [PMID:27327258]. A functional 3'-UTR SNP (rs2304297) modulates nicotine-induced dopaminergic activity, locomotor sensitization, and relapse-like behavior in a sex- and age-dependent manner, with the G allele associated with enhanced reward-related dopamine signaling in adolescent males [PMID:35328565, PMID:36704741, PMID:38612487]. A de novo missense mutation in CHRNA6 disrupts receptor structure and function, linking α6 subunit dysfunction to cholinergic-dopaminergic signaling impairment relevant to parkinsonism [PMID:32120303]."},"prefetch_data":{"uniprot":{"accession":"Q15825","full_name":"Neuronal acetylcholine receptor subunit alpha-6","aliases":[],"length_aa":494,"mass_kda":56.9,"function":"Component of neuronal acetylcholine receptors (nAChRs) that function as pentameric, ligand-gated cation channels with high calcium permeability among other activities. nAChRs are excitatory neurotrasnmitter receptors formed by a collection of nAChR subunits known to mediate synaptic transmission in the nervous system and the neuromuscular junction. Each nAchR subunit confers differential attributes to channel properties, including activation, deactivation and desensitization kinetics, pH sensitivity, cation permeability, and binding to allosteric modulators (Probable). CHRNA6 forms pentameric channels with CHRNB2, CHRNB3 and CHRNA4 that exhibit high sensitivity to ACh and nicotine and are predominantly expressed in only a few brain areas, including dopaminergic neurons, norepirephrine neurons and cells of the visual system (PubMed:16835356). nAChrs containing CHRNA6 subunits mediate endogenous cholinergic modulation of dopamine and gamma-aminobutyric acid (GABA) release in response to nicotine at nerve terminals","subcellular_location":"Synaptic cell membrane","url":"https://www.uniprot.org/uniprotkb/Q15825/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CHRNA6","classification":"Not Classified","n_dependent_lines":2,"n_total_lines":1208,"dependency_fraction":0.0016556291390728477},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/CHRNA6","total_profiled":1310},"omim":[{"mim_id":"612052","title":"SMOKING AS A QUANTITATIVE TRAIT LOCUS 3; SQTL3","url":"https://www.omim.org/entry/612052"},{"mim_id":"611003","title":"SMOKING AS A QUANTITATIVE TRAIT LOCUS 1; SQTL1","url":"https://www.omim.org/entry/611003"},{"mim_id":"606888","title":"CHOLINERGIC RECEPTOR, NEURONAL NICOTINIC, ALPHA POLYPEPTIDE 6; CHRNA6","url":"https://www.omim.org/entry/606888"},{"mim_id":"188890","title":"TOBACCO ADDICTION, SUSCEPTIBILITY TO","url":"https://www.omim.org/entry/188890"},{"mim_id":"118507","title":"CHOLINERGIC RECEPTOR, NEURONAL NICOTINIC, BETA POLYPEPTIDE 2; CHRNB2","url":"https://www.omim.org/entry/118507"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in single","driving_tissues":[{"tissue":"retina","ntpm":3.0}],"url":"https://www.proteinatlas.org/search/CHRNA6"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"Q15825","domains":[{"cath_id":"2.70.170.10","chopping":"34-238","consensus_level":"high","plddt":92.8663,"start":34,"end":238},{"cath_id":"1.20.58.390","chopping":"240-356_437-494","consensus_level":"medium","plddt":86.5525,"start":240,"end":494}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q15825","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q15825-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q15825-F1-predicted_aligned_error_v6.png","plddt_mean":79.44},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CHRNA6","jax_strain_url":"https://www.jax.org/strain/search?query=CHRNA6"},"sequence":{"accession":"Q15825","fasta_url":"https://rest.uniprot.org/uniprotkb/Q15825.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q15825/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q15825"}},"corpus_meta":[{"pmid":"20418888","id":"PMC_20418888","title":"Sequence variants at CHRNB3-CHRNA6 and CYP2A6 affect smoking behavior.","date":"2010","source":"Nature genetics","url":"https://pubmed.ncbi.nlm.nih.gov/20418888","citation_count":556,"is_preprint":false},{"pmid":"18055561","id":"PMC_18055561","title":"The neuronal nicotinic receptor subunit genes (CHRNA6 and CHRNB3) are associated with subjective responses to tobacco.","date":"2007","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/18055561","citation_count":84,"is_preprint":false},{"pmid":"24253422","id":"PMC_24253422","title":"Significant associations of CHRNA2 and CHRNA6 with nicotine dependence in European American and African American populations.","date":"2013","source":"Human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/24253422","citation_count":34,"is_preprint":false},{"pmid":"24401102","id":"PMC_24401102","title":"Multiple distinct CHRNB3-CHRNA6 variants are genetic risk factors for nicotine dependence in African Americans and European Americans.","date":"2014","source":"Addiction (Abingdon, England)","url":"https://pubmed.ncbi.nlm.nih.gov/24401102","citation_count":25,"is_preprint":false},{"pmid":"27327258","id":"PMC_27327258","title":"Crucial roles of the CHRNB3-CHRNA6 gene cluster on chromosome 8 in nicotine dependence: update and subjects for future research.","date":"2016","source":"Translational psychiatry","url":"https://pubmed.ncbi.nlm.nih.gov/27327258","citation_count":21,"is_preprint":false},{"pmid":"32120303","id":"PMC_32120303","title":"Co-occurring WARS2 and CHRNA6 mutations in a child with a severe form of infantile parkinsonism.","date":"2020","source":"Parkinsonism & related disorders","url":"https://pubmed.ncbi.nlm.nih.gov/32120303","citation_count":14,"is_preprint":false},{"pmid":"28851948","id":"PMC_28851948","title":"Significant association of the CHRNB3-CHRNA6 gene cluster with nicotine dependence in the Chinese Han population.","date":"2017","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/28851948","citation_count":13,"is_preprint":false},{"pmid":"24675634","id":"PMC_24675634","title":"Variants near CHRNB3-CHRNA6 are associated with DSM-5 cocaine use disorder: evidence for pleiotropy.","date":"2014","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/24675634","citation_count":11,"is_preprint":false},{"pmid":"35328565","id":"PMC_35328565","title":"Sex- and Genotype-Dependent Nicotine-Induced Behaviors in Adolescent Rats with a Human Polymorphism (rs2304297) in the 3'-UTR of the CHRNA6 Gene.","date":"2022","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/35328565","citation_count":9,"is_preprint":false},{"pmid":"23002780","id":"PMC_23002780","title":"Effects of glaucoma on Chrna6 expression in the retina.","date":"2012","source":"Current eye research","url":"https://pubmed.ncbi.nlm.nih.gov/23002780","citation_count":9,"is_preprint":false},{"pmid":"35063497","id":"PMC_35063497","title":"Inhibition of TRPC1, TRPM4 and CHRNA6 ion channels ameliorates depression-like behavior in rats.","date":"2022","source":"Behavioural brain research","url":"https://pubmed.ncbi.nlm.nih.gov/35063497","citation_count":8,"is_preprint":false},{"pmid":"24792900","id":"PMC_24792900","title":"Combined effect between CHRNB3-CHRNA6 region gene variant (rs6474412) and smoking in psoriasis vulgaris severity.","date":"2014","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/24792900","citation_count":6,"is_preprint":false},{"pmid":"25110504","id":"PMC_25110504","title":"Genetic Association of CHRNB3 and CHRNA6 Gene Polymorphisms with Nicotine Dependence Syndrome Scale in Korean Population.","date":"2014","source":"Psychiatry investigation","url":"https://pubmed.ncbi.nlm.nih.gov/25110504","citation_count":6,"is_preprint":false},{"pmid":"25823894","id":"PMC_25823894","title":"A genetic variant in CHRNB3-CHRNA6 increases risk of esophageal squamous cell carcinoma in Chinese populations.","date":"2015","source":"Carcinogenesis","url":"https://pubmed.ncbi.nlm.nih.gov/25823894","citation_count":6,"is_preprint":false},{"pmid":"36704741","id":"PMC_36704741","title":"Sex- and genotype-dependent nicotine plus cue-primed reinstatement is enhanced in adolescent Sprague Dawley rats containing the human CHRNA6 3'-UTR polymorphism (rs2304297).","date":"2023","source":"Frontiers in psychiatry","url":"https://pubmed.ncbi.nlm.nih.gov/36704741","citation_count":5,"is_preprint":false},{"pmid":"38447752","id":"PMC_38447752","title":"CHRNA6 RNA In Situ Hybridization Is a Useful Tool for the Diagnosis of Extraskeletal Myxoid Chondrosarcoma.","date":"2024","source":"Modern pathology : an official journal of the United States and Canadian Academy of Pathology, Inc","url":"https://pubmed.ncbi.nlm.nih.gov/38447752","citation_count":5,"is_preprint":false},{"pmid":"21831805","id":"PMC_21831805","title":"[Human chromosome 8p11 (CHRNB3-CHRNA6) region gene polymorphisms and susceptibility to lung cancer in Chinese Han population].","date":"2011","source":"Yi chuan = Hereditas","url":"https://pubmed.ncbi.nlm.nih.gov/21831805","citation_count":5,"is_preprint":false},{"pmid":"39206256","id":"PMC_39206256","title":"Sub-chronic nicotine exposure influences methamphetamine self-administration and dopamine overflow in a sex-and genotype-dependent manner in humanized CHRNA6 3'-UTR SNP (rs2304297) adolescent rats.","date":"2024","source":"Frontiers in pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/39206256","citation_count":4,"is_preprint":false},{"pmid":"38612487","id":"PMC_38612487","title":"Dopamine and Norepinephrine Tissue Levels in the Developing Limbic Brain Are Impacted by the Human CHRNA6 3'-UTR Single-Nucleotide Polymorphism (rs2304297) in Rats.","date":"2024","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/38612487","citation_count":4,"is_preprint":false},{"pmid":"37680128","id":"PMC_37680128","title":"Involvement of CHRNA6 in the Immune Response in Lung Squamous Cell Carcinoma and its Potential as a Drug Target for the Disease.","date":"2023","source":"Current pharmaceutical design","url":"https://pubmed.ncbi.nlm.nih.gov/37680128","citation_count":3,"is_preprint":false},{"pmid":"27085880","id":"PMC_27085880","title":"Evidence for Association Between Low Frequency Variants in CHRNA6/CHRNB3 and Antisocial Drug Dependence.","date":"2016","source":"Behavior genetics","url":"https://pubmed.ncbi.nlm.nih.gov/27085880","citation_count":3,"is_preprint":false},{"pmid":"40331132","id":"PMC_40331132","title":"\"Unraveling the role of CHRNA6, the neuronal α6 nicotinic acetylcholine receptor subunit\".","date":"2025","source":"Receptors (Basel, Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/40331132","citation_count":3,"is_preprint":false},{"pmid":"40736212","id":"PMC_40736212","title":"Sex- and Genotype-Dependent Nicotine-Induced Behaviors in Adult Rats With a Human Polymorphism (rs2304297) in the 3'-Untranslated Region of the CHRNA6 Gene.","date":"2026","source":"Nicotine & tobacco research : official journal of the Society for Research on Nicotine and Tobacco","url":"https://pubmed.ncbi.nlm.nih.gov/40736212","citation_count":1,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":13910,"output_tokens":2505,"usd":0.039653},"stage2":{"model":"claude-opus-4-6","input_tokens":5869,"output_tokens":1986,"usd":0.118493},"total_usd":0.158146,"stage1_batch_id":"msgbatch_011kfMfE81o6CTcyhVUqumuW","stage2_batch_id":"msgbatch_01DTputS6WNkH745x1nVSoBo","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2020,\n      \"finding\": \"A de novo missense mutation in CHRNA6 (encoding the α6 subunit of neuronal nicotinic receptors) disrupts acetylcholine receptor structure and function, as demonstrated by in silico modeling, in vitro expression in Xenopus oocytes and GH4C1 cells, and in vivo studies in C. elegans; the α6 subunit is involved in cholinergic modulation of dopamine release in the striatum.\",\n      \"method\": \"In silico structural modeling, in vitro electrophysiology in Xenopus oocytes, cell-based assay in GH4C1 cells, and in vivo C. elegans functional studies\",\n      \"journal\": \"Parkinsonism & related disorders\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 — multiple orthogonal methods in a single study; functional disruption validated in vitro and in vivo\",\n      \"pmids\": [\"32120303\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"α6-containing nAChRs (α6*-nAChRs), located in the ventral tegmental area (VTA), are required for nicotine self-administration; selective re-expression of the α6 subunit in the VTA of α6-knockout mice via lentiviral vector restores the reinforcing properties of nicotine.\",\n      \"method\": \"Genetic knockout mouse model with lentiviral rescue of α6 expression in the VTA; nicotine self-administration behavioral assay\",\n      \"journal\": \"Translational psychiatry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis (knockout + region-specific rescue) with defined behavioral readout, consistent with broader literature on α6 nAChRs\",\n      \"pmids\": [\"27327258\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Substitution of Leu with Ser at the 9' residue in the M2 domain (pore-lining transmembrane segment) of the α6 subunit produces nicotine-hypersensitive knock-in mice with enhanced dopamine release, establishing that this residue is critical for α6-mediated channel function and dopaminergic reward signaling.\",\n      \"method\": \"Knock-in mouse (α6 L9'S gain-of-function mutation); nicotine-induced behavior and dopamine release measurements\",\n      \"journal\": \"Translational psychiatry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — active-site mutagenesis via knock-in with defined physiological readout (dopamine release), replicated across multiple labs as cited in review\",\n      \"pmids\": [\"27327258\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"The human CHRNA6 3'-UTR SNP (rs2304297) is functional in vivo: knock-in rats with the G allele show genotype- and sex-specific enhancement of nicotine-induced locomotion and anxiolytic behavior after 4-day nicotine pretreatment, but no effect on baseline food reinforcement or locomotion.\",\n      \"method\": \"CRISPR-Cas9 knock-in rat model; behavioral assays (open-field locomotion, anxiety tests, food self-administration)\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct genetic manipulation with defined behavioral phenotype; single lab\",\n      \"pmids\": [\"35328565\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"The human CHRNA6 3'-UTR SNP (rs2304297) sex-dependently enhances nicotine + cue-primed reinstatement of nicotine-seeking in adolescent male rats (α6GG > α6CC), but not cue-only or nicotine-only reinstatement, and has no effect on natural food reward or nicotine self-administration acquisition.\",\n      \"method\": \"CRISPR-Cas9 knock-in rat model; intravenous nicotine self-administration, extinction, and reinstatement paradigm\",\n      \"journal\": \"Frontiers in psychiatry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct genetic manipulation with defined behavioral phenotype; single lab\",\n      \"pmids\": [\"36704741\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"The CHRNA6 3'-UTR SNP (rs2304297) sex- and genotype-dependently modulates dopamine (DA) and norepinephrine (NE) tissue levels in limbic reward regions (including nucleus accumbens) during development and after nicotine + cue reinstatement, with male α6GG rats showing suppressed NAc DA levels post-reinstatement.\",\n      \"method\": \"CRISPR-Cas9 knock-in rat model; HPLC-based tissue neurochemistry for DA, NE, and metabolites across brain regions\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct genetic manipulation with neurochemical readout; single lab\",\n      \"pmids\": [\"38612487\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"The CHRNA6 3'-UTR SNP (rs2304297) sex- and genotype-dependently enhances nicotine-induced methamphetamine self-administration and modulates nicotine/METH-induced dopamine overflow in the nucleus accumbens shell of adolescent rats, measured by in vivo microdialysis.\",\n      \"method\": \"CRISPR-Cas9 knock-in rat model; intravenous METH self-administration; in vivo microdialysis with HPLC-ECD for DA overflow in NAc shell\",\n      \"journal\": \"Frontiers in pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct genetic manipulation with orthogonal in vivo neurochemical and behavioral readouts; single lab\",\n      \"pmids\": [\"39206256\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"The CHRNA6 3'-UTR SNP (rs2304297) produces age-, sex-, and genotype-dependent differences in nicotine-induced locomotor activity and tyrosine hydroxylase (dopamine synthesis marker) levels in the VTA; adolescent male α6GG rats have higher TH levels in the VTA than α6CC rats independent of drug exposure.\",\n      \"method\": \"CRISPR-Cas9 knock-in rat model; locomotor behavioral assay; western blot or immunohistochemistry for tyrosine hydroxylase in VTA and NAc\",\n      \"journal\": \"Nicotine & tobacco research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct genetic manipulation with protein expression and behavioral readouts; single lab\",\n      \"pmids\": [\"40736212\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Chrna6 is preferentially expressed by retinal ganglion cells (RGCs) in the mouse retina, as confirmed by immunofluorescence; Chrna6 expression decreases progressively with RGC death in glaucomatous DBA/2J mice and after optic nerve crush injury, and is expressed by RGCs independently of photoreceptor-derived stimuli.\",\n      \"method\": \"Immunofluorescence, gene expression arrays, RT-PCR in mouse retina; genetic model (DBA/2J glaucoma), optic nerve crush model, C3H/HeJ photoreceptor-less retinas\",\n      \"journal\": \"Current eye research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct protein localization confirmed by immunofluorescence with functional correlation in disease model; single lab\",\n      \"pmids\": [\"23002780\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Inhibition of CHRNA6 (using the antagonist BPiDl) ameliorates depression-like behavior in a chronic unpredictable mild stress rat model and alters dopamine levels in the brain, suggesting CHRNA6 channel activity contributes to dopaminergic regulation relevant to mood.\",\n      \"method\": \"Pharmacological inhibition with BPiDl in CUMS rat model; behavioral tests; ELISA for neurotransmitters; qRT-PCR for gene expression and miRNAs\",\n      \"journal\": \"Behavioural brain research\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — pharmacological inhibition in vivo with behavioral readout but limited mechanistic resolution for CHRNA6 specifically\",\n      \"pmids\": [\"35063497\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CHRNA6 encodes the α6 subunit of neuronal nicotinic acetylcholine receptors (nAChRs), which are ligand-gated ion channels; α6-containing receptors in the ventral tegmental area are required for nicotine self-administration and dopamine release (demonstrated by knockout/rescue in mice), the M2 domain 9' leucine residue is critical for channel gating (gain-of-function knock-in mice show enhanced dopamine release and nicotine hypersensitivity), a functional 3'-UTR SNP (rs2304297) sex- and genotype-dependently modulates nicotine-induced dopaminergic activity and reward behaviors in adolescent rats, and a missense mutation disrupts receptor structure and function as shown in Xenopus oocytes and C. elegans.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"CHRNA6 encodes the α6 subunit of neuronal nicotinic acetylcholine receptors (nAChRs), a ligand-gated ion channel subunit that is critical for dopaminergic neurotransmission and nicotine reward signaling in the mesolimbic system. α6-containing nAChRs in the ventral tegmental area are required for nicotine self-administration, as demonstrated by knockout/lentiviral rescue experiments, and the M2 domain 9' leucine residue is essential for channel gating and dopamine release [PMID:27327258]. A functional 3'-UTR SNP (rs2304297) modulates nicotine-induced dopaminergic activity, locomotor sensitization, and relapse-like behavior in a sex- and age-dependent manner, with the G allele associated with enhanced reward-related dopamine signaling in adolescent males [PMID:35328565, PMID:36704741, PMID:38612487]. A de novo missense mutation in CHRNA6 disrupts receptor structure and function, linking α6 subunit dysfunction to cholinergic-dopaminergic signaling impairment relevant to parkinsonism [PMID:32120303].\",\n  \"teleology\": [\n    {\n      \"year\": 2012,\n      \"claim\": \"Establishing that Chrna6 is not exclusively a midbrain dopaminergic gene, this study showed preferential expression in retinal ganglion cells and its progressive loss accompanying RGC death, broadening the known expression map of α6 nAChR subunits.\",\n      \"evidence\": \"Immunofluorescence and gene expression arrays in mouse retina, DBA/2J glaucoma model, and optic nerve crush model\",\n      \"pmids\": [\"23002780\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Functional role of α6-containing nAChRs in retinal ganglion cell physiology or survival not established\",\n        \"No electrophysiological characterization of α6 currents in RGCs\"\n      ]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Two critical mechanistic questions were answered simultaneously: α6-containing nAChRs in the VTA are necessary and sufficient for nicotine reinforcement (knockout/rescue), and the M2 9' leucine is a key gating determinant whose mutation produces hypersensitive channels and enhanced dopamine release (gain-of-function knock-in).\",\n      \"evidence\": \"α6-knockout mice with lentiviral VTA rescue; α6 L9'S gain-of-function knock-in mice; nicotine self-administration and dopamine release assays\",\n      \"pmids\": [\"27327258\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Subunit stoichiometry of native α6-containing receptors mediating reinforcement not defined\",\n        \"Whether α6 acts in VTA cell bodies versus terminals for dopamine release not resolved\",\n        \"No structural data for the α6 M2 domain pore region\"\n      ]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"A de novo missense mutation demonstrated that single amino acid changes in the α6 subunit can disrupt receptor assembly and function, providing the first human genetic variant with validated loss-of-function mechanism.\",\n      \"evidence\": \"In silico modeling, Xenopus oocyte electrophysiology, GH4C1 cell expression, and C. elegans in vivo functional assays\",\n      \"pmids\": [\"32120303\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Single patient/variant; broader genotype-phenotype spectrum for CHRNA6 coding mutations unknown\",\n        \"Mechanism of disruption (assembly vs. trafficking vs. gating) not fully dissected\",\n        \"No mammalian in vivo validation of this specific mutation\"\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"The CHRNA6 3'-UTR SNP rs2304297 was shown to be functional in vivo by CRISPR knock-in, producing genotype- and sex-specific differences in nicotine-induced locomotion and anxiety, establishing that non-coding variation at CHRNA6 directly modulates nicotine behavioral pharmacology.\",\n      \"evidence\": \"CRISPR-Cas9 knock-in rat model with behavioral assays for locomotion, anxiety, and food self-administration\",\n      \"pmids\": [\"35328565\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Molecular mechanism by which the G allele alters α6 mRNA or protein levels not determined\",\n        \"Effects observed in a single lab; independent replication pending\"\n      ]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Extending the functional characterization of rs2304297, the G allele was shown to selectively enhance nicotine + cue-primed reinstatement of drug-seeking in adolescent males, dissociating relapse vulnerability from acquisition of self-administration.\",\n      \"evidence\": \"CRISPR knock-in rats; intravenous nicotine self-administration with extinction and reinstatement paradigm\",\n      \"pmids\": [\"36704741\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Neural circuit through which the SNP modulates reinstatement not mapped\",\n        \"Whether the SNP affects α6 protein expression in the VTA/NAc not directly measured\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"The neurochemical basis of the rs2304297 behavioral phenotype was identified: the G allele sex-dependently modulates dopamine and norepinephrine tissue levels in reward regions and alters nicotine-induced dopamine overflow in the nucleus accumbens shell, directly linking the SNP to mesolimbic catecholamine signaling.\",\n      \"evidence\": \"CRISPR knock-in rats; HPLC tissue neurochemistry and in vivo microdialysis in NAc shell\",\n      \"pmids\": [\"38612487\", \"39206256\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether altered dopamine levels reflect changes in α6 receptor density, affinity, or downstream signaling unknown\",\n        \"All rs2304297 studies from a single laboratory\",\n        \"Post-translational or trafficking effects of the 3'-UTR variant not examined\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The molecular mechanism by which rs2304297 alters α6 subunit expression or receptor function remains undefined, and the subunit stoichiometry and interacting partners of native α6-containing nAChRs in specific circuits are incompletely characterized.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No direct measurement of how rs2304297 affects mRNA stability, translation, or miRNA binding in native neurons\",\n        \"Crystal or cryo-EM structure of α6-containing nAChR not available\",\n        \"Role of α6 nAChRs in non-dopaminergic circuits (e.g., retinal, cortical) functionally unexplored\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": [0, 1, 2]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 1, 2, 8]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [1, 2, 5, 6]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [1, 2, 3, 5]}\n    ],\n    \"complexes\": [\n      \"neuronal nicotinic acetylcholine receptor (α6-containing)\"\n    ],\n    \"partners\": [],\n    \"other_free_text\": []\n  }\n}\n```"}