{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\n The CHRNA6 gene encodes the α6 subunit of neuronal nicotinic acetylcholine receptors (nAChRs), which are widely expressed in brain reward circuits and other specialized neuronal populations. Genetic studies in diverse populations have repeatedly implicated CHRNA6 variants as contributors to smoking behavior and nicotine dependence, with certain single‐nucleotide polymorphisms associating with higher cigarette consumption and increased risk of dependence."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "1", "end_ref": "4"}]}, {"type": "t", "text": " In addition, CHRNA6 is frequently examined as part of gene clusters (often together with CHRNB3) that influence the transition from smoking to nicotine dependence and may underlie tobacco‐related disease vulnerability, including risk associations noted in smoking‐related cancers and other disorders."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "5"}]}, {"type": "t", "text": ""}]}, {"type": "t", "text": "\n \n "}, {"type": "p", "children": [{"type": "t", "text": "\n Functional experiments in animal models further support a key role for CHRNA6 in substance use phenotypes. For example, mice lacking CHRNA6 do not exhibit altered ethanol consumption per se; however, they demonstrate prolonged recovery from ethanol‐induced sedation, indicating that receptors containing the α6 subunit modulate some of alcohol’s central effects."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "7"}]}, {"type": "t", "text": " Moreover, association studies in humans have identified specific CHRNA6 variants that correlate with nicotine dependence severity and have been replicated in independent samples."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "8", "end_ref": "11"}]}, {"type": "t", "text": ""}]}, {"type": "t", "text": "\n \n "}, {"type": "p", "children": [{"type": "t", "text": "\n Recent investigations have also explored the role of CHRNA6 in neuropsychiatric and behavioral domains beyond nicotine addiction. Associations between CHRNA6 variants and bipolar disorder and attention‐deficit/hyperactivity disorder suggest that the α6 subunit may participate in a common neurobiological substrate for reward and impulsivity."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "12"}]}, {"type": "t", "text": " In a different context, CHRNA6 expression is highly enriched in retinal ganglion cells, and its decline correlates with neuronal loss in glaucomatous degeneration, further highlighting its role as a cell‐type–specific marker."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "14"}]}, {"type": "t", "text": " Emerging evidence from studies of reward circuitry also implicates CHRNA6‐containing nAChRs in modulating addiction‐related signaling in response to both nicotine and alcohol, suggesting that α6 subunits contribute to the sensitivity of these neural pathways."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "15"}]}, {"type": "t", "text": "\n "}]}, {"type": "t", "text": "\n \n "}, {"type": "p", "children": [{"type": "t", "text": "\n Together, these findings highlight the multifaceted contributions of CHRNA6 to the etiology of nicotine dependence and related substance use behaviors, as well as to neurophysiological processes in other systems. The integration of genetic association data with functional and preclinical studies supports a model in which α6‐containing nAChRs modulate neuronal excitability and neurotransmitter release in key reward and sensory circuits, thereby influencing both addiction liability and aspects of neural cell survival.\n "}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Thorgeir E Thorgeirsson, Daniel F Gudbjartsson, Ida Surakka, et al. 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