{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\nThe MTNR1A gene encodes the MT1 melatonin receptor, a G protein–coupled receptor that exhibits a unique mode of homo‐oligomerization in living cells. Studies have shown that under physiological expression, MT1 receptors form stable dimers that do not appreciably change their oligomeric state upon ligand binding—with agonists inducing specific conformational shifts rather than receptor association changes. High‐resolution structural analyses have further revealed a compact ligand‐binding pocket defined by aromatic stacking and discrete hydrogen bonds, and molecular studies indicate that interactions with PDZ domain–containing scaffolding proteins (e.g., MUPP1) are crucial for efficient G protein coupling. Additionally, receptor desensitization dynamics are modulated by both agonists and inverse agonists."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "1", "end_ref": "4"}]}, {"type": "t", "text": "\n"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nMT1 plays a pivotal role in mediating melatonin’s diverse physiological actions in both the central nervous system and peripheral tissues. In bone, activation of MT1 enhances osteoblast proliferation, differentiation, and mineralized matrix formation—processes that are fundamental for skeletal growth and repair. In the brain, MT1 receptor expression in hippocampal and other neural regions is linked to neuroprotection; reduced receptor levels have been implicated in neurodegenerative disorders such as Huntington’s and Alzheimer’s diseases, while presynaptic localization coupled with inhibition of voltage‐gated Ca²⁺ channels contributes to fine regulation of neurotransmission. In addition, MT1 is widely expressed in the skin, where it modulates cell proliferation and viability."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "5", "end_ref": "11"}]}, {"type": "t", "text": "\n"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nIn various cancer models, the MT1 receptor mediates melatonin’s oncostatic properties. In estrogen receptor–positive breast cancer cells, for example, MT1 receptor overexpression significantly enhances melatonin-induced growth suppression and modulation of nuclear receptor activity. Similarly, diminished MT1 expression—whether by gene deletion or epigenetic silencing—in oral squamous-cell carcinoma correlates with larger tumor size and poorer patient survival outcomes. Moreover, altered MT1 receptor signaling has been implicated in reproductive disorders, with genetic variation in MTNR1A suggested to affect polycystic ovary syndrome and other endocrine functions."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "12", "end_ref": "17"}]}, {"type": "t", "text": "\n"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nGenetic and epigenetic studies further underscore the significance of MTNR1A in human disease. A functional piRNA located within intron 1 of MTNR1A has been shown to negatively regulate its expression, adding complexity to its transcriptional control. Moreover, deleterious non-synonymous mutations and premature stop codons in MTNR1A have been detected in patients with neuropsychiatric disorders such as attention-deficit/hyperactivity disorder, while promoter polymorphisms have been associated with schizophrenia. Variants in MTNR1A may also contribute to altered tolerance to shift work and have been implicated in the etiopathogenesis of adolescent idiopathic scoliosis, further emphasizing the receptor’s broad clinical relevance."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "18", "end_ref": "24"}]}, {"type": "t", "text": "\n"}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Mohammed A Ayoub, Cyril Couturier, Estelle Lucas-Meunier, et al. 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