{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\n GRM7 encodes the metabotropic glutamate receptor 7 (mGluR7), a G protein–coupled receptor that plays a central role in modulating synaptic transmission in the central nervous system. At presynaptic sites, mGluR7 regulates neurotransmitter release and synaptic plasticity, thereby influencing excitatory signaling, stress reactivity, emotional learning, and cognitive processing. Genetic and functional studies have implicated GRM7 in a range of neuropsychiatric and sensory disorders. For example, genome‐wide association studies have identified intronic variants in GRM7 that confer risk for major depressive disorder"}, {"type": "fg", "children": [{"type": "fg_f", "ref": "1"}]}, {"type": "t", "text": "and schizophrenia"}, {"type": "fg", "children": [{"type": "fg_f", "ref": "2"}]}, {"type": "t", "text": ", while GRM7 variants and copy‐number changes have also been associated with autism spectrum disorders"}, {"type": "fg", "children": [{"type": "fg_f", "ref": "3"}]}, {"type": "t", "text": "and attention‐deficit/hyperactivity disorder."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "4"}]}, {"type": "t", "text": ""}]}, {"type": "t", "text": "\n \n "}, {"type": "p", "children": [{"type": "t", "text": "\n In the auditory system, GRM7 is expressed in inner ear hair cells and spiral ganglion neurons, and common alleles of GRM7 have been linked to age‐related hearing impairment, possibly by modulating susceptibility to glutamate excitotoxicity"}, {"type": "fg", "children": [{"type": "fg_f", "ref": "5"}]}, {"type": "t", "text": "and influencing peripheral auditory measures such as speech detection."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "6"}]}, {"type": "t", "text": " In the visual system, mGluR7 immunoreactivity has been used as a marker for a subset of ON cone bipolar cells that receive direct rod input, delineating a novel pathway for rod signal transmission."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "7"}]}, {"type": "t", "text": ""}]}, {"type": "t", "text": "\n \n "}, {"type": "p", "children": [{"type": "t", "text": "\n At the molecular level, mGluR7 function is dynamically regulated by interactions with several proteins. Transsynaptic binding with extracellular partners such as ELFN1 can allosterically modulate receptor activity by engaging a binding pocket in the Venus flytrap domain"}, {"type": "fg", "children": [{"type": "fg_f", "ref": "8"}]}, {"type": "t", "text": "and by contributing to clustering that reduces the initial probability of neurotransmitter release at specific synapses."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "9"}]}, {"type": "t", "text": " In addition, PICK1 interacts with the receptor’s C-terminal domain to facilitate protein kinase C–mediated modulation of presynaptic signaling, a mechanism that is critical for spatial working memory and resistance to convulsive insults."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "10"}]}, {"type": "t", "text": " Furthermore, post-translational modifications such as Nedd4/β-arrestin–mediated ubiquitination control surface expression and degradation of mGluR7, impacting its downstream MAPK signaling."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "11"}]}, {"type": "t", "text": "\n "}]}, {"type": "t", "text": "\n \n "}, {"type": "p", "children": [{"type": "t", "text": "\n Functionally, loss- or gain-of-function studies in rodents underscore mGluR7’s role in regulating neural circuit activity related to emotion and cognition. Knockout or suppression of GRM7 in mice results in impairments in fear conditioning, delayed extinction learning, and altered acquisition of conditioned responses, highlighting its contribution to emotional and associative learning processes."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "12"}]}, {"type": "t", "text": " Conversely, pharmacological modulation using selective agonists (e.g., AMN082) and antagonists (e.g., XAP044) produces anxiolytic effects and modulates synaptic plasticity in stress-responsive brain regions such as the amygdala and prefrontal cortex"}, {"type": "fg", "children": [{"type": "fg_f", "ref": "13"}]}, {"type": "t", "text": ", and GRM7 expression is further implicated in the regulation of N-methyl-D-aspartate receptor trafficking."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "15"}]}, {"type": "t", "text": "\n "}]}, {"type": "t", "text": "\n \n "}, {"type": "p", "children": [{"type": "t", "text": "\n Moreover, GRM7 contributes to brain development and neural progenitor cell differentiation. Disruption of GRM7 signaling alters the phosphorylation status of key transcriptional regulators such as CREB and influences levels of YAP and CyclinD1, thereby affecting neurogenesis and neuronal morphology during early cortical development."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "16"}]}, {"type": "t", "text": " Collectively, these findings indicate that GRM7 serves as a multifunctional modulator of synaptic transmission and neural circuit development, with its genetic variants and regulation tightly linked to common brain disorders including depression, schizophrenia, ADHD, autism, and sensory deficits.\n "}]}, {"type": "t", "text": "\n \n "}, {"type": "p", "children": [{"type": "t", "text": "\n In addition, evidence indicates that GRM7 polymorphisms may affect treatment response to antipsychotic medications in first episode psychosis, suggesting that GRM7 genotype could serve as a predictive marker for therapeutic efficacy"}, {"type": "fg", "children": [{"type": "fg_f", "ref": "17"}]}, {"type": "t", "text": ", and altered regulation by microRNAs (such as miR-34c) may further modulate its expression in conditions like epilepsy"}, {"type": "fg", "children": [{"type": "fg_f", "ref": "18"}]}, {"type": "t", "text": "as well as in stress-induced responses."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "19"}]}, {"type": "t", "text": "\n "}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "S I Shyn, J Shi, J B Kraft, et al. 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