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Magielski J, Ruggiero SM, Xian J, Parthasarathy S, Galer P, Ganesan S, Back A, McKee J, McSalley I, Gonzalez AK, Morgan A, Donaher J, Helbig I. The clinical and genetic spectrum of paediatric speech and language disorders in 52,143 individuals. MEDRXIV : THE PREPRINT SERVER FOR HEALTH SCIENCES 2024:2024.04.23.24306192. [PMID: 38712155 PMCID: PMC11071575 DOI: 10.1101/2024.04.23.24306192] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2024]
Abstract
Speech and language disorders are known to have a substantial genetic contribution. Although frequently examined as components of other conditions, research on the genetic basis of linguistic differences as separate phenotypic subgroups has been limited so far. Here, we performed an in-depth characterization of speech and language disorders in 52,143 individuals, reconstructing clinical histories using a large-scale data mining approach of the Electronic Medical Records (EMR) from an entire large paediatric healthcare network. The reported frequency of these disorders was the highest between 2 and 5 years old and spanned a spectrum of twenty-six broad speech and language diagnoses. We used Natural Language Processing to assess to which degree clinical diagnosis in full-text notes were reflected in ICD-10 diagnosis codes. We found that aphasia and speech apraxia could be easily retrieved through ICD-10 diagnosis codes, while stuttering as a speech phenotype was only coded in 12% of individuals through appropriate ICD-10 codes. We found significant comorbidity of speech and language disorders in neurodevelopmental conditions (30.31%) and to a lesser degree with epilepsies (6.07%) and movement disorders (2.05%). The most common genetic disorders retrievable in our EMR analysis were STXBP1 (n=21), PTEN (n=20), and CACNA1A (n=18). When assessing associations of genetic diagnoses with specific linguistic phenotypes, we observed associations of STXBP1 and aphasia (P=8.57 × 10-7, CI=18.62-130.39) and MYO7A with speech and language development delay due to hearing loss (P=1.24 × 10-5, CI=17.46-Inf). Finally, in a sub-cohort of 726 individuals with whole exome sequencing data, we identified an enrichment of rare variants in synaptic protein and neuronal receptor pathways and associations of UQCRC1 with expressive aphasia and WASHC4 with abnormality of speech or vocalization. In summary, our study outlines the landscape of paediatric speech and language disorders, confirming the phenotypic complexity of linguistic traits and novel genotype-phenotype associations. Subgroups of paediatric speech and language disorders differ significantly with respect to the composition of monogenic aetiologies.
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Affiliation(s)
- Jan Magielski
- Division of Neurology, Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
- The Epilepsy NeuroGenetics Initiative (ENGIN), Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
- Department of Biomedical and Health Informatics (DBHi), Children’s Hospital of Philadelphia, Philadelphia, PA, 19146, USA
| | - Sarah M. Ruggiero
- Division of Neurology, Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
- The Epilepsy NeuroGenetics Initiative (ENGIN), Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
| | - Julie Xian
- Division of Neurology, Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
- The Epilepsy NeuroGenetics Initiative (ENGIN), Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
- Department of Biomedical and Health Informatics (DBHi), Children’s Hospital of Philadelphia, Philadelphia, PA, 19146, USA
| | - Shridhar Parthasarathy
- Division of Neurology, Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
- The Epilepsy NeuroGenetics Initiative (ENGIN), Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
- Department of Biomedical and Health Informatics (DBHi), Children’s Hospital of Philadelphia, Philadelphia, PA, 19146, USA
| | - Peter Galer
- Division of Neurology, Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
- The Epilepsy NeuroGenetics Initiative (ENGIN), Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
- Department of Biomedical and Health Informatics (DBHi), Children’s Hospital of Philadelphia, Philadelphia, PA, 19146, USA
- Center for Neuroengineering and Therapeutics, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Shiva Ganesan
- Division of Neurology, Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
- The Epilepsy NeuroGenetics Initiative (ENGIN), Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
- Department of Biomedical and Health Informatics (DBHi), Children’s Hospital of Philadelphia, Philadelphia, PA, 19146, USA
| | - Amanda Back
- Division of Neurology, Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
- The Epilepsy NeuroGenetics Initiative (ENGIN), Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
| | - Jillian McKee
- Division of Neurology, Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
- The Epilepsy NeuroGenetics Initiative (ENGIN), Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
- Department of Biomedical and Health Informatics (DBHi), Children’s Hospital of Philadelphia, Philadelphia, PA, 19146, USA
- Department of Neurology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, 19104, USA
| | - Ian McSalley
- Division of Neurology, Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
- The Epilepsy NeuroGenetics Initiative (ENGIN), Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
- Department of Biomedical and Health Informatics (DBHi), Children’s Hospital of Philadelphia, Philadelphia, PA, 19146, USA
| | - Alexander K. Gonzalez
- Department of Biomedical and Health Informatics (DBHi), Children’s Hospital of Philadelphia, Philadelphia, PA, 19146, USA
| | - Angela Morgan
- Murdoch Children’s Research Institute, Parkville 3052, Australia
- Department of Audiology and Speech Pathology, University of Melbourne, Parkville 3052, Australia
| | - Joseph Donaher
- Center for Childhood Communication, Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
- Department of Otorhinolaryngology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, 19104, USA
| | - Ingo Helbig
- Division of Neurology, Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
- The Epilepsy NeuroGenetics Initiative (ENGIN), Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
- Department of Biomedical and Health Informatics (DBHi), Children’s Hospital of Philadelphia, Philadelphia, PA, 19146, USA
- Department of Neurology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, 19104, USA
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Parent HH, Niswender CM. Therapeutic Potential for Metabotropic Glutamate Receptor 7 Modulators in Cognitive Disorders. Mol Pharmacol 2024; 105:348-358. [PMID: 38423750 PMCID: PMC11026152 DOI: 10.1124/molpharm.124.000874] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2024] [Revised: 02/05/2024] [Accepted: 02/12/2024] [Indexed: 03/02/2024] Open
Abstract
Metabotropic glutamate receptor 7 (mGlu7) is the most highly conserved and abundantly expressed mGlu receptor in the human brain. The presynaptic localization of mGlu7, coupled with its low affinity for its endogenous agonist, glutamate, are features that contribute to the receptor's role in modulating neuronal excitation and inhibition patterns, including long-term potentiation, in various brain regions. These characteristics suggest that mGlu7 modulation may serve as a novel therapeutic strategy in disorders of cognitive dysfunction, including neurodevelopmental disorders that cause impairments in learning, memory, and attention. Primary mutations in the GRM7 gene have recently been identified as novel causes of neurodevelopmental disorders, and these patients exhibit profound intellectual and cognitive disability. Pharmacological tools, such as agonists, antagonists, and allosteric modulators, have been the mainstay for targeting mGlu7 in its endogenous homodimeric form to probe effects of its function and modulation in disease models. However, recent research has identified diversity in dimerization, as well as trans-synaptic interacting proteins, that also play a role in mGlu7 signaling and pharmacological properties. These novel findings represent exciting opportunities in the field of mGlu receptor drug discovery and highlight the importance of further understanding the functions of mGlu7 in complex neurologic conditions at both the molecular and physiologic levels. SIGNIFICANCE STATEMENT: Proper expression and function of mGlu7 is essential for learning, attention, and memory formation at the molecular level within neural circuits. The pharmacological targeting of mGlu7 is undergoing a paradigm shift by incorporating an understanding of receptor interaction with other cis- and trans- acting synaptic proteins, as well as various intracellular signaling pathways. Based upon these new findings, mGlu7's potential as a drug target in the treatment of cognitive disorders and learning impairments is primed for exploration.
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Affiliation(s)
- Harrison H Parent
- Department of Pharmacology (H.H.P., C.M.N.), Warren Center for Neuroscience Drug Discovery (H.H.P., C.M.N.), Vanderbilt Brain Institute (C.M.N.), and Vanderbilt Institute for Chemical Biology (C.M.N.), Vanderbilt University, Nashville, Tennessee; and Vanderbilt Kennedy Center, Vanderbilt University Medical Center, Nashville, Tennessee (C.M.N.)
| | - Colleen M Niswender
- Department of Pharmacology (H.H.P., C.M.N.), Warren Center for Neuroscience Drug Discovery (H.H.P., C.M.N.), Vanderbilt Brain Institute (C.M.N.), and Vanderbilt Institute for Chemical Biology (C.M.N.), Vanderbilt University, Nashville, Tennessee; and Vanderbilt Kennedy Center, Vanderbilt University Medical Center, Nashville, Tennessee (C.M.N.)
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Lin KY, Gujar MR, Lin J, Ding WY, Huang J, Gao Y, Tan YS, Teng X, Christine LSL, Kanchanawong P, Toyama Y, Wang H. Astrocytes control quiescent NSC reactivation via GPCR signaling-mediated F-actin remodeling. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.11.584337. [PMID: 38903085 PMCID: PMC11188063 DOI: 10.1101/2024.03.11.584337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/22/2024]
Abstract
The transitioning of neural stem cells (NSCs) between quiescent and proliferative states is fundamental for brain development and homeostasis. Defects in NSC reactivation are associated with neurodevelopmental disorders. Drosophila quiescent NSCs extend an actin-rich primary protrusion toward the neuropil. However, the function of the actin cytoskeleton during NSC reactivation is unknown. Here, we reveal the fine F-actin structures in the protrusions of quiescent NSCs by expansion and super-resolution microscopy. We show that F-actin polymerization promotes the nuclear translocation of Mrtf, a microcephaly-associated transcription factor, for NSC reactivation and brain development. F-actin polymerization is regulated by a signaling cascade composed of G-protein-coupled receptor (GPCR) Smog, G-protein αq subunit, Rho1 GTPase, and Diaphanous (Dia)/Formin during NSC reactivation. Further, astrocytes secrete a Smog ligand Fog to regulate Gαq-Rho1-Dia-mediated NSC reactivation. Together, we establish that the Smog-Gαq-Rho1 signaling axis derived from astrocytes, a NSC niche, regulates Dia-mediated F-actin dynamics in NSC reactivation.
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Januel L, Chatron N, Rivier-Ringenbach C, Cabet S, Labalme A, Sahin Y, Darvish H, Kruer M, Bakhtiari S, Sanlaville D, de Sainte Agathe JM, Lesca G. GRM7-related disorder: five additional patients from three independent families and review of the literature. Eur J Med Genet 2024; 67:104893. [PMID: 38070825 DOI: 10.1016/j.ejmg.2023.104893] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Revised: 10/22/2023] [Accepted: 12/03/2023] [Indexed: 12/19/2023]
Abstract
Developmental and epileptic encephalopathies (DEEs) refer to a group of severe epileptic syndromes characterized by seizures as well as a developmental delay which can be a consequence of the underlying etiology and/or the epileptic encephalopathy. The genes responsible for DEEs are numerous and their number is increasing since the availability of Next-Generation Sequencing. Pathogenic variants in GRM7, encoding the metabotropic glutamate receptor 7, were recently shown as a cause of a severe DEE with autosomal recessive inheritance. To date, only ten patients have been reported in the literature, generally with severe phenotypes including early-onset epilepsy, microcephaly, brain anomalies, and spasticity. We report here 5 patients from 3 independent families with biallelic variants in the GRM7 gene. We review the literature and provide further elements for the understanding of the genotype-phenotype correlation of this rare syndrome.
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Affiliation(s)
- Louis Januel
- Hospices Civils de Lyon, Groupe Hospitalier Est, Service de Génétique, Bron, France.
| | - Nicolas Chatron
- Hospices Civils de Lyon, Groupe Hospitalier Est, Service de Génétique, Bron, France; Institut NeuroMyoGene PNMG, CNRS UMR5310, INSERM U1217, Université Claude Bernard Lyon 1, Lyon, France
| | | | - Sara Cabet
- Hospices Civils de Lyon, Groupe Hospitalier Est, Service de Radiologie, Bron, France
| | - Audrey Labalme
- Hospices Civils de Lyon, Groupe Hospitalier Est, Service de Génétique, Bron, France
| | | | - Hossein Darvish
- Pediatric Movement Disorders Program, Division of Pediatric Neurology, Barrow Neurological Institute, Phoenix Children's Hospital, Phoenix, AZ, USA
| | - Michael Kruer
- Pediatric Movement Disorders Program, Division of Pediatric Neurology, Barrow Neurological Institute, Phoenix Children's Hospital, Phoenix, AZ, USA
| | - Somayeh Bakhtiari
- Pediatric Movement Disorders Program, Division of Pediatric Neurology, Barrow Neurological Institute, Phoenix Children's Hospital, Phoenix, AZ, USA
| | - Damien Sanlaville
- Hospices Civils de Lyon, Groupe Hospitalier Est, Service de Génétique, Bron, France; Institut NeuroMyoGene PNMG, CNRS UMR5310, INSERM U1217, Université Claude Bernard Lyon 1, Lyon, France
| | | | - Gaetan Lesca
- Hospices Civils de Lyon, Groupe Hospitalier Est, Service de Génétique, Bron, France; Institut NeuroMyoGene PNMG, CNRS UMR5310, INSERM U1217, Université Claude Bernard Lyon 1, Lyon, France
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5
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Lei X, Hofmann CS, Rodriguez AL, Niswender CM. Differential Activity of Orthosteric Agonists and Allosteric Modulators at Metabotropic Glutamate Receptor 7. Mol Pharmacol 2023; 104:17-27. [PMID: 37105671 PMCID: PMC10289241 DOI: 10.1124/molpharm.123.000678] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2023] [Revised: 03/23/2023] [Accepted: 03/28/2023] [Indexed: 04/29/2023] Open
Abstract
Metabotropic glutamate receptor 7 (mGlu7) is a G protein coupled receptor that has demonstrated promise as a therapeutic target across a number of neurologic and psychiatric diseases. Compounds that modulate the activity of mGlu7, such as positive and negative allosteric modulators, may represent new therapeutic strategies to modulate receptor activity. The endogenous neurotransmitter associated with the mGlu receptor family, glutamate, exhibits low efficacy and potency in activating mGlu7, and surrogate agonists, such as the compound L-(+)-2-Amino-4-phosphonobutyric acid (L-AP4), are often used for receptor activation and compound profiling. To understand the implications of the use of such agonists in the development of positive allosteric modulators (PAMs), we performed a systematic evaluation of receptor activation using a system in which mutations can be made in either protomer of the mGlu7 dimer; we employed mutations that prevent interaction with the orthosteric site as well as the G-protein coupling site of the receptor. We then measured increases in calcium levels downstream of a promiscuous G protein to assess the effects of mutations in one of the two protomers in the presence of two different agonists and three positive allosteric modulators. Our results reveal that distinct PAMs, for example N-[3-Chloro-4-[(5-chloro-2-pyridinyl)oxy]phenyl]-2-pyridinecarboxamide (VU0422288) and 3-(2,3-Difluoro-4-methoxyphenyl)-2,5-dimethyl-7-(trifluoromethyl)pyrazolo[1,5-a]pyrimidine (VU6005649), do exhibit different maximal levels of potentiation with L-AP4 versus glutamate, but there appear to be common stable receptor conformations that are shared among all of the compounds examined here. SIGNIFICANCE STATEMENT: This manuscript describes the systematic evaluation of the mGlu7 agonists glutamate and L-(+)-2-Amino-4-phosphonobutyric acid (L-AP4) in the presence and absence of three distinct potentiators examining possible mechanistic differences. These findings demonstrate that mGlu7 potentiators display subtle variances in response to glutamate versus L-AP4.
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Affiliation(s)
- Xia Lei
- Department of Pharmacology (X.L., C.S.H., A.L.R., C.M.N.), Warren Center for Neuroscience Drug Discovery (X.L., A.L.R., C.M.N.), Vanderbilt Institute of Chemical Biology (C.M.N.), and Vanderbilt Brain Institute, Vanderbilt University, Nashville, Tennesee (C.M.N.); and Vanderbilt Kennedy Center, Vanderbilt University Medical Center, Nashville, Tennessee (C.M.N.)
| | - Christopher S Hofmann
- Department of Pharmacology (X.L., C.S.H., A.L.R., C.M.N.), Warren Center for Neuroscience Drug Discovery (X.L., A.L.R., C.M.N.), Vanderbilt Institute of Chemical Biology (C.M.N.), and Vanderbilt Brain Institute, Vanderbilt University, Nashville, Tennesee (C.M.N.); and Vanderbilt Kennedy Center, Vanderbilt University Medical Center, Nashville, Tennessee (C.M.N.)
| | - Alice L Rodriguez
- Department of Pharmacology (X.L., C.S.H., A.L.R., C.M.N.), Warren Center for Neuroscience Drug Discovery (X.L., A.L.R., C.M.N.), Vanderbilt Institute of Chemical Biology (C.M.N.), and Vanderbilt Brain Institute, Vanderbilt University, Nashville, Tennesee (C.M.N.); and Vanderbilt Kennedy Center, Vanderbilt University Medical Center, Nashville, Tennessee (C.M.N.)
| | - Colleen M Niswender
- Department of Pharmacology (X.L., C.S.H., A.L.R., C.M.N.), Warren Center for Neuroscience Drug Discovery (X.L., A.L.R., C.M.N.), Vanderbilt Institute of Chemical Biology (C.M.N.), and Vanderbilt Brain Institute, Vanderbilt University, Nashville, Tennesee (C.M.N.); and Vanderbilt Kennedy Center, Vanderbilt University Medical Center, Nashville, Tennessee (C.M.N.)
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6
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Nicoletti F, Di Menna L, Iacovelli L, Orlando R, Zuena AR, Conn PJ, Dogra S, Joffe ME. GPCR interactions involving metabotropic glutamate receptors and their relevance to the pathophysiology and treatment of CNS disorders. Neuropharmacology 2023; 235:109569. [PMID: 37142158 DOI: 10.1016/j.neuropharm.2023.109569] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Revised: 04/18/2023] [Accepted: 05/02/2023] [Indexed: 05/06/2023]
Abstract
Cellular responses to metabotropic glutamate (mGlu) receptor activation are shaped by mechanisms of receptor-receptor interaction. mGlu receptor subtypes form homodimers, intra- or inter-group heterodimers, and heteromeric complexes with other G protein-coupled receptors (GPCRs). In addition, mGlu receptors may functionally interact with other receptors through the βγ subunits released from G proteins in response to receptor activation or other mechanisms. Here, we discuss the interactions between (i) mGlu1 and GABAB receptors in cerebellar Purkinje cells; (ii) mGlu2 and 5-HT2Aserotonergic receptors in the prefrontal cortex; (iii) mGlu5 and A2A receptors or mGlu5 and D1 dopamine receptors in medium spiny projection neurons of the indirect and direct pathways of the basal ganglia motor circuit; (iv) mGlu5 and A2A receptors in relation to the pathophysiology of Alzheimer's disease; and (v) mGlu7 and A1 adenosine or α- or β1 adrenergic receptors. In addition, we describe in detail a novel form of non-heterodimeric interaction between mGlu3 and mGlu5 receptors, which appears to be critically involved in mechanisms of activity-dependent synaptic plasticity in the prefrontal cortex and hippocampus. Finally, we highlight the potential implication of these interactions in the pathophysiology and treatment of cerebellar disorders, schizophrenia, Alzheimer's disease, Parkinson's disease, l-DOPA-induced dyskinesias, stress-related disorders, and cognitive dysfunctions.
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Affiliation(s)
- Ferdinando Nicoletti
- Department of Physiology and Pharmacology, Sapienza University of Rome, Italy; IRCCS Neuromed, Pozzilli, Italy.
| | | | - Luisa Iacovelli
- Department of Physiology and Pharmacology, Sapienza University of Rome, Italy
| | - Rosamaria Orlando
- Department of Physiology and Pharmacology, Sapienza University of Rome, Italy; IRCCS Neuromed, Pozzilli, Italy
| | - Anna Rita Zuena
- Department of Physiology and Pharmacology, Sapienza University of Rome, Italy
| | - P Jeffrey Conn
- Department of Pharmacology, Italy; Warren Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, TN, 37232, USA
| | - Shalini Dogra
- Department of Pharmacology, Italy; Warren Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, TN, 37232, USA
| | - Max E Joffe
- Translational Neuroscience Program, Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA, 15219, USA
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Freitas GA, Niswender CM. GRM7 gene mutations and consequences for neurodevelopment. Pharmacol Biochem Behav 2023; 225:173546. [PMID: 37003303 PMCID: PMC10192299 DOI: 10.1016/j.pbb.2023.173546] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/24/2023] [Revised: 03/22/2023] [Accepted: 03/28/2023] [Indexed: 04/03/2023]
Abstract
The metabotropic glutamate receptor 7 (mGlu7), encoded by the GRM7 gene in humans, is a presynaptic, G protein-coupled glutamate receptor that is essential for modulating neurotransmission. Mutations in or reduced expression of GRM7 have been identified in different genetic neurodevelopmental disorders (NDDs), and rare biallelic missense variants have been proposed to underlie a subset of NDDs. Clinical GRM7 variants have been associated with a range of symptoms consistent with neurodevelopmental molecular features, including hypomyelination, brain atrophy and defects in axon outgrowth. Here, we review the newest findings regarding the cellular and molecular defects caused by GRM7 variants in NDD patients.
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Affiliation(s)
- Geanne A Freitas
- Department of Pharmacology and Warren Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, TN 37212, United States of America
| | - Colleen M Niswender
- Department of Pharmacology and Warren Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, TN 37212, United States of America; Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, TN 37212, United States of America; Vanderbilt Brain Institute, Vanderbilt University, Nashville, TN 37212, United States of America; Vanderbilt Kennedy Center, Vanderbilt University Medical Center, Nashville, TN 37232, United States of America.
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Kalbfleisch JJ, Rodriguez AL, Lei X, Weiss K, Blobaum AL, Boutaud O, Niswender CM, Lindsley CW. Persistent challenges in the development of an mGlu 7 PAM in vivo tool compound: The discovery of VU6046980. Bioorg Med Chem Lett 2023; 80:129106. [PMID: 36528230 PMCID: PMC10201562 DOI: 10.1016/j.bmcl.2022.129106] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Revised: 12/06/2022] [Accepted: 12/11/2022] [Indexed: 12/16/2022]
Abstract
Herein, we report on the further chemical optimization of the first reported mGlu7 positive allosteric modulator (PAM), VU6027459. Replacement of the quinoline core by a cinnoline scaffold increased mGlu7 PAM potency by ∼ 10-fold, and concomitant introduction of a chiral tricyclic motif led to potent mGlu7 PAMs with enantioselective mGlu receptor selectivity profiles. Of these, VU6046980 emerged as a putative in vivo tool compound with excellent CNS penetration (Kp = 4.1; Kp,uu = 0.7) and efficacy in preclinical models. However, either off-target activity at the sigma-1 receptor or activity at a target not elucidated by large ancillary pharmacology panels led to sedation not driven by activation of mGlu7 (validated in Grm7 knockout mice). Thus, despite a significant advance, a viable mGlu7 PAM in vivo tool remains elusive.
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Affiliation(s)
- Jacob J Kalbfleisch
- Warren Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, TN 37232, USA; Department of Chemistry, Vanderbilt University, Nashville, TN 37232, USA
| | - Alice L Rodriguez
- Warren Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, TN 37232, USA; Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Xia Lei
- Warren Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, TN 37232, USA; Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Kelly Weiss
- Warren Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, TN 37232, USA; Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Annie L Blobaum
- Warren Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, TN 37232, USA; Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Olivier Boutaud
- Warren Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, TN 37232, USA; Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Colleen M Niswender
- Warren Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, TN 37232, USA; Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA; Vanderbilt Kennedy Center, Vanderbilt University Medical Center, Nashville, TN 37232, USA; Vanderbilt Brain Institute, Vanderbilt University School of Medicine, Nashville, TN 37232, USA; Vanderbilt Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
| | - Craig W Lindsley
- Warren Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, TN 37232, USA; Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA; Department of Chemistry, Vanderbilt University, Nashville, TN 37232, USA; Vanderbilt Brain Institute, Vanderbilt University School of Medicine, Nashville, TN 37232, USA; Vanderbilt Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
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Feng Y, Zhang C, Wei Z, Li G, Gan Y, Liu C, Deng Y. Gene variations of glutamate metabolism pathway and epilepsy. ACTA EPILEPTOLOGICA 2022. [DOI: 10.1186/s42494-022-00103-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Abstract
Background
Epilepsy is a paroxysmal disorder of the brain, caused by an imbalance of neuronal excitation and inhibition. Glutamate is the most important excitatory neurotransmitter in the brain and plays an important role in epileptogenesis. Mutations in genes at any step/component of the glutamate metabolic pathway may lead to the development of epilepsy or epileptic encephalopathy.
Methods
Clinical history of 3 epilepsy patients with genetic variations of the glutamate metabolism pathway was collected. Electroencephalogram recording and magnetic resonance imaging were performed in each patient. We also reviewed recent literature for a variety of the genetic variations involved in epilepsy.
Results
Case 1 was a SLC1A2 mutation-carrier diagnosed with developmental and epileptic encephalopathy (DEE) 41, whose seizures decreased after start of the ketogenic diet. Case 2 carried a GRIN2A gene mutation and was seizure-free for three years after taking levetiracetam and vitamin B6. Case 3 was a GRIN2B mutation-carrier diagnosed with DEE 27, who seizures diminished after taking oxcarbazepine.
Conclusions
Preclinical and clinical evidence supports the therapeutic potential of glutamatergic signaling-targeting treatments for epilepsy. More studies are needed to discover novel DEE-related genetic mutations in the glutamate metabolic pathway.
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Baxter SM, Posey JE, Lake NJ, Sobreira N, Chong JX, Buyske S, Blue EE, Chadwick LH, Coban-Akdemir ZH, Doheny KF, Davis CP, Lek M, Wellington C, Jhangiani SN, Gerstein M, Gibbs RA, Lifton RP, MacArthur DG, Matise TC, Lupski JR, Valle D, Bamshad MJ, Hamosh A, Mane S, Nickerson DA, Rehm HL, O'Donnell-Luria A. Centers for Mendelian Genomics: A decade of facilitating gene discovery. Genet Med 2022; 24:784-797. [PMID: 35148959 PMCID: PMC9119004 DOI: 10.1016/j.gim.2021.12.005] [Citation(s) in RCA: 41] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Revised: 12/08/2021] [Accepted: 12/12/2021] [Indexed: 12/27/2022] Open
Abstract
PURPOSE Mendelian disease genomic research has undergone a massive transformation over the past decade. With increasing availability of exome and genome sequencing, the role of Mendelian research has expanded beyond data collection, sequencing, and analysis to worldwide data sharing and collaboration. METHODS Over the past 10 years, the National Institutes of Health-supported Centers for Mendelian Genomics (CMGs) have played a major role in this research and clinical evolution. RESULTS We highlight the cumulative gene discoveries facilitated by the program, biomedical research leveraged by the approach, and the larger impact on the research community. Beyond generating a list of gene-phenotype relationships and participating in widespread data sharing, the CMGs have created resources, tools, and training for the larger community to foster understanding of genes and genome variation. The CMGs have participated in a wide range of data sharing activities, including deposition of all eligible CMG data into the Analysis, Visualization, and Informatics Lab-space (AnVIL), sharing candidate genes through the Matchmaker Exchange and the CMG website, and sharing variants in Genotypes to Mendelian Phenotypes (Geno2MP) and VariantMatcher. CONCLUSION The work is far from complete; strengthening communication between research and clinical realms, continued development and sharing of knowledge and tools, and improving access to richly characterized data sets are all required to diagnose the remaining molecularly undiagnosed patients.
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Affiliation(s)
- Samantha M Baxter
- Program in Medical and Population Genetics, Broad Institute of MIT and Harvard, Cambridge, MA.
| | - Jennifer E Posey
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX
| | - Nicole J Lake
- Department of Genetics, Yale School of Medicine, New Haven, CT; Murdoch Children's Research Institute, Melbourne, Victoria, Australia
| | - Nara Sobreira
- McKusick-Nathans Department of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD
| | - Jessica X Chong
- Department of Pediatrics, Division of Genetic Medicine, University of Washington and Seattle Children's Hospital, Seattle, WA; Brotman Baty Institute for Precision Medicine, Seattle, WA
| | - Steven Buyske
- Department of Statistics, Rutgers University, Piscataway, NJ; Department of Genetics, Rutgers University, Piscataway, NJ
| | - Elizabeth E Blue
- Brotman Baty Institute for Precision Medicine, Seattle, WA; Division of Medical Genetics, Department of Medicine, University of Washington, Seattle, WA
| | - Lisa H Chadwick
- Division of Genome Sciences, National Human Genome Research Institute, Bethesda, MD
| | - Zeynep H Coban-Akdemir
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX; Human Genetics Center, Department of Epidemiology, Human Genetics, and Environmental Sciences, School of Public Health, The University of Texas Health Science Center at Houston, Houston, TX
| | - Kimberly F Doheny
- McKusick-Nathans Department of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD
| | - Colleen P Davis
- Department of Genome Sciences, University of Washington School of Medicine, Seattle, WA
| | - Monkol Lek
- Program in Medical and Population Genetics, Broad Institute of MIT and Harvard, Cambridge, MA; Department of Genetics, Yale School of Medicine, New Haven, CT
| | | | | | - Mark Gerstein
- Program in Computational Biology and Bioinformatics, Yale University, New Haven, CT; Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT
| | - Richard A Gibbs
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX; Human Genome Sequencing Center, Baylor College of Medicine, Houston, TX
| | - Richard P Lifton
- Department of Genetics, Yale School of Medicine, New Haven, CT; Laboratory of Human Genetics and Genomics, The Rockefeller University, New York, NY
| | - Daniel G MacArthur
- Program in Medical and Population Genetics, Broad Institute of MIT and Harvard, Cambridge, MA; Centre for Population Genomics, Garvan Institute of Medical Research and UNSW Sydney, Sydney, New South Wales, Australia; Centre for Population Genomics, Murdoch Children's Research Institute, Melbourne, Victoria, Australia
| | - Tara C Matise
- Department of Genetics, Rutgers University, Piscataway, NJ
| | - James R Lupski
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX; Human Genome Sequencing Center, Baylor College of Medicine, Houston, TX; Department of Pediatrics, Baylor College of Medicine, Houston, TX
| | - David Valle
- McKusick-Nathans Department of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD
| | - Michael J Bamshad
- Department of Pediatrics, Division of Genetic Medicine, University of Washington and Seattle Children's Hospital, Seattle, WA; Brotman Baty Institute for Precision Medicine, Seattle, WA; Department of Genome Sciences, University of Washington School of Medicine, Seattle, WA
| | - Ada Hamosh
- McKusick-Nathans Department of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD
| | - Shrikant Mane
- Department of Genetics, Yale School of Medicine, New Haven, CT
| | - Deborah A Nickerson
- Brotman Baty Institute for Precision Medicine, Seattle, WA; Department of Genome Sciences, University of Washington School of Medicine, Seattle, WA
| | - Heidi L Rehm
- Program in Medical and Population Genetics, Broad Institute of MIT and Harvard, Cambridge, MA; Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA; Analytic and Translational Genetics Unit, Massachusetts General Hospital, Boston, MA.
| | - Anne O'Donnell-Luria
- Program in Medical and Population Genetics, Broad Institute of MIT and Harvard, Cambridge, MA; Analytic and Translational Genetics Unit, Massachusetts General Hospital, Boston, MA; Department of Pediatrics, Division of Genetics and Genomics, Boston Children's Hospital, Boston, MA.
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11
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Jdila MB, Mignon-Ravix C, Ncir SB, Kammoun F, Fakhfakh F, Villard L, Triki C. A large consanguineous family with a homozygous Metabotropic Glutamate Receptor 7 (mGlu7) variant and developmental epileptic encephalopathy: Effect on protein structure and ligand affinity. Orphanet J Rare Dis 2021; 16:317. [PMID: 34273994 PMCID: PMC8286605 DOI: 10.1186/s13023-021-01951-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Accepted: 07/11/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Developmental and epileptic encephalopathies (DEE) are chronic neurological conditions where epileptic activity contributes to the progressive disruption of brain function, frequently leading to impaired motor, cognitive and sensory development. PATIENTS AND METHODS The present study reports a clinical investigation and a molecular analysis by Next Generation Sequencing (NGS) of a large consanguineous family comprising several cases of developmental and epileptic encephalopathy. Bioinformatic prediction and molecular docking analysis were also carried out. RESULTS The majority of patients in our studied family had severe developmental impairments, early-onset seizures, brain malformations such as cortical atrophy and microcephaly, developmental delays and intellectual disabilities. The molecular investigations revealed a novel homozygous variant c.1411G>A (p.Gly471Arg) in the GRM7 gene which was segregating with the disease in the family. Bioinformatic tools predicted its pathogenicity and docking analysis revealed its potential effects on mGlu7 protein binding to its ligand. CONCLUSION Our results contribute to a better understanding of the impact of GRM7 variants for the newly described associated phenotype.
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Affiliation(s)
- Marwa Ben Jdila
- Research Laboratory 'NeuroPédiatrie' (LR19ES15), Sfax Medical School, Sfax University, Sfax, Tunisia. .,Laboratory of Molecular and Functional Genetics, Faculty of Science of Sfax, Sfax University, Sfax, Tunisia.
| | | | - Sihem Ben Ncir
- Research Laboratory 'NeuroPédiatrie' (LR19ES15), Sfax Medical School, Sfax University, Sfax, Tunisia.,Child Neurology Department, Hedi Chaker Universitary Hospital of Sfax, Sfax, Tunisia
| | - Fatma Kammoun
- Research Laboratory 'NeuroPédiatrie' (LR19ES15), Sfax Medical School, Sfax University, Sfax, Tunisia.,Child Neurology Department, Hedi Chaker Universitary Hospital of Sfax, Sfax, Tunisia
| | - Faiza Fakhfakh
- Laboratory of Molecular and Functional Genetics, Faculty of Science of Sfax, Sfax University, Sfax, Tunisia
| | - Laurent Villard
- Inserm, MMG, Aix Marseille Univ, Marseille, France.,Département de Génétique Médicale, Hôpital d'Enfants de la Timone, Assistance Publique Hôpitaux de Marseille, 13385, Marseille, France
| | - Chahnez Triki
- Research Laboratory 'NeuroPédiatrie' (LR19ES15), Sfax Medical School, Sfax University, Sfax, Tunisia.,Child Neurology Department, Hedi Chaker Universitary Hospital of Sfax, Sfax, Tunisia
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12
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Matsunaga H, Aruga J. Trans-Synaptic Regulation of Metabotropic Glutamate Receptors by Elfn Proteins in Health and Disease. Front Neural Circuits 2021; 15:634875. [PMID: 33790745 PMCID: PMC8005653 DOI: 10.3389/fncir.2021.634875] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2020] [Accepted: 02/08/2021] [Indexed: 12/20/2022] Open
Abstract
Trans-regulation of G protein-coupled receptors (GPCRs) by leucine-rich repeat (LRR) transmembrane proteins has emerged as a novel type of synaptic molecular interaction in the last decade. Several studies on LRR–GPCR interactions have revealed their critical role in synapse formation and in establishing synaptic properties. Among them, LRR–GPCR interactions between extracellular LRR fibronectin domain-containing family proteins (Elfn1 and Elfn2) and metabotropic glutamate receptors (mGluRs) are particularly interesting as they can affect a broad range of synapses through the modulation of signaling by glutamate, the principal excitatory transmitter in the mammalian central nervous system (CNS). Elfn–mGluR interactions have been investigated in hippocampal, cortical, and retinal synapses. Postsynaptic Elfn1 in the hippocampus and cerebral cortex mediates the tonic regulation of excitatory input onto somatostatin-positive interneurons (INs) through recruitment of presynaptic mGluR7. In the retina, presynaptic Elfn1 binds to mGluR6 and is necessary for synapse formation between rod photoreceptor cells and rod-bipolar cells. The repertoire of binding partners for Elfn1 and Elfn2 includes all group III mGluRs (mGluR4, mGluR6, mGluR7, and mGluR8), and both Elfn1 and Elfn2 can alter mGluR-mediated signaling through trans-interaction. Importantly, both preclinical and clinical studies have provided support for the involvement of the Elfn1–mGluR7 interaction in attention-deficit hyperactivity disorder (ADHD), post-traumatic stress disorder (PTSD), and epilepsy. In fact, Elfn1–mGluR7-associated disorders may reflect the altered function of somatostatin-positive interneuron inhibitory neural circuits, the mesolimbic and nigrostriatal dopaminergic pathway, and habenular circuits, highlighting the need for further investigation into this interaction.
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Affiliation(s)
- Hayato Matsunaga
- Department of Medical Pharmacology, Nagasaki University Institute of Biomedical Sciences, Nagasaki, Japan
| | - Jun Aruga
- Department of Medical Pharmacology, Nagasaki University Institute of Biomedical Sciences, Nagasaki, Japan
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13
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Fisher NM, AlHashim A, Buch AB, Badivuku H, Samman MM, Weiss KM, Cestero GI, Does MD, Rook JM, Lindsley CW, Conn PJ, Gogliotti RG, Niswender CM. A GRM7 mutation associated with developmental delay reduces mGlu7 expression and produces neurological phenotypes. JCI Insight 2021; 6:143324. [PMID: 33476302 PMCID: PMC7934925 DOI: 10.1172/jci.insight.143324] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Accepted: 01/13/2021] [Indexed: 12/29/2022] Open
Abstract
The metabotropic glutamate receptor 7 (mGlu7) is a G protein–coupled receptor that has been recently linked to neurodevelopmental disorders. This association is supported by the identification of GRM7 variants in patients with autism spectrum disorder, attention deficit hyperactivity disorder, and severe developmental delay. One GRM7 mutation previously reported in 2 patients results in a single amino acid change, I154T, within the mGlu7 ligand-binding domain. Here, we report 2 new patients with this mutation who present with severe developmental delay and epilepsy. Functional studies of the mGlu7-I154T mutant reveal that this substitution resulted in significant loss of mGlu7 protein expression in HEK293A cells and in mice. We show that this occurred posttranscriptionally at the level of protein expression and trafficking. Similar to mGlu7–global KO mice, mGlu7-I154T animals exhibited reduced motor coordination, deficits in contextual fear learning, and seizures. This provides functional evidence that a disease-associated mutation affecting the mGlu7 receptor was sufficient to cause neurological dysfunction in mice and further validates GRM7 as a disease-causing gene in the human population.
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Affiliation(s)
- Nicole M Fisher
- Department of Pharmacology and.,Warren Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, Tennessee, USA
| | | | - Aditi B Buch
- Department of Pharmacology and.,Warren Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, Tennessee, USA
| | - Hana Badivuku
- Department of Pharmacology and.,Warren Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, Tennessee, USA
| | | | - Kelly M Weiss
- Department of Pharmacology and.,Warren Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, Tennessee, USA
| | - Gabriela I Cestero
- Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA
| | - Mark D Does
- Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA
| | - Jerri M Rook
- Department of Pharmacology and.,Warren Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, Tennessee, USA
| | - Craig W Lindsley
- Department of Pharmacology and.,Warren Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, Tennessee, USA.,Department of Chemistry and.,Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee, USA
| | - P Jeffrey Conn
- Department of Pharmacology and.,Warren Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, Tennessee, USA.,Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee, USA.,Vanderbilt Kennedy Center, Vanderbilt University Medical Center, Nashville, Tennessee USA
| | - Rocco G Gogliotti
- Department of Pharmacology and.,Warren Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, Tennessee, USA.,Department of Molecular Pharmacology and Neuroscience, Loyola University Chicago, Maywood, Illinois, USA
| | - Colleen M Niswender
- Department of Pharmacology and.,Warren Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, Tennessee, USA.,Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee, USA.,Vanderbilt Kennedy Center, Vanderbilt University Medical Center, Nashville, Tennessee USA
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14
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Pathogenic GRM7 Mutations Associated with Neurodevelopmental Disorders Impair Axon Outgrowth and Presynaptic Terminal Development. J Neurosci 2021; 41:2344-2359. [PMID: 33500274 DOI: 10.1523/jneurosci.2108-20.2021] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Revised: 01/11/2021] [Accepted: 01/16/2021] [Indexed: 12/18/2022] Open
Abstract
Metabotropic glutamate receptor 7 (mGlu7) is an inhibitory heterotrimeric G-protein-coupled receptor that modulates neurotransmitter release and synaptic plasticity at presynaptic terminals in the mammalian central nervous system. Recent studies have shown that rare mutations in glutamate receptors and synaptic scaffold proteins are associated with neurodevelopmental disorders (NDDs). However, the role of presynaptic mGlu7 in the pathogenesis of NDDs remains largely unknown. Recent whole-exome sequencing (WES) studies in families with NDDs have revealed that several missense mutations (c.1865G>A:p.R622Q; c.461T>C:p.I154T; c.1972C>T:p.R658W and c.2024C>A:p.T675K) or a nonsense mutation (c.1757G>A:p.W586X) in the GRM7 gene may be linked to NDDs. In the present study, we investigated the mechanistic links between GRM7 point mutations and NDD pathology. We find that the pathogenic GRM7 I154T and R658W/T675K mutations lead to the degradation of the mGlu7 protein. In particular, the GRM7 R658W/T675K mutation results in a lack of surface mGlu7 expression in heterologous cells and cultured neurons isolated from male and female rat embryos. We demonstrate that the expression of mGlu7 variants or exposure to mGlu7 antagonists impairs axon outgrowth through the mitogen-activated protein kinase (MAPK)-cAMP-protein kinase A (PKA) signaling pathway during early neuronal development, which subsequently leads to a decrease in the number of presynaptic terminals in mature neurons. Treatment with an mGlu7 agonist restores the pathologic phenotypes caused by mGlu7 I154T but not by mGlu7 R658W/T675K because of its lack of neuronal surface expression. These findings provide evidence that stable neuronal surface expression of mGlu7 is essential for neural development and that mGlu7 is a promising therapeutic target for NDDs.SIGNIFICANCE STATEMENT Neurodevelopmental disorders (NDDs) affect brain development and function by multiple etiologies. Metabotropic glutamate receptor 7 (mGlu7) is a receptor that controls excitatory neurotransmission and synaptic plasticity. Since accumulating evidence indicates that the GRM7 gene locus is associated with NDD risk, we analyzed the functional effects of human GRM7 variants identified in patients with NDDs. We demonstrate that stable neuronal surface expression of mGlu7 is essential for axon outgrowth and presynaptic terminal development in neurons. We found that mitogen-activated protein kinase (MAPK)-cAMP-protein kinase A (PKA) signaling and subsequent cytoskeletal dynamics are defective because of the degradation of mGlu7 variants. Finally, we show that the defects caused by mGlu7 I154T can be reversed by agonists, providing the rationale for proposing mGlu7 as a potential therapeutic target for NDDs.
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