Biology subjects

Traynelis, S. F.

Publications and source records attributed to Traynelis, S. F..

6 recordsLinked to original sources

bioRxiv2025

Discrete interneuron subsets participate in GluN1/GluN3A excitatory glycine receptor (eGlyR)-mediated regulation of hippocampal network activity throughout development and evolution.

Decades of studies implicating GluN3A N-methyl-D-aspartate receptor (NMDAR) subunits in physiological and pathological function have largely been interpreted through direct regulation of conventional glutamatergic NMDARs. However, emerging evidence indicates that GluN3A frequently assembles with GluN1 forming unconventional glutamate-insensitive NMDARs that operate as native excitatory glycine receptors (eGlyRs). Here we demonstrate that hippocampal somatostatin and neurogliaform interneurons (Sst-INs and NGFCs) express functional eGlyRs from early postnatal through adult ages. In the developing hippocampus eGlyR-mediated excitation of NGFCs with ambient glycine dramatically increases GABAergic tone, with consequences for the generation of giant depolarizing potentials (GDPs). In the mature hippocampus, eGlyR- mediated excitation of Sst-INs regulates sharp wave ripples (SWRs). Finally, we reveal evolutionary conservation of hippocampal Sst-IN eGlyRs and eGlyR- mediated SWR regulation in non-human primates confirming functional eGlyR availability for therapeutic potential in higher species. Our findings underscore that eGlyR mediated regulation of cell and circuit excitability through both cell autonomous and cell non-autonomous mechanisms must be considered to understand GluN3A roles in brain development, plasticity, and disease.

neuroscience↗

bioRxiv2024

Selective Enhancement of the Interneuron Network and Gamma-Band Power via GluN2C/GluN2D NMDA Receptor Potentiation

N-methyl-D-aspartate receptors (NMDARs) comprise a family of ligand-gated ionotropic glutamate receptors that mediate a slow, calcium-permeable component to excitatory neurotransmission. The GluN2D subunit is enriched in GABAergic inhibitory interneurons in cortical tissue. Diminished levels of GABAergic inhibition contribute to multiple neuropsychiatric conditions, suggesting that enhancing inhibition may have therapeutic utility, thus making GluN2D modulation an attractive drug target. Here, we describe the actions of a GluN2C/GluN2D-selective positive allosteric modulator (PAM), (+)-EU1180-453, which has improved drug-like properties such as increased aqueous solubility compared to the first-in-class GluN2C/GluN2D-selective prototypical PAM (+)-CIQ. (+)-EU1180-453 doubles the NMDAR response at lower concentrations (< 10 {micro}M) compared to (+)-CIQ, and produces a greater degree of maximal potentiation at 30 {micro}M. Using in vitro electrophysiological recordings, we show that (+)-EU1180-453 potentiates triheteromeric NMDARs containing at least one GluN2C or GluN2D subunit, and is active at both exon5-lacking and exon5-containing GluN1 splice variants. (+)-EU1180-453 increases glutamate efficacy for GluN2C/GluN2D-containing NMDARs by both prolonging the deactivation time and potentiating the peak response amplitude. We show that (+)-EU1180-453 selectively increases synaptic NMDAR-mediated charge transfer onto P11-15 CA1 stratum radiatum hippocampal interneurons, but is without effect on CA1 pyramidal cells. This increased charge transfer enhances inhibitory output from GABAergic interneurons onto CA1 pyramidal cells in a GluN2D-dependent manner. (+)-EU1180-453 also shifts excitatory-to-inhibitory coupling towards increased inhibition and produces enhanced gamma band power from carbachol-induced field potential oscillations in hippocampal slices. Thus, (+)-EU1180-453 can enhance overall circuit inhibition, which could prove therapeutically useful for the treatment of anxiety, depression, schizophrenia, and other neuropsychiatric disorders. Significance StatementInterneuron dysfunction and diminished GABAergic inhibition in neocortical and hippocampal circuits remains a prominent molecular hypothesis for neuropsychiatric diseases including anxiety, depression, and schizophrenia. Pharmacological agents that boost GABA receptor function have shown utility in various forms of depression and treating symptoms of schizophrenia. Cortical GABAergic interneurons, unlike their excitatory pyramidal cell counterparts, are enriched for the GluN2D subunit of the NMDA receptor. Thus, GluN2D subunit-selective modulation could be a useful therapeutic tool to enhance local inhibition, improving the prognosis for neuropsychiatric diseases for which interneuron dysfunction is prominent and causal to circuit aberration.

neuroscience↗

bioRxiv2024

Grin1Y647S/+ Mice: A Preclinical Model of GRIN1-Related Neurodevelopmental Disorder

GRIN1-related neurodevelopmental disorder (GRIN1-NDD) is characterized by clinically significant variation in the GRIN1 gene, which encodes the obligatory GluN1 subunit of N-methyl-D-aspartate receptors (NMDARs). The identified p.Tyr647Ser (Y647S) variant is carried by a 34-year-old female with seizures and intellectual disability. This study builds upon initial in vitro investigations of the functional impacts of this variant in the SYTANLAAF domain of the GluN1 M3 helix and examines its in vivo consequences in a mouse model. To investigate in vitro functional impacts of NMDARs containing GluN1-Y647S variant subunits, GluN1-Y647S was co-expressed with wildtype GluN2A or GluN2B subunits in Xenopus laevis oocytes and HEK cells. Grin1Y647S/+ mice were created by CRISPR-Cas9 endonuclease-mediated transgenesis and the molecular, electrophysiological, and behavioural consequences of the variant were examined. Additionally, de-identified patient data were collected to examine the representative nature of Grin1Y647S/+ mice in modelling specific aspects of patient symptomology. In vitro, NMDARs containing GluN1-Y647S showed altered sensitivity to endogenous agonists and negative allosteric modulators, and reduced cell surface trafficking. Ex vivo, Grin1Y647S/+ mice displayed a reduction in whole brain GluN1 levels and a deficiency in NMDAR-mediated synaptic transmission in the hippocampus. Behaviourally, Grin1Y647S/+ mice exhibited altered vocalizations, muscle strength, sociability, and problem-solving, as well as spontaneous convulsions that were ameliorated with supplementation of {beta}-hydroxybutyrate (BHB), an endogenously produced ketone body. The Y647S variant confers a complex in vivo phenotype, which reflects largely diminished properties of NMDAR function. As a result, Grin1Y647S/+ mice display atypical behaviour in domains relevant to the clinical characteristics of GRIN1-NDD and the individual carrying the variant, which allowed for the identification of BHB supplementation as a potential anti-convulsant treatment. Ultimately, the characterization of Grin1Y647S/+ mice accomplished in the present work, expands our understanding of the mechanisms underlying GRIN1-NDD and provides a foundation for the continued development of novel therapeutics.

neuroscience↗

bioRxiv2022

Conserved patterns across ion channels correlate with variant pathogenicity and clinical phenotypes

Clinically identified genetic variants in ion channels can be benign or cause disease by increasing or decreasing the protein function. Consequently, therapeutic decision-making is challenging without molecular testing of each variant. Our biophysical knowledge of ion channel structures and function is just emerging, and it is currently not well understood which amino acid residues cause disease when mutated. We sought to systematically identify biological properties associated with variant pathogenicity across all major voltage and ligand-gated ion channel families. We collected and curated 3,049 pathogenic variants from hundreds of neurodevelopmental and other disorders and 12,546 population variants for 30 ion channel or channel subunits for which a high-quality protein structure was available. Using a wide range of bioinformatics approaches, we computed 163 structural features and tested them for pathogenic variant enrichment. We developed a novel 3D spatial distance scoring approach that enables comparisons of pathogenic and population variant distribution across protein structures. We discovered and independently replicated that several pore residue properties and proximity to the pore axis were most significantly enriched for pathogenic variants compared to population variants. Using our novel 3D scoring approach, we showed that the strongest pathogenic variant enrichment was observed for pore-lining residues and alpha-helix residues within 5[A] distance from the pore axis center and not involved in gating. Within the subset of residues located at the pore, the hydrophobicity of the pore was the feature most strongly associated with variant pathogenicity. We also found an association between the identified properties and both clinical phenotypes and fucntional in vitro assays for voltage-gated sodium channels (SCN1A, SCN2A, SCN8A) and N-methyl-D-aspartate (NMDA) receptor (GRIN1, GRIN2A, GRIN2B) encoding genes. In an independent expert-curated dataset of 1,422 neurodevelopmental disorder pathogenic patient variants, and 679 electrophysiological experiments that pore axis distance is associated with seizure age of onset and cognitive performance as well as differential gain vs. loss-of-channel function. In summary, we identified biological properties associated with ion-channel malfunction and show that these are correlated with in vitro functional read-outs and clinical phenotypes in patients with neurodevelopmental disorders. Our results suggest that clinical decision support algorithms that predict variant pathogenicity and function are feasible in the future.

genetics↗

bioRxiv2021

The GluN2A subunit of the NMDA receptor modulates the rate of functional maturation in parvalbumin-positive interneurons

N-methyl-D-aspartate receptors (NMDARs) comprise a family of ligand-gated ionotropic glutamate receptors that mediate a calcium-permeable component to fast excitatory neurotransmission. NMDARs are heterotetrameric assemblies of two obligate GluN1 subunits (encoded by the GRIN1 gene) and two GluN2 subunits (encoded by the GRIN2A-GRIN2D genes). Sequencing data shows that 43% (297/679) of all currently known NMDAR disease-associated genetic variants are within the GRIN2A gene, which encodes the GluN2A subunit. Here, we show that unlike missense GRIN2A variants, individuals affected with disease-associated null GRIN2A variants demonstrate a transient period of seizure susceptibility that begins during infancy and diminishes near adolescence. To explore this new clinical finding at that circuit and cellular level, we conducted studies using Grin2a+/- and Grin2a-/-mice at various stages during neurodevelopment. We show increased circuit excitability and CA1 pyramidal cell output in juvenile mice of both Grin2a+/- and Grin2a-/- mice. These alterations in somatic spiking are not due to global upregulation other GRIN genes (including Grin2b) nor can they be attributed to perturbations in the intrinsic excitability or action-potential firing properties of CA1 pyramidal cells. Deeper evaluation of the developing CA1 circuit led us to uncover age- and Grin2a gene dosing-dependent transient delays in the electrophysiological maturation programs of PV interneurons. Overall, we report that Grin2a+/+ mice reach electrophysiological maturation between the neonatal and juvenile neurodevelopmental timepoints, with Grin2a+/- mice not reaching electrophysiological maturation until preadolescence, and Grin2a-/- not reaching electrophysiological maturation until adulthood. Overall, these data may represent a molecular mechanism describing the transient nature of seizure burden in disease-associated null GRIN2A patients.

neuroscience↗

bioRxiv2019

Modeling and treating GRIN2A developmental and epileptic encephalopathy in mice

NMDA receptors (NMDAR) play crucial roles in excitatory synaptic transmission. Rare variants of GRIN2A, which encodes the GluN2A NMDAR subunit, are associated with several intractable neurodevelopmental disorders, including developmental and epileptic encephalopathy (DEE). A de novo missense variant, p.Ser644Gly (c.1930A>G), was identified in a child with DEE, and Grin2a knockin mice were generated to model and extend understanding of this intractable childhood disease. Homozygous and heterozygous mutant mice exhibit altered hippocampal morphology at two weeks of age, and homozygotes exhibit lethal tonic-clonic seizures in the third week. Heterozygous adult mice display a variety of distinct features, including resistance to electrically induced partial seizures, as well as hyperactivity and repetitive and reduced anxiety behaviors. Multielectrode recordings of mutant neuronal networks reveal hyperexcitability and altered bursting and synchronicity. When expressed in heterologous cells, mutant receptors exhibit enhanced NMDAR agonist potency and slow deactivation following rapid removal of glutamate, as occurs at synapses. Consistent with these observations, NMDAR-mediated synaptic currents in hippocampal slices from mutant mice show a prolonged deactivation time course. Standard antiepileptic drug monotherapy was ineffective in the patient, but combined treatment of NMDAR antagonists with antiepileptic drugs substantially reduced the seizure burden albeit without appreciable developmental improvement. Chronic treatment of homozygous mutant mouse pups with NMDAR antagonists delayed the onset of lethal seizures but did not prevent them. These studies illustrate the power of modeling severe neurodevelopmental seizure disorders using multiple experimental modalities and suggest their extended utility in identifying and evaluating new therapies.

neuroscience↗