Neurodevelopmental disorders are associated with disabilities in brain function that affect a child's behavior, memory or ability to learn. Such disabilities carry devastating mental, emotional, and economic consequences for the individuals, their families, as well as society. The molecular bases for a subset of disabilities involve disease-causing mutations in various ion channel families, including NMDA receptors (NMDARs). The cation-selective NMDAR channels formed from assembly of two glycine-binding GluN1 subunits and two glutamate-binding GluN2 subunits mediate a slow, Ca2+-permeable component of excitatory synaptic currents that can trigger changes in synaptic strength, a cellular correlate of learning. NMDARs also play an important role in normal brain development. A large number of mutations (>140) have been reported in just the last three years, leading to the view that these mutations are present in a subset of patients with neurological disorders, particularly early onset intractable seizures. Surprisingly, the incidence of NMDAR mutations found in pediatric patients presenting with neurological problems is 5.7%, similar to or higher than that for Na+, K+ , Ca2+ channels and GABA receptors. Mutations in NMDAR subunits have been identified in children with a broad range of neurodevelopmental problems, including attention deficit hyperactivity disorder (ADHD), autism spectrum disorders, developmental delay, mental retardation, schizophrenia, intellectual disability, and intractable seizures. Unfortunately, virtually no functional analysis of these mutations exists, making it impossible to evaluate effects of mutations in the context of clinical phenotype. We proposed 4 lines of experimentation addressing the molecular mechanism underlying neurological diseases suggested to arise from mutations in NMDAR subunits. We will study the functional effects of mutations in the transmembrane domain (TM), linkers, and ligand binding domains (LBD) and test the ability of FDA-approved drugs to rectify the mutation-induced gain-of-function. All experiments will utilize receptors that contain 0, 1, or 2 mutant NMDAR subunits, enabling an assessment of function in heterozygous patients.
Aim 1. How do human NMDAR mutations in the TM- linker regions impact function? We will analyze 26 mutations in the transmembrane domain or associated linkers. We will collaborate on efforts to obtain crystals of the open channel configuration.
Aim 2. How do human NMDAR mutations in the ligand binding domains impact function? We will evaluate the functional effects of 36 mutations in the ligand binding domain, and collaborate to obtain crystallographic data.
Aim 3. How do human NMDAR mutations influence neuronal trafficking and function? We will analyze the properties of NMDAR-mediated synaptic current in slice cultures transfected with mutant NMDAR subunits.
Aim 4. Are NMDAR channelopathies treatable? We will evaluate the potency (IC50) of FDA-approved NMDAR antagonists at gain-of-function NMDAR mutations and evaluate the neurotoxic potential of NMDAR mutations.

Public Health Relevance

NMDA receptors mediate communication between neurons and thus play important roles in normal brain functions and a wide range of neurological diseases. Genetic mutations of NMDA receptor genes have been identified in children with profound neurodevelopmental problems, including intractable seizures, attention deficit hyperactivity disorder (ADHD), autism spectrum disorders, developmental delay or mental retardation, schizophrenia, and intellectual disability. We will determine functional changes of these mutations and their pharmacological profiles, which provide the first opportunity to understand the molecular mechanism and targeted therapeutic strategies for these neurological disorders.

Agency
National Institute of Health (NIH)
Institute
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Type
Research Project (R01)
Project #
5R01HD082373-05
Application #
9628022
Study Section
Developmental Brain Disorders Study Section (DBD)
Program Officer
Bardhan, Sujata
Project Start
2015-04-01
Project End
2021-01-31
Budget Start
2019-02-01
Budget End
2021-01-31
Support Year
5
Fiscal Year
2019
Total Cost
Indirect Cost
Name
Emory University
Department
Pharmacology
Type
Schools of Medicine
DUNS #
066469933
City
Atlanta
State
GA
Country
United States
Zip Code
30322
Fernández-Marmiesse, Ana; Kusumoto, Hirofumi; Rekarte, Saray et al. (2018) A novel missense mutation in GRIN2A causes a nonepileptic neurodevelopmental disorder. Mov Disord 33:992-999
Wells, Gordon; Yuan, Hongjie; McDaniel, Miranda J et al. (2018) The GluN2B-Glu413Gly NMDA receptor variant arising from a de novo GRIN2B mutation promotes ligand-unbinding and domain opening. Proteins 86:1265-1276
Bhattacharya, Subhrajit; Khatri, Alpa; Swanger, Sharon A et al. (2018) Triheteromeric GluN1/GluN2A/GluN2C NMDARs with Unique Single-Channel Properties Are the Dominant Receptor Population in Cerebellar Granule Cells. Neuron 99:315-328.e5
Fry, Andrew E; Fawcett, Katherine A; Zelnik, Nathanel et al. (2018) De novo mutations in GRIN1 cause extensive bilateral polymicrogyria. Brain :
XiangWei, Wenshu; Jiang, Yuwu; Yuan, Hongjie (2018) De Novo Mutations and Rare Variants Occurring in NMDA Receptors. Curr Opin Physiol 2:27-35
Liu, Shuxi; Zhou, Liang; Yuan, Hongjie et al. (2017) A Rare Variant Identified Within the GluN2B C-Terminus in a Patient with Autism Affects NMDA Receptor Surface Expression and Spine Density. J Neurosci 37:4093-4102
Platzer, Konrad; Yuan, Hongjie; Schütz, Hannah et al. (2017) GRIN2B encephalopathy: novel findings on phenotype, variant clustering, functional consequences and treatment aspects. J Med Genet 54:460-470
Ogden, Kevin K; Chen, Wenjuan; Swanger, Sharon A et al. (2017) Molecular Mechanism of Disease-Associated Mutations in the Pre-M1 Helix of NMDA Receptors and Potential Rescue Pharmacology. PLoS Genet 13:e1006536
Gao, Kai; Tankovic, Anel; Zhang, Yujia et al. (2017) A de novo loss-of-function GRIN2A mutation associated with childhood focal epilepsy and acquired epileptic aphasia. PLoS One 12:e0170818
Chen, Wenjuan; Shieh, Christine; Swanger, Sharon A et al. (2017) GRIN1 mutation associated with intellectual disability alters NMDA receptor trafficking and function. J Hum Genet 62:589-597

Showing the most recent 10 out of 15 publications