ENOrphanet Journal of Rare Diseases | Neurodevelopmental Phenotypes and Therapeutic Implications of GRIN2B Variants
Date: --
Classification: Frontiers
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This article systematically distinguishes loss-of-function (LOF) and gain-of-function (GOF) types of GRIN2B variants for the first time, revealing significant clinical phenotypic differences. It found that TMD domain variants are more likely to cause GOF effects and are highly associated with epilepsy and microcephaly. Additionally, memantine shows therapeutic benefits in controlling epilepsy and improving cognition, providing new clinical references.
Literature Overview
This article titled 'GRIN2B-related neurodevelopmental disorders: genotype-phenotype correlations and therapeutic implications', published in the Orphanet Journal of Rare Diseases, reviews research progress on GRIN2B variant-induced neurodevelopmental disorders. It incorporates 7 de novo cases from Xiangya Hospital and combines them with 98 cases reported in literature, totaling 105 patients for analyzing phenotypic spectrum and treatment responses. The study further compares clinical features between GOF and LOF variants, finding that GOF variants are more frequently associated with epilepsy and microcephaly, while LOF variants present relatively milder phenotypes. Notably, missense variants in LOF cases tend to cause more severe neurodevelopmental phenotypes, including profound developmental delay (DD), intellectual disability (ID), language impairments, and motor deficits. The study also evaluates anti-seizure medications (ASMs) and memantine efficacy, showing seizure control in approximately 25.93% of patients, with significant therapeutic benefits observed for memantine in certain GOF variant carriers.
Background Knowledge
The GRIN2B gene encodes the GluN2B subunit of NMDA receptors, which respond to glutamate and glycine in the central nervous system, mediating synaptic transmission and participating in neuronal development, learning, and memory. GRIN2B variants have been extensively linked to neurodevelopmental disorders (NDDs), including developmental delay (DD), intellectual disability (ID), autism spectrum disorder (ASD), and schizophrenia-like phenotypes. However, the correlation between GRIN2B variant types (LOF vs. GOF) and phenotypes remains incompletely understood, with therapeutic strategies lacking systematic summaries. By integrating new cases with literature data, this study further explores genotype-phenotype relationships and evaluates treatment efficacy differences, including memantine, across variant types. It highlights that TMD domain variants predominantly induce GOF effects, whereas ABD domain variants are mostly LOF. Additionally, missense variants in LOF demonstrate more severe clinical phenotypes than truncating variants, underscoring the critical impact of variant types on disease manifestations. These findings provide novel molecular insights and clinical evidence for diagnosing, classifying, and managing GRIN2B-related disorders.
Research Methods and Experiments
The research team collected 7 GRIN2B variant patients from Xiangya Hospital, including 5 de novo and 2 known variants. All variants were validated via Sanger sequencing and classified according to ACMG guidelines. Patient information encompassed seizure types, EEG characteristics, developmental milestones, MRI findings, and drug treatment responses. Additionally, a systematic PubMed literature review was conducted using keywords including 'GRIN2B', 'epilepsy', 'neurodevelopmental disorders', 'developmental delay', 'intellectual disability', and 'autism spectrum disorder', incorporating 23 publications with 98 patient records. All variants were categorized as LOF or GOF based on electrophysiological functions and further analyzed for phenotypic differences. Statistical analysis employed χ² or Fisher's exact tests, with P < 0.05 considered statistically significant.
Key Findings and Perspectives
Research Significance and Future Directions
This is the first systematic study distinguishing GRIN2B variant types (LOF/GOF) and analyzing their phenotypic differences, offering new molecular evidence for clinical diagnosis and treatment. The findings suggest variant type and location can predict disease severity and therapeutic responses, particularly for TMD domain variants that may exhibit heightened sensitivity to memantine. Larger prospective clinical trials are needed to validate these genotype-therapy response correlations and further explore GOF variant molecular mechanisms. The study also emphasizes the importance of functional experiments in variant classification, recommending combined use of bioinformatics tools and functional validation in clinical practice to enhance diagnostic and therapeutic precision.
Conclusion
This study systematically analyzed genotype-phenotype correlations in GRIN2B-related neurodevelopmental disorders, making the first distinction between GOF and LOF variant clinical manifestations. TMD domain variants were confirmed to predominantly cause GOF effects, strongly linked to epilepsy and microcephaly. In LOF variants, missense mutations produce more severe phenotypes than truncating variants. Memantine demonstrated significant anti-seizure and cognitive-enhancing effects in GOF variant patients, suggesting its potential as a therapeutic agent. These results provide critical references for clinical classification, diagnosis, and treatment strategies of GRIN2B-related disorders, while highlighting the need for multicenter prospective studies due to current limitations of high heterogeneity and inconsistent evaluation methods.
