Myoclonic status epilepticus and cerebellar hypoplasia associated with a novel variant in the GRIA3 gene

• Published in: Neurogenetics Vol. 23; no. 1; pp. 27 - 35
• Main Authors: Rinaldi, Berardo, Ge, Yu-Han, Freri, Elena, Tucci, Arianna, Granata, Tiziana, Estienne, Margherita, Sun, Jia-Hui, Gérard, Bénédicte, Bayat, Allan, Efthymiou, Stephanie, Gervasini, Cristina, Shi, Yun Stone, Houlden, Henry, Marchisio, Paola, Milani, Donatella
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.01.2022; Springer Nature B.V
• Subjects: Cerebellum; Cerebellum - abnormalities; Child; Chromosomes; Developmental Disabilities; Epilepsy; Gene mapping; Genes; Glutamic acid receptors; Human Genetics; Humans; Hypoplasia; Intellectual disabilities; Intellectual Disability - genetics; Ion channels (ligand-gated); Male; Medicine; Medicine & Public Health; Molecular Medicine; Nervous System Malformations; Neurology; Neurosciences; Original; Original Article; Pedigree; Seizures; Status Epilepticus; α-Amino-3-hydroxy-5-methyl-4-isoxazole propionic acid; AMPARs; Glutamate; Myoclonic status epilepticus; Cerebellar hypoplasia; GRIA3
• ISSN: 1364-6745; 1364-6753
• DOI: 10.1007/s10048-021-00666-1

AMPA-type glutamate receptors (AMPARs) are postsynaptic ionotropic receptors which mediate fast excitatory currents. AMPARs have a heterotetrameric structure, variably composed by the four subunits GluA1-4 which are encoded by genes GRIA1 - 4 . Increasing evidence support the role of pathogenic variants in GRIA1-4 genes as causative for syndromic intellectual disability (ID). We report an Italian pedigree where some male individuals share ID, seizures and facial dysmorphisms. The index subject was referred for severe ID, myoclonic seizures, cerebellar signs and short stature. Whole exome sequencing identified a novel variant in GRIA3 , c.2360A > G, p.(Glu787Gly). The GRIA3 gene maps to chromosome Xq25 and the c.2360A > G variant was transmitted by his healthy mother. Subsequent analysis in the family showed a segregation pattern compatible with the causative role of this variant, further supported by preliminary functional insights. We provide a detailed description of the clinical evolution of the index subjects and stress the relevance of myoclonic seizures and cerebellar syndrome as cardinal features of his presentation.