Back to Publications

Delineating the GRIN1 phenotypic spectrum: A distinct genetic NMDA receptor encephalopathy

Specialty Areas:
Date: June 23, 2017
Authors:
Amy Goldstein, Bernd A. Neubauer, Bobby P. C. Koeleman, Carolina Courage, Caroline Nava, Christeen Ramane J. Pedurupillay, Christel Depienne, Claudia A. Ruivenkamp, Deborah Bartholdi, Deepa S. Rajan, Delphine Heron, Dennis J. Dlugos, Dennis Lal, Doriana Misceo, Eirik Frengen, Emilia K. Bijlsma, Emily S. Doherty, Georgianne L. Arnold, Gerhard Kurlemann, Hannah Schütz, Helle Hjalgrim, Henrike O. Heyne, Holger Thiele, Isabelle Schrauwen, Johannes R. Lemke, Julia Hentschel, Katherine L. Helbig, Keri Ramsey, Kirsten Geider, Mariette J.V. Hoffer, Newell Belnap, Peter Nürnberg, Petter Strømme, Rikke S. Møller, Ryan Richholt, Vikas Bhambhani, Vinodh Narayanan MD
Journal: Neurology
Topics:
Read Abstract

Abstract

Objective

To determine the phenotypic spectrum caused by mutations in GRIN1 encoding the NMDA receptor subunit GluN1 and to investigate their underlying functional pathophysiology.

Methods

We collected molecular and clinical data from several diagnostic and research cohorts. Functional consequences of GRIN1 mutations were investigated in Xenopus laevis oocytes.

Results

We identified heterozygous de novo GRIN1 mutations in 14 individuals and reviewed the phenotypes of all 9 previously reported patients. These 23 individuals presented with a distinct phenotype of profound developmental delay, severe intellectual disability with absent speech, muscular hypotonia, hyperkinetic movement disorder, oculogyric crises, cortical blindness, generalized cerebral atrophy, and epilepsy. Mutations cluster within transmembrane segments and result in loss of channel function of varying severity with a dominant-negative effect. In addition, we describe 2 homozygous GRIN1 mutations (1 missense, 1 truncation), each segregating with severe neurodevelopmental phenotypes in consanguineous families.

Conclusions

De novo GRIN1 mutations are associated with severe intellectual disability with cortical visual impairment as well as oculomotor and movement disorders being discriminating phenotypic features. Loss of NMDA receptor function appears to be the underlying disease mechanism. The identification of both heterozygous and homozygous mutations blurs the borders of dominant and recessive inheritance of GRIN1-associated disorders