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Pathophysiological Mechanisms of Dominant and Recessive GLRA1 Mutations in Hyperekplexia

Chung, S.-K., Vanbellinghen, J.-F., Mullins, J. G. L., Robinson, A., Hantke, J., Hammond, C. L., Gilbert, D. F., Freilinger, M., Ryan, M., Kruer, M. C., Masri, A., Gurses, C., Ferrie, C., Harvey, K., Shiang, R., Christodoulou, J., Andermann, F., Andermann, E., Thomas, Rhys Huw, Harvey, R. J., Lynch, J. W. and Rees, M. I. 2010. Pathophysiological Mechanisms of Dominant and Recessive GLRA1 Mutations in Hyperekplexia. Journal of Neuroscience 30 (28) , pp. 9612-9620. 10.1523/JNEUROSCI.1763-10.2010

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Hyperekplexia is a rare, but potentially fatal, neuromotor disorder characterized by exaggerated startle reflexes and hypertonia in response to sudden, unexpected auditory or tactile stimuli. This disorder is primarily caused by inherited mutations in the genes encoding the glycine receptor (GlyR) α1 subunit (GLRA1) and the presynaptic glycine transporter GlyT2 (SLC6A5). In this study, systematic DNA sequencing of GLRA1 in 88 new unrelated human hyperekplexia patients revealed 19 sequence variants in 30 index cases, of which 21 cases were inherited in recessive or compound heterozygote modes. This indicates that recessive hyperekplexia is far more prevalent than previous estimates. From the 19 GLRA1 sequence variants, we have investigated the functional effects of 11 novel and 2 recurrent mutations. The expression levels and functional properties of these hyperekplexia mutants were analyzed using a high-content imaging system and patch-clamp electrophysiology. When expressed in HEK293 cells, either as homomeric α1 or heteromeric α1β GlyRs, subcellular localization defects were the major mechanism underlying recessive mutations. However, mutants without trafficking defects typically showed alterations in the glycine sensitivity suggestive of disrupted receptor function. This study also reports the first hyperekplexia mutation associated with a GlyR leak conductance, suggesting tonic channel opening as a new mechanism in neuronal ligand-gated ion channels.

Item Type: Article
Status: Published
Schools: Medicine
MRC Centre for Neuropsychiatric Genetics and Genomics (CNGG)
Subjects: R Medicine > R Medicine (General)
R Medicine > RC Internal medicine > RC0321 Neuroscience. Biological psychiatry. Neuropsychiatry
Publisher: Society for Neuroscience
ISSN: 0270-6474
Last Modified: 04 Jun 2017 08:59

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