Dataset Information

A recessive Nav1.4 mutation underlies congenital myasthenic syndrome with periodic paralysis.

ABSTRACT:

Objective

To determine the molecular basis of a complex phenotype of congenital muscle weakness observed in an isolated but consanguineous patient.

Methods

The proband was evaluated clinically and neurophysiologically over a period of 15 years. Genetic testing of candidate genes was performed. Functional characterization of the candidate mutation was done in mammalian cell background using whole cell patch clamp technique.

Results

The proband had fatigable muscle weakness characteristic of congenital myasthenic syndrome with acute and reversible attacks of most severe muscle weakness as observed in periodic paralysis. We identified a novel homozygous SCN4A mutation (p.R1454W) linked to this recessively inherited phenotype. The p.R1454W substitution induced an important enhancement of fast and slow inactivation, a slower recovery for these inactivated states, and a frequency-dependent regulation of Nav1.4 channels in the heterologous expression system.

Conclusion

We identified a novel loss-of-function mutation of Nav1.4 that leads to a recessive phenotype combining clinical symptoms and signs of congenital myasthenic syndrome and periodic paralysis, probably by decreasing channel availability for muscle action potential genesis at the neuromuscular junction and propagation along the sarcolemma.

SUBMITTER: Habbout K

PROVIDER: S-EPMC4731685 | biostudies-literature | 2016 Jan

REPOSITORIES: biostudies-literature

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Publications

A recessive Nav1.4 mutation underlies congenital myasthenic syndrome with periodic paralysis.

Habbout Karima K Poulin Hugo H Rivier François F Giuliano Serena S Sternberg Damien D Fontaine Bertrand B Eymard Bruno B Morales Raul Juntas RJ Echenne Bernard B King Louise L Hanna Michael G MG Männikkö Roope R Chahine Mohamed M Nicole Sophie S Bendahhou Said S

Neurology 20151211 2

<h4>Objective</h4>To determine the molecular basis of a complex phenotype of congenital muscle weakness observed in an isolated but consanguineous patient.<h4>Methods</h4>The proband was evaluated clinically and neurophysiologically over a period of 15 years. Genetic testing of candidate genes was performed. Functional characterization of the candidate mutation was done in mammalian cell background using whole cell patch clamp technique.<h4>Results</h4>The proband had fatigable muscle weakness c ...[more]

PMID: 26659129

Similar Datasets

Project description:Hypokalaemic periodic paralysis is typically associated with mutations of voltage sensor residues in calcium or sodium channels of skeletal muscle. To date, causative sodium channel mutations have been studied only for the two outermost arginine residues in S4 voltage sensor segments of domains I to III. These mutations produce depolarization of skeletal muscle fibres in response to reduced extracellular potassium, owing to an inward cation-selective gating pore current activated by hyperpolarization. Here, we describe mutations of the third arginine, R3, in the domain III voltage sensor i.e. an R1135H mutation which was found in two patients in separate families and a novel R1135C mutation identified in a third patient in another family. Muscle fibres from a patient harbouring the R1135H mutation showed increased depolarization tendency at normal and reduced extracellular potassium compatible with the diagnosis. Additionally, amplitude and rise time of action potentials were reduced compared with controls, even for holding potentials at which all NaV1.4 are fully recovered from inactivation. These findings may be because of an outward omega current activated at positive potentials. Expression of R1135H/C in mammalian cells indicates further gating defects that include significantly enhanced entry into inactivation and prolonged recovery that may additionally contribute to action potential inhibition at the physiological resting potential. After S4 immobilization in the outward position, mutant channels produce an inward omega current that most likely depolarizes the resting potential and produces the hypokalaemia-induced weakness. Gating current recordings reveal that mutations at R3 inhibit S4 deactivation before recovery, and molecular dynamics simulations suggest that this defect is caused by disrupted interactions of domain III S2 countercharges with S4 arginines R2 to R4 during repolarization of the membrane. This work reveals a novel mechanism of disrupted S4 translocation for hypokalaemic periodic paralysis mutations at arginine residues located below the gating pore constriction of the voltage sensor module.

Dataset Information

A recessive Nav1.4 mutation underlies congenital myasthenic syndrome with periodic paralysis.

Objective

Methods

Results

Conclusion

Publications

A recessive Nav1.4 mutation underlies congenital myasthenic syndrome with periodic paralysis.

Similar Datasets

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