GLUT1 mutations are a cause of paroxysmal exertion-induced dyskinesias and induce hemolytic anemia by a cation leak
Yvonne G. Weber, … , Frank Lehmann-Horn, Holger Lerche
Yvonne G. Weber, … , Frank Lehmann-Horn, Holger Lerche
Published May 1, 2008
Citation Information: J Clin Invest. 2008;118(6):2157-2168. https://doi.org/10.1172/JCI34438.
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GLUT1 mutations are a cause of paroxysmal exertion-induced dyskinesias and induce hemolytic anemia by a cation leak

Abstract

Paroxysmal dyskinesias are episodic movement disorders that can be inherited or are sporadic in nature. The pathophysiology underlying these disorders remains largely unknown but may involve disrupted ion homeostasis due to defects in cell-surface channels or nutrient transporters. In this study, we describe a family with paroxysmal exertion-induced dyskinesia (PED) over 3 generations. Their PED was accompanied by epilepsy, mild developmental delay, reduced CSF glucose levels, hemolytic anemia with echinocytosis, and altered erythrocyte ion concentrations. Using a candidate gene approach, we identified a causative deletion of 4 highly conserved amino acids (Q282_S285del) in the pore region of the glucose transporter 1 (GLUT1). Functional studies in Xenopus oocytes and human erythrocytes revealed that this mutation decreased glucose transport and caused a cation leak that alters intracellular concentrations of sodium, potassium, and calcium. We screened 4 additional families, in which PED is combined with epilepsy, developmental delay, or migraine, but not with hemolysis or echinocytosis, and identified 2 additional GLUT1 mutations (A275T, G314S) that decreased glucose transport but did not affect cation permeability. Combining these data with brain imaging studies, we propose that the dyskinesias result from an exertion-induced energy deficit that may cause episodic dysfunction of the basal ganglia, and that the hemolysis with echinocytosis may result from alterations in intracellular electrolytes caused by a cation leak through mutant GLUT1.

Authors

Yvonne G. Weber, Alexander Storch, Thomas V. Wuttke, Knut Brockmann, Judith Kempfle, Snezana Maljevic, Lucia Margari, Christoph Kamm, Susanne A. Schneider, Stephan M. Huber, Arnulf Pekrun, Robert Roebling, Guiscard Seebohm, Saisudha Koka, Camelia Lang, Eduard Kraft, Dragica Blazevic, Alberto Salvo-Vargas, Michael Fauler, Felix M. Mottaghy, Alexander Münchau, Mark J. Edwards, Anna Presicci, Francesco Margari, Thomas Gasser, Florian Lang, Kailash P. Bhatia, Frank Lehmann-Horn, Holger Lerche

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Figure 4

Functional analysis of the cation leak in erythrocytes from patients of family PED1.

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Functional analysis of the cation leak in erythrocytes from patients of ...
(A and B) Representative whole-cell current traces recorded from erythrocytes of a control (A) and a patient (B) with Na-gluconate in the pipette and NaCl in the bath solution (left panel) and after isoosmotic replacement of NaCl by n-methyl-d-glucamine–chloride (NMDG-Cl) in the bath (right panel). (C and D) Mean current-voltage (I-V) relationships (± SEM) for control (C) (n = 3–4) and patients’ erythrocytes (D) (n = 5–6) recorded as in A and B with NaCl bath solution (open circles) and after isoosmotic replacement of NaCl by NMDG-Cl (closed triangles), CaCl2 (open diamonds), or KCl (open triangles) in the bath. In patients’ erythrocytes (D), the reversal potential of the I-V curve shifted by –30 ± 4, –20 ± 2, and +11 ± 2 mV (mean ± SEM; n = 5–6) from that recorded in NaCl solution following substitution with NMDG-Cl, CaCl2, and KCl, respectively. (E) Histogram recorded by flow cytometry in erythrocytes from controls (black line) and patients (red line) incubated in Ca2+-containing NaCl solution, depicting the fluo3 fluorescence intensity as a measure of the steady-state intracellular ([Ca2+]i). (F and G) Histograms (F) and time course (G) of changes in fluo3 fluorescence intensity of control (black line in F; open circles in G) and patients’ erythrocytes (red line in F; close triangles in G) following Ca2+ depletion by incubation for 30 minutes in Ca2+-free NaCl solution (F, left panel, and G, 0-minute values) and Ca2+ repletion (F, middle panel, and G). As a positive control experiment, the histogram in (F, right panel) shows the fluo3 fluorescence of Ca2+-permeabilized erythrocytes from controls (black line) and patients (red line) indicating equal fluo3 dye loading of both cell populations under these conditions (mean values ± SEM, 49 ± 8 and 55 ± 8 relative fluorescence units in erythrocytes from controls and patients, respectively; n = 4). The data in G are averaged geometrical means (± SEM; n = 14–16) of the fluorescence distribution. Lines represent exponential fits yielding the time constant of [Ca2+]i repletion (controls, τ = 16.3 ± 3.4 min; patients, τ = 7.1 ± 1.6 min; n = 14–16, P < 0.05; 2-tailed Welch-corrected t test).