Mutational and functional analysis of Glucose transporter I deficiency syndrome

• Mutations in the SLC2A1 gene were functionally studied by enzymatic photometric 2-deoxyglucose (2DG) uptake assays.
• Immunoblotting, immunofluorescence as well as enzymatic 2DG uptake assays were correlated with disease phenotype.
• 2DG uptake assay is suitable to monitor GLUT1 transport.

ObjectiveWe investigated a correlation between a mutation in the SLC2A1 gene and functional disorders in Glucose transporter I deficiency syndrome (GLUT1DS).MethodsWe performed direct sequence analysis of SLC2A1 in a severe GLUT1DS patient and identified a novel frame shift mutation, c.906_907insG, p.V303fs. We created a plasmid vector carrying the c.906_907insG mutation, as well as A405D or R333W in the SLC2A1, which are found in patients with mild and moderate GLUT1DS severity, respectively. We transiently expressed these mutants and wild type SLC2A1 plasmids in a human embryonic kidney cell line (HEK293), and performed immunoblotting, immunofluorescence, and enzymatic photometric 2-deoxyglucose (2DG) uptake assays.ResultsGLUT1 was not detected after transient expression of the SLC2A1 plasmid carrying c.906_907insG by either immunoblotting or immunofluorescence. The degree of glucose transport reduction as determined by enzymatic photometric 2DG assay uptake correlated with disease severity.ConclusionsEnzymatic photometric 2DG uptake study appears to be a suitable functional assay to predict the effect of SLC2A1 mutations on GLUT1 transport.