Human GM3 synthase deficiency: a new severe epilepsy syndrome. (360G-Wellcome-081559_B_06_Z)

To determine the biochemical basis for severe epilepsy in a new human disease resulting from defective ganglioside biosynthesis. Set up a fluorescent GM3 synthase assay to measure GM3 synthase activity in cultured fibroblasts from carriers and patients. Look for evidence of alternative enzyme up-regulation that may account for a milder phenotype in a sub-set of patients with GM3 synthase deficiency. Characterise cerebrospinal fluid (CSF) glycosphingolipid (GSL) profiles of carriers and patients to determine relative flux through the o-series pathway in the absence of GM3 synthase. Study the neutral and charged GSL pathways in the asymptomatic GM3 synthase null mouse brain and blood cells. Investigate the potential of exogenous GM3 to restore synthesis of complex gangliosides in patient fibroblasts and in the mouse model by intracerebroventricular GM3 infusion. "Stop codon read-through" with gentamicin may be a therapeutic option and will be tested in patient fibroblasts. Use RNA interference in murine and human neuronal cultures to evaluate up and down- regulation of genes as well as alternative pathways in response to GM3 synthase knockdown. Study plasma of patients with other epilepsy phenotypes to determine if any are associated with abnormal GSL metabolism.