Autosomal recessive Hereditary Inclusion Body Myopathy (HIBM) is a progressive adult onset skeletal muscle wasting disorder characterized by limb weakness with sparing of the quadriceps. This disorder has been described predominantly in Middle-Eastern groups and in Japanese. HIBM is associated with mutations in the gene, GNE which encodes UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE). GNE is the rate-limiting enzyme of N-acetylneuraminic acid (Neu5Ac; sialic acid) biosynthesis and hyposialylation has been associated with HIBM. Currently, there is no treatment or cure for HIBM. Deleterious mutations were identified in the GNE gene in affected individuals in order to characterize the gene more thoroughly. The research had a second component, which is a first step toward gene therapy for HIBM. An expression construct was developed for transfection of cells lacking GNE. The GNE coding region of sixty-four symptomatic patients was sequenced. Twenty-eight patients were found to bear GNE mutations. Ten novel variations were identified amongst nine non-Middle Eastern patients, including four nonsense (p.R8X, p.W204X, p.Q436X, p.S615X), five missense (p.E2G, p.R71 W, p.I142T, p.I298T, p.L556S), and one synonymous variation (p. Y591 Y) spanning both the epimerase and X kinase domains of GNE. These mutations observed, with the exception of Y591 Y, are thought to lead to decreased production of sialic acid. In contrast, the previously known mutation, p. R266Q has been correlated with the disorder, sialuria. In the GNE construct expression assay, R266Q or wild-type was cloned in CHO cells. Transfection of the R266Q construct showed elevated production of sialic acid at 9.53 nmoles compared to the wild-type at 5.67 nmoles. Replenishing sialic acid through gene transfection may be potentially beneficial as a means to gene therapy in patients with HIBM.California State University, Northridge. Department of Biology.Includes bibliographical references (leaves 48-52
