Therapeutic Biomarker Validation in an In Vitro Model of GNE Myopathy

Abstract

GNE myopathy (GNEM) is an adult-onset, autosomal recessive disease that causes severe muscle wasting. Pathology in GNEM occurs due to mutations in the GNE gene. This gene encodes an enzyme of the biosynthetic pathway of sialic acid (SA), a terminal glycan of the cellular membrane. In GNEM, mutations in the GNE gene typically result in reductions in the levels of SA. Gene therapy is currently in development for GNEM; this therapy aims to restore the GNE gene, and thus SA, to the cellular membrane. Our goal is to develop a robust biomarker to detect changes in sialylation that would occur during such a gene therapy. Here, we assess the ability of lectins, glycan-binding proteins, to reflect sialylation changes in an in vitro model of GNEM. Specifically, we have used immunostaining with several lectins in a cellular model of GNEM in which SA is absent due to genetic or enzymatic modifications. We show that a subset of tested lectins can differentially bind cells with differing levels of SA. Furthermore, we show the extent to which this altered binding is rescued when the GNE gene is restored via transient transfection. This work allows for an understanding of the extent to which potential GNEM lectin staining biomarkers can reflect increased sialylation after GNE gene restoration, such as that which would occur after GNE gene therapy.