Quantification of lectin fluorescence in GNE myopathy muscle biopsies.

INTRODUCTION: GNE myopathy is an adult-onset muscle disorder characterized by impaired sialylation of (muscle) glycans, detectable by lectin histochemistry. We describe a standardized method to quantify (lectin-) fluorescence in muscle sections, applicable for diagnosis and response to therapy for GNE myopathy. METHODS: Muscle sections were fluorescently labeled with the sialic acid-binding Sambucus nigra agglutinin (SNA) lectin and antibodies to sarcolemma residence protein caveolin-3 (CAV-3). Entire tissue sections were imaged in tiles and fluorescence was quantified. RESULTS: SNA fluorescence co-localizing with CAV-3 was ∼50% decreased in GNE myopathy biopsies compared with muscle-matched controls, confirming previous qualitative results. DISCUSSION: This quantitative fluorescence method can accurately determine sialylation status of GNE myopathy muscle biopsies. This method is adaptable for expression of other membrane-associated muscle proteins, and may be of benefit for disorders in which therapeutic changes in expression are subtle and difficult to assess by other methods. Muscle Nerve 58: 286-292, 2018.