Repulsive Guidance Molecules a, b and c Are Skeletal Muscle Proteins, and Repulsive Guidance Molecule a Promotes Cellular Hypertrophy and Is Necessary for Myotube Fusion

• Published in: Cells, tissues, organs Vol. 200; no. 5; p. 326
• Main Authors: Martins, Aline Fagundes, Xavier Neto, José, Azambuja, Ana, Sereno, Maria Lorena, Figueira, Antonio, Campos-Junior, Paulo Henrique, Rosário, Millor Fernandes, Toledo, Cristiane Bittencourt Barroso, Silva, Gerluza Aparecida Borges, Kitten, Gregory Thomas, Coutinho, Luiz Lehmann, Dietrich, Susanne, Jorge, Erika Cristina
• Format: Journal Article
• Language: English
• Published: Switzerland 2015
• Subjects: Animals; Cell Differentiation - physiology; Cell Enlargement; Hypertrophy - metabolism; Male; Membrane Proteins - metabolism; Mice; Muscle Development - physiology; Muscle Fibers, Skeletal - metabolism; Muscle Proteins - metabolism; Muscle, Skeletal - metabolism; Muscle, Skeletal - pathology; Nerve Tissue Proteins - genetics; Nerve Tissue Proteins - metabolism; Neurogenesis - physiology
• ISSN: 1422-6421
• DOI: 10.1159/000433491

Repulsive guidance molecules (RGMs) compose a family of glycosylphosphatidylinositol (GPI)-anchored axon guidance molecules and perform several functions during neural development. New evidence has suggested possible new roles for these axon guidance molecules during skeletal muscle development, which has not been investigated thus far. In the present study, we show that RGMa, RGMb and RGMc are all induced during skeletal muscle differentiation in vitro. Immunolocalization performed on adult skeletal muscle cells revealed that RGMa, RGMb and RGMc are sarcolemmal proteins. Additionally, RGMa was found to be a sarcoplasmic protein with a surprisingly striated pattern. RGMa colocalization with known sarcoplasmic proteins suggested that this axon guidance molecule is a skeletal muscle sarcoplasmic protein. Western blot analysis revealed two RGMa fragments of 60 and 33 kDa, respectively, in adult skeletal muscle samples. RGMa phenotypes in skeletal muscle cells (C2C12 and primary myoblasts) were also investigated. RGMa overexpression produced hypertrophic cells, whereas RGMa knockdown resulted in the opposite phenotype. RGMa knockdown also blocked myotube formation in both skeletal muscle cell types. Our results are the first to show an axon guidance molecule as a skeletal muscle sarcoplasmic protein and to include RGMa in a system that regulates skeletal muscle cell size and differentiation.