Muscle-related plectinopathies

Abstract

Plectin is a giant cytoskeletal crosslinker and intermediate filament stabilizing protein. Mutations in the human plectin gene (PLEC) cause several rare diseases that are grouped under the term plectinopathies. The most common disorder is autosomal recessive disease epidermolysis bullosa simplex with muscular dystrophy (EBS-MD), which is characterized by skin blistering and pro-gressive muscle weakness. Besides EBS-MD, PLEC mutations lead to EBS with nail dystrophy, EBS-MD with a myasthenic syndrome, EBS with pyloric atresia, limb-girdle muscular dystrophy type R17, or EBS-Ogna. In this review, we focus on the clinical and pathological manifestations caused by PLEC mutations on skeletal and cardiac muscle. Skeletal muscle biopsies from EBS-MD patients and plectin-deficient mice revealed severe dystrophic features with variation in fiber size, degener-ative myofibrillar changes, mitochondrial alterations, and pathological desmin-positive protein ag-gregates. Ultrastructurally, PLEC mutations lead to a disorganization of myofibrils and sarcomeres, Z-and I-band alterations, autophagic vacuoles and cytoplasmic bodies, and misplaced and degen-erating mitochondria. We also summarize a variety of genetically manipulated mouse and cell mod-els, which are either plectin-deficient or that specifically lack a skeletal muscle-expressed plectin isoform. These models are powerful tools to study functional and molecular consequences of PLEC defects and their downstream effects on the skeletal muscle organization.