Dysregulated autophagy in restrictive cardiomyopathy due to Pro209Leu mutation in BAG3.

Authors

Schänzer A1, Rupp S2, Gräf S3, Zengeler D4, Jux C2, Akintürk H2, Gulatz L3, Mazhari N2, Acker T3, Van Coster R5, Garvalov BK6, Hahn A7.
  1. Institute of Neuropathology, Justus Liebig University Giessen, 35392 Giessen, Germany. Electronic address: anne.schaenzer@patho.med.uni-giessen.de.
  2. Pediatric Heart Center, Justus Liebig University Giessen, 35392 Giessen, Germany.
  3. Institute of Neuropathology, Justus Liebig University Giessen, 35392 Giessen, Germany.
  4. Center for Genomics and Transcriptomics (CeGat) GmbH, 72076 Tübingen, Germany.
  5. Division of Child Neurology, Department of Pediatrics, University Hospital Gent, 9000 Gent, Belgium.
  6. Institute of Neuropathology, Justus Liebig University Giessen, 35392 Giessen, Germany; Department of Microvascular Biology and Pathobiology, Centre for Biomedicine and Medical Technology Mannheim (CBTM), Medical Faculty Mannheim, University of Heidelberg, 68167 Mannheim, Germany.
  7. Department of Child Neurology, Justus Liebig University Giessen, 35392 Giessen, Germany.

Abstract

Myofibrillary myopathies (MFM) are hereditary myopathies histologically characterized by degeneration of myofibrils and aggregation of proteins in striated muscle. Cardiomyopathy is common in MFM but the pathophysiological mechanisms are not well understood. The BAG3Pro209Leu mutation is associated with early onset MFM and severe restrictive cardiomyopathy (RCM), often necessitating heart transplantation during childhood. We report on a young male patient with a BAG3Pro209Leu mutation who underwent heart transplantation at eight years of age. Detailed morphological analyses of the explanted heart tissue showed intracytoplasmic inclusions, aggregation of BAG3 and desmin, disintegration of myofibers and Z-disk alterations. The presence of undegraded autophagosomes, seen by electron microscopy, as well as increased levels of p62, LC3-I and WIPI1, detected by immunohistochemistry and western blot analyses, indicated a dysregulation of autophagy. Parkin and PINK1, proteins involved in mitophagy, were slightly increased whereas mitochondrial OXPHOS activities were not altered. These findings indicate that altered autophagy plays a role in the pathogenesis and rapid progression of RCM in MFM caused by the BAG3Pro209Leu mutation, which could have implications for future therapeutic strategies.