Haploinsufficiency of mechanistic target of rapamycin ameliorates bag3 cardiomyopathy in adult zebrafish

Dis Model Mech. 2019 Oct 1;12(10):dmm040154. doi: 10.1242/dmm.040154.


The adult zebrafish is an emerging vertebrate model for studying human cardiomyopathies; however, whether the simple zebrafish heart can model different subtypes of cardiomyopathies, such as dilated cardiomyopathy (DCM), remains elusive. Here, we generated and characterized an inherited DCM model in adult zebrafish and used this model to search for therapeutic strategies. We employed transcription activator-like effector nuclease (TALEN) genome editing technology to generate frame-shift mutants for the zebrafish ortholog of human BCL2-associated athanogene 3 (BAG3), an established DCM-causative gene. As in mammals, the zebrafish bag3 homozygous mutant (bag3e2/e2 ) exhibited aberrant proteostasis, as indicated by impaired autophagy flux and elevated ubiquitinated protein aggregation. Through comprehensive phenotyping analysis of the mutant, we identified phenotypic traits that resembled DCM phenotypes in mammals, including cardiac chamber enlargement, reduced ejection fraction characterized by increased end-systolic volume/body weight (ESV/BW), and reduced contractile myofibril activation kinetics. Nonbiased transcriptome analysis identified the hyperactivation of the mechanistic target of rapamycin (mTOR) signaling in bag3e2/e2 mutant hearts. Further genetic studies showed that mtorxu015/+ , an mTOR haploinsufficiency mutant, repaired abnormal proteostasis, improved cardiac function and rescued the survival of the bag3e2/e2 mutant. This study established the bag3e2/e2 mutant as a DCM model in adult zebrafish and suggested mtor as a candidate therapeutic target gene for BAG3 cardiomyopathy.

Keywords: BCL2-associated athanogene 3; Danio rerio; Dilated cardiomyopathy; mTOR.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / genetics
  • Adaptor Proteins, Signal Transducing / metabolism*
  • Amino Acid Sequence
  • Animals
  • Apoptosis Regulatory Proteins / genetics
  • Apoptosis Regulatory Proteins / metabolism*
  • Base Sequence
  • Cardiomyopathies / genetics*
  • Cardiomyopathies / pathology
  • Gene Expression Profiling
  • Haploinsufficiency / genetics*
  • Mutation / genetics
  • Myocardium / metabolism
  • Myocardium / pathology
  • Phenotype
  • Signal Transduction
  • TOR Serine-Threonine Kinases / metabolism*
  • Transcription Activator-Like Effector Nucleases
  • Zebrafish / genetics*
  • Zebrafish Proteins / genetics
  • Zebrafish Proteins / metabolism*


  • Adaptor Proteins, Signal Transducing
  • Apoptosis Regulatory Proteins
  • BAG3 protein, zebrafish
  • Zebrafish Proteins
  • TOR Serine-Threonine Kinases
  • mTOR protein, zebrafish
  • Transcription Activator-Like Effector Nucleases