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

• Published in: Disease models & mechanisms Vol. 12; no. 10
• Main Authors: Ding, Yonghe, Dvornikov, Alexey V., Ma, Xiao, Zhang, Hong, Wang, Yong, Lowerison, Matthew, Packard, Rene R., Wang, Lei, Chen, Jun, Zhang, Yuji, Hsiai, Tzung, Lin, Xueying, Xu, Xiaolei
• Format: Journal Article
• Language: English
• Published: England The Company of Biologists Ltd 01.10.2019; The Company of Biologists
• Subjects: Adaptor Proteins, Signal Transducing - genetics; Adaptor Proteins, Signal Transducing - metabolism; Amino Acid Sequence; Anemia; Animals; Apoptosis Regulatory Proteins - genetics; Apoptosis Regulatory Proteins - metabolism; Base Sequence; bcl2-associated athanogene 3; Cardiac function; Cardiomyopathies - genetics; Cardiomyopathies - pathology; Cardiomyopathy; danio rerio; dilated cardiomyopathy; Enzymes; Gene Expression Profiling; Genes; Genetic engineering; Genome editing; Genomes; Haploinsufficiency - genetics; Heart; Kinases; mtor; Mutation; Mutation - genetics; Myocardium - metabolism; Myocardium - pathology; Phenotype; Proteins; Signal Transduction; TOR Serine-Threonine Kinases - metabolism; Transcription Activator-Like Effector Nucleases; Zebra; Zebrafish; Zebrafish - genetics; Zebrafish Proteins - genetics; Zebrafish Proteins - metabolism; mTOR; BCL2-associated athanogene 3; Dilated cardiomyopathy; Danio rerio
• DOI: 10.1242/dmm.040154
• ISSN: 1754-8403; 1754-8411

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.