Overexpression of human BAG3P209L in mice causes restrictive cardiomyopathy

Kenichi Kimura,Sean M Wu,Dieter O Fürst,Jörg Höhfeld,Wilhelm Röll,Guang Li,Satoru Takahashi,Caroline Geisen,Kathrin Graf-Riesen,Julia Schuld,Wolfgang A Linke,Wilhelm Bloch,Lutz Hein,Maithreyan Kuppusamy,Bernd K Fleischmann,Peter F.m Van Der Ven ,Astrid Ooms,Achim Lother,Pitter F Huesgen,Jan Daerr,Andreas Unger,Michael Hesse

doi:10.1038/s41467-021-23858-7

Abstract

An amino acid exchange (P209L) in the HSPB8 binding site of the human co-chaperone BAG3 gives rise to severe childhood cardiomyopathy. To phenocopy the disease in mice and gain insight into its mechanisms, we generated humanized transgenic mouse models. Expression of human BAG3P209L-eGFP in mice caused Z-disc disintegration and formation of protein aggregates. This was accompanied by massive fibrosis resulting in early-onset restrictive cardiomyopathy with increased mortality as observed in patients. RNA-Seq and proteomics revealed changes in the protein quality control system and increased autophagy in hearts from hBAG3P209L-eGFP mice. The mutation renders hBAG3P209L less soluble in vivo and induces protein aggregation, but does not abrogate hBAG3 binding properties. In conclusion, we report a mouse model mimicking the human disease. Our data suggest that the disease mechanism is due to accumulation of hBAG3P209L and mouse Bag3, causing sequestering of components of the protein quality control system and autophagy machinery leading to sarcomere disruption.

Highlights

An amino acid exchange (P209L) in the HSPB8 binding site of the human co-chaperone Bcl2-associated athanogene 3 (BAG3) gives rise to severe childhood cardiomyopathy
The hearts did not display any differences at 3- and 10-weeks of age and cardiac dry weights to tibia lengths did not differ between αMHC-BAG3WT, αMHC-BAG3P209L, and control (WT) mice (Supplementary Fig. 1b)
Quantification of eGFP expression in sections from αMHC-BAG3WT and αMHCBAG3P209L hearts revealed that 83.13 ± 2.58% of CMs (n = 3) expressed BAG3WT, while expression of BAG3P209L was found in only 36.28 ± 5.56% of CMs (n = 3)

Summary

Introduction

An amino acid exchange (P209L) in the HSPB8 binding site of the human co-chaperone BAG3 gives rise to severe childhood cardiomyopathy. In humans with the BAG3 (P209L) mutation, Z-disc disruption and formation of protein aggregates have been reported[1] pointing to a possible disease mechanism in agreement with recent in vitro work[5,6] This aspect needs to be explored in vivo but this has not been possible because of the lack of a mouse model displaying the typical features of the human disease. We report the establishment of several transgenic mouse lines expressing hBAG3P209L in striated muscle cells We find that these humanized mouse models mimic key pathophysiological features of patients enabling us to explore the underlying molecular disease mechanisms and its rescue via an AAV-mediated gene therapy approach

Methods

Results

Conclusion