A modifier screen identifies DNAJB6 as a cardiomyopathy susceptibility gene
Yonghe Ding, … , Timothy M. Olson, Xiaolei Xu
Yonghe Ding, … , Timothy M. Olson, Xiaolei Xu
Published September 8, 2016
Citation Information: JCI Insight. 2016;1(14):e88797. https://doi.org/10.1172/jci.insight.88797.
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Research Article Cardiology Genetics

A modifier screen identifies DNAJB6 as a cardiomyopathy susceptibility gene

Abstract

Mutagenesis screening is a powerful forward genetic approach that has been successfully applied in lower-model organisms to discover genetic factors for biological processes. This phenotype-based approach has yet to be established in vertebrates for probing major human diseases, largely because of the complexity of colony management. Herein, we report a rapid strategy for identifying genetic modifiers of cardiomyopathy (CM). Based on the application of doxorubicin stress to zebrafish insertional cardiac (ZIC) mutants, we identified 4 candidate CM-modifying genes, of which 3 have been linked previously to CM. The long isoform of DnaJ (Hsp40) homolog, subfamily B, member 6b (dnajb6b(L)) was identified as a CM susceptibility gene, supported by identification of rare variants in its human ortholog DNAJB6 from CM patients. Mechanistic studies indicated that the deleterious, loss-of-function modifying effects of dnajb6b(L) can be ameliorated by inhibition of ER stress. In contrast, overexpression of dnajb6(L) exerts cardioprotective effects on both fish and mouse CM models. Together, our findings establish a mutagenesis screening strategy that is scalable for systematic identification of genetic modifiers of CM, feasible to suggest therapeutic targets, and expandable to other major human diseases.

Authors

Yonghe Ding, Pamela A. Long, J. Martijn Bos, Yu-Huan Shih, Xiao Ma, Rhianna S. Sundsbak, Jianhua Chen, Yiwen Jiang, Liqun Zhao, Xinyang Hu, Jianan Wang, Yongyong Shi, Michael J. Ackerman, Xueying Lin, Stephen C. Ekker, Margaret M. Redfield, Timothy M. Olson, Xiaolei Xu

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Figure 4

Inhibition of ER stress protected against DOX-induced zebrafish death.

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Inhibition of ER stress protected against DOX-induced zebrafish death. (...
(A) Western blot (upper panel) and quantification (lower panel) analysis of glucose-regulated protein (Grp78) levels in adult WT fish heart at indicated time points after a single bolus of 20 μg/gram body mass (gbm) doxorubicin (DOX) injection. DOX injection results in elevation of Grp78 protein since 7 days after injection. Values are expressed relative to WT controls. Data represent mean ±SEM; *P < 0.05, 1-way ANOVA comparisons. (B) Western blot (upper) and quantification (lower) analysis of Grp78 protein levels at 2 months after DOX injection in indicated mutants and/or double-transgenic fish hearts. Grp78 protein level was further elevated in the GBT0411 mutant fish heart after DOX injection. Cardiomyocyte-specific overexpression of dnajb6b(L) inhibited the elevated ER stress in the GBT0411 mutant fish heart at 2 months after DOX injection. Values are expressed relative to WT controls. Data represent mean ±SEM; 1-way ANOVA comparisons, *P < 0.05. (C) Kaplan-Meier survival curves of indicated adult fish injected with a single bolus of 20 μg/gbm DOX with or without incubation with sodium phenylbutyrate (PBA), a chemical chaperone of ER stress inhibitor (250 μM, 10 hours/day, 5 days/week for the entire experiment). PBA administration protected against DOX-induced fish death in both WT and the GBT0411 mutant. *P < 0.05, log-rank test.