An internal promoter underlies the difference in disease severity between N- and C-terminal truncation mutations of Titin
- University of California, San Francisco, United States
- University of North Carolina at Chapel Hill, United States
- Brigham Young University, United States
- University of Zurich, United States
Abstract
Truncating mutations in the giant sarcomeric protein Titin result in dilated cardiomyopathy (DCM) and skeletal myopathy. The most severely affected DCM patients harbor Titin truncations in the C-terminal two-thirds of the protein, suggesting that mutation position might influence disease mechanism. Using CRISPR/Cas9 technology, we generated six zebrafish lines with Titin truncations in the N-terminal (Z-disk and I-band) and C-terminal (A-band) regions. Although all exons were constitutive, C-terminal mutations caused severe myopathy whereas N-terminal mutations demonstrated mild phenotypes. Surprisingly, neither mutation type acted as a dominant negative. Instead, we found a conserved internal promoter at the precise position where divergence in disease severity occurs, with the resulting protein product partially rescuing N-terminal truncations. In addition to its clinical implications, our work may shed light on a long-standing mystery regarding the architecture of the sarcomere.
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Animal experimentation: All zebrafish and mouse experimental work conformed to the 'Guide for the Care and Use of Laboratory Animals' published by the US National Institutes of Health (NIH Publication No. 85-23, revised 1996). Animal work was performed according to institutional guidelines with the full approval of the University of California Institutional Animal Care and Use Committee (protocols AN090013-03 and AN107039-01)
Human subjects: Human genetic studies were performed according to institutional guidelines and with the full approval of the University of California San Francisco Committee on Human Research (CHR#10-00207) and all studies performed were in keeping with the original informed consent forms. Informed consent and consent to publish was obtained from all participants.
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© 2015, Zou et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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An internal promoter underlies the difference in disease severity between N- and C-terminal truncation mutations of Titin
eLife 4:e09406.
https://doi.org/10.7554/eLife.09406
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