The sarcomere is the basic contractile unit in striated muscle. While mutations in sarcomeric proteins have been linked to various human cardiovascular diseases, it is unclear why mutations in different sarcomeric genes or even different mutations in the same gene result in distinct diseases. The goal of this proposal is to use titin as a paradigm to investigate molecular mechanisms of sarcomere assembly and sarcomeric diseases. We have identified six titin mutants in zebrafish from mutagenesis screens and demonstrated that phenotypes from one mutant allele resemble human dilated cardiomyopathy. We recently identified the full-length genomic sequence for zebrafish titin (tinl) and cloned the other titin homologue (tin2) in zebrafish. Our preliminary data support the central hypothesis of this proposal, which predicts that different domains of Titin participate in distinct steps of myofibrillogenesis disruption of which results in different sarcomeric diseases. In our Specific Aim 1, we will investigate the functional divergence of tinl and tin2. By leveraging morpholino technology, we will test the hypothesis that different isoforms of titin have different functions in myofibrillogenesis. In our Specific Aim 2, we will test the hypothesis that different domains of titin have different functions in myofibrillogenesis. We will generate a series of truncations of both tinl and tin2 in vivo to reveal the functions of the C-terminal domains, including the kinase domain. We will also investigate the function of a Titin N-terminal domain by knocking out a titin interacting protein, Tcap. In our Specific Aim3, we will determine the pathological consequences of different titin mutations in zebrafish. We will first identify the location of mutations in all six titin mutants and then characterize the pathological phenotypes in both embryonic and adult fish. By generating and characterizing a series of titin mutations, these experiments will deepen our understanding of why mutations in different titin exons result in distinct structural changes of the sarcomere and different phenotypes of sarcomeric diseases, including dilated cardiomyopathy, hypertrophic cardiomyopathy, and muscular dystrophy.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL081753-03
Application #
7269343
Study Section
Cardiac Contractility, Hypertrophy, and Failure Study Section (CCHF)
Program Officer
Evans, Frank
Project Start
2005-08-01
Project End
2010-07-31
Budget Start
2007-08-01
Budget End
2008-07-31
Support Year
3
Fiscal Year
2007
Total Cost
$348,551
Indirect Cost
Name
Mayo Clinic, Rochester
Department
Type
DUNS #
006471700
City
Rochester
State
MN
Country
United States
Zip Code
55905
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Ding, Yonghe; Long, Pamela A; Bos, J Martijn et al. (2016) A modifier screen identifies DNAJB6 as a cardiomyopathy susceptibility gene. JCI Insight 1:
Shih, Yu-Huan; Zhang, Yuji; Ding, Yonghe et al. (2015) Cardiac transcriptome and dilated cardiomyopathy genes in zebrafish. Circ Cardiovasc Genet 8:261-9

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