Author + information
- Received November 6, 2014
- Revision received January 7, 2015
- Accepted January 13, 2015
- Published online March 31, 2015.
- Khaushik Subramanian, BS∗,
- Davide Gianni, PhD∗,
- Cristina Balla, MD, PhD∗,†,
- Gabriele Egidy Assenza, MD†,
- Mugdha Joshi, BS‡,
- Marc J. Semigran, MD§,
- Thomas E. Macgillivray, MD‖,
- Jennifer E. Van Eyk, PhD¶,
- Giulio Agnetti, PhD¶,#,
- Nazareno Paolocci, MD, PhD∗∗,
- James R. Bamburg, PhD††,
- Pankaj B. Agrawal, MD‡ and
- Federica del Monte, MD, PhD∗,§∗ ()
- ∗Cardiovascular Institute, Beth Israel Deaconess Medical Center, Boston, Massachusetts
- †Division of Cardiology, Sapienza University, Rome, Italy
- ‡Divisions of Newborn Medicine and Genetics and Program in Genomics, Children’s Hospital, Boston, Massachusetts
- §Heart Center, Massachusetts General Hospital, Boston, Massachusetts
- ‖Cardiovascular Surgery, Massachusetts General Hospital, Boston, Massachusetts
- ¶National Heart Lung Blood Institute Proteomics Center, Johns Hopkins University School of Medicine, Baltimore, Maryland
- #Department of Biomedical and Neuromotor Sciences (DIBINEM), University of Bologna, Bologna, Italy
- ∗∗Heart and Vascular Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland
- ††Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado
- ↵∗Reprint requests and correspondence:
Dr. Federica del Monte, Cardiovascular Intitute, Beth Israel Deaconess Medical Center, 3 Blackfan Circle, E/CLS9-911, Boston, Massachusetts 02215.
Background Recently, tangles and plaque-like aggregates have been identified in certain cases of dilated cardiomyopathy (DCM), traditionally labeled idiopathic (iDCM), where there is no specific diagnostic test or targeted therapy. This suggests a potential underlying cause for some of the iDCM cases.
Objectives This study sought to identify the make-up of myocardial aggregates to understand the molecular mechanisms of these cases of DCM; this strategy has been central to understanding Alzheimer’s disease.
Methods Aggregates were extracted from human iDCM samples with high congophilic reactivity (an indication of plaque presence), and the findings were validated in a larger cohort of samples. We tested the expression, distribution, and activity of cofilin in human tissue and generated a cardiac-specific knockout mouse model to investigate the functional impact of the human findings. We also modeled cofilin inactivity in vitro by using pharmacological and genetic gain- and loss-of-function approaches.
Results Aggregates in human myocardium were enriched for cofilin-2, an actin-depolymerizing protein known to participate in neurodegenerative diseases and nemaline myopathy. Cofilin-2 was predominantly phosphorylated, rendering it inactive. Cardiac-specific haploinsufficiency of cofilin-2 in mice recapitulated the human disease’s morphological, functional, and structural phenotype. Pharmacological stimulation of cofilin-2 phosphorylation and genetic overexpression of the phosphomimetic protein promoted the accumulation of “stress-like” fibers and severely impaired cardiomyocyte contractility.
Conclusions Our study provides the first biochemical characterization of prefibrillar myocardial aggregates in humans and the first report to link cofilin-2 to cardiomyopathy. The findings suggest a common pathogenetic mechanism connecting certain iDCMs and other chronic degenerative diseases, laying the groundwork for new therapeutic strategies.
In one-third of dilated cardiomyopathy (DCM) cases, the disease’s origin remains unknown. Consequently, for those cases traditionally labeled “idiopathic” (iDCM), there is no specific diagnostic test, or targeted therapies. With the advent of a new nomenclature for classifying cardiomyopathies, patients are being grouped on the basis of morphofunctional phenotype, involved organ(s), genetics, and disease cause (1). Under the new classification rubric MOGES, iDCM cases would be described as dilated morphofunctional phenotype (M), involving the heart (O), in sporadic cases (G) of unknown etiology (E) and classified as MDOHGSEO (where D = dilated; H = heart; S = sporadic; and O = no known etiology) (1).
Myofibrillar accumulation of β-sheet fibrils with structural and tintorial properties of amyloid fibers, and their precursor seeds have been recently identified in certain iDCM hearts (2,3). They were not related to primary amyloid systemic disorders or to the normal aging process. With physiological aging, aggregates derived from defective folding or clearance of proteins accumulate as amyloid β-sheet fibrils, adversely affecting organ function (4,5). Their premature appearance underpins numerous degenerative diseases, affecting various organs.
In the heart, the currently known illnesses due to protein aggregates are systemic and senile amyloidosis or desmin and amylin cardiomyopathies. In these conditions, the major peptides composing the fibrillar aggregates are known (monoclonal immunoglobulin κ or λ light chains, wild-type [WT] or mutated transthyretin, αβ-crystallin or desmin, and amylin, respectively). Conversely, constituents of the iDCM aggregates and their pathogenetic role remain unknown. A milestone in understanding the pathophysiology of the first disease described with protein aggregates, Alzheimer’s disease (AD), was recognizing that fragments of the amyloid precursor protein (Aβ42) are the primary constituents of amyloid plaques (6,7). Therefore, identifying the components of the iDCM deposits is critical to understanding the mechanisms of the disease.
In the current study, we purified the soluble cardiac pre-amyloid seeds, which will be referred to here as pre-amyloid oligomers (PAO), providing (to our knowledge) the first evidence that cofilin-2 is a critical component within iDCM aggregates.
A 19-kDa protein, cofilin is a member of the ADF/cofilin family of actin-binding proteins, named for its ability to form actin filaments (COFILamentous structures of actIN). It participates in the disassembly of actin filaments as well as the pathogenesis of nemaline skeletal myopathy and AD (8–10). There are 3 isoforms: cofilin-1, which is ubiquitously expressed; cofilin-2, which is expressed mainly in muscle cells; and destrin or ADF, which is expressed primarily in epithelial and endothelial cells (11). Cofilin-1 and cofilin-2 have overlapping functions and are both present in the heart (8,10,12).
Considering its known involvement in protein aggregate disorders in other organs such as brain (AD) and skeletal muscle (nemaline myopathy), and because mass spectroscopy (MS) identified cofilin with its functional interactome, we focused on the contribution of cofilin to the pathogenesis of iDCM. We validated the initial discovery in a larger cohort of human heart tissues in which we tested the expression and activity of cofilin-2 and its colocalization with the PAO. We then generated a cardiac-specific cofilin-2 (CSC2) heterozygous knockout mouse to model cofilin-2 reduced activity. The in vivo analysis at the organ level was complemented with in vitro measurements of contractility of isolated cardiomyocytes to provide a better understanding of the cellular defects caused by cofilin alterations.
To establish a direct causal link between the altered pattern of cofilin-2 phosphorylation and sarcomeric structure and function, we stimulated or inhibited upstream kinases pharmacologically and overexpressed the phosphomimetic or the constitutively inactive form of cofilin in vitro by using adenovirus.
Frozen myocardial samples from the anterior wall of the left ventricle (LV) isolated from explanted failing hearts at the time of transplantation (MOGES designation MDOHGSE0SIV [where S refers to stage]) and non-failing donor hearts were used to purify protein aggregates under native conditions.
To resolve composition, we capitalized on the common conformation of the soluble PAO and on the availability of conformational antibodies (e.g., A11) to immunoprecipitate them. A11s have been made to recognize an epitope common to the conformation of PAO rather than the unique sequence of the specific protein forming them (13). We used MS to identify the components of the immunoprecipitate and validated the results by immunoblotting, immunohistochemistry, 2-dimensational (2D) gel electrophoresis, phosphate affinity assay (Phos-tag), and dot blotting analysis.
For cardiac-specific expression, Cofilin-2-flox mice were crossed with αMHC-Cre mice. Cardiomyocytes were isolated from 2-month-old CSC2 mice and WT littermates by enzymatic digestion; cultured and analyzed as previously described (2,14). The Online Appendix contains a detailed description of the methods.
Continuous variables were reported as mean ± SD or median (interquartile range), as appropriate, and then compared using Student t test or Wilcoxon rank sum test if not normally distributed. Categorical variables were analyzed using the Fisher exact test. Mixed effects model was used to compare cell-derived, continuous variables between WT and transgenic mice, using a random effect to account for data correlation within each mouse. Whisker lengths are covering the 5th to 95th percentile interval. A p value of <0.05 was considered significant. For multiple comparison of continuous, normally distributed data, a post hoc analysis was performed using the Bonferroni method. Analysis was performed using STATA data analysis software (StataCorp LP, College Station, Texas).
We previously reported detection, characterization, and distribution of myocardial aggregates positive for amyloid staining dyes in 74% of explanted iDCM heart samples (2). From those samples, we selected 5 iDCM samples (Table 1) with the highest presence of congophilic inclusions to isolate the PAO and characterize their biochemical composition. Three donor hearts were used as controls. A validation cohort consisting of 10 iDCM and 10 donor samples (Table 2) was used to subsequently determine the expression and distribution of cofilin-2 in the myocardium. Myocardial tissue was also obtained from a patient with a diagnosis of nemaline cardiomyopathy (Table 2).
Before acquiring the β-sheet amyloid structure, misfolded proteins undergo progressive maturation steps from monomers to multiple “mers-”generating PAO (up to 24 mers). These coexist with the mature fibers in the tissues (Online Figure 1) (15–17). In this process, proteins lose their sequence specificity and acquire a common conformation. By using A11 conformational antibodies (13), we enriched samples for soluble PAO from human hearts and confirmed their presence by electron microscopy (EM) (Figures 1A and 1B).
Following immunoprecipitation, denatured PAO components were separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Seven bands differentially expressed in iDCM hearts and 1 in donor heart were excised and analyzed by MS. Within the peptides identified in the bands having higher expression intensity in iDCM cases, cofilin-2 actin and MLC-II were present with a high percent of coverage by MS analysis (Figure 1C).
The expression of cofilin-2 in the human myocardium was evaluated by SDS-PAGE. Samples were prepared using 2 lysis buffers, one containing the non-ionic detergent Triton-X-100, able to extract the more soluble fraction, and one containing a high percent of the ionic detergent SDS to extract the less soluble aggregates. Cofilin-2 expression was similar in lysates from iDCM and in donor hearts when Triton-X-100 was used but significantly higher in iDCM samples than in donor myocardium in the SDS extracts (Figure 2A). These data suggest that much of the cofilin-2 in the iDCM hearts we studied is in a Triton-X-100–insoluble form. Interestingly, once samples were plotted individually, it appeared that cofilin expression in the SDS fraction was increased in the donor hearts from older individuals (Online Figure 2, Online Table 1).
Cofilin activity is regulated by reversible phosphorylation on Ser3. Phosphorylation inactivates and dephosphorylation activates cofilin, regulating its ability to bind G- or F-actin (Online Figure 3) (8,18–21). The relative amount of Ser3-phosphorylated cofilin-2 was quantified in donor and iDCM tissue to determine how much of the total pool was unable to interact with actin. Phospho-cofilin-2 increased significantly in iDCM tissue by either Triton-X-100 or SDS extraction (Figure 2B). We acknowledge the limitation of using human heart samples that present inevitable variability. However, differences in cofilin expression/activity between iDCM and donor samples were statistically significant despite the relatively small number of cases. We also measured the fraction of total cofilin-2 that was phosphorylated by using 2D Western and Phos-tag (Online Figures 4 and 5). Phos-tag analysis confirmed cofilin phosphorylation increased in iDCM hearts. Finally, the amount of α-sarcomeric actin was increased in the A11 pull-down fraction from iDCM compared to donor hearts (Online Figure 6), indicating that actin coprecipitates with cofilin in the aggregates, validating the MS data.
To obtain further evidence of the presence of cofilin-2 within PAO in the myocardium of patients with iDCM, we stained frozen tissue sections for A11-reactive PAO and cofilin-2. As shown in Figure 2C, there was little A11 staining (Figure 2, red) in the donor sample. Cofilin (Figure 2, green) did not colocalize with the PAO (Figure 2C). In iDCM hearts, PAOs were scattered within the sarcomeres in the less damaged case (Figure 2D) and were more abundant and clumped in larger deposits in the more damaged case (Figure 2E, Online Figure 7). The extent of colocalization was quantified from randomly chosen confocal images taken from each section of the iDCM and donor hearts using the Manders overlap coefficient (MOC) (22). The average MOC-M2 represents the percentage of PAO staining colocalized with cofilin-2 in the region analyzed. We found that cofilin-2 colocalized with PAO in 70% of the iDCM samples we studied but in none of the donor hearts. The calculated average M2 value was significantly higher in the images from iDCM than in donor samples (p = 0.000029; n = 5 each group) (Figure 2F).
In vivo model
The results in human specimens suggest that a loss in cofilin-2 actin-binding activity may have important implications in cardiac structural and functional disarray found in iDCM with protein aggregates. However, the assays possible in human hearts are limited. Although severe inactivation or depletion of cofilin causes early onset myopathy in skeletal muscle, our series of cases consisted of adult onset iDCM, where the inactivation of cofilin by phosphorylation was incomplete. This poses the question of whether a partial defect in cofilin activity would contribute to development of contractile dysfunction and cardiac muscle myopathy. Hence, we created a mouse model of cardiac-specific cofilin-2 haploinsufficiency (CSC2).
Compared to their WT littermates, heterozygous CSC2 mice showed a 60% reduction in cofilin-2 expression (Figure 3A). Using echocardiography, we observed 2-month-old CSC2 mice already manifested a marked decrease in LV wall thickness, ejection fraction (EF), and fractional shortening (FS), as well as increased LV end-diastolic diameter (LVEDD) and LV end-systolic diameter (LVESD) (Figures 3B to 3D, Online Figure 8). The statistical significance of the echocardiographic data was confirmed by Bonferroni post-hoc analysis (Online Appendix). At this stage, interstitial fibrosis was not detected (Online Figure 9). Myofibrils were altered in CSC2 animals showing abnormal actin pattern, a lack of proper orientation, and poorly organized sarcomeres as revealed by immunohistochemistry (Figure 3G) and EM (Figures 3J and 3L, inset 2, Online Figure 10). The I and M bands were frequently absent in sarcomeres, which were often hypercontracted, and the Z lines were interrupted (Figure 3J, inset 2 and arrowheads). Mice also displayed structures similar to actin rods described in nemaline myopathy (23) (Figures 3J and 3L, inset 1). Notably, we observed by EM that the pathological features of the CSC2 mice myocardium closely recapitulated the pathology shown in a case of human nemaline cardiomyopathy (Figure 3K, Online Figure 10).
The morphological defects of the myocardium of CSC2 mice were accompanied by abnormalities in cell function. In comparison with WT cardiomyocytes, CSC2 cardiomyocytes showed a prolongation in cell shortening and Ca2+ transient velocities (Figure 4, Table 3).
Knockout mouse models have previously served well to model the biological and pathological effect of a prevalent inactive cofilin-1 (24,25). However, the cofilin/actin ratio may also modulate formation of actin bundles and rods, thus affecting the sarcomeric machinery structure and function (10). Therefore, we determined the impact of altered patterns of cofilin-2 phosphorylation on cardiomyocyte structure and function by pharmacologic manipulation of cofilin upstream signaling and genetic modulation of cofilin phosphorylation.
Cofilin-1 and -2 are phosphorylated on Ser3 by LIM-domain kinase (LIMK) and TES kinase (TESK); both are downstream of the Ras-homolog gene family member A (RhoA) and the Rho-associated protein-kinase (ROCK) (Online Figure 11) (18). RhoA stimulation significantly increased the phosphorylation levels of cofilin-2 and led to the formation of “stress-like” fibers in adult mice cardiomyocytes (p < 0.05) (26). Conversely, “stress-like” fibers were not observed with inhibition of ROCK that reduced cofilin-2 phosphorylation (although the p value did not reach statistical significance; p = 0.09) (Figures 5A and 5B).
Because pharmacological stimulation may lead to specificity issues with dosing, we used an adenoviral (Ad.) gene transfer approach to express the phosphomimetic (Ad.S3E), constitutively active (Ad.S3A), and WT form of cofilin-1 in neonatal rat cardiomyocytes (Figure 6). Compared to adenoviral overexpression levels of WT or S3A, only Ad.S3E induced the formation of “stress-like” fibers in cardiomyocytes (Figure 6C). Overexpressing the phosphomimetic form of cofilin-2 (Ad.S3E) abrogated contractile function and impaired survival of adult cardiomyocytes, impeding functional measurement.
Lack of knowledge regarding the mechanisms that initiate the myocardial defect in iDCM is the critical barrier to early screening and prevention, and ultimately to a cure for this devastating disease. The recent discovery of the presence in iDCM of plaque- and tangle-like aggregates that impair cell function in cardiomyocytes (2,3) identifies a new pathogenesis for at least some cases. However, the aggregates’ composition, which has contributed to the understanding of the pathogenesis and consequently progress toward new AD therapies, is a critical but unresolved issue in the pathogenesis of iDCM.
Our study demonstrates that the actin-depolymerizing protein cofilin-2, along with its interacting proteins actin and MLC-II, are incorporated within the iDCM aggregates. In most of our human iDCM samples, cofilin-2 expression was increased, and most were found within the aggregates recognized by the A11 structural antibody (Central Illustration). Moreover, cofilin-2 activity in iDCM tissue was decreased owing to its enhanced degree of phosphorylation. Together, cofilin-2 sequestration in the aggregates and inactivation by enhanced phosphorylation will interfere with its critical function in maintaining actin filament homeostasis, affecting myocyte contractility.
Cofilin contributes to the dynamic turnover of actin composing the thin filaments in contractile cells and microfilaments in non-contractile cells (10). Consequently, cofilin is an essential protein that maintains the myofilament architecture needed for the mechanical properties of sarcomeres, cell motility, and intracellular transport (8,10,27). Abnormalities at this level will critically hamper cardiomyocyte function, as was shown for skeletal myocytes and neurons. In fact, cofilin is thought to be involved in the pathogenesis of neurodegenerative diseases (including corticobasal degeneration, William’s syndrome, fragile X syndrome, and spinal muscular atrophy), and skeletal muscle myopathy, where it accumulates as cofilin/actin rods (9,23,28,29). Consistent with these findings, the presence of cofilin-2, actin, and MLC-II in the PAO-enriched lysate in iDCM points toward similar structures forming in cardiomyocytes. Interestingly, the differences between cofilin sequestration in iDCM hearts and that in donor hearts were reduced with age. These data are consistent with the hypothesis that iDCM, like AD, is a pathology bearing an anticipated aging phenotype.
Functionally, cofilin regulation of actin dynamics is controlled by reversible phosphorylation. Cofilin phosphorylation on Ser3 by TESK or LIMK inactivates, and dephosphorylation by “slingshot” or chronophin phosphatases activates cofilin to bind either G- or F-actin (18). Consequently, the proper balance of phosphorylated/dephosphorylated cofilin is required for cytoskeleton organization, sarcomeric homeostasis, and contractile function. Here we add pristine evidence of unbalanced cofilin-2 phosphorylation in iDCM heart samples. Lack of cofilin activity would lead to the accumulation of polymerized F-actin filaments and impaired contractility, as shown here, either directly by pharmacological stimulation of cofilin phosphorylation and by genetic expression of the phosphomimetic cofilin mutant in cardiomyocytes or indirectly by means of the CSC2 mouse model. In vitro cardiomyocyte pharmacological stimulation of the endogenous protein phosphorylation resulted in fibrillar accumulation. Likewise, genetic expression of human phosphomimetic cofilin generated “stress-like” fibers and hampered cardiomyocyte contractility. The mouse model of cardiac-specific cofilin-2 haploinsufficiency aptly recapitulated the human cardiac phenotype. Disorganized myofibrils, immature hypercontracted sarcomeres and aggregates, and disruption of the Z-bands, typical of nemaline myopathic skeletal and cardiac muscle, were apparent in CSC2 cardiomyocytes, accounting for a decline in these cells’ contribution to cardiac function. Indeed, the coexistence of intact and disrupted sarcomeres can be expected to interfere with sarcomere mechanics, affecting cardiac function.
In vitro modulation of cofilin activity and the structural abnormalities developed in the CSC2 mouse may not entirely reproduce the pathological changes found in human iDCM. Likewise, cofilin abnormalities may not represent the pathogenetic factor in all cases of iDCM. However, the pathology of the CSC2 mouse myocardium recapitulates the pathology of human nemaline (cardio)myopathy, and cofilin may participate in the pathogenesis of iDCM in a subgroup of patients, as is the case of other amyloid-related cardiomyopathies. Additional large-scale studies are warranted to determine how many cases of iDCM with amyloid-like aggregates have cofilin-2 defects as a pathological substrate.
Notably, active cofilin competitively inhibits myosin-II binding to F-actin, and loss of this modulatory mechanism in cofilin-depleted cells increases myosin-II/actin assembly, leading to further accumulation of abnormal F-actin (30). Interestingly, both actin and MLC-II were found to be enriched in cardiac PAO. Thus, in addition to the effects of loss of cofilin-2 function on actin, changes in the amount of MLC-II could contribute to disorganization of the contractile apparatus, further impairing cardiomyocyte function (2,27,31). Furthermore, by accumulating in PAO, cofilin-2, actin, and MLC-II will alter myocardial function through PAO direct toxicity. Hence, cofilin pathology may alter myocardial contractility by a triple mechanism: “aggregate-independent” loss of function of the sequestered sarcomeric protein(s); “aggregate-dependent” gain of PAO toxicity; and mechanical disruption of sarcomeric integrity, as previously shown for other misfolded-prone proteins (2,32).
In addition to contractility, cofilin has essential functions in other actin-related cellular processes, including trafficking of intracellular molecules, directional motility, cell division, and viability (10,33). As a main structural component of the cytoskeletal network, actin also organizes receptors through interactions on the cytosolic side of the cell membrane, mediating intracellular signaling in response to extracellular matrix deformation and mechanical stress. Furthermore, the upstream regulator of cofilin activity, RhoA, cooperatively coordinates cell migration and motility with the small GTPase RhoA subfamily member Rac. Their reciprocal functions in mediating cytoskeletal plasticity may regulate cell geometry and rigidity in response to extracellular stress and force generation (34). Finally, actomyosin dynamic polymerization coordinates the appropriate distribution of the duplicated chromosomes during cytokinesis (27,30,31,35,36). Thus, abnormalities in cofilin regulation of actin networks may also negatively affect the replicating capacity, shaping, and maturing of the developing heart. At the same time, although not univocally accepted (24,37), when in its active form, cofilin promotes the translocation of Bax to the mitochondria, triggering the cell death pathway. This process of cell clearance is impaired in the presence of increased phospho-cofilin-2, interfering with its beneficial effects on cellular survival and aging. Thus, changes in normal cofilin pattern may further contribute to the development of cardiomyopathy by affecting tissue remodeling and impairing the myocardial ability to respond to stress.
We acknowledge the limitation of using human heart samples that present inevitable variability. We minimized the variability by matching the samples at best for age, sex, and ethnicity between iDCM and control samples. We acknowledge the differences in structural appearance of the stress-like and the rod-like structures, which warrant further studies.
Whether cofilin appears to provide a new pathogenetic mechanism for iDCM, its primary role in the development of iDCM could not be proven in the human samples, as presently there are no known mutations in cofilin human gene (CFL) leading to iDCM.
Our study demonstrates that cofilin-2 and its interactome are present in human and experimental myocardial aggregates and that abnormalities in this protein complex alter myocyte structure and function. Moreover, cofilin-2 activity is decreased in iDCM tissue due to its enhanced degree of phosphorylation. Therefore, cofilin-2 sequestration in aggregates, in tandem with its inactivation, is likely to interfere with critical cofilin-2 functions in the maintenance of actin filament homeostasis for effective myocyte contraction and relaxation. Thus, abnormal cofilin regulation provides a novel pathogenetic mechanism for iDCM and a novel conceptual ground for future development of personalized therapies.
COMPETENCY IN MEDICAL KNOWLEDGE: The actin-depolymerizing protein cofilin occurs in the cellular aggregates in nemaline skeletal myopathy and Alzheimer’s disease, and in recently identified aggregates in patients with iDCM. This suggests a common pathogenic mechanism linking inactivation and sequestration of cofilin in cerebral and skeletal muscle and cardiac tissue.
TRANSLATIONAL OUTLOOK: In the new classification, MOGES(1), an additional etiological category for the dilated morphofunctional phenotype (M) could be included as EA-C: cofilin-type. Whether other organs, other than the heart, would be involved, these cases could be classified as MDOH+B+MGSEA-C. An immediate translational implication of the findings is the possibility that patients with this form of iDCM may have organ alterations more diffuse than originally anticipated.
The authors thank Dr. Alexander Ivanov, Northeastern University, for assistance with mass spectrometry; Dr. Towia Libermann, Beth Israel Deaconess Medical Center, for critical interpretation of mass spectrometry data; the BWH for assistance with confocal microscopy and echocardiography; Dr. Dale Abel, University of Iowa, for the generous donation of the αMHC-Cre mice; and Alisa Shaw, Bamburg Laboratory at Colorado State University, for assistance with adenovirus constructs.
This study was supported by Beth Israel Deaconess Medical Center departmental funds and by National Institutes of Health grants R21HL102716 and R01HL098468, and America Heart Association grant IRG18980028 to Dr. del Monte and by National Institutes of Health grant K08 AR055072 to Dr. Agrawal. Dr. Gianni is currently working for Biogen. Dr. Bamburg is a member of the Scientific Advisory Board of Rapid Pharmaceuticals. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.
- Abbreviations and Acronyms
- Alzheimer’s disease
- actin depolymerizing factor
- cardiac-specific cofilin-2 knockout mouse
- idiopathic dilated cardiomyopathy
- pre-amyloid oligomers
- constitutively active cofilin mutant
- phosphomimetic cofilin mutant
- Received November 6, 2014.
- Revision received January 7, 2015.
- Accepted January 13, 2015.
- 2015 American College of Cardiology Foundation
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