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Abstract
Autophagy is an evolutionarily conserved catabolic process that targets different types of cytoplasmic cargo (such as bulk cytoplasm, damaged cellular organelles, and misfolded protein aggregates) for lysosomal degradation. Autophagy is activated in response to biological stress and also plays a critical role in the maintenance of normal cellular homeostasis; the latter function is particularly important for the integrity of postmitotic, metabolically active tissues, such as skeletal muscle. Through impairment of muscle homeostasis, autophagy dysfunction contributes to the pathogenesis of many different skeletal myopathies; the observed autophagy defects differ from disease to disease but have been shown to involve all steps of the autophagic cascade (from induction to lysosomal cargo degradation) and to impair both bulk and selective autophagy. To highlight the molecular and cellular mechanisms that are shared among different myopathies with deficient autophagy, these disorders are discussed based on the nature of the underlying autophagic defect rather than etiology or clinical presentation.
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Affiliation(s)
- Marta Margeta
- Department of Pathology, University of California, San Francisco, California 94143, USA;
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52
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Regulatory RNA binding proteins contribute to the transcriptome-wide splicing alterations in human cellular senescence. Aging (Albany NY) 2019; 10:1489-1505. [PMID: 29936497 PMCID: PMC6046225 DOI: 10.18632/aging.101485] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Accepted: 06/14/2018] [Indexed: 01/01/2023]
Abstract
Dysregulation of mRNA splicing has been observed in certain cellular senescence process. However, the common splicing alterations on the whole transcriptome shared by various types of senescence are poorly understood. In order to systematically identify senescence-associated transcriptomic changes in genome-wide scale, we collected RNA sequencing datasets of different human cell types with a variety of senescence-inducing methods from public databases and performed meta-analysis. First, we discovered that a group of RNA binding proteins were consistently down-regulated in diverse senescent samples and identified 406 senescence-associated common differential splicing events. Then, eight differentially expressed RNA binding proteins were predicted to regulate these senescence-associated splicing alterations through an enrichment analysis of their RNA binding information, including motif scanning and enhanced cross-linking immunoprecipitation data. In addition, we constructed the splicing regulatory modules that might contribute to senescence-associated biological processes. Finally, it was confirmed that knockdown of the predicted senescence-associated potential splicing regulators through shRNAs in HepG2 cell line could result in senescence-like splicing changes. Taken together, our work demonstrated a broad range of common changes in mRNA splicing switches and detected their central regulatory RNA binding proteins during senescence. These findings would help to better understand the coordinating splicing alterations in cellular senescence.
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53
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Dvornikov AV, Wang M, Yang J, Zhu P, Le T, Lin X, Cao H, Xu X. Phenotyping an adult zebrafish lamp2 cardiomyopathy model identifies mTOR inhibition as a candidate therapy. J Mol Cell Cardiol 2019; 133:199-208. [PMID: 31228518 PMCID: PMC6705397 DOI: 10.1016/j.yjmcc.2019.06.013] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Revised: 05/31/2019] [Accepted: 06/18/2019] [Indexed: 12/23/2022]
Abstract
Adult zebrafish is an emerging vertebrate model for studying genetic basis of cardiomyopathies; but whether the simple fish heart can model essential features of hypertrophic cardiomyopathy (HCM) remained unknown. Here, we report a comprehensive phenotyping of a lamp2 knockout (KO) mutant. LAMP2 encodes a lysosomal protein and is a causative gene of Danon disease that is characterized by HCM and massive autophagic vacuoles accumulation in the tissues. There is no effective therapy yet to treat this most lethal cardiomyopathy in the young. First, we did find the autophagic vacuoles accumulation in cardiac tissues from lamp2 KO. Next, through employing a set of emerging phenotyping tools, we revealed heart failure phenotypes in the lamp2 KO mutants, including decreased ventricular ejection fraction, reduced physical exercise capacity, blunted β-adrenergic contractile response, and enlarged atrium. We also noted changes of the following indices suggesting cardiac hypertrophic remodeling in lamp2 KO: a rounded heart shape, increased end-systolic ventricular volume and density of ventricular myocardium, elevated actomyosin activation kinetics together with increased maximal isometric tension at the level of cardiac myofibrils. Lastly, we assessed the function of lysosomal-localized mTOR on the lamp2-associated Danon disease. We found that haploinsufficiency of mtor was able to normalize some characteristics of the lamp2 KO, including ejection fraction, β-adrenergic response, and the actomyosin activation kinetics. In summary, we demonstrate the feasibility of modeling the inherited HCM in the adult zebrafish, which can be used to develop potential therapies.
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Affiliation(s)
- Alexey V Dvornikov
- Department of Biochemistry and Molecular Biology, Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, USA
| | - Mingmin Wang
- Department of Biochemistry and Molecular Biology, Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, USA; Dongzhimen Hospital, Beijing University of Chinese Medicine, Beijing, China
| | - Jingchun Yang
- Department of Biochemistry and Molecular Biology, Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, USA
| | - Ping Zhu
- Department of Biochemistry and Molecular Biology, Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, USA
| | - Tai Le
- Department of Electrical Engineering and Computer Science, University of California Irvine, CA, USA
| | - Xueying Lin
- Department of Biochemistry and Molecular Biology, Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, USA
| | - Hung Cao
- Department of Electrical Engineering and Computer Science, University of California Irvine, CA, USA; Department of Biomedical Engineering, University of California Irvine, CA, USA
| | - Xiaolei Xu
- Department of Biochemistry and Molecular Biology, Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, USA.
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54
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Mahapatra KK, Panigrahi DP, Praharaj PP, Bhol CS, Patra S, Mishra SR, Behera BP, Bhutia SK. Molecular interplay of autophagy and endocytosis in human health and diseases. Biol Rev Camb Philos Soc 2019; 94:1576-1590. [PMID: 30989802 DOI: 10.1111/brv.12515] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Revised: 03/27/2019] [Accepted: 03/29/2019] [Indexed: 12/14/2022]
Abstract
Autophagy, an evolutionarily conserved process for maintaining the physio-metabolic equilibrium of cells, shares many common effector proteins with endocytosis. For example, tethering proteins involved in fusion like Ras-like GTPases (Rabs), soluble N-ethylmaleimide sensitive factor attachment protein receptors (SNAREs), lysosomal-associated membrane protein (LAMP), and endosomal sorting complex required for transport (ESCRT) have a dual role in endocytosis and autophagy, and the trafficking routes of these processes converge at lysosomes. These common effectors indicate an association between budding and fusion of membrane-bound vesicles that may have a substantial role in autophagic lysosome reformation, by sensing cellular stress levels. Therefore, autophagy-endocytosis crosstalk may be significant and implicates a novel endocytic regulatory pathway of autophagy. Moreover, endocytosis has a pivotal role in the intake of signalling molecules, which in turn activates cascades that can result in pathophysiological conditions. This review discusses the basic mechanisms of this crosstalk and its implications in order to identify potential novel therapeutic targets for various human diseases.
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Affiliation(s)
- Kewal K Mahapatra
- Department of Life Science, National Institute of Technology Rourkela, Sundergarh, Odisha 769008, India
| | - Debasna P Panigrahi
- Department of Life Science, National Institute of Technology Rourkela, Sundergarh, Odisha 769008, India
| | - Prakash P Praharaj
- Department of Life Science, National Institute of Technology Rourkela, Sundergarh, Odisha 769008, India
| | - Chandra S Bhol
- Department of Life Science, National Institute of Technology Rourkela, Sundergarh, Odisha 769008, India
| | - Srimanta Patra
- Department of Life Science, National Institute of Technology Rourkela, Sundergarh, Odisha 769008, India
| | - Soumya R Mishra
- Department of Life Science, National Institute of Technology Rourkela, Sundergarh, Odisha 769008, India
| | - Bishnu P Behera
- Department of Life Science, National Institute of Technology Rourkela, Sundergarh, Odisha 769008, India
| | - Sujit K Bhutia
- Department of Life Science, National Institute of Technology Rourkela, Sundergarh, Odisha 769008, India
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55
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Zech ATL, Singh SR, Schlossarek S, Carrier L. Autophagy in cardiomyopathies. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2019; 1867:118432. [PMID: 30831130 DOI: 10.1016/j.bbamcr.2019.01.013] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2018] [Revised: 01/24/2019] [Accepted: 01/28/2019] [Indexed: 12/19/2022]
Abstract
Autophagy (greek auto: self; phagein: eating) is a highly conserved process within eukaryotes that degrades long-lived proteins and organelles within lysosomes. Its accurate and constant operation in basal conditions ensures cellular homeostasis by degrading damaged cellular components and thereby acting not only as a quality control but as well as an energy supplier. An increasing body of evidence indicates a major role of autophagy in the regulation of cardiac homeostasis and function. In this review, we describe the different forms of mammalian autophagy, their regulations and monitoring with a specific emphasis on the heart. Furthermore, we address the role of autophagy in several forms of cardiomyopathy and the options for therapy.
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Affiliation(s)
- Antonia T L Zech
- Institute of Experimental Pharmacology and Toxicology, University Medical Center Hamburg, Hamburg, Germany; German Centre for Cardiovascular Research, Partner Site Hamburg/Kiel/Lübeck, Hamburg, Germany
| | - Sonia R Singh
- Division of Molecular Cardiovascular Biology, The Heart Institute, Cincinnati Children's Hospital, Cincinnati, OH, United States of America
| | - Saskia Schlossarek
- Institute of Experimental Pharmacology and Toxicology, University Medical Center Hamburg, Hamburg, Germany; German Centre for Cardiovascular Research, Partner Site Hamburg/Kiel/Lübeck, Hamburg, Germany
| | - Lucie Carrier
- Institute of Experimental Pharmacology and Toxicology, University Medical Center Hamburg, Hamburg, Germany; German Centre for Cardiovascular Research, Partner Site Hamburg/Kiel/Lübeck, Hamburg, Germany.
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56
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Aghaei M, Motallebnezhad M, Ghorghanlu S, Jabbari A, Enayati A, Rajaei M, Pourabouk M, Moradi A, Alizadeh AM, Khori V. Targeting autophagy in cardiac ischemia/reperfusion injury: A novel therapeutic strategy. J Cell Physiol 2019; 234:16768-16778. [PMID: 30807647 DOI: 10.1002/jcp.28345] [Citation(s) in RCA: 60] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Revised: 01/17/2019] [Accepted: 01/22/2019] [Indexed: 12/31/2022]
Abstract
Acute myocardial infarction (AMI) is one of the leading causes of morbidity worldwide. Myocardial reperfusion is known as an effective therapeutic choice against AMI. However, reperfusion of blood flow induces ischemia/reperfusion (I/R) injury through different complex processes including ion accumulation, disruption of mitochondrial membrane potential, the formation of reactive oxygen species, and so forth. One of the processes that gets activated in response to I/R injury is autophagy. Indeed, autophagy acts as a "double-edged sword" in the pathology of myocardial I/R injury and there is a controversy about autophagy being beneficial or detrimental. On the basis of the autophagy effect and regulation on myocardial I/R injury, many studies targeted it as a therapeutic strategy. In this review, we discuss the role of autophagy in I/R injury and its targeting as a therapeutic strategy.
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Affiliation(s)
- Mehrdad Aghaei
- Rheumatology Research Center, Golestan University of Medical Sciences, Gorgan, Iran
| | - Morteza Motallebnezhad
- Immunology Research Center, Tabriz University of Medical Sciences, Tabriz, Iran.,Department of Immunology, Faculty of Medicine, Iran University of Medical Sciences, Tehran, Iran.,Student Research Committee, Iran University of Medical Sciences, Tehran, Iran
| | - Sajjad Ghorghanlu
- Ischemic Disorders Research Center, Golestan University of Medical Sciences, Gorgan, Iran
| | - Ali Jabbari
- Ischemic Disorders Research Center, Golestan University of Medical Sciences, Gorgan, Iran
| | - Ayesheh Enayati
- Ischemic Disorders Research Center, Golestan University of Medical Sciences, Gorgan, Iran.,Department of Pharmacognosy, Faculty of Pharmacy and Medicinal Plants Research Center, Tehran University of Medical Sciences, Tehran, Iran
| | - Maryam Rajaei
- Ischemic Disorders Research Center, Golestan University of Medical Sciences, Gorgan, Iran
| | - Mona Pourabouk
- Ischemic Disorders Research Center, Golestan University of Medical Sciences, Gorgan, Iran
| | - Alireza Moradi
- Department of Physiology, Medical School, Ardabil University of Medical Sciences, Ardabil, Iran
| | | | - Vahid Khori
- Ischemic Disorders Research Center, Golestan University of Medical Sciences, Gorgan, Iran
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57
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Davegårdh C, Hall Wedin E, Broholm C, Henriksen TI, Pedersen M, Pedersen BK, Scheele C, Ling C. Sex influences DNA methylation and gene expression in human skeletal muscle myoblasts and myotubes. Stem Cell Res Ther 2019; 10:26. [PMID: 30646953 PMCID: PMC6332625 DOI: 10.1186/s13287-018-1118-4] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2018] [Revised: 12/07/2018] [Accepted: 12/20/2018] [Indexed: 12/12/2022] Open
Abstract
Background Sex differences are known to impact muscle phenotypes, metabolism, and disease risk. Skeletal muscle stem cells (satellite cells) are important for muscle repair and to maintain functional skeletal muscle. Here we studied, for the first time, effects of sex on DNA methylation and gene expression in primary human myoblasts (activated satellite cells) before and after differentiation into myotubes. Method We used an array-based approach to analyse genome-wide DNA methylation and gene expression in myoblasts and myotubes from 13 women and 13 men. The results were followed up with a reporter gene assay. Results Genome-wide DNA methylation and gene expression differences between the sexes were detected in both myoblasts and myotubes, on the autosomes as well as the X-chromosome, despite lack of exposure to sex hormones and other factors that differ between sexes. Pathway analysis revealed higher expression of oxidative phosphorylation and other metabolic pathways in myoblasts from women compared to men. Oxidative phosphorylation was also enriched among genes with higher expression in myotubes from women. Forty genes in myoblasts and 9 in myotubes had differences in both DNA methylation and gene expression between the sexes, including LAMP2 and SIRT1 in myoblasts and KDM6A in myotubes. Furthermore, increased DNA methylation of LAMP2 promoter had negative effects on reporter gene expression. Five genes (CREB5, RPS4X, SYAP1, XIST, and ZRSR2) showed differential DNA methylation and gene expression between the sexes in both myoblasts and myotubes. Interestingly, differences in DNA methylation and expression between women and men were also found during differentiation (myoblasts versus myotubes), e.g., in genes involved in energy metabolism. Interestingly, more DNA methylation changes occur in women compared to men on autosomes. Conclusion All together, we show that epigenetic and transcriptional differences exist in human myoblasts and myotubes as well as during differentiation between women and men. We believe that these intrinsic differences might contribute to sex dependent differences in muscular phenotypes. Electronic supplementary material The online version of this article (10.1186/s13287-018-1118-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Cajsa Davegårdh
- Department of Clinical Sciences, Lund University Diabetes Centre, Lund University, Scania University Hospital, 20502, Malmö, Sweden.
| | - Elin Hall Wedin
- Department of Clinical Sciences, Lund University Diabetes Centre, Lund University, Scania University Hospital, 20502, Malmö, Sweden
| | - Christa Broholm
- Department of Endocrinology, Rigshospitalet, 2100, Copenhagen, Denmark.,The Centre of Inflammation and Metabolism and the Centre for Physical Activity Research, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Tora Ida Henriksen
- Department of Endocrinology, Rigshospitalet, 2100, Copenhagen, Denmark.,The Centre of Inflammation and Metabolism and the Centre for Physical Activity Research, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Maria Pedersen
- The Centre of Inflammation and Metabolism and the Centre for Physical Activity Research, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Bente Klarlund Pedersen
- The Centre of Inflammation and Metabolism and the Centre for Physical Activity Research, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Camilla Scheele
- The Centre of Inflammation and Metabolism and the Centre for Physical Activity Research, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.,Novo Nordisk Foundation Center, Section for Basic Metabolic Research, Faculty of Health and Medical Science, University of Copenhagen, Copenhagen, Denmark
| | - Charlotte Ling
- Department of Clinical Sciences, Lund University Diabetes Centre, Lund University, Scania University Hospital, 20502, Malmö, Sweden.
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58
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Li S, Jiang Z, Chai W, Xu Y, Wang Y. Autophagy activation alleviates nonylphenol-induced apoptosis in cultured cortical neurons. Neurochem Int 2019; 122:73-84. [DOI: 10.1016/j.neuint.2018.11.009] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Revised: 11/12/2018] [Accepted: 11/13/2018] [Indexed: 01/19/2023]
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59
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Triolo M, Hood DA. Mitochondrial breakdown in skeletal muscle and the emerging role of the lysosomes. Arch Biochem Biophys 2018; 661:66-73. [PMID: 30439362 DOI: 10.1016/j.abb.2018.11.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Revised: 10/13/2018] [Accepted: 11/05/2018] [Indexed: 11/15/2022]
Abstract
Skeletal muscle mitochondria are essential in providing the energy required for locomotion. In response to contractile activity, the production of mitochondria is upregulated to meet the energy demands placed upon muscle cells. In a coordinated fashion, exercise also promotes the breakdown of dysfunctional mitochondria via mitophagy. Mitophagy is characterized by the selection of poorly functioning organelles, engulfment in an autophagosome and transport to lysosomes for degradation. In addition to the activation of mitophagy, exercise also elevates lysosome biogenesis. This coordinated increase in mitophagy targeting and lysosomal biogenesis serves to enhance the capacity for autophagosomal degradation, thereby aiding in the maintenance of mitochondrial quality. Lysosome dysfunction, as observed in lysosomal storage disorders (LSDs), negatively impacts mitochondrial function likely through the suppression of mitophagy. Since exercise is capable of activating mitophagy and lysosome biogenesis, researchers have begun to investigate physical activity as an effective therapy for LSDs. This review summarizes the current understanding of how mitophagy and lysosomal biogenesis are regulated in exercising skeletal, with potential therapeutic implications.
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Affiliation(s)
- Matthew Triolo
- Muscle Health Research Centre, York University, Toronto, Ontario, M3J 1P3, Canada; School of Kinesiology and Health Science, York University, Toronto, Ontario, M3J 1P3, Canada.
| | - David A Hood
- Muscle Health Research Centre, York University, Toronto, Ontario, M3J 1P3, Canada; School of Kinesiology and Health Science, York University, Toronto, Ontario, M3J 1P3, Canada.
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60
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A Nationwide Survey on Danon Disease in Japan. Int J Mol Sci 2018; 19:ijms19113507. [PMID: 30413001 PMCID: PMC6274850 DOI: 10.3390/ijms19113507] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Revised: 11/04/2018] [Accepted: 11/05/2018] [Indexed: 01/01/2023] Open
Abstract
Danon disease, an X-linked dominant cardioskeletal myopathy, is caused by primary deficiency of lysosome-associated membrane protein-2 (LAMP-2). To clarify the clinicopathological features and management, we performed the first nationwide, questionnaire-based survey on Danon disease in Japan. A total of 39 patients (17 males, 22 females) from 20 families were identified in the analysis. All patients had cardiomyopathy. Of the 21 patients who died, 20 (95%) died of cardiac failure or sudden cardiac arrest. Most patients had hypertrophic cardiomyopathy. Wolf–Parkinson–White syndrome was present at a comparatively high incidence (54% in males, 22% in females). Only one female patient received a heart transplant, which is the most effective therapy. Histopathologically, all male patients showed autophagic vacuoles with sarcolemmal features in muscle. Half of the probands showed de novo mutations. Male patients showed completely absent LAMP-2 expression in muscle. In contrast, female patients showed decreased LAMP-2 expression, which is suggested to reflect LAMP-2 haploinsufficiency due to a heterozygous null mutation. In conclusion, Danon disease is an extremely rare muscular disorder in Japan. Cardiomyopathy is the most significant prognostic factor and the main cause of death. Our findings suggest that the present survey can extend our understanding of the clinical features of this rare disease.
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61
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Tan Y, Gong Y, Dong M, Pei Z, Ren J. Role of autophagy in inherited metabolic and endocrine myopathies. Biochim Biophys Acta Mol Basis Dis 2018; 1865:48-55. [PMID: 30343140 DOI: 10.1016/j.bbadis.2018.10.023] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Revised: 10/11/2018] [Accepted: 10/17/2018] [Indexed: 12/11/2022]
Abstract
The prevalence of cardiometabolic disease has reached an exponential rate of rise over the last decades owing to high fat/high caloric diet intake and satiety life style. Although the presence of dyslipidemia, insulin resistance, hypertension and obesity mainly contributes to the increased incidence of cardiometabolic diseases, population-based, clinical and genetic studies have revealed a rather important role for inherited myopathies and endocrine disorders in the ever-rising metabolic anomalies. Inherited metabolic and endocrine diseases such as glycogen storage and lysosomal disorders have greatly contributed to the overall prevalence of cardiometabolic diseases. Recent evidence has demonstrated an essential role for proteotoxicity due to autophagy failure and/or dysregulation in the onset of inherited metabolic and endocrine disorders. Given the key role for autophagy in the degradation and removal of long-lived or injured proteins and organelles for the maintenance of cellular and organismal homeostasis, this mini-review will discuss the potential contribution of autophagy dysregulation in the pathogenesis of inherited myopathies and endocrine disorders, which greatly contribute to an overall rise in prevalence of cardiometabolic disorders. Molecular, clinical, and epidemiological aspects will be covered as well as the potential link between autophagy and metabolic anomalies thus target therapy may be engaged for these comorbidities.
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Affiliation(s)
- Ying Tan
- Department of Emergency Medicine, Nanfang Hospital, Southern Medical University, Guangzhou 510515, China; Center for Cardiovascular Research and Alternative Medicine, University of Wyoming College of Health Sciences, Laramie, WY 82071, USA
| | - Yan Gong
- The Second Department of Cardiology, The Third Hospital of Nanchang, Nanchang, Jiangxi 330009, China
| | - Maolong Dong
- Department of Emergency Medicine, Nanfang Hospital, Southern Medical University, Guangzhou 510515, China; Center for Cardiovascular Research and Alternative Medicine, University of Wyoming College of Health Sciences, Laramie, WY 82071, USA; Department of Burns, Nanfang Hospital, Southern Medical University, Guangzhou 510515, China
| | - Zhaohui Pei
- The Second Department of Cardiology, The Third Hospital of Nanchang, Nanchang, Jiangxi 330009, China.
| | - Jun Ren
- Center for Cardiovascular Research and Alternative Medicine, University of Wyoming College of Health Sciences, Laramie, WY 82071, USA.
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Multiple recycling routes: Canonical vs. non-canonical mitophagy in the heart. Biochim Biophys Acta Mol Basis Dis 2018; 1865:797-809. [PMID: 30290272 DOI: 10.1016/j.bbadis.2018.09.034] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Revised: 09/13/2018] [Accepted: 09/27/2018] [Indexed: 12/14/2022]
Abstract
The heart is composed of cardiomyocytes that require large amounts of energy to sustain contraction. Mitochondria are distinctive organelles of bacterial origin that generate most of the energy for the heart via oxidative phosphorylation. To ensure a healthy population of mitochondria that efficiently produce ATP, myocytes quickly eliminate any unhealthy or unwanted mitochondria via a process known as mitochondrial autophagy, or mitophagy. It is especially important to selectively remove damaged or aged mitochondria since they can become excessive producers of reactive oxygen species and release pro-death proteins. Because this is such a crucial cellular process, cells have several mechanisms in place to deal with potentially harmful mitochondria. Here, we review the various pathways identified to date and how they are regulated. We also discuss the importance of these canonical and non-canonical pathways in the heart and their link to cardiovascular health, disease and aging.
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63
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Ellingwood SS, Cheng A. Biochemical and clinical aspects of glycogen storage diseases. J Endocrinol 2018; 238:R131-R141. [PMID: 29875163 PMCID: PMC6050127 DOI: 10.1530/joe-18-0120] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Accepted: 06/04/2018] [Indexed: 12/29/2022]
Abstract
The synthesis of glycogen represents a key pathway for the disposal of excess glucose while its degradation is crucial for providing energy during exercise and times of need. The importance of glycogen metabolism is also highlighted by human genetic disorders that are caused by mutations in the enzymes involved. In this review, we provide a basic summary on glycogen metabolism and some of the clinical aspects of the classical glycogen storage diseases. Disruptions in glycogen metabolism usually result in some level of dysfunction in the liver, muscle, heart, kidney and/or brain. Furthermore, the spectrum of symptoms observed is very broad, depending on the affected enzyme. Finally, we briefly discuss an aspect of glycogen metabolism related to the maintenance of its structure that seems to be gaining more recent attention. For example, in Lafora progressive myoclonus epilepsy, patients exhibit an accumulation of inclusion bodies in several tissues, containing glycogen with increased phosphorylation, longer chain lengths and irregular branch points. This abnormal structure is thought to make glycogen insoluble and resistant to degradation. Consequently, its accumulation becomes toxic to neurons, leading to cell death. Although the genes responsible have been identified, studies in the past two decades are only beginning to shed light into their molecular functions.
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Affiliation(s)
- Sara S Ellingwood
- Department of Biochemistry and Molecular GeneticsUniversity of Louisville School of Medicine, Louisville, Kentucky, USA
| | - Alan Cheng
- Department of Biochemistry and Molecular GeneticsUniversity of Louisville School of Medicine, Louisville, Kentucky, USA
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Issa AR, Sun J, Petitgas C, Mesquita A, Dulac A, Robin M, Mollereau B, Jenny A, Chérif-Zahar B, Birman S. The lysosomal membrane protein LAMP2A promotes autophagic flux and prevents SNCA-induced Parkinson disease-like symptoms in the Drosophila brain. Autophagy 2018; 14:1898-1910. [PMID: 29989488 PMCID: PMC6152503 DOI: 10.1080/15548627.2018.1491489] [Citation(s) in RCA: 85] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Revised: 06/05/2018] [Accepted: 06/13/2018] [Indexed: 02/03/2023] Open
Abstract
The autophagy-lysosome pathway plays a fundamental role in the clearance of aggregated proteins and protection against cellular stress and neurodegenerative conditions. Alterations in autophagy processes, including macroautophagy and chaperone-mediated autophagy (CMA), have been described in Parkinson disease (PD). CMA is a selective autophagic process that depends on LAMP2A (lysosomal-associated membrane protein 2A), a mammal and bird-specific membrane glycoprotein that translocates cytosolic proteins containing a KFERQ-like peptide motif across the lysosomal membrane. Drosophila reportedly lack CMA and use endosomal microautophagy (eMI) as an alternative selective autophagic process. Here we report that neuronal expression of human LAMP2A protected Drosophila against starvation and oxidative stress, and delayed locomotor decline in aging flies without extending their lifespan. LAMP2A also prevented the progressive locomotor and oxidative defects induced by neuronal expression of PD-associated human SNCA (synuclein alpha) with alanine-to-proline mutation at position 30 (SNCAA30P). Using KFERQ-tagged fluorescent biosensors, we observed that LAMP2A expression stimulated selective autophagy in the adult brain and not in the larval fat body, but did not increase this process under starvation conditions. Noteworthy, we found that neurally expressed LAMP2A markedly upregulated levels of Drosophila Atg5, a key macroautophagy initiation protein, and that it increased the density of Atg8a/LC3-positive puncta, which reflects the formation of autophagosomes. Furthermore, LAMP2A efficiently prevented accumulation of the autophagy defect marker Ref(2)P/p62 in the adult brain under acute oxidative stress. These results indicate that LAMP2A can potentiate autophagic flux in the Drosophila brain, leading to enhanced stress resistance and neuroprotection. ABBREVIATIONS Act5C: actin 5C; a.E.: after eclosion; Atg5: autophagy-related 5; Atg8a/LC3: autophagy-related 8a; CMA: chaperone-mediated autophagy; DHE: dihydroethidium; elav: embryonic lethal abnormal vision; eMI: endosomal microautophagy; ESCRT: endosomal sorting complexes required for transport; GABARAP: GABA typeA receptor-associated protein; Hsc70-4: heat shock protein cognate 4; HSPA8/Hsc70: heat shock protein family A (Hsp70) member 8; LAMP2: lysosomal associated membrane protein 2; MDA: malondialdehyde; PA-mCherry: photoactivable mCherry; PBS: phosphate-buffered saline; PCR: polymerase chain reaction; PD: Parkinson disease; Ref(2)P/p62: refractory to sigma P; ROS: reactive oxygen species; RpL32/rp49: ribosomal protein L32; RT-PCR: reverse transcription polymerase chain reaction; SING: startle-induced negative geotaxis; SNCA/α-synuclein: synuclein alpha; SQSTM1/p62: sequestosome 1; TBS: Tris-buffered saline; UAS: upstream activating sequence.
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Affiliation(s)
- Abdul-Raouf Issa
- Genes Circuits Rhythms and Neuropathology, Brain Plasticity Unit, CNRS, ESPCI Paris, PSL Research University, Paris, France
| | - Jun Sun
- Genes Circuits Rhythms and Neuropathology, Brain Plasticity Unit, CNRS, ESPCI Paris, PSL Research University, Paris, France
| | - Céline Petitgas
- Genes Circuits Rhythms and Neuropathology, Brain Plasticity Unit, CNRS, ESPCI Paris, PSL Research University, Paris, France
| | - Ana Mesquita
- Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, New York, NY, USA
| | - Amina Dulac
- Genes Circuits Rhythms and Neuropathology, Brain Plasticity Unit, CNRS, ESPCI Paris, PSL Research University, Paris, France
| | - Marion Robin
- ENSL, UCBL, CNRS, LBMC, UMS 3444 Biosciences Lyon Gerland, Université de Lyon, Lyon, France
| | - Bertrand Mollereau
- ENSL, UCBL, CNRS, LBMC, UMS 3444 Biosciences Lyon Gerland, Université de Lyon, Lyon, France
| | - Andreas Jenny
- Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, New York, NY, USA
| | - Baya Chérif-Zahar
- Genes Circuits Rhythms and Neuropathology, Brain Plasticity Unit, CNRS, ESPCI Paris, PSL Research University, Paris, France
| | - Serge Birman
- Genes Circuits Rhythms and Neuropathology, Brain Plasticity Unit, CNRS, ESPCI Paris, PSL Research University, Paris, France
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Sánchez-Lanzas R, Castaño JG. Inhibitors of lysosomal function or serum starvation in control or LAMP2 deficient cells do not modify the cellular levels of Parkinson disease-associated DJ-1/PARK 7 protein. PLoS One 2018; 13:e0201152. [PMID: 30048497 PMCID: PMC6062081 DOI: 10.1371/journal.pone.0201152] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Accepted: 06/21/2018] [Indexed: 11/30/2022] Open
Abstract
Mutations in PARK7/DJ-1 gene are associated with familial autosomal recessive Parkinson disease. Recently, lysosomes and chaperone mediated autophagy (CMA) has been reported to participate in the degradation of DJ-1/PARK7 protein. Lamp-2A isoform is considered as the lysosomal receptor for the uptake of proteins being degraded by the CMA pathway. We have used several cell lines with disrupted LAMP2 gene expression and their respective control cells to test the possible role of lysosomal degradation and in particular CMA in DJ-1 /PARK7 degradation. Interruption of LAMP-2 expression did not result in an increase of the steady-state protein levels of DJ-1 /PARK7, as it would have been expected. Furthermore, no change in DJ-1 /PARK7 protein levels were observed upon inhibition of lysosomal function with NH4Cl or NH4Cl plus leupeptin, or after activation of CMA by serum starvation for 24h. Accordingly, we have not found any evidence that DJ-1 /PARK7 protein levels are regulated via lysosomal degradation or the CMA pathway.
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Affiliation(s)
- Raúl Sánchez-Lanzas
- Departamento de Bioquímica, Instituto de Investigaciones Biomédicas “Alberto Sols”, UAM-CSIC, Facultad de Medicina UAM, Madrid, Spain
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Facultad de Medicina UAM, Madrid, Spain
| | - José G. Castaño
- Departamento de Bioquímica, Instituto de Investigaciones Biomédicas “Alberto Sols”, UAM-CSIC, Facultad de Medicina UAM, Madrid, Spain
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Facultad de Medicina UAM, Madrid, Spain
- * E-mail:
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Zheng H, Yang Y, Ye C, Li PP, Wang ZG, Xing H, Ren H, Zhou WP. Lamp2 inhibits epithelial-mesenchymal transition by suppressing Snail expression in HCC. Oncotarget 2018; 9:30240-30252. [PMID: 30100986 PMCID: PMC6084387 DOI: 10.18632/oncotarget.25367] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Accepted: 11/10/2017] [Indexed: 01/15/2023] Open
Abstract
Lysosomal associated membrane protein 2 (Lamp2) influences a broad range of physiological and pathological processes. However, little is known about the role of Lamp2 in hepatocellular carcinoma (HCC) metastasis. This study found that Lamp2 expression was significantly lower in HCC tissues than in adjacent nontumor tissues (ANTs), and its expression level correlated with HCC metastasis. Low Lamp2 expression was significantly correlated with the AFP serum level (> 20 ng/Ml, P = 0.024), capsular formation (absent, P = 0.024), and microvascular invasion (present, P < 0.001), and low expression of Lamp2 indicated a poor prognosis in HCC. LowLamp2 expression was an independent and significant risk factor for recurrence-free survival (RFS; P < 0.001) and overall survival (OS; P < 0.001) in HCC. In this study, we demonstrated that Lamp2 overexpression inhibited cell motility and invasiveness in vitro and inhibited lung metastasis in vivo. In addition, Lamp2 could reverse the EMT program. Lamp2 silencing by siRNA in HCC cell lines enhanced the expression of mesenchymal markers and decreased the expression of epithelial markers. Consistent with these findings, Lamp2 overexpression had the opposite effects. Mechanistically, we found that Lamp2 could suppress Snail expression, upregulate E-cadherin, and inhibit HCC cell epithelial-mesenchymal transition (EMT).Together, these findings suggest that Lamp2 attenuates EMT by suppressing Snail expression in HCC.
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Affiliation(s)
- Hao Zheng
- The Third Department of Hepatic Surgery, Eastern Hepatobiliary Surgery Hospital, Second Military Medical University, Shanghai 200433, China
| | - Yuan Yang
- The Third Department of Hepatic Surgery, Eastern Hepatobiliary Surgery Hospital, Second Military Medical University, Shanghai 200433, China
| | - Chen Ye
- Department of Urology, Changhai Hospital, Second Military Medical University, Shanghai 200433, China
| | - Peng-Peng Li
- The Third Department of Hepatic Surgery, Eastern Hepatobiliary Surgery Hospital, Second Military Medical University, Shanghai 200433, China
| | - Zhen-Guang Wang
- The Third Department of Hepatic Surgery, Eastern Hepatobiliary Surgery Hospital, Second Military Medical University, Shanghai 200433, China
| | - Hao Xing
- The Third Department of Hepatic Surgery, Eastern Hepatobiliary Surgery Hospital, Second Military Medical University, Shanghai 200433, China
| | - Hao Ren
- Department of Microbiology, Shanghai Key Laboratory of Medical Biodefense, Second Military Medical University, Shanghai 200433, China
| | - Wei-Ping Zhou
- The Third Department of Hepatic Surgery, Eastern Hepatobiliary Surgery Hospital, Second Military Medical University, Shanghai 200433, China
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Sakamoto H, Yamashita K, Okamoto K, Kadowaki T, Sakai E, Umeda M, Tsukuba T. Transcription factor EB influences invasion and migration in oral squamous cell carcinomas. Oral Dis 2018; 24:741-748. [PMID: 29316035 DOI: 10.1111/odi.12826] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2017] [Revised: 12/25/2017] [Accepted: 01/03/2018] [Indexed: 12/16/2022]
Abstract
OBJECTIVE Transcription factor EB (TFEB) is a master regulator of lysosomal biogenesis and plays an important role in various cancers. However, the function of TFEB in oral squamous cell carcinomas has not been examined. The aim of this study was to elucidate the role of TFEB in oral squamous cell carcinomas. MATERIALS AND METHODS Expression levels of TFEB were examined in six different human oral squamous carcinoma cells: HSC2, HSC3, HSC4, SAS, OSC20, and SCC25. Knockdown of TFEB using small interfering RNA in HSC2 and HSC4 cells was performed. Cell morphology was observed by immunofluorescence microscopy. Cell proliferation, invasion, and adhesion were analyzed. RESULTS Expression levels of TFEB were high in HSC2, moderate in HSC4 and SCC25, and low in HSC3 and OSC20 cells. Knockdown of TFEB did not affect proliferation of HSC2 and HSC4 cells, but did induced enlargement of lysosomes and endosomes in HSC4 cells. TFEB silencing reduced invasion and migration of these HSC cell squamous carcinoma cells; however, increased cell adhesion was also observed. CONCLUSION TFEB knockdown reduces invasion and migration of cancer cells, likely through lysosomal regulation. Taken together, TFEB influences cell invasion and migration of oral squamous cell carcinomas.
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Affiliation(s)
- H Sakamoto
- Department of Dental Pharmacology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
- Department of Clinical Oral Oncology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
| | - K Yamashita
- Department of Dental Pharmacology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
- Department of Clinical Oral Oncology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
| | - K Okamoto
- Department of Dental Pharmacology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan
| | - T Kadowaki
- Division of Frontier Life Science, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan
| | - E Sakai
- Department of Dental Pharmacology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
| | - M Umeda
- Department of Clinical Oral Oncology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
| | - T Tsukuba
- Department of Dental Pharmacology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
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A new phenotype of severe dilated cardiomyopathy associated with a mutation in the LAMP2 gene previously known to cause hypertrophic cardiomyopathy in the context of Danon disease. Eur J Med Genet 2018; 62:77-80. [PMID: 29753918 DOI: 10.1016/j.ejmg.2018.05.015] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Revised: 05/02/2018] [Accepted: 05/08/2018] [Indexed: 11/20/2022]
Abstract
Danon disease is a rare X-linked cardiac and skeletal muscle disorder with multisystem clinical manifestations. Genetic defects at the lysosome-associated membrane 2 protein (LAMP2) are the cause of the disorder. Due to the rarity of the disease, there is limited progress in understanding the correlation between genotype and phenotype, and explaining the large variability of the clinical features of the disease. In this study, we report two patients, twin sisters, referred to our hospital for end stage heart failure due to dilated cardiomyopathy, requiring heart transplant evaluation. Genetic analysis, using targeted next generation sequencing, showed that the proband carried a LAMP2 missense variant, c.928G > A. The mutation was also detected in her twin sister by sanger sequencing. This variant has already been reported by other investigators and was correlated with the clinical triad of Danon disease i.e. hypertrophic cardiomyopathy, mental retardation and peripheral myopathy. The new phenotype of dilated cardiomyopathy associated with this mutation, confirms the phenotypic heterogeneity of the particular mutation, as well as of Danon disease.
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Ma S, Zhang M, Zhang S, Wang J, Zhou X, Guo G, Wang L, Wang M, Peng Z, Guo C, Zheng X, Zhou X, Wang J, Han Y. Characterisation of Lamp2-deficient rats for potential new animal model of Danon disease. Sci Rep 2018; 8:6932. [PMID: 29720683 PMCID: PMC5932014 DOI: 10.1038/s41598-018-24351-w] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2017] [Accepted: 03/22/2018] [Indexed: 12/18/2022] Open
Abstract
Danon disease (DD) is caused by the absence or malfunction of lysosomal-associated membrane protein 2 (LAMP2). Although Lamp2-deficient mice and DD patients have similar characteristics, these mice have clear limitations and are clinically inconsistent. The aim of our paper is to outline the characteristics of Lamp2-deficient rats and to contrast this model with currently available DD mouse models. The baseline levels of some serum enzymes were elevated in Lamp2y/− rats along with hypercholesterolemia and hyperglycaemia at 8 weeks. Echocardiography showed that IVSd (1.500 ± 0.071 vs. 2.200 ± 1.147, P < 0.01) and LVPWd (1.575 ± 0.063 vs. 1.850 ± 0.029, P < 0.01) were significantly increased, and GCS (−13.20 ± 0.4814 vs. −6.954 ± 0.665) and GRS (21.42 ± 1.807 vs. 7.788 ± 1.140) were sharply decreased. Meanwhile, substantial myocyte disruption, hypertrophic muscle fibres, interstitial fibrosis and microvascular hyperplasia could be observed in the heart tissue. Lamp2y/− rats also displayed abnormal behaviours in the open field and fear conditioning tests. Notably, Lamp2y/− rats manifested other system dysfunctions, such as retinopathy, chronic kidney injury and sterility. Based on these results, Lamp2-deficient rats exhibited greater similarity to DD patients in terms of onset and multisystem lesions than did mouse models, and these rats could be used as a valuable animal model for DD.
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Affiliation(s)
- Shuoyi Ma
- State Key Laboratory of Cancer Biology, National Clinical Research Centre for Digestive Diseases and Xijing Hospital of Digestive Diseases, Fourth Military Medical University, Xi'an, China
| | - Miao Zhang
- State Key Laboratory of Cancer Biology, National Clinical Research Centre for Digestive Diseases and Xijing Hospital of Digestive Diseases, Fourth Military Medical University, Xi'an, China
| | - Shuai Zhang
- State Key Laboratory of Cancer Biology, National Clinical Research Centre for Digestive Diseases and Xijing Hospital of Digestive Diseases, Fourth Military Medical University, Xi'an, China
| | - Jing Wang
- Division of Ultrasonography, Xijing Hospital, Fourth Military Medical University, Xi'an, China
| | - Xia Zhou
- State Key Laboratory of Cancer Biology, National Clinical Research Centre for Digestive Diseases and Xijing Hospital of Digestive Diseases, Fourth Military Medical University, Xi'an, China
| | - Guanya Guo
- State Key Laboratory of Cancer Biology, National Clinical Research Centre for Digestive Diseases and Xijing Hospital of Digestive Diseases, Fourth Military Medical University, Xi'an, China
| | - Lu Wang
- State Key Laboratory of Cancer Biology, National Clinical Research Centre for Digestive Diseases and Xijing Hospital of Digestive Diseases, Fourth Military Medical University, Xi'an, China
| | - Min Wang
- State Key Laboratory of Cancer Biology, National Clinical Research Centre for Digestive Diseases and Xijing Hospital of Digestive Diseases, Fourth Military Medical University, Xi'an, China
| | - Zhengwu Peng
- Division of Psychiatry, Xijing Hospital, Fourth Military Medical University, Xi'an, China
| | - Changcun Guo
- State Key Laboratory of Cancer Biology, National Clinical Research Centre for Digestive Diseases and Xijing Hospital of Digestive Diseases, Fourth Military Medical University, Xi'an, China
| | - Xiaohong Zheng
- State Key Laboratory of Cancer Biology, National Clinical Research Centre for Digestive Diseases and Xijing Hospital of Digestive Diseases, Fourth Military Medical University, Xi'an, China
| | - Xinmin Zhou
- State Key Laboratory of Cancer Biology, National Clinical Research Centre for Digestive Diseases and Xijing Hospital of Digestive Diseases, Fourth Military Medical University, Xi'an, China.
| | - Jingbo Wang
- State Key Laboratory of Cancer Biology, National Clinical Research Centre for Digestive Diseases and Xijing Hospital of Digestive Diseases, Fourth Military Medical University, Xi'an, China.
| | - Ying Han
- State Key Laboratory of Cancer Biology, National Clinical Research Centre for Digestive Diseases and Xijing Hospital of Digestive Diseases, Fourth Military Medical University, Xi'an, China.
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Wang L, Wang J, Cai W, Shi Y, Zhou X, Guo G, Guo C, Huang X, Han Z, Zhang S, Ma S, Zhou X, Fan D, Gershwin ME, Han Y. A Critical Evaluation of Liver Pathology in Humans with Danon Disease and Experimental Correlates in a Rat Model of LAMP-2 Deficiency. Clin Rev Allergy Immunol 2018; 53:105-116. [PMID: 28124283 DOI: 10.1007/s12016-017-8598-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Danon disease is a genetic deficiency in lysosome-associated membrane protein 2 (LAMP-2), a highly glycosylated constituent of the lysosomal membrane and characterized by a cardiomyopathy, skeletal muscle myopathy, and cognitive impairment. Patients, however, often manifest hepatic abnormalities, but liver function has not been well evaluated and the syndrome is relatively uncommon. Hence, we have taken advantage of a rat that has been deleted of LAMP-2 to study the relative role of LAMP-2 on liver function. Interestingly, rats deficient in LAMP-2 develop a striking increase in serum alkaline phosphatase (ALP) and a decrease in bile flow compared with wild-type littermates. Importantly and by ultrastructural analysis, deficient rats manifest dilated canaliculi that lack microvilli with evidence of bile-containing bodies. Moreover, following bile duct ligation, LAMP-2-deficient rats develop rapid and severe evidence of advanced cholestasis, with an increase in serum bilirubin, as early as 6 h later. In wild-type control rats, multidrug resistance-associated protein 2 (Mrp2) normally concentrates at the bile canalicular membranes to secrete conjugated bilirubin into bile. However, in LAMP-2y/- rats, Mrp2 was detected in hepatocytes compared with other canalicular proteins including P-glycoproteins, dipeptidyl peptidase IV (CD26), and aminopeptidase (CD13). Our data further suggest that LAMP-2 interacts with the membrane cytoskeletal proteins radixin and F-actin in determining the localization of integral membrane proteins.
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Affiliation(s)
- Lu Wang
- Xijing Hospital of Digestive Diseases, The Fourth Military Medical University, 127 Changle West Road, Xi'an, Shaanxi Province, 710032, China
| | - Jingbo Wang
- Xijing Hospital of Digestive Diseases, The Fourth Military Medical University, 127 Changle West Road, Xi'an, Shaanxi Province, 710032, China
| | - Weile Cai
- Xijing Hospital of Digestive Diseases, The Fourth Military Medical University, 127 Changle West Road, Xi'an, Shaanxi Province, 710032, China
| | - Yongquan Shi
- Xijing Hospital of Digestive Diseases, The Fourth Military Medical University, 127 Changle West Road, Xi'an, Shaanxi Province, 710032, China
| | - Xinmin Zhou
- Xijing Hospital of Digestive Diseases, The Fourth Military Medical University, 127 Changle West Road, Xi'an, Shaanxi Province, 710032, China
| | - Guanya Guo
- Xijing Hospital of Digestive Diseases, The Fourth Military Medical University, 127 Changle West Road, Xi'an, Shaanxi Province, 710032, China
| | - Changcun Guo
- Xijing Hospital of Digestive Diseases, The Fourth Military Medical University, 127 Changle West Road, Xi'an, Shaanxi Province, 710032, China
| | - Xiaofeng Huang
- Center of Electron Microscope, The Fourth Military Medical University, Xi'an, Shaanxi Province, 710032, China
| | - Zheyi Han
- Xijing Hospital of Digestive Diseases, The Fourth Military Medical University, 127 Changle West Road, Xi'an, Shaanxi Province, 710032, China
| | - Shuai Zhang
- Xijing Hospital of Digestive Diseases, The Fourth Military Medical University, 127 Changle West Road, Xi'an, Shaanxi Province, 710032, China
| | - Shuoyi Ma
- Xijing Hospital of Digestive Diseases, The Fourth Military Medical University, 127 Changle West Road, Xi'an, Shaanxi Province, 710032, China
| | - Xia Zhou
- Xijing Hospital of Digestive Diseases, The Fourth Military Medical University, 127 Changle West Road, Xi'an, Shaanxi Province, 710032, China
| | - Daiming Fan
- Xijing Hospital of Digestive Diseases, The Fourth Military Medical University, 127 Changle West Road, Xi'an, Shaanxi Province, 710032, China
| | - M Eric Gershwin
- Division of Rheumatology, Allergy and Clinical Immunology, University of California at Davis School of Medicine, 451 Health Sciences Drive, Suite 6510, Davis, CA, 95616, USA.
| | - Ying Han
- Xijing Hospital of Digestive Diseases, The Fourth Military Medical University, 127 Changle West Road, Xi'an, Shaanxi Province, 710032, China.
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van Bavel JJA, Vos MA, van der Heyden MAG. Cardiac Arrhythmias and Antiarrhythmic Drugs: An Autophagic Perspective. Front Physiol 2018. [PMID: 29527175 PMCID: PMC5829447 DOI: 10.3389/fphys.2018.00127] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Degradation of cellular material by lysosomes is known as autophagy, and its main function is to maintain cellular homeostasis for growth, proliferation and survival of the cell. In recent years, research has focused on the characterization of autophagy pathways. Targeting of autophagy mediators has been described predominantly in cancer treatment, but also in neurological and cardiovascular diseases. Although the number of studies is still limited, there are indications that activity of autophagy pathways increases under arrhythmic conditions. Moreover, an increasing number of antiarrhythmic and non-cardiac drugs are found to affect autophagy pathways. We, therefore, suggest that future work should recognize the largely unaddressed effects of antiarrhythmic agents and other classes of drugs on autophagy pathway activation and inhibition.
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Affiliation(s)
- Joanne J A van Bavel
- Department of Medical Physiology, Division of Heart and Lungs, University Medical Center Utrecht, Utrecht, Netherlands
| | - Marc A Vos
- Department of Medical Physiology, Division of Heart and Lungs, University Medical Center Utrecht, Utrecht, Netherlands
| | - Marcel A G van der Heyden
- Department of Medical Physiology, Division of Heart and Lungs, University Medical Center Utrecht, Utrecht, Netherlands
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Small-Vessel Vasculopathy Due to Aberrant Autophagy in LAMP-2 Deficiency. Sci Rep 2018; 8:3326. [PMID: 29463847 PMCID: PMC5820257 DOI: 10.1038/s41598-018-21602-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2017] [Accepted: 02/06/2018] [Indexed: 02/02/2023] Open
Abstract
Lysosomal associated membrane protein 2 (LAMP2) is physiologically implicated in autophagy. A genetic LAMP2 defect causes Danon disease, which consists of two major phenotypes of myopathy and cardiomyopathy. In addition, arteriopathy may manifest on rare occasions but the pathological basis remains unknown. We encountered two Danon families that developed small-vessel vasculopathy in the coronary or cerebral arteries. To investigate the underlying mechanisms, we characterized the biological features of LAMP-2–deficient mice and cultured cells. LAMP-2–deficient mice at 9–24 months of age showed medial thickening with luminal stenosis due to proliferation of vascular smooth muscle cells (VSMC) in muscular arteries. Ultrastructural analysis of VSMC revealed various autophagic vacuoles scattered throughout the cytoplasm, suggesting impaired autophagy of long-lived metabolites and degraded organelles (i.e., mitochondria). The VSMC in Lamp2 null mice expressed more vimentin but less α-smooth muscle actin (α-SMA), indicating a switch from contractile to synthetic phenotype. Silencing of LAMP2 in cultured human brain VSMC showed the same phenotypic transition with mitochondrial fragmentation, enhanced mitochondrial respiration, and overproduction of reactive oxygen species (ROS). These findings indicate that LAMP-2 deficiency leads to arterial medial hypertrophy with the phenotypic conversion of VSMC, resulting from age-dependent accumulation of cellular waste generated by aberrant autophagy.
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Podinovskaia M, Spang A. The Endosomal Network: Mediators and Regulators of Endosome Maturation. ENDOCYTOSIS AND SIGNALING 2018; 57:1-38. [DOI: 10.1007/978-3-319-96704-2_1] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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Imaging of Left Ventricular Hypertrophy: a Practical Utility for Differential Diagnosis and Assessment of Disease Severity. Curr Cardiol Rep 2017. [PMID: 28639223 DOI: 10.1007/s11886-017-0875-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
PURPOSE OF REVIEW Left ventricular hypertrophy (LVH) is often encountered in clinical practice, and it is a risk factor for cardiac mortality and morbidity. Determination of the etiology and disease severity is important for the management of patients with LVH. The aim of this review is to show the remarkable progress in cardiac imaging and its importance in clinical practice. RECENT FINDINGS This review focuses on clinical features and characteristic cardiac imaging in LVH caused by various diseases including hypertension, aortic valve stenosis, hypertrophic cardiomyopathy, and secondary cardiomyopathies. The usefulness of echocardiography as a tool of general versatility including hemodynamic evaluation and the usefulness of cardiac magnetic resonance imaging for assessment of cardiac morphology and myocardial tissue characteristics of relevance for LVH are described. Imaging modalities now have central roles in the differentiation and prognostic assessment of LVH.
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Nelson BC, Hashem SI, Adler ED. Human-Induced Pluripotent Stem Cell-Based Modeling of Cardiac Storage Disorders. Curr Cardiol Rep 2017; 19:26. [PMID: 28251514 DOI: 10.1007/s11886-017-0829-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
PURPOSE OF REVIEW The aim of this study is to review the published human-induced pluripotent stem cell-derived cardiomyocyte (hiPSC-CM) models of cardiac storage disorders and to evaluate the limitations and future applications of this technology. RECENT FINDINGS Several cardiac storage disorders (CSDs) have been modeled using patient-specific hiPSC-CMs, including Anderson-Fabry disease, Danon disease, and Pompe disease. These models have shown that patient-specific hiPSC-CMs faithfully recapitulate key phenotypic features of CSDs and respond predictably to pharmacologic manipulation. hiPSC-CMs generated from patients with CSDs are representative models of the patient disease state and can be used as an in vitro system for the study of human cardiomyocytes. While these models suffer from several limitations, they are likely to play an important role in future mechanistic studies of cardiac storage disorders and the development of targeted therapeutics for these diseases.
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Affiliation(s)
- Bradley C Nelson
- Department of Medicine, Division of Cardiology, University of California San Diego, 9500 Gilman Drive, Biomedical Research Facility, Room 1217 AA, La Jolla, CA, 92093, USA
| | - Sherin I Hashem
- Department of Medicine, Division of Cardiology, University of California San Diego, 9500 Gilman Drive, Biomedical Research Facility, Room 1217 AA, La Jolla, CA, 92093, USA
| | - Eric D Adler
- Department of Medicine, Division of Cardiology, University of California San Diego, 9500 Gilman Drive, Biomedical Research Facility, Room 1217 AA, La Jolla, CA, 92093, USA.
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76
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Loss of APOBEC1 RNA-editing function in microglia exacerbates age-related CNS pathophysiology. Proc Natl Acad Sci U S A 2017; 114:13272-13277. [PMID: 29167375 DOI: 10.1073/pnas.1710493114] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Microglia (MG), a heterogeneous population of phagocytic cells, play important roles in central nervous system (CNS) homeostasis and neural plasticity. Under steady-state conditions, MG maintain homeostasis by producing antiinflammatory cytokines and neurotrophic factors, support myelin production, and remove synapses and cellular debris, as well as participating in "cross-correction," a process that supplies neurons with key factors for executing autophagy-lysosomal function. As sentinels for the immune system, MG also detect "danger" signals (pathogenic or traumatic insult), become activated, produce proinflammatory cytokines, and recruit monocytes and dendritic cells to the site of damage through a breached blood-brain barrier or via brain lymphatics. Failure to effectively resolve MG activation can be problematic and can lead to chronic inflammation, a condition proposed to underlie CNS pathophysiology in heritable brain disorders and age-related neurodegenerative and cognitive decline. Here, we show that APOBEC1-mediated RNA editing occurs within MG and is key to maintaining their resting status. Like bone marrow-derived macrophages, RNA editing in MG leads to overall changes in the abundance of edited proteins that coordinate the function of multiple cellular pathways. Conversely, mice lacking the APOBEC1 editing function in MG display evidence of dysregulation, with progressive age-related signs of neurodegeneration, characterized by clustering of activated MG, aberrant myelination, increased inflammation, and lysosomal anomalies that culminate in behavioral and motor deficiencies. Collectively, our study identifies posttranscriptional modification by RNA editing as a critical regulatory mechanism of vital cellular functions that maintain overall brain health.
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Menzies FM, Fleming A, Caricasole A, Bento CF, Andrews SP, Ashkenazi A, Füllgrabe J, Jackson A, Jimenez Sanchez M, Karabiyik C, Licitra F, Lopez Ramirez A, Pavel M, Puri C, Renna M, Ricketts T, Schlotawa L, Vicinanza M, Won H, Zhu Y, Skidmore J, Rubinsztein DC. Autophagy and Neurodegeneration: Pathogenic Mechanisms and Therapeutic Opportunities. Neuron 2017; 93:1015-1034. [PMID: 28279350 DOI: 10.1016/j.neuron.2017.01.022] [Citation(s) in RCA: 766] [Impact Index Per Article: 109.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Revised: 01/23/2017] [Accepted: 01/24/2017] [Indexed: 12/11/2022]
Abstract
Autophagy is a conserved pathway that delivers cytoplasmic contents to the lysosome for degradation. Here we consider its roles in neuronal health and disease. We review evidence from mouse knockout studies demonstrating the normal functions of autophagy as a protective factor against neurodegeneration associated with intracytoplasmic aggregate-prone protein accumulation as well as other roles, including in neuronal stem cell differentiation. We then describe how autophagy may be affected in a range of neurodegenerative diseases. Finally, we describe how autophagy upregulation may be a therapeutic strategy in a wide range of neurodegenerative conditions and consider possible pathways and druggable targets that may be suitable for this objective.
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Affiliation(s)
- Fiona M Menzies
- Department of Medical Genetics, Cambridge Institute for Medical Research, Cambridge Biomedical Campus, Wellcome Trust/MRC Building, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0XY, UK
| | - Angeleen Fleming
- Department of Medical Genetics, Cambridge Institute for Medical Research, Cambridge Biomedical Campus, Wellcome Trust/MRC Building, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0XY, UK
| | - Andrea Caricasole
- Alzheimer's Research UK Cambridge Drug Discovery Institute, University of Cambridge, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0AH, UK
| | - Carla F Bento
- Department of Medical Genetics, Cambridge Institute for Medical Research, Cambridge Biomedical Campus, Wellcome Trust/MRC Building, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0XY, UK
| | - Stephen P Andrews
- Alzheimer's Research UK Cambridge Drug Discovery Institute, University of Cambridge, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0AH, UK
| | - Avraham Ashkenazi
- Department of Medical Genetics, Cambridge Institute for Medical Research, Cambridge Biomedical Campus, Wellcome Trust/MRC Building, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0XY, UK
| | - Jens Füllgrabe
- Department of Medical Genetics, Cambridge Institute for Medical Research, Cambridge Biomedical Campus, Wellcome Trust/MRC Building, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0XY, UK
| | - Anne Jackson
- Department of Medical Genetics, Cambridge Institute for Medical Research, Cambridge Biomedical Campus, Wellcome Trust/MRC Building, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0XY, UK
| | - Maria Jimenez Sanchez
- Department of Medical Genetics, Cambridge Institute for Medical Research, Cambridge Biomedical Campus, Wellcome Trust/MRC Building, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0XY, UK
| | - Cansu Karabiyik
- Department of Medical Genetics, Cambridge Institute for Medical Research, Cambridge Biomedical Campus, Wellcome Trust/MRC Building, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0XY, UK
| | - Floriana Licitra
- Department of Medical Genetics, Cambridge Institute for Medical Research, Cambridge Biomedical Campus, Wellcome Trust/MRC Building, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0XY, UK
| | - Ana Lopez Ramirez
- Department of Medical Genetics, Cambridge Institute for Medical Research, Cambridge Biomedical Campus, Wellcome Trust/MRC Building, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0XY, UK
| | - Mariana Pavel
- Department of Medical Genetics, Cambridge Institute for Medical Research, Cambridge Biomedical Campus, Wellcome Trust/MRC Building, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0XY, UK
| | - Claudia Puri
- Department of Medical Genetics, Cambridge Institute for Medical Research, Cambridge Biomedical Campus, Wellcome Trust/MRC Building, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0XY, UK
| | - Maurizio Renna
- Department of Medical Genetics, Cambridge Institute for Medical Research, Cambridge Biomedical Campus, Wellcome Trust/MRC Building, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0XY, UK
| | - Thomas Ricketts
- Department of Medical Genetics, Cambridge Institute for Medical Research, Cambridge Biomedical Campus, Wellcome Trust/MRC Building, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0XY, UK
| | - Lars Schlotawa
- Department of Medical Genetics, Cambridge Institute for Medical Research, Cambridge Biomedical Campus, Wellcome Trust/MRC Building, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0XY, UK
| | - Mariella Vicinanza
- Department of Medical Genetics, Cambridge Institute for Medical Research, Cambridge Biomedical Campus, Wellcome Trust/MRC Building, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0XY, UK
| | - Hyeran Won
- Department of Medical Genetics, Cambridge Institute for Medical Research, Cambridge Biomedical Campus, Wellcome Trust/MRC Building, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0XY, UK
| | - Ye Zhu
- Department of Medical Genetics, Cambridge Institute for Medical Research, Cambridge Biomedical Campus, Wellcome Trust/MRC Building, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0XY, UK
| | - John Skidmore
- Alzheimer's Research UK Cambridge Drug Discovery Institute, University of Cambridge, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0AH, UK
| | - David C Rubinsztein
- Department of Medical Genetics, Cambridge Institute for Medical Research, Cambridge Biomedical Campus, Wellcome Trust/MRC Building, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0XY, UK.
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Hashem SI, Murphy AN, Divakaruni AS, Klos ML, Nelson BC, Gault EC, Rowland TJ, Perry CN, Gu Y, Dalton ND, Bradford WH, Devaney EJ, Peterson KL, Jones KL, Taylor MR, Chen J, Chi NC, Adler ED. Impaired mitophagy facilitates mitochondrial damage in Danon disease. J Mol Cell Cardiol 2017; 108:86-94. [DOI: 10.1016/j.yjmcc.2017.05.007] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Revised: 05/14/2017] [Accepted: 05/15/2017] [Indexed: 12/27/2022]
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Leone DA, Peschel A, Brown M, Schachner H, Ball MJ, Gyuraszova M, Salzer-Muhar U, Fukuda M, Vizzardelli C, Bohle B, Rees AJ, Kain R. Surface LAMP-2 Is an Endocytic Receptor That Diverts Antigen Internalized by Human Dendritic Cells into Highly Immunogenic Exosomes. THE JOURNAL OF IMMUNOLOGY 2017; 199:531-546. [DOI: 10.4049/jimmunol.1601263] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Accepted: 05/10/2017] [Indexed: 12/13/2022]
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80
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Munteanu I, Kalimo H, Saraste A, Nishino I, Minassian BA. Cardiac autophagic vacuolation in severe X-linked myopathy with excessive autophagy. Neuromuscul Disord 2017; 27:185-187. [DOI: 10.1016/j.nmd.2016.10.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2015] [Revised: 08/19/2016] [Accepted: 10/17/2016] [Indexed: 12/24/2022]
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81
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High resolution structural evidence suggests the Sarcoplasmic Reticulum forms microdomains with Acidic Stores (lysosomes) in the heart. Sci Rep 2017; 7:40620. [PMID: 28094777 PMCID: PMC5240626 DOI: 10.1038/srep40620] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Accepted: 12/09/2016] [Indexed: 01/10/2023] Open
Abstract
Nicotinic Acid Adenine Dinucleotide Phosphate (NAADP) stimulates calcium release from acidic stores such as lysosomes and is a highly potent calcium-mobilising second messenger. NAADP plays an important role in calcium signalling in the heart under basal conditions and following β-adrenergic stress. Nevertheless, the spatial interaction of acidic stores with other parts of the calcium signalling apparatus in cardiac myocytes is unknown. We present evidence that lysosomes are intimately associated with the sarcoplasmic reticulum (SR) in ventricular myocytes; a median separation of 20 nm in 2D electron microscopy and 3.3 nm in 3D electron tomography indicates a genuine signalling microdomain between these organelles. Fourier analysis of immunolabelled lysosomes suggests a sarcomeric pattern (dominant wavelength 1.80 μm). Furthermore, we show that lysosomes form close associations with mitochondria (median separation 6.2 nm in 3D studies) which may provide a basis for the recently-discovered role of NAADP in reperfusion-induced cell death. The trigger hypothesis for NAADP action proposes that calcium release from acidic stores subsequently acts to enhance calcium release from the SR. This work provides structural evidence in cardiac myocytes to indicate the formation of microdomains between acidic and SR calcium stores, supporting emerging interpretations of NAADP physiology and pharmacology in heart.
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Marino M, Musumeci O, Paleologo G, Cucinotta M, Migliorato A, Rodolico C, Toscano A. Ischemic stroke due to hypoperfusion in a patient with a previously unrecognized Danon disease. Neuromuscul Disord 2016; 26:890-894. [PMID: 27816333 DOI: 10.1016/j.nmd.2016.09.025] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Revised: 09/29/2016] [Accepted: 09/30/2016] [Indexed: 12/27/2022]
Abstract
Danon disease, an X-linked multisystemic disorder, is due to deficiency of Lysosome-Associated Membrane Protein 2 (LAMP2). It is usually characterized by hypertrophic cardiomyopathy, mental retardation and skeletal myopathy, sometimes also with atypical features. A 20-year-old man with cognitive impairment was admitted to the Emergency Room because of a sudden chest pain. ECG showed Wolff-Parkinson-White syndrome; echocardiography revealed hypertrophic cardiomyopathy, and, shortly after, he experienced a cardiac arrest followed by an occipital ischemic stroke. On neurological examination, he complained of visual loss, and diffuse muscle wasting and weakness were also unexpectedly noted. Electromyography evidenced a myopathic pattern and a peripheral neuropathy. A muscle biopsy disclosed vacuolar myopathy with glycogen storage; immunohistochemical studies demonstrated a LAMP-2 deficiency. LAMP2 molecular analysis identified a "de novo" mutation (p. Q353X). This patient with a neglected Danon disease, experienced an unusual complication as a stroke due to cerebral hypoperfusion after cardiac arrest caused by WPW syndrome.
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Affiliation(s)
- Marco Marino
- Department of Clinical and Experimental Medicine, University of Messina, Messina, Italy
| | - Olimpia Musumeci
- Department of Clinical and Experimental Medicine, University of Messina, Messina, Italy
| | - Giuseppe Paleologo
- Department of Cardiovascular Diseases, Papardo - Piemonte Hospital, Messina, Italy
| | - Maria Cucinotta
- Department of Clinical and Experimental Medicine, University of Messina, Messina, Italy
| | - Alba Migliorato
- Department of Clinical and Experimental Medicine, University of Messina, Messina, Italy
| | - Carmelo Rodolico
- Department of Clinical and Experimental Medicine, University of Messina, Messina, Italy
| | - Antonio Toscano
- Department of Clinical and Experimental Medicine, University of Messina, Messina, Italy.
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83
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Kraker J, Viswanathan SK, Knöll R, Sadayappan S. Recent Advances in the Molecular Genetics of Familial Hypertrophic Cardiomyopathy in South Asian Descendants. Front Physiol 2016; 7:499. [PMID: 27840609 PMCID: PMC5083855 DOI: 10.3389/fphys.2016.00499] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Accepted: 10/12/2016] [Indexed: 12/14/2022] Open
Abstract
The South Asian population, numbered at 1.8 billion, is estimated to comprise around 20% of the global population and 1% of the American population, and has one of the highest rates of cardiovascular disease. While South Asians show increased classical risk factors for developing heart failure, the role of population-specific genetic risk factors has not yet been examined for this group. Hypertrophic cardiomyopathy (HCM) is one of the major cardiac genetic disorders among South Asians, leading to contractile dysfunction, heart failure, and sudden cardiac death. This disease displays autosomal dominant inheritance, and it is associated with a large number of variants in both sarcomeric and non-sarcomeric proteins. The South Asians, a population with large ethnic diversity, potentially carries region-specific polymorphisms. There is high variability in disease penetrance and phenotypic expression of variants associated with HCM. Thus, extensive studies are required to decipher pathogenicity and the physiological mechanisms of these variants, as well as the contribution of modifier genes and environmental factors to disease phenotypes. Conducting genotype-phenotype correlation studies will lead to improved understanding of HCM and, consequently, improved treatment options for this high-risk population. The objective of this review is to report the history of cardiovascular disease and HCM in South Asians, present previously published pathogenic variants, and introduce current efforts to study HCM using induced pluripotent stem cell-derived cardiomyocytes, next-generation sequencing, and gene editing technologies. The authors ultimately hope that this review will stimulate further research, drive novel discoveries, and contribute to the development of personalized medicine with the aim of expanding therapeutic strategies for HCM.
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Affiliation(s)
- Jessica Kraker
- Department of Internal Medicine, Heart, Lung and Vascular Institute, Division of Cardiovascular Health and Sciences, University of Cincinnati College of Medicine Cincinnati, OH, USA
| | - Shiv Kumar Viswanathan
- Department of Internal Medicine, Heart, Lung and Vascular Institute, Division of Cardiovascular Health and Sciences, University of Cincinnati College of Medicine Cincinnati, OH, USA
| | - Ralph Knöll
- AstraZeneca R&D Mölndal, Innovative Medicines and Early Development, Cardiovascular and Metabolic Diseases iMedMölndal, Sweden; Integrated Cardio Metabolic Centre, Karolinska Institutet, Myocardial Genetics, Karolinska University Hospital in HuddingeHuddinge, Sweden
| | - Sakthivel Sadayappan
- Department of Internal Medicine, Heart, Lung and Vascular Institute, Division of Cardiovascular Health and Sciences, University of Cincinnati College of Medicine Cincinnati, OH, USA
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Hubert V, Peschel A, Langer B, Gröger M, Rees A, Kain R. LAMP-2 is required for incorporating syntaxin-17 into autophagosomes and for their fusion with lysosomes. Biol Open 2016; 5:1516-1529. [PMID: 27628032 PMCID: PMC5087675 DOI: 10.1242/bio.018648] [Citation(s) in RCA: 78] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Autophagy is an evolutionarily conserved process used for removing surplus and damaged proteins and organelles from the cytoplasm. The unwanted material is incorporated into autophagosomes that eventually fuse with lysosomes, leading to the degradation of their cargo. The fusion event is mediated by the interaction between the Qa-SNARE syntaxin-17 (STX17) on autophagosomes and the R-SNARE VAMP8 on lysosomes. Cells deficient in lysosome membrane-associated protein-2 (LAMP-2) have increased numbers of autophagosomes but the underlying mechanism is poorly understood. By transfecting LAMP-2-deficient and LAMP-1/2-double-deficient mouse embryonic fibroblasts (MEFs) with a tandem fluorescent-tagged LC3 we observed a failure of fusion between the autophagosomes and the lysosomes that could be rescued by complementation with LAMP-2A. Although we observed no change in expression and localization of VAMP8, its interacting partner STX17 was absent from autophagosomes of LAMP-2-deficient cells. Thus, LAMP-2 is essential for STX17 expression by the autophagosomes and this absence is sufficient to explain their failure to fuse with lysosomes. The results have clear implications for situations associated with a reduction of LAMP-2 expression. Summary: LAMP-2 is required for autophagosome-lysosome fusion. Its absence does not affect the lysosomal SNARE VAMP8 while its interacting partner STX17 is absent from the autophagosomes providing a molecular explanation for this fusion failure.
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Affiliation(s)
- Virginie Hubert
- Clinical Institute of Pathology, Medical University of Vienna, Vienna 1090, Austria
| | - Andrea Peschel
- Clinical Institute of Pathology, Medical University of Vienna, Vienna 1090, Austria
| | - Brigitte Langer
- Clinical Institute of Pathology, Medical University of Vienna, Vienna 1090, Austria
| | - Marion Gröger
- Core Facilities, Medical University of Vienna, Vienna 1090, Austria
| | - Andrew Rees
- Clinical Institute of Pathology, Medical University of Vienna, Vienna 1090, Austria
| | - Renate Kain
- Clinical Institute of Pathology, Medical University of Vienna, Vienna 1090, Austria
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85
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Morell C, Bort A, Vara-Ciruelos D, Ramos-Torres Á, Altamirano-Dimas M, Díaz-Laviada I, Rodríguez-Henche N. Up-Regulated Expression of LAMP2 and Autophagy Activity during Neuroendocrine Differentiation of Prostate Cancer LNCaP Cells. PLoS One 2016; 11:e0162977. [PMID: 27627761 PMCID: PMC5023108 DOI: 10.1371/journal.pone.0162977] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Accepted: 08/31/2016] [Indexed: 11/18/2022] Open
Abstract
Neuroendocrine (NE) prostate cancer (PCa) is a highly aggressive subtype of prostate cancer associated with resistance to androgen ablation therapy. In this study, we used LNCaP prostate cancer cells cultured in a serum-free medium for 6 days as a NE model of prostate cancer. Serum deprivation increased the expression of NE markers such as neuron-specific enolase (NSE) and βIII tubulin (βIII tub) and decreased the expression of the androgen receptor protein in LNCaP cells. Using cDNA microarrays, we compared gene expression profiles of NE cells and non-differentiated LNCaP cells. We identified up-regulation of 155 genes, among them LAMP2, a lysosomal membrane protein involved in lysosomal stability and autophagy. We then confirmed up-regulation of LAMP2 in NE cells by qRT-PCR, Western blot and confocal microscopy assays, showing that mRNA up-regulation correlated with increased levels of LAMP2 protein. Subsequently, we determined autophagy activity in NE cells by assessing the protein levels of SQSTM/p62 and LC3 by Western blot and LC3 and Atg5 mRNAs content by qRT-PCR. The decreased levels of SQSTM/p62 was accompanied by an enhanced expression of LC3 and ATG5, suggesting activation of autophagy in NE cells. Blockage of autophagy with 1μM AKT inhibitor IV, or by silencing Beclin 1 and Atg5, prevented NE cell differentiation, as revealed by decreased levels of the NE markers. In addition, AKT inhibitor IV as well as Beclin1 and Atg5 kwockdown attenuated LAMP2 expression in NE cells. On the other hand, LAMP2 knockdown by siRNA led to a marked blockage of autophagy, prevention of NE differentiation and decrease of cell survival. Taken together, these results suggest that LAMP2 overexpression assists NE differentiation of LNCaP cells induced by serum deprivation and facilitates autophagy activity in order to attain the NE phenotype and cell survival. LAMP2 could thus be a potential biomarker and potential target for NE prostate cancer.
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Affiliation(s)
- Cecilia Morell
- Department of Systems Biology, Biochemistry and Molecular Biology Unit, School of Medicine and Health Sciences, University of Alcalá, Alcalá de Henares, Spain
| | - Alicia Bort
- Department of Systems Biology, Biochemistry and Molecular Biology Unit, School of Medicine and Health Sciences, University of Alcalá, Alcalá de Henares, Spain
| | - Diana Vara-Ciruelos
- Cell Signalling and Immunology, College of Life Sciences, University of Dundee, Dundee, United Kingdom
| | - Ágata Ramos-Torres
- Department of Systems Biology, Biochemistry and Molecular Biology Unit, School of Medicine and Health Sciences, University of Alcalá, Alcalá de Henares, Spain
| | | | - Inés Díaz-Laviada
- Department of Systems Biology, Biochemistry and Molecular Biology Unit, School of Medicine and Health Sciences, University of Alcalá, Alcalá de Henares, Spain
| | - Nieves Rodríguez-Henche
- Department of Systems Biology, Biochemistry and Molecular Biology Unit, School of Medicine and Health Sciences, University of Alcalá, Alcalá de Henares, Spain
- * E-mail:
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86
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Riquelme JA, Chavez MN, Mondaca-Ruff D, Bustamante M, Vicencio JM, Quest AFG, Lavandero S. Therapeutic targeting of autophagy in myocardial infarction and heart failure. Expert Rev Cardiovasc Ther 2016; 14:1007-19. [PMID: 27308848 DOI: 10.1080/14779072.2016.1202760] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
INTRODUCTION Myocardial infarction (MI) is the leading cause of death. When MI is not lethal, heart failure (HF) is a major consequence with high prevalence and poor prognosis. The targeting of autophagy represents a potentially therapeutic approach for the treatment of both pathologies. AREAS COVERED PubMed searches were performed to discuss the current state of the art regarding the role of autophagy in MI and HF. We review available and potential approaches to modulate autophagy from a pharmacological and genetic perspective. We also discuss the targeting of autophagy in myocardial regeneration. Expert commentary: The targeting of autophagy has potential for the treatment of MI and HF. Autophagy is a process that takes place in virtually all cells of the body and thus, in order to evaluate this therapeutic approach in clinical trials, strategies that specifically target this process in the myocardium is required to avoid unwanted effects in other organs.
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Affiliation(s)
- Jaime A Riquelme
- a Advanced Center for Chronic Disease (ACCDiS) & Center for Molecular Studies of the Cell (CEMC), Facultad de Ciencias Químicas y Farmacéuticas & Facultad de Medicina , Universidad de Chile , Santiago , Chile
| | - Myra N Chavez
- a Advanced Center for Chronic Disease (ACCDiS) & Center for Molecular Studies of the Cell (CEMC), Facultad de Ciencias Químicas y Farmacéuticas & Facultad de Medicina , Universidad de Chile , Santiago , Chile.,b FONDAP Center for Genome Regulation, Facultad de Ciencias , Universidad de Chile , Santiago , Chile
| | - David Mondaca-Ruff
- a Advanced Center for Chronic Disease (ACCDiS) & Center for Molecular Studies of the Cell (CEMC), Facultad de Ciencias Químicas y Farmacéuticas & Facultad de Medicina , Universidad de Chile , Santiago , Chile
| | - Mario Bustamante
- a Advanced Center for Chronic Disease (ACCDiS) & Center for Molecular Studies of the Cell (CEMC), Facultad de Ciencias Químicas y Farmacéuticas & Facultad de Medicina , Universidad de Chile , Santiago , Chile.,c Advanced Center for Chronic Disease (ACCDiS), Division Enfermedades Cardiovasculares, Facultad de Medicina , Pontificia Universidad Catolica de Chile , Santiago , Chile
| | - Jose Miguel Vicencio
- a Advanced Center for Chronic Disease (ACCDiS) & Center for Molecular Studies of the Cell (CEMC), Facultad de Ciencias Químicas y Farmacéuticas & Facultad de Medicina , Universidad de Chile , Santiago , Chile.,d Cancer Institute , University College London , London , UK
| | - Andrew F G Quest
- a Advanced Center for Chronic Disease (ACCDiS) & Center for Molecular Studies of the Cell (CEMC), Facultad de Ciencias Químicas y Farmacéuticas & Facultad de Medicina , Universidad de Chile , Santiago , Chile
| | - Sergio Lavandero
- a Advanced Center for Chronic Disease (ACCDiS) & Center for Molecular Studies of the Cell (CEMC), Facultad de Ciencias Químicas y Farmacéuticas & Facultad de Medicina , Universidad de Chile , Santiago , Chile.,e Department of Internal Medicine, Cardiology Division , University of Texas Southwestern Medical Center , Dallas , TX , USA
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87
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Rowland TJ, Sweet ME, Mestroni L, Taylor MRG. Danon disease - dysregulation of autophagy in a multisystem disorder with cardiomyopathy. J Cell Sci 2016; 129:2135-43. [PMID: 27165304 PMCID: PMC4920246 DOI: 10.1242/jcs.184770] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Danon disease is a rare, severe X-linked form of cardiomyopathy caused by deficiency of lysosome-associated membrane protein 2 (LAMP-2). Other clinical manifestations include skeletal myopathy, cognitive defects and visual problems. Although individuals with Danon disease have been clinically described since the early 1980s, the underlying molecular mechanisms involved in pathological progression remain poorly understood. LAMP-2 is known to be involved in autophagy, and a characteristic accumulation of autophagic vacuoles in the affected tissues further supports the idea that autophagy is disrupted in this disease. The LAMP2 gene is alternatively spliced to form three splice isoforms, which are thought to play different autophagy-related cellular roles. This Commentary explores findings from genetic, histological, functional and tissue expression studies that suggest that the specific loss of the LAMP-2B isoform, which is likely to be involved in macroautophagy, plays a crucial role in causing the Danon phenotype. We also compare findings from mouse and cellular models, which have allowed for further molecular characterization but have also shown phenotypic differences that warrant attention. Overall, there is a need to better functionally characterize the LAMP-2B isoform in order to rationally explore more effective therapeutic options for individuals with Danon disease.
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Affiliation(s)
- Teisha J Rowland
- Cardiovascular Institute and Adult Medical Genetics Program, University of Colorado Denver, Aurora, CO 80045, USA
| | - Mary E Sweet
- Cardiovascular Institute and Adult Medical Genetics Program, University of Colorado Denver, Aurora, CO 80045, USA
| | - Luisa Mestroni
- Cardiovascular Institute and Adult Medical Genetics Program, University of Colorado Denver, Aurora, CO 80045, USA
| | - Matthew R G Taylor
- Cardiovascular Institute and Adult Medical Genetics Program, University of Colorado Denver, Aurora, CO 80045, USA
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88
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Approaching a Unified Theory for Particle-Induced Inflammation. CURRENT TOPICS IN ENVIRONMENTAL HEALTH AND PREVENTIVE MEDICINE 2016. [DOI: 10.1007/978-4-431-55732-6_3] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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89
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Berger S, Maccalli E. A 17-Year-Old Boy with Cardiac Arrest Occurring during Exercise. Pediatr Ann 2015; 44:530, 532. [PMID: 26678231 DOI: 10.3928/00904481-20151111-03] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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90
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Saraste A, Koskenvuo JW, Airaksinen J, Ramachandran N, Munteanu I, Udd B, Huovinen S, Kalimo H, Minassian BA. No cardiomyopathy in X-linked myopathy with excessive autophagy. Neuromuscul Disord 2015; 25:485-7. [PMID: 25845477 DOI: 10.1016/j.nmd.2015.03.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Revised: 03/05/2015] [Accepted: 03/09/2015] [Indexed: 01/12/2023]
Abstract
In X-linked myopathy with excessive autophagy (XMEA) progressive sarcoplasmic accumulation of autolysosomes filled with undegraded debris leads to atrophy and weakness of skeletal muscles. XMEA is caused by compromised acidification of lysosomes resulting from hypofunction of the proton pump vacuolar ATPase (V-ATPase), due to hypomorphic mutations in VMA21, whose protein product assembles V-ATPase. To what extent the cardiac muscle is affected is unknown. Therefore we performed a comprehensive cardiac evaluation in four male XMEA patients, and also examined pathology of one deceased patient's cardiac and skeletal muscle. None of the symptomatic men (aged 25-48 years) had history or symptoms of cardiomyopathy. Resting electrocardiograms and echocardiographies were normal. MRI showed normal left ventricle ejection fraction and myocardial mass. Myocardial late-gadolinium enhancement was not detected. The deceased patient's skeletal but not cardiac muscle showed characteristic accumulation of autophagic vacuoles. In conclusion, in classic XMEA the myocardium is structurally, electrically and clinically spared.
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Affiliation(s)
- Antti Saraste
- Heart Center, Turku University Hospital and University of Turku, Turku FI-20520, Finland; PET Centre, Turku University Hospital and University of Turku, Finland
| | - Juha W Koskenvuo
- Department of Clinical Physiology, Nuclear Medicine and PET, Turku University Hospital, Turku, Finland
| | - Juhani Airaksinen
- Heart Center, Turku University Hospital and University of Turku, Turku FI-20520, Finland
| | - Nivetha Ramachandran
- Program in Genetics and Genome Biology and Division of Neurology, Department of Paediatrics, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Iulia Munteanu
- Program in Genetics and Genome Biology and Division of Neurology, Department of Paediatrics, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Bjarne Udd
- Folkhälsan Institute of Genetics and Department of Medical Genetics, University of Helsinki, Helsinki, Finland; Neuromuscular Research Unit, Department of Neurology, University Hospital and University of Tampere, Tampere, Finland
| | - Sanna Huovinen
- Department of Pathology, Fimlab Laboratories, Tampere University Hospital, Tampere, Finland
| | - Hannu Kalimo
- Department of Pathology, University of Helsinki, Helsinki, Finland; Department of Forensic Medicine, Institute of Biomedicine, University of Turku, Turku, Finland.
| | - Berge A Minassian
- Program in Genetics and Genome Biology and Division of Neurology, Department of Paediatrics, The Hospital for Sick Children, Toronto, Ontario, Canada
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91
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Dowling JJ, Moore SA, Kalimo H, Minassian BA. X-linked myopathy with excessive autophagy: a failure of self-eating. Acta Neuropathol 2015; 129:383-90. [PMID: 25644398 DOI: 10.1007/s00401-015-1393-4] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Accepted: 01/22/2015] [Indexed: 12/15/2022]
Abstract
Autophagic vacuolar myopathies (AVMs) are a group of disorders united by shared histopathological features on muscle biopsy that include the aberrant accumulation of autophagic vacuoles. The classic conditions that compose the AVMs include Pompe Disease, Danon Disease and X-linked myopathy with excessive autophagy (XMEA). Other disorders, including acquired myopathies like chloroquine toxicity, also have features of an autophagic myopathy. This review is focused on XMEA, a myopathy with onset of slowly progressive proximal weakness and elevated serum creatine kinase (2× to 20× normal) typically in the first decade of life. However, both late-adult onset and severe, sometimes lethal, neonatal cases also occur. Skeletal muscle pathology is characterized by numerous cytoplasmic autophagic vacuoles, complex muscle fiber splitting with internalization of capillaries, and complement C5b-9 deposition within vacuoles and along the sarcolemma. The autophagic vacuoles have sarcolemmal features. Mutations in the VMA21 gene at Xq28 cause XMEA by reducing the activity of lysosomal hydrolases. The VMA21 protein regulates the assembly of the V-ATPase required to acidify the lysosome. Increased lysosomal pH and poor degradation of cellular debris may secondarily induce autophagy, the net effect being accumulation of autophagolysosomes. The relationship of XMEA to other lysosomal disorders of muscle and potential therapeutic interventions for XMEA are discussed.
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Affiliation(s)
- James J Dowling
- Division of Neurology and Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, ON, M5G 0A4, Canada,
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