Rejuvenation of the muscle stem cell population restores strength to injured aged muscles.
Role of Telomere Dysfunction in Cardiac Failure in Duchenne Muscular Dystrophy
Nature Cell Biology
2013; 15 (8): 895-904
Short Telomeres and Stem Cell Exhaustion Model Duchenne Muscular Dystrophy in mdx/mTR Mice
2010; 143 (7): 1059-1071
The elderly often suffer from progressive muscle weakness and regenerative failure. We demonstrate that muscle regeneration is impaired with aging owing in part to a cell-autonomous functional decline in skeletal muscle stem cells (MuSCs). Two-thirds of MuSCs from aged mice are intrinsically defective relative to MuSCs from young mice, with reduced capacity to repair myofibers and repopulate the stem cell reservoir in vivo following transplantation. This deficiency is correlated with a higher incidence of cells that express senescence markers and is due to elevated activity of the p38α and p38β mitogen-activated kinase pathway. We show that these limitations cannot be overcome by transplantation into the microenvironment of young recipient muscles. In contrast, subjecting the MuSC population from aged mice to transient inhibition of p38α and p38β in conjunction with culture on soft hydrogel substrates rapidly expands the residual functional MuSC population from aged mice, rejuvenating its potential for regeneration and serial transplantation as well as strengthening of damaged muscles of aged mice. These findings reveal a synergy between biophysical and biochemical cues that provides a paradigm for a localized autologous muscle stem cell therapy for the elderly.
View details for DOI 10.1038/nm.3464
View details for PubMedID 24531378
Distinct Roles for Cell-Autonomous Notch Signaling in Cardiomyocytes of the Embryonic and Adult Heart
2010; 106 (3): 559-572
In Duchenne muscular dystrophy (DMD), dystrophin mutation leads to progressive lethal skeletal muscle degeneration. For unknown reasons, dystrophin deficiency does not recapitulate DMD in mice (mdx), which have mild skeletal muscle defects and potent regenerative capacity. We postulated that human DMD progression is a consequence of loss of functional muscle stem cells (MuSC), and the mild mouse mdx phenotype results from greater MuSC reserve fueled by longer telomeres. We report that mdx mice lacking the RNA component of telomerase (mdx/mTR) have shortened telomeres in muscle cells and severe muscular dystrophy that progressively worsens with age. Muscle wasting severity parallels a decline in MuSC regenerative capacity and is ameliorated histologically by transplantation of wild-type MuSC. These data show that DMD progression results, in part, from a cell-autonomous failure of MuSC to maintain the damage-repair cycle initiated by dystrophin deficiency. The essential role of MuSC function has therapeutic implications for DMD.
View details for DOI 10.1016/j.cell.2010.11.039
View details for Web of Science ID 000285625400005
View details for PubMedID 21145579
Antioxidant Amelioration of Dilated Cardiomyopathy Caused by Conditional Deletion of NEMO/IKK gamma in Cardiomyocytes
2010; 106 (1): 133-144
The Notch signaling pathway is important for cell-cell communication that controls tissue formation and homeostasis during embryonic and adult life, but the precise cell targets of Notch signaling in the mammalian heart remain poorly defined.To investigate the functional role of Notch signaling in the cardiomyocyte compartment of the embryonic and adult heart.Here, we report that either conditional overexpression of Notch1 intracellular domain (NICD1) or selective silencing of Notch signaling in the embryonic cardiomyocyte compartment results in developmental defects and perinatal lethality. In contrast, augmentation of endogenous Notch reactivation after myocardial infarction in the adult, either by inducing cardiomyocyte-specific Notch1 transgene expression or by intramyocardial delivery of a Notch1 pseudoligand, increases survival rate, improves cardiac functional performance, and minimizes fibrosis, promoting antiapoptotic and angiogenic mechanisms.These results reveal a strict requirement for cell-autonomous modulation of Notch signaling during heart morphogenesis, and illustrate how the same signaling pathway that promotes congenital heart defects when perturbed in the embryo can be therapeutically redeployed for the treatment of adult myocardial damage.
View details for DOI 10.1161/CIRCRESAHA.109.203034
View details for Web of Science ID 000274651400019
View details for PubMedID 20007915
A CREB-C/EBP beta cascade induces M2 macrophage-specific gene expression and promotes muscle injury repair
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2009; 106 (41): 17475-17480
Insight into the function of nuclear factor (NF)-kappaB in the adult heart has been hampered by the embryonic lethality of constitutive NF-kappaB inactivation.The goal of the present study was therefore to gain insights into the role of NF-kappaB pathway specifically in mouse cardiomyocytes by conditional deletion of the NF-kappaB essential modulator (NEMO).Using a Cre/loxP system, we disrupted the Nemo gene in a cardiomyocyte-specific manner in the heart, which simulated gene expression changes underlying human heart failure and caused adult-onset dilated cardiomyopathy accompanied by inflammation and apoptosis. Pressure overload challenges of NEMO-deficient young hearts precociously induced the functional decrements that develop spontaneously in older knockout animals. Moreover, oxidative stress in NEMO-deficient cardiomyocytes is a critical pathological component that can be attenuated with antioxidant diet in vivo.These results reveal an essential physiological role for NEMO-mediated signaling in the adult heart to maintain cardiac function in response to age-related or mechanical challenges, in part through modulation of oxidative stress.
View details for DOI 10.1161/CIRCRESAHA.109.202200
View details for Web of Science ID 000273403600022
View details for PubMedID 19850942
Targeted ablation of IKK2 improves skeletal muscle strength, maintains mass, and promotes regeneration
JOURNAL OF CLINICAL INVESTIGATION
2006; 116 (11): 2945-2954
Macrophages play an essential role in the resolution of tissue damage through removal of necrotic cells, thus paving the way for tissue regeneration. Macrophages also directly support the formation of new tissue to replace the injury, through their acquisition of an anti-inflammatory, or M2, phenotype, characterized by a gene expression program that includes IL-10, the IL-13 receptor, and arginase 1. We report that deletion of two CREB-binding sites from the Cebpb promoter abrogates Cebpb induction upon macrophage activation. This blocks the downstream induction of M2-specific Msr1, Il10, II13ra, and Arg-1 genes, whereas the inflammatory (M1) genes Il1, Il6, Tnfa, and Il12 are not affected. Mice carrying the mutated Cebpb promoter (betaDeltaCre) remove necrotic tissue from injured muscle, but exhibit severe defects in muscle fiber regeneration. Conditional deletion of the Cebpb gene in muscle cells does not affect regeneration, showing that the C/EBPbeta cascade leading to muscle repair is muscle-extrinsic. While betaDeltaCre macrophages efficiently infiltrate injured muscle they fail to upregulate Cebpb, leading to decreased Arg-1 expression. CREB-mediated induction of Cebpb expression is therefore required in infiltrating macrophages for upregulation of M2-specific genes and muscle regeneration, providing a direct genetic link between these two processes.
View details for DOI 10.1073/pnas.0908641106
View details for Web of Science ID 000270754400047
View details for PubMedID 19805133
Analysis of CRE-mediated recombination driven by myosin light chain 1/3 regulatory elements in embryonic and adult skeletal muscle: A tool to study fiber specification
2008; 46 (8): 424-430
NF-kappaB is a major pleiotropic transcription factor modulating immune, inflammatory, cell survival, and proliferative responses, yet the relevance of NF-kappaB signaling in muscle physiology and disease is less well documented. Here we show that muscle-restricted NF-kappaB inhibition in mice, through targeted deletion of the activating kinase inhibitor of NF-kappaB kinase 2 (IKK2), shifted muscle fiber distribution and improved muscle force. In response to denervation, IKK2 depletion protected against atrophy, maintaining fiber type, size, and strength, increasing protein synthesis, and decreasing protein degradation. IKK2-depleted mice with a muscle-specific transgene expressing a local Igf-1 isoform (mIgf-1) showed enhanced protection against muscle atrophy. In response to muscle damage, IKK2 depletion facilitated skeletal muscle regeneration through enhanced satellite cell activation and reduced fibrosis. Our results establish IKK2/NF-kappaB signaling as an important modulator of muscle homeostasis and suggest a combined role for IKK inhibitors and growth factors in the therapy of muscle diseases.
View details for DOI 10.1171/JCI28721
View details for Web of Science ID 000241810900018
View details for PubMedID 17080195
NF-kappa B signaling in skeletal muscle: prospects for intervention in muscle diseases
JOURNAL OF MOLECULAR MEDICINE-JMM
2008; 86 (7): 747-759
An increasing number of genes have been implicated in skeletal muscle fiber diversity. To study the contribution of diverse genetic elements to the regulation of fiber-type composition, we generated a transgenic mouse in which CRE recombinase expression is driven by muscle-specific regulatory sequences of the myosin light chain 1/3 locus (MLC). Using ROSA26 conditional reporter mice, we detected expression of the MLC-Cre transgene starting from embryonic day 12.5 (E12.5). By E15, recombination was detected in all muscle-derived structures. Immunohistochemical analysis revealed CRE activity was restricted to fast-twitch (type II) and excluded from slow-twitch (type I) fibers of skeletal muscle. The MLC-Cre transgenic mouse can be used in conjunction with conditional alleles to study both developmental patterning and maintenance of fast fiber-type phenotypes.
View details for DOI 10.1002/dvg.20419
View details for Web of Science ID 000258889900006
View details for PubMedID 18693277
A naturally occurring calcineurin variant inhibits FoxO activity and enhances skeletal muscle regeneration
JOURNAL OF CELL BIOLOGY
2007; 179 (6): 1205-1218
Muscle remodeling is an important physiological process that promotes adaptive changes in cytoarchitecture and protein composition after exercise, aging, or disease conditions. Numerous transcription factors have been reported to regulate skeletal muscle homeostasis. NF-kappaB is a major pleiotropic transcription factor modulating immune, inflammatory, cell survival, and proliferating responses; however, its role in muscle development, physiology, and disease has just started to be elucidated. The current review article aims to summarize the literature on the role of NF-kappaB signaling in skeletal muscle pathophysiology, investigated over the last years using in vitro and more recently in vivo systems. Understanding the exact role of NF-kappaB in muscle cells will allow better therapeutic manipulations in the setting of human muscle diseases.
View details for DOI 10.1007/s00109-008-0308-4
View details for Web of Science ID 000257123600003
View details for PubMedID 18246321
IGF-1, inflammation and stem cells: interactions during muscle regeneration
TRENDS IN IMMUNOLOGY
2005; 26 (10): 535-542
The calcium-activated phosphatase calcineurin (Cn) transduces physiological signals through intracellular pathways to influence the expression of specific genes. Here, we characterize a naturally occurring splicing variant of the CnAbeta catalytic subunit (CnAbeta1) in which the autoinhibitory domain that controls enzyme activation is replaced with a unique C-terminal region. The CnAbeta1 enzyme is constitutively active and dephosphorylates its NFAT target in a cyclosporine-resistant manner. CnAbeta1 is highly expressed in proliferating myoblasts and regenerating skeletal muscle fibers. In myoblasts, CnAbeta1 knockdown activates FoxO-regulated genes, reduces proliferation, and induces myoblast differentiation. Conversely, CnAbeta1 overexpression inhibits FoxO and prevents myotube atrophy. Supplemental CnAbeta1 transgene expression in skeletal muscle leads to enhanced regeneration, reduced scar formation, and accelerated resolution of inflammation. This unique mode of action distinguishes the CnAbeta1 isoform as a candidate for interventional strategies in muscle wasting treatment.
View details for DOI 10.1083/jcb.200704179
View details for Web of Science ID 000251697300014
View details for PubMedID 18086917
Mapping and identification of essential gene functions on the X chromosome of Drosophila
2002; 3 (1): 34-38
Insulin-like growth factor-I (IGF-1) is an important mediator in numerous developmental processes, such as proliferation, differentiation, survival, growth, apoptosis and regeneration. Mouse genetics have provided important insights into the signalling mechanisms that are necessary for the coordination of muscle repair. Recent studies on the role of IGF-1 in the promotion of cell recruitment to the injured muscle and the subsequent resolution of the inflammatory response have unveiled new perspectives into local repair mechanisms.
View details for DOI 10.1016/j.it.2005.08.002
View details for Web of Science ID 000232477600008
View details for PubMedID 16109502
From first base: The sequence of the tip of the X chromosome of Drosophila melanogaster, a comparison of two sequencing strategies
2001; 11 (5): 710-730
The Drosophila melanogaster genome consists of four chromosomes that contain 165 Mb of DNA, 120 Mb of which are euchromatic. The two Drosophila Genome Projects, in collaboration with Celera Genomics Systems, have sequenced the genome, complementing the previously established physical and genetic maps. In addition, the Berkeley Drosophila Genome Project has undertaken large-scale functional analysis based on mutagenesis by transposable P element insertions into autosomes. Here, we present a large-scale P element insertion screen for vital gene functions and a BAC tiling map for the X chromosome. A collection of 501 X-chromosomal P element insertion lines was used to map essential genes cytogenetically and to establish short sequence tags (STSs) linking the insertion sites to the genome. The distribution of the P element integration sites, the identified genes and transcription units as well as the expression patterns of the P-element-tagged enhancers is described and discussed.
View details for DOI 10.1093/embo-reports/kvf012
View details for Web of Science ID 000173651300009
View details for PubMedID 11751581
From sequence to chromosome: The tip of the X chromosome of D. melanogaster
2000; 287 (5461): 2220-2222
We present the sequence of a contiguous 2.63 Mb of DNA extending from the tip of the X chromosome of Drosophila melanogaster. Within this sequence, we predict 277 protein coding genes, of which 94 had been sequenced already in the course of studying the biology of their gene products, and examples of 12 different transposable elements. We show that an interval between bands 3A2 and 3C2, believed in the 1970s to show a correlation between the number of bands on the polytene chromosomes and the 20 genes identified by conventional genetics, is predicted to contain 45 genes from its DNA sequence. We have determined the insertion sites of P-elements from 111 mutant lines, about half of which are in a position likely to affect the expression of novel predicted genes, thus representing a resource for subsequent functional genomic analysis. We compare the European Drosophila Genome Project sequence with the corresponding part of the independently assembled and annotated Joint Sequence determined through "shotgun" sequencing. Discounting differences in the distribution of known transposable elements between the strains sequenced in the two projects, we detected three major sequence differences, two of which are probably explained by errors in assembly; the origin of the third major difference is unclear. In addition there are eight sequence gaps within the Joint Sequence. At least six of these eight gaps are likely to be sites of transposable elements; the other two are complex. Of the 275 genes in common to both projects, 60% are identical within 1% of their predicted amino-acid sequence and 31% show minor differences such as in choice of translation initiation or termination codons; the remaining 9% show major differences in interpretation.
View details for Web of Science ID 000168501600011
View details for PubMedID 11337470
One of the rewards of having a Drosophila melanogaster whole-genome sequence will be the potential to understand the molecular bases for structural features of chromosomes that have been a long-standing puzzle. Analysis of 2.6 megabases of sequence from the tip of the X chromosome of Drosophila identifies 273 genes. Cloned DNAs from the characteristic bulbous structure at the tip of the X chromosome in the region of the broad complex display an unusual pattern of in situ hybridization. Sequence analysis revealed that this region comprises 154 kilobases of DNA flanked by 1.2-kilobases of inverted repeats, each composed of a 350-base pair satellite related element. Thus, some aspects of chromosome structure appear to be revealed directly within the DNA sequence itself.
View details for Web of Science ID 000086049100038
View details for PubMedID 10731137