scholarly journals Cofilin loss in Drosophila contributes to myopathy through defective sarcomerogenesis and aggregate formation during muscle growth

2019 ◽  
Author(s):  
Mridula Balakrishnan ◽  
Shannon F. Yu ◽  
Samantha M. Chin ◽  
David B. Soffar ◽  
Stefanie E. Windner ◽  
...  
Keyword(s):  
Point Mutation ◽  
Muscle Function ◽  
Muscle Growth ◽  
Nemaline Myopathy ◽  
Aggregate Formation ◽  
Thin Filaments ◽  
Sarcomeric Protein ◽  
Thick Filaments

SUMMARYSarcomeres, the fundamental contractile units of muscles, are conserved structures composed of actin thin filaments and myosin thick filaments. How sarcomeres are formed and maintained is not well understood. Here, we show that knockdown of Drosophila Cofilin (DmCFL), an actin depolymerizing factor, leads to the progressive disruption of sarcomere structure and muscle function in vivo. Loss of DmCFL also results in the formation of sarcomeric protein aggregates and impairs sarcomere addition during growth. Strikingly, activation of the proteasome delayed muscle deterioration in our model. Further, we investigate how a point mutation in CFL2 that causes nemaline myopathy (NM) in humans, affects CFL function and leads to the muscle phenotypes observed in vivo. Our data provide significant insights to the role of CFLs during sarcomere formation as well as mechanistic implications for disease progression in NM patients.

scholarly journals Dysregulation of NRAP degradation by KLHL41 contributes to pathophysiology in Nemaline Myopathy

2018 ◽  
Author(s):  
Caroline Jirka ◽  
Jasmine H Pak ◽  
Claire A Grosgogeat ◽  
Michael M Marchetti ◽  
Vandana A Gupta
Keyword(s):  
Skeletal Muscle ◽  
Thin Filament ◽  
Muscle Development ◽  
Nemaline Myopathy ◽  
Therapeutic Interventions ◽  
Transgenic Zebrafish ◽  
Sarcomeric Protein ◽  
And Function

Nemaline myopathy (NM) is the most common form of congenital myopathy that results in hypotonia and muscle weakness. This disease is clinically and genetically heterogeneous, but three recently discovered genes in NM encode for members of the Kelch family of proteins. Kelch proteins act as substrate-specific-adapters for CUL3 E3 ubiquitin ligase to regulate protein turn-over through the ubiquitin-proteasome machinery. Defects in thin filament formation and/or stability are key molecular processes that underlie the disease pathology in NM, however, the role of Kelch proteins in these processes in normal and diseases conditions remains elusive in vivo. Here, we describe a role of NM causing Kelch protein, KLHL41, in premyofibil-myofibil transition during skeletal muscle development through a regulation of the thin filament chaperone, NRAP. KLHL41 binds to the thin filament chaperone NRAP and promotes ubiquitination and subsequent degradation of NRAP, a process that is critical for the formation of mature myofibrils. KLHL41 deficiency results in abnormal accumulation of NRAP in muscle cells. NRAP overexpression in transgenic zebrafish resulted in a severe myopathic phenotype and absence of mature myofibrils demonstrating a role in disease pathology. Reducing Nrap levels in KLHL41 deficient zebrafish rescues the structural and function defects associated with disease pathology. We conclude that defects in KLHL41-mediated ubiquitination of sarcomeric protein contribute to structural and functional deficits in skeletal muscle. These findings further our understanding of how the sarcomere assembly is regulated by disease causing factors in vivo, which will be imperative for developing mechanism-based specific therapeutic interventions.

scholarly journals Structural basis for a complex I mutation that blocks pathological ROS production

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Zhan Yin ◽  
Nils Burger ◽  
Duvaraka Kula-Alwar ◽  
Dunja Aksentijević ◽  
Hannah R. Bridges ◽  
...  
Keyword(s):  
Point Mutation ◽  
Complex I ◽  
Structural Changes ◽  
Ischemia Reperfusion ◽  
Single Point ◽  
Structural Basis ◽  
Single Point Mutation ◽  
Ros Production

AbstractMitochondrial complex I is central to the pathological reactive oxygen species (ROS) production that underlies cardiac ischemia–reperfusion (IR) injury. ND6-P25L mice are homoplasmic for a disease-causing mtDNA point mutation encoding the P25L substitution in the ND6 subunit of complex I. The cryo-EM structure of ND6-P25L complex I revealed subtle structural changes that facilitate rapid conversion to the “deactive” state, usually formed only after prolonged inactivity. Despite its tendency to adopt the “deactive” state, the mutant complex is fully active for NADH oxidation, but cannot generate ROS by reverse electron transfer (RET). ND6-P25L mitochondria function normally, except for their lack of RET ROS production, and ND6-P25L mice are protected against cardiac IR injury in vivo. Thus, this single point mutation in complex I, which does not affect oxidative phosphorylation but renders the complex unable to catalyse RET, demonstrates the pathological role of ROS production by RET during IR injury.

scholarly journals FGF-2–dependent signaling activated in aged human skeletal muscle promotes intramuscular adipogenesis

2021 ◽  
Vol 118 (37) ◽  
pp. e2021013118 ◽  
Author(s):  
Sebastian Mathes ◽  
Alexandra Fahrner ◽  
Umesh Ghoshdastider ◽  
Hannes A. Rüdiger ◽  
Michael Leunig ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Transcriptional Activation ◽  
Human Skeletal Muscle ◽  
Muscle Growth ◽  
Muscle Cells ◽  
Adeno Associated Virus ◽  
Adult Skeletal Muscle

Aged skeletal muscle is markedly affected by fatty muscle infiltration, and strategies to reduce the occurrence of intramuscular adipocytes are urgently needed. Here, we show that fibroblast growth factor-2 (FGF-2) not only stimulates muscle growth but also promotes intramuscular adipogenesis. Using multiple screening assays upstream and downstream of microRNA (miR)-29a signaling, we located the secreted protein and adipogenic inhibitor SPARC to an FGF-2 signaling pathway that is conserved between skeletal muscle cells from mice and humans and that is activated in skeletal muscle of aged mice and humans. FGF-2 induces the miR-29a/SPARC axis through transcriptional activation of FRA-1, which binds and activates an evolutionary conserved AP-1 site element proximal in the miR-29a promoter. Genetic deletions in muscle cells and adeno-associated virus–mediated overexpression of FGF-2 or SPARC in mouse skeletal muscle revealed that this axis regulates differentiation of fibro/adipogenic progenitors in vitro and intramuscular adipose tissue (IMAT) formation in vivo. Skeletal muscle from human donors aged >75 y versus <55 y showed activation of FGF-2–dependent signaling and increased IMAT. Thus, our data highlights a disparate role of FGF-2 in adult skeletal muscle and reveals a pathway to combat fat accumulation in aged human skeletal muscle.

scholarly journals miR-206 family is important for mitochondrial and muscle function, but not essential for myogenesis in vitro

2019 ◽  
Author(s):  
Roza K. Przanowska ◽  
Ewelina Sobierajska ◽  
Zhangli Su ◽  
Kate Jensen ◽  
Piotr Przanowski ◽  
...  
Keyword(s):  
Muscle Function ◽  
Skeletal Muscle Regeneration ◽  
C2c12 Myoblasts ◽  
Skeletal Myoblasts ◽  
Microrna Targets ◽  
Microrna Family ◽  
Differentiation Pathways

AbstractmiR-206, miR-1a-1 and miR-1a-2 are induced during differentiation of skeletal myoblasts and promote myogenesis in vitro. miR-206 is required for skeletal muscle regeneration in vivo. Although this microRNA family is hypothesized to play an essential role in differentiation, a triple knockout of the three genes has not been done to test this hypothesis. We report that triple KO C2C12 myoblasts generated using CRISPR/Cas9 method differentiate despite the expected de-repression of the microRNA targets. Surprisingly, their mitochondrial function is diminished. Triple KO mice demonstrate partial embryonic lethality, most likely due to the role of miR-1a in cardiac muscle differentiation. Two triple KO mice survive and grow normally to adulthood with smaller myofiber diameter and diminished physical performance. Thus, unlike other microRNAs important in other differentiation pathways, the miR-206 family is not absolutely essential for myogenesis and is instead a modulator of optimal differentiation of skeletal myoblasts.

scholarly journals The nebulin repeat protein Lasp regulates I-band architecture and filament spacing in myofibrils

2014 ◽  
Vol 206 (4) ◽  
pp. 559-572 ◽  
Author(s):  
Isabelle Fernandes ◽  
Frieder Schöck
Keyword(s):  
Thin Filament ◽  
Muscle Protein ◽  
Nemaline Myopathy ◽  
Single Amino Acid ◽  
Actin Binding ◽  
Filament Length ◽  
Thin Filaments ◽  
Single Amino Acid Change ◽  
Filament Spacing

Mutations in nebulin, a giant muscle protein with 185 actin-binding nebulin repeats, are the major cause of nemaline myopathy in humans. Nebulin sets actin thin filament length in sarcomeres, potentially by stabilizing thin filaments in the I-band, where nebulin and thin filaments coalign. However, the precise role of nebulin in setting thin filament length and its other functions in regulating power output are unknown. Here, we show that Lasp, the only member of the nebulin family in Drosophila melanogaster, acts at two distinct sites in the sarcomere and controls thin filament length with just two nebulin repeats. We found that Lasp localizes to the Z-disc edges to control I-band architecture and also localizes at the A-band, where it interacts with both actin and myosin to set proper filament spacing. Furthermore, introducing a single amino acid change into the two nebulin repeats of Lasp demonstrated different roles for each domain and established Lasp as a suitable system for studying nebulin repeat function.

The influence of temperature on the thick filaments of vertebrate smooth muscle

1973 ◽  
Vol 265 (867) ◽  
pp. 197-202 ◽  
Keyword(s):  
Smooth Muscle ◽  
Guinea Pigs ◽  
Taenia Coli ◽  
Thin Filaments ◽  
Influence Of Temperature ◽  
Thick Filaments ◽  
Influence Of Temperature On ◽  
10 Nm Filaments ◽  
Ion Analysis

When fixation of taenia coli from adult guinea-pigs is initiated at 37 °C only thin filaments and 10 nm filaments are preserved. At 37 °G (i.e. as in vivo ) thick filaments are very labile; to preserve them during fixation much thinner muscles must be used such as taenia coli from very young animals. The thick filaments from taenia coli of adult guinea-pigs can however be stabilized by pre-cooling the living muscles before fixation at 37 °C. An ion analysis of these muscles in vivo, and during fixation at 37 and 4 °C, showed that there is a K and Na ion exchange in the tissue both on cooling and during fixation; the exchange is most rapid on fixation particularly when it takes place at 37 °C. The Mg 2+ content appears to be unaffected by these conditions, but the Ca 2+ content rises both on cooling and during fixation (when the uptake is unexpectedly large). The selective destruction of the cell membrane is greatest when fixation is carried out at 37 °C. It is suggested that pre-cooling may alter thick filaments.

scholarly journals Alterations at the Cross-Bridge Level Are Associated with a Paradoxical Gain of Muscle Function In Vivo in a Mouse Model of Nemaline Myopathy

PLoS ONE ◽  
2014 ◽  
Vol 9 (9) ◽  
pp. e109066 ◽  
Author(s):  
Charlotte Gineste ◽  
Coen Ottenheijm ◽  
Yann Le Fur ◽  
Sébastien Banzet ◽  
Emilie Pecchi ◽  
...  
Keyword(s):  
Mouse Model ◽  
Muscle Function ◽  
Nemaline Myopathy ◽  
Cross Bridge ◽  
The Cross

scholarly journals Multimodal MRI and 31P-MRS Investigations of the ACTA1(Asp286Gly) Mouse Model of Nemaline Myopathy Provide Evidence of Impaired In Vivo Muscle Function, Altered Muscle Structure and Disturbed Energy Metabolism

PLoS ONE ◽  
2013 ◽  
Vol 8 (8) ◽  
pp. e72294 ◽  
Author(s):  
Charlotte Gineste ◽  
Guillaume Duhamel ◽  
Yann Le Fur ◽  
Christophe Vilmen ◽  
Patrick J. Cozzone ◽  
...  
Keyword(s):  
Energy Metabolism ◽  
Mouse Model ◽  
Muscle Function ◽  
Nemaline Myopathy ◽  
Muscle Structure ◽  
31P Mrs ◽  
Multimodal Mri

Inflammation influences vascular remodeling through AT2 receptor expression and signaling

2000 ◽  
Vol 2 (1) ◽  
pp. 13-20 ◽  
Author(s):  
MASAHIRO AKISHITA ◽  
MASATSUGU HORIUCHI ◽  
HIROYUKI YAMADA ◽  
LUNAN ZHANG ◽  
GOTARO SHIRAKAMI ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Vascular Remodeling ◽  
Muscle Growth ◽  
Vascular Diseases ◽  
Lesion Size ◽  
Receptor Expression ◽  
Growth Inhibitory ◽  
Interferon Regulatory Factor 1

Akishita, Masahiro, Masatsugu Horiuchi, Hiroyuki Yamada, Lunan Zhang, Gotaro Shirakami, Kouichi Tamura, Yasuyoshi Ouchi, and Victor J. Dzau. Inflammation influences vascular remodeling through AT2 receptor expression and signaling. Physiol. Genomics 2: 13–20, 2000.—The AT2 receptor, which exerts growth inhibitory effects in cell culture, is present scantily in the adult vasculature but is reexpressed after vascular injury. To examine the in vivo role of this receptor in vascular diseases, we developed a mouse model of vascular remodeling and compared the responses in wild-type ( Agtr2+) and AT2 receptor knockout ( Agtr2−) mice. Polyethylene cuff placement on the femoral artery led to the vascular expression of cytokines, the transcriptional factor interferon regulatory factor-1 (IRF-1), and both the AT1 and AT2 receptors. Although the expressions of IRF-1 and AT1 receptor were induced to comparable levels in both the Agtr2+ and Agtr2− mice, the neointimal lesion size and the smooth muscle cell proliferation were twice greater in the Agtr2− than in the Agtr2+ mouse. Correlated with this difference, AT2 receptor expression was induced predominantly in the smooth muscle cells of Agtr2+ mouse. These results demonstrate that the AT2 receptor plays an important role in nonocclusive inflammatory injury by mediating the effects of inflammation on vascular smooth muscle growth inhibition.

scholarly journals Comparative Biomechanics of Thick Filaments and Thin Filaments with Functional Consequences for Muscle Contraction

2010 ◽  
Vol 2010 ◽  
pp. 1-14 ◽  
Author(s):  
Mark S. Miller ◽  
Bertrand C. W. Tanner ◽  
Lori R. Nyland ◽  
Jim O. Vigoreaux
Keyword(s):  
Mechanical Properties ◽  
Muscle Contraction ◽  
Material Properties ◽  
Muscle Function ◽  
Striated Muscle ◽  
Muscle Performance ◽  
Thin Filaments ◽  
Thick Filaments ◽  
Functional Consequences

The scaffold of striated muscle is predominantly comprised of myosin and actin polymers known as thick filaments and thin filaments, respectively. The roles these filaments play in muscle contraction are well known, but the extent to which variations in filament mechanical properties influence muscle function is not fully understood. Here we review information on the material properties of thick filaments, thin filaments, and their primary constituents; we also discuss ways in which mechanical properties of filaments impact muscle performance.

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