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Ochala, Julien
Publications (10 of 22) Show all publications
Lindqvist, J., Cheng, A. J., Renaud, G., Hardeman, E. C. & Ochala, J. (2013). Distinct Underlying Mechanisms of Limb and Respiratory Muscle Fiber Weaknesses in Nemaline Myopathy. Journal of Neuropathology and Experimental Neurology, 72(6), 472-481
Open this publication in new window or tab >>Distinct Underlying Mechanisms of Limb and Respiratory Muscle Fiber Weaknesses in Nemaline Myopathy
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2013 (English)In: Journal of Neuropathology and Experimental Neurology, ISSN 0022-3069, E-ISSN 1554-6578, Vol. 72, no 6, p. 472-481Article in journal (Refereed) Published
Abstract [en]

Nemaline myopathy is the most common congenital myopathy and is caused by mutations in various genes such as ACTA1 (encoding skeletal alpha-actin). It is associated with limb and respiratory muscle weakness. Despite increasing clinical and scientific interest, the molecular and cellular events leading to such weakness remain unknown, which prevents the development of specific therapeutic interventions. To unravel the potential mechanisms involved, we dissected lower limb and diaphragm muscles from a knock-in mouse model of severe nemaline myopathy expressing the ACTA1 His40Tyr actin mutation found in human patients. We then studied a broad range of structural and functional characteristics assessing single-myofiber contraction, protein expression, and electron microscopy. One of the major findings in the diaphragm was the presence of numerous noncontractile areas (including disrupted sarcomeric structures and nemaline bodies). This greatly reduced the number of functional sarcomeres, decreased the force generation capacity at the muscle fiber level, and likely would contribute to respiratory weakness. In limb muscle, by contrast, there were fewer noncontractile areas and they did not seem to have a major role in the pathogenesis of weakness. These divergent muscle-specific results provide new important insights into the pathophysiology of severe nemaline myopathy and crucial information for future development of therapeutic strategies.

Keywords
Actin, Contractile dysfunction, Limb muscle, Nemaline myopathy, Respiratory muscle, Weakness
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-204291 (URN)10.1097/NEN.0b013e318293b1cc (DOI)000319454400003 ()
Available from: 2013-07-30 Created: 2013-07-29 Last updated: 2017-12-06Bibliographically approved
Ochala, J. & Iwamoto, H. (2013). Myofilament lattice structure in presence of a skeletal myopathy-related tropomyosin mutation. Journal of Muscle Research and Cell Motility, 34(3-4), 171-175
Open this publication in new window or tab >>Myofilament lattice structure in presence of a skeletal myopathy-related tropomyosin mutation
2013 (English)In: Journal of Muscle Research and Cell Motility, ISSN 0142-4319, E-ISSN 1573-2657, Vol. 34, no 3-4, p. 171-175Article in journal (Refereed) Published
Abstract [en]

Human tropomyosin mutations deregulate skeletal muscle contraction at the cellular level. One key feature is the slowing of the kinetics of force development. The aim of the present study was to characterize the potential underlying molecular mechanisms by recording and analyzing the X-ray diffraction patterns of human membrane-permeabilized muscle cells expressing a particular beta-tropomyosin mutation (E41K). During resting conditions, the d(1,0) lattice spacing, Delta(1,0) and I-1,I-1 to I-1,I-0 ratio were not different from control values. These results suggest that, in presence of the E41K beta-tropomyosin mutation, the myofilament lattice geometry is well maintained and therefore may not have any detrimental influence on the contraction mechanisms and thus, on the rate of force generation.

Keywords
Tropomyosin, Muscle fibre, X-ray diffraction, Myopathy
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-214058 (URN)10.1007/s10974-013-9345-x (DOI)000328210800004 ()
Available from: 2014-01-07 Created: 2014-01-07 Last updated: 2017-12-06Bibliographically approved
Renaud, G., Llano-Diez, M., Ravar, B., Gorza, L., Feng, H.-Z., Jin, J.-P., . . . Larsson, L. (2013). Sparing of muscle mass and function by passive loading in an experimental intensive care unit model. Journal of Physiology, 591(5), 1385-1402
Open this publication in new window or tab >>Sparing of muscle mass and function by passive loading in an experimental intensive care unit model
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2013 (English)In: Journal of Physiology, ISSN 0022-3751, E-ISSN 1469-7793, Vol. 591, no 5, p. 1385-1402Article in journal (Refereed) Published
Abstract [en]

The response to mechanical stimuli, i.e., tensegrity, plays an important role in regulating cell physiological and pathophysiological function and the mechanical silencing observed in intensive care unit (ICU) patients leads to a severe and specific muscle wasting condition. This study aims at unravelling the underlying mechanisms and the effects of passive mechanical loading on skeletal muscle mass and function at the gene, protein and cellular levels. A unique experimental rat ICU model has been used allowing long-term (weeks) time-resolved analyses of the effects of standardized unilateral passive mechanical loading on skeletal muscle size and function and underlying mechanisms. Results show that passive mechanical loading alleviated the muscle wasting and the loss of force-generation associated with the ICU intervention, resulting in a doubling of the functional capacity of the loaded vs. the unloaded muscles after a 2-week ICU intervention. We demonstrated that the improved maintenance of muscle mass and function is likely a consequence of a reduced oxidative stress revealed by lower levels of carbonylated proteins, and a reduced loss of the molecular motor protein myosin. A complex temporal gene expression pattern, delineated by microarray analysis, was observed with loading-induced changes in transcript levels of sarcomeric proteins, muscle developmental processes, stress response, ECM/cell adhesion proteins and metabolism. Thus, the results from this study show that passive mechanical loading alleviates the severe negative consequences on muscle size and function associated with the mechanical silencing in ICU patients, strongly supporting early and intense physical therapy in immobilized ICU patients.

National Category
Clinical Laboratory Medicine
Research subject
Clinical Neurophysiology
Identifiers
urn:nbn:se:uu:diva-189247 (URN)10.1113/jphysiol.2012.248724 (DOI)000315514300018 ()23266938 (PubMedID)
Available from: 2012-12-28 Created: 2012-12-28 Last updated: 2017-12-06Bibliographically approved
Lindqvist, J. M. & Ochala, J. (2013). The Cardiac Alkali Myosin Light Chain Can Restore Skeletal Muscle Function in a Mouse Model of Nemaline Myopathy. Paper presented at 16th Annual Meeting of the American-Society-of-Gene-and-Cell-Therapy (ASGCT), MAY 15-18, 2013, Salt Lake City, UT. Molecular Therapy, 21, S68-S68
Open this publication in new window or tab >>The Cardiac Alkali Myosin Light Chain Can Restore Skeletal Muscle Function in a Mouse Model of Nemaline Myopathy
2013 (English)In: Molecular Therapy, ISSN 1525-0016, E-ISSN 1525-0024, Vol. 21, p. S68-S68Article in journal, Meeting abstract (Other academic) Published
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-203416 (URN)000319858400173 ()
Conference
16th Annual Meeting of the American-Society-of-Gene-and-Cell-Therapy (ASGCT), MAY 15-18, 2013, Salt Lake City, UT
Available from: 2013-07-10 Created: 2013-07-10 Last updated: 2017-12-06Bibliographically approved
Lindqvist, J., Iwamoto, H., Blanco, G. & Ochala, J. (2013). The fraction of strongly bound cross-bridges is increased in mice that carry the myopathy-linked myosin heavy chain mutation MYH4(L342Q). Disease Models and Mechanisms, 6(3), 834-840
Open this publication in new window or tab >>The fraction of strongly bound cross-bridges is increased in mice that carry the myopathy-linked myosin heavy chain mutation MYH4(L342Q)
2013 (English)In: Disease Models and Mechanisms, ISSN 1754-8403, E-ISSN 1754-8411, Vol. 6, no 3, p. 834-840Article in journal (Refereed) Published
Abstract [en]

Myosinopathies have emerged as a new group of diseases and are caused by mutations in genes encoding myosin heavy chain (MyHC) isoforms. One major hallmark of these diseases is skeletal muscle weakness or paralysis, but the underlying molecular mechanisms remain unclear. Here, we have undertaken a detailed functional study of muscle fibers from Myh4(arl) mice, which carry a mutation that provokes an L342Q change within the catalytic domain of the type IIb skeletal muscle myosin protein MYH4. Because homozygous animals develop rapid muscle-structure disruption and lower-limb paralysis, they must be killed by postnatal day 13, so all experiments were performed using skeletal muscles from adult heterozygous animals (Myh4(arl)/+). Myh4(arl)/+ mice contain MYH4(L342Q) expressed at 7% of the levels of the wild-type (WT) protein, and are overtly and histologically normal. However, mechanical and X-ray diffraction pattern analyses of single membrane-permeabilized fibers revealed, upon maximal Ca2+ activation, higher stiffness as well as altered meridional and equatorial reflections in Myh4(arl)/+ mice when compared with age-matched WT animals. Under rigor conditions, by contrast, no difference was observed between Myh4(arl)/+ and WT mice. Altogether, these findings prove that, in adult MYH4(L342Q) heterozygous mice, the transition from weak to strong myosin cross-bridge binding is facilitated, increasing the number of strongly attached myosin heads, thus enhancing force production. These changes are predictably exacerbated in the type IIb fibers of homozygous mice, in which the embryonic myosin isoform is fully replaced by MYH4(L342Q), leading to a hypercontraction, muscle-structure disruption and lower-limb paralysis. Overall, these findings provide important insights into the molecular pathogenesis of skeletal myosinopathies.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-202382 (URN)10.1242/dmm.011155 (DOI)000318847400029 ()
Available from: 2013-06-24 Created: 2013-06-24 Last updated: 2017-12-06Bibliographically approved
Lindqvist, J., Penisson-Besnier, I., Iwamoto, H., Li, M., Yagi, N. & Ochala, J. (2012). A myopathy-related actin mutation increases contractile function. Acta Neuropathologica, 123(5), 739-746
Open this publication in new window or tab >>A myopathy-related actin mutation increases contractile function
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2012 (English)In: Acta Neuropathologica, ISSN 0001-6322, E-ISSN 1432-0533, Vol. 123, no 5, p. 739-746Article in journal (Refereed) Published
Abstract [en]

Nemaline myopathy (NM) is the most common congenital myopathy and is caused by mutations in various genes including NEB (nebulin), TPM2 (beta-tropomyosin), TPM3 (gamma-tropomyosin), and ACTA1 (skeletal alpha-actin). 20-25% of NM cases carry ACTA1 defects and these particular mutations usually induce substitutions of single residues in the actin protein. Despite increasing clinical and scientific interest, the contractile consequences of these subtle amino acid substitutions remain obscure. To decipher them, in the present study, we originally recorded and analysed the mechanics as well as the X-ray diffraction patterns of human membrane-permeabilized single muscle fibres with a particular peptide substitution in actin, i.e. p.Phe352Ser. Results unravelled an unexpected cascade of molecular and cellular events. During contraction, p.Phe352Ser greatly enhances the strain of individual cross-bridges. Paradoxically, p.Phe352Ser also slightly lowers the number of cross-bridges by altering the rate of myosin head attachment to actin monomers. Overall, at the cell level, these divergent mechanisms conduct to an improved steady-state force production. Such results provide new surprising scientific insights and crucial information for future therapeutic strategies.

Keywords
Nemaline myopathy, ACTA1 mutation, Skeletal muscle, Force, Actin, Myosin cross-bridge
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-173318 (URN)10.1007/s00401-012-0962-z (DOI)000302255000009 ()
Available from: 2012-04-25 Created: 2012-04-23 Last updated: 2017-12-07Bibliographically approved
Ochala, J., Gokhin, D. S., Penisson-Besnier, I., Quijano-Roy, S., Monnier, N., Lunardi, J., . . . Fowler, V. M. (2012). Congenital myopathy-causing tropomyosin mutations induce thin filament dysfunction via distinct physiological mechanisms. Human Molecular Genetics, 21(20), 4473-4485
Open this publication in new window or tab >>Congenital myopathy-causing tropomyosin mutations induce thin filament dysfunction via distinct physiological mechanisms
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2012 (English)In: Human Molecular Genetics, ISSN 0964-6906, E-ISSN 1460-2083, Vol. 21, no 20, p. 4473-4485Article in journal (Refereed) Published
Abstract [en]

In humans, congenital myopathy-linked tropomyosin mutations lead to skeletal muscle dysfunction, but the cellular and molecular mechanisms underlying such dysfunction remain obscure. Recent studies have suggested a unifying mechanism by which tropomyosin mutations partially inhibit thin filament activation and prevent proper formation and cycling of myosin cross-bridges, inducing force deficits at the fiber and whole-muscle levels. Here, we aimed to verify this mechanism using single membrane-permeabilized fibers from patients with three tropomyosin mutations (TPM2-null, TPM3-R167H and TPM2-E181K) and measuring a broad range of parameters. Interestingly, we identified two divergent, mutation-specific pathophysiological mechanisms. (i) The TPM2-null and TPM3-R167H mutations both decreased cooperative thin filament activation in combination with reductions in the myosin cross-bridge number and force production. The TPM3-R167H mutation also induced a concomitant reduction in thin filament length. (ii) In contrast, the TPM2-E181K mutation increased thin filament activation, cross-bridge binding and force generation. In the former mechanism, modulating thin filament activation by administering troponin activators (CK-1909178 and EMD 57033) to single membrane-permeabilized fibers carrying tropomyosin mutations rescued the thin filament activation defect associated with the pathophysiology. Therefore, administration of troponin activators may constitute a promising therapeutic approach in the future.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-184452 (URN)10.1093/hmg/dds289 (DOI)000309460300009 ()
Available from: 2012-11-09 Created: 2012-11-07 Last updated: 2017-12-07Bibliographically approved
Joanne, P., Hourdé, C., Ochala, J., Caudéran, Y., Medja, F., Vignaud, A., . . . Ferry, A. (2012). Impaired Adaptive Response to Mechanical Overloading in Dystrophic Skeletal Muscle. PLoS ONE, 7(4), e35346
Open this publication in new window or tab >>Impaired Adaptive Response to Mechanical Overloading in Dystrophic Skeletal Muscle
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2012 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 7, no 4, p. e35346-Article in journal (Refereed) Published
Abstract [en]

Dystrophin contributes to force transmission and has a protein-scaffolding role for a variety of signaling complexes in skeletal muscle. In the present study, we tested the hypothesis that the muscle adaptive response following mechanical overloading (ML) would be decreased in MDX dystrophic muscle lacking dystrophin. We found that the gains in muscle maximal force production and fatigue resistance in response to ML were both reduced in MDX mice as compared to healthy mice. MDX muscle also exhibited decreased cellular and molecular muscle remodeling (hypertrophy and promotion of slower/oxidative fiber type) in response to ML, and altered intracellular signalings involved in muscle growth and maintenance (mTOR, myostatin, follistatin, AMPK alpha 1, REDD1, atrogin-1, Bnip3). Moreover, dystrophin rescue via exon skipping restored the adaptive response to ML. Therefore our results demonstrate that the adaptive response in response to ML is impaired in dystrophic MDX muscle, most likely because of the dystrophin crucial role.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-177635 (URN)10.1371/journal.pone.0035346 (DOI)000305338600072 ()
Available from: 2012-07-17 Created: 2012-07-17 Last updated: 2017-12-07Bibliographically approved
Kurapati, R., McKenna, C., Lindqvist, J., Williams, D., Simon, M., LeProust, E., . . . Blanco, G. (2012). Myofibrillar myopathy caused by a mutation in the motor domain of mouse MyHC IIb. Human Molecular Genetics, 21(8), 1706-1724
Open this publication in new window or tab >>Myofibrillar myopathy caused by a mutation in the motor domain of mouse MyHC IIb
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2012 (English)In: Human Molecular Genetics, ISSN 0964-6906, E-ISSN 1460-2083, Vol. 21, no 8, p. 1706-1724Article in journal (Refereed) Published
Abstract [en]

Ariel is a mouse mutant that suffers from skeletal muscle myofibrillar degeneration due to the rapid accumulation of large intracellular protein aggregates. This fulminant disease is caused by an ENU-induced recessive mutation resulting in an L342Q change within the motor domain of the skeletal muscle myosin protein MYH4 (MyHC IIb). Although normal at birth, homozygous mice develop hindlimb paralysis from Day 13, consistent with the timing of the switch from developmental to adult myosin isoforms in mice. The mutated myosin (MYH4(L342Q)) is an aggregate-prone protein. Notwithstanding the speed of the process, biochemical analysis of purified aggregates showed the presence of proteins typically found in human myofibrillar myopathies, suggesting that the genesis of ariel aggregates follows a pathogenic pathway shared with other conformational protein diseases of skeletal muscle. In contrast, heterozygous mice are overtly and histologically indistinguishable from control mice. MYH4(L342Q) is present in muscles from heterozygous mice at only 7% of the levels of the wild-type protein, resulting in a small but significant increase in force production in isolated single fibres and indicating that elimination of the mutant protein in heterozygotes prevents the pathological changes observed in homozygotes. Recapitulation of the L342Q change in the functional equivalent of mouse MYH4 in human muscles, MYH1, results in a more aggregate-prone protein.

National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:uu:diva-173625 (URN)10.1093/hmg/ddr605 (DOI)000302302400004 ()
Available from: 2012-05-09 Created: 2012-05-02 Last updated: 2017-12-07Bibliographically approved
Ochala, J., Ravenscroft, G., Laing, N. G. & Nowak, K. J. (2012). Nemaline Myopathy-Related Skeletal Muscle alpha-Actin (ACTA1) Mutation, Asp286Gly, Prevents Proper Strong Myosin Binding and Triggers Muscle Weakness. PLoS ONE, 7(9), e45923
Open this publication in new window or tab >>Nemaline Myopathy-Related Skeletal Muscle alpha-Actin (ACTA1) Mutation, Asp286Gly, Prevents Proper Strong Myosin Binding and Triggers Muscle Weakness
2012 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 7, no 9, p. e45923-Article in journal (Refereed) Published
Abstract [en]

Many mutations in the skeletal muscle alpha-actin gene (ACTA1) lead to muscle weakness and nemaline myopathy. Despite increasing clinical and scientific interest, the molecular and cellular pathogenesis of weakness remains unclear. Therefore, in the present study, we aimed at unraveling these mechanisms using muscles from a transgenic mouse model of nemaline myopathy expressing the ACTA1 Asp286Gly mutation. We recorded and analyzed the mechanics of membranepermeabilized single muscle fibers. We also performed molecular energy state computations in the presence or absence of Asp286Gly. Results demonstrated that during contraction, the Asp286Gly acts as a "poison-protein'' and according to the computational analysis it modifies the actin-actin interface. This phenomenon is likely to prevent proper myosin crossbridge binding, limiting the fraction of actomyosin interactions in the strong binding state. At the cell level, this decreases the force-generating capacity, and, overall, induces muscle weakness. To counterbalance such negative events, future potential therapeutic strategies may focus on the inappropriate actin-actin interface or myosin binding.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-184466 (URN)10.1371/journal.pone.0045923 (DOI)000309388900112 ()
Available from: 2012-11-09 Created: 2012-11-07 Last updated: 2017-12-07Bibliographically approved
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