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Sleigh JN, Villarroel-Campos D, Surana S, Wickenden T, Tong Y, Simkin RL, Vargas JNS, Rhymes ER, Tosolini AP, West SJ, Zhang Q, Yang XL, Schiavo G. Boosting peripheral BDNF rescues impaired in vivo axonal transport in CMT2D mice. JCI Insight 2023; 8:e157191. [PMID: 36928301 PMCID: PMC10243821 DOI: 10.1172/jci.insight.157191] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Accepted: 03/15/2023] [Indexed: 03/18/2023] Open
Abstract
Gain-of-function mutations in the housekeeping gene GARS1, which lead to the expression of toxic versions of glycyl-tRNA synthetase (GlyRS), cause the selective motor and sensory pathology characterizing Charcot-Marie-Tooth disease (CMT). Aberrant interactions between GlyRS mutants and different proteins, including neurotrophin receptor tropomyosin receptor kinase receptor B (TrkB), underlie CMT type 2D (CMT2D); however, our pathomechanistic understanding of this untreatable peripheral neuropathy remains incomplete. Through intravital imaging of the sciatic nerve, we show that CMT2D mice displayed early and persistent disturbances in axonal transport of neurotrophin-containing signaling endosomes in vivo. We discovered that brain-derived neurotrophic factor (BDNF)/TrkB impairments correlated with transport disruption and overall CMT2D neuropathology and that inhibition of this pathway at the nerve-muscle interface perturbed endosome transport in wild-type axons. Accordingly, supplementation of muscles with BDNF, but not other neurotrophins, completely restored physiological axonal transport in neuropathic mice. Together, these findings suggest that selectively targeting muscles with BDNF-boosting therapies could represent a viable therapeutic strategy for CMT2D.
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Affiliation(s)
- James N. Sleigh
- Department of Neuromuscular Diseases and UCL Queen Square Motor Neuron Disease Centre, UCL Queen Square Institute of Neurology, and
- UK Dementia Research Institute, University College London (UCL), London, United Kingdom
| | - David Villarroel-Campos
- Department of Neuromuscular Diseases and UCL Queen Square Motor Neuron Disease Centre, UCL Queen Square Institute of Neurology, and
| | - Sunaina Surana
- Department of Neuromuscular Diseases and UCL Queen Square Motor Neuron Disease Centre, UCL Queen Square Institute of Neurology, and
- UK Dementia Research Institute, University College London (UCL), London, United Kingdom
| | - Tahmina Wickenden
- Department of Neuromuscular Diseases and UCL Queen Square Motor Neuron Disease Centre, UCL Queen Square Institute of Neurology, and
| | - Yao Tong
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, California, USA
| | - Rebecca L. Simkin
- Department of Neuromuscular Diseases and UCL Queen Square Motor Neuron Disease Centre, UCL Queen Square Institute of Neurology, and
| | - Jose Norberto S. Vargas
- Department of Neuromuscular Diseases and UCL Queen Square Motor Neuron Disease Centre, UCL Queen Square Institute of Neurology, and
| | - Elena R. Rhymes
- Department of Neuromuscular Diseases and UCL Queen Square Motor Neuron Disease Centre, UCL Queen Square Institute of Neurology, and
| | - Andrew P. Tosolini
- Department of Neuromuscular Diseases and UCL Queen Square Motor Neuron Disease Centre, UCL Queen Square Institute of Neurology, and
| | | | - Qian Zhang
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, California, USA
| | - Xiang-Lei Yang
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, California, USA
| | - Giampietro Schiavo
- Department of Neuromuscular Diseases and UCL Queen Square Motor Neuron Disease Centre, UCL Queen Square Institute of Neurology, and
- UK Dementia Research Institute, University College London (UCL), London, United Kingdom
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Eraslan G, Drokhlyansky E, Anand S, Fiskin E, Subramanian A, Slyper M, Wang J, Van Wittenberghe N, Rouhana JM, Waldman J, Ashenberg O, Lek M, Dionne D, Win TS, Cuoco MS, Kuksenko O, Tsankov AM, Branton PA, Marshall JL, Greka A, Getz G, Segrè AV, Aguet F, Rozenblatt-Rosen O, Ardlie KG, Regev A. Single-nucleus cross-tissue molecular reference maps toward understanding disease gene function. Science 2022; 376:eabl4290. [PMID: 35549429 PMCID: PMC9383269 DOI: 10.1126/science.abl4290] [Citation(s) in RCA: 157] [Impact Index Per Article: 78.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Understanding gene function and regulation in homeostasis and disease requires knowledge of the cellular and tissue contexts in which genes are expressed. Here, we applied four single-nucleus RNA sequencing methods to eight diverse, archived, frozen tissue types from 16 donors and 25 samples, generating a cross-tissue atlas of 209,126 nuclei profiles, which we integrated across tissues, donors, and laboratory methods with a conditional variational autoencoder. Using the resulting cross-tissue atlas, we highlight shared and tissue-specific features of tissue-resident cell populations; identify cell types that might contribute to neuromuscular, metabolic, and immune components of monogenic diseases and the biological processes involved in their pathology; and determine cell types and gene modules that might underlie disease mechanisms for complex traits analyzed by genome-wide association studies.
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Affiliation(s)
- Gökcen Eraslan
- Klarman Cell Observatory, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Eugene Drokhlyansky
- Klarman Cell Observatory, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Shankara Anand
- The Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Evgenij Fiskin
- Klarman Cell Observatory, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Ayshwarya Subramanian
- Klarman Cell Observatory, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Michal Slyper
- Klarman Cell Observatory, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Jiali Wang
- Department of Ophthalmology, Harvard Medical School, Boston, MA 02115, USA
- Ocular Genomics Institute, Department of Ophthalmology, Massachusetts Eye and Ear, Harvard Medical School, Boston, MA 02114, USA
- Medical and Population Genetics Program, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | | | - John M. Rouhana
- Department of Ophthalmology, Harvard Medical School, Boston, MA 02115, USA
- Ocular Genomics Institute, Department of Ophthalmology, Massachusetts Eye and Ear, Harvard Medical School, Boston, MA 02114, USA
- Medical and Population Genetics Program, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Julia Waldman
- Klarman Cell Observatory, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Orr Ashenberg
- Klarman Cell Observatory, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Monkol Lek
- Department of Genetics, Yale School of Medicine, New Haven, CT 06510, USA
| | - Danielle Dionne
- Klarman Cell Observatory, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Thet Su Win
- Department of Dermatology, Brigham and Women’s Hospital, Boston, MA 02115, USA
| | - Michael S. Cuoco
- Klarman Cell Observatory, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Olena Kuksenko
- Klarman Cell Observatory, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | | | - Philip A. Branton
- The Joint Pathology Center Gynecologic/Breast Pathology, Silver Spring, MD 20910, USA
| | | | - Anna Greka
- The Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
- Department of Medicine, Brigham and Women’s Hospital, Boston, MA 02115, USA
| | - Gad Getz
- The Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
- Center for Cancer Research and Department of Pathology, Massachusetts General Hospital, Boston, MA 02114, USA
- Harvard Medical School, Boston, MA 02115, USA
| | - Ayellet V. Segrè
- Department of Ophthalmology, Harvard Medical School, Boston, MA 02115, USA
- Ocular Genomics Institute, Department of Ophthalmology, Massachusetts Eye and Ear, Harvard Medical School, Boston, MA 02114, USA
- Medical and Population Genetics Program, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - François Aguet
- The Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Orit Rozenblatt-Rosen
- Klarman Cell Observatory, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | | | - Aviv Regev
- Klarman Cell Observatory, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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3
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Involvement of neuronal and muscular Trk-fused gene (TFG) defects in the development of neurodegenerative diseases. Sci Rep 2022; 12:1966. [PMID: 35121777 PMCID: PMC8816932 DOI: 10.1038/s41598-022-05884-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Accepted: 01/13/2022] [Indexed: 11/19/2022] Open
Abstract
Trk-fused gene (TFG) mutations have been identified in patients with several neurodegenerative diseases. In this study, we attempted to clarify the effects of TFG deletions in motor neurons and in muscle fibers, using tissue-specific TFG knockout (vMNTFG KO and MUSTFG KO) mice. vMNTFG KO, generated by crossing TFG floxed with VAChT-Cre, showed deterioration of motor function and muscle atrophy especially in slow-twitch soleus muscle, in line with the predominant Cre expression in slow-twitch fatigue-resistant (S) and fast-twitch fatigue-resistant (FR) motor neurons. Consistently, denervation of the neuromuscular junction (NMJ) was apparent in the soleus, but not in the extensor digitorum longus, muscle. Muscle TFG expressions were significantly downregulated in vMNTFG KO, presumably due to decreased muscle IGF-1 concentrations. However, interestingly, MUSTFG KO mice showed no apparent impairment of muscle movements, though a denervation marker, AChRγ, was elevated and Agrin-induced AChR clustering in C2C12 myotubes was inhibited. Our results clarify that loss of motor neuron TFG is sufficient for the occurrence of NMJ degeneration and muscle atrophy, though lack of muscle TFG may exert an additional effect. Reduced muscle TFG, also observed in aged mice, might be involved in age-related NMJ degeneration, and this issue merits further study.
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Mravec B, Tibensky M. Increased cancer risk in polycystic ovary syndrome: An (un)sympathetic connection? Med Hypotheses 2019; 134:109437. [PMID: 31655360 DOI: 10.1016/j.mehy.2019.109437] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Accepted: 10/17/2019] [Indexed: 10/25/2022]
Abstract
Women with polycystic ovary syndrome (PCOS) have been shown to have a higher incidence of cancer. It is suggested that several factors, including hyperinsulinemia, dyslipidemia, raised estrogen levels, chronic inflammation, and reduced apoptosis are responsible for this association. However, in this paper we propose the hypothesis that increased sympathetic activity may represent an important factor that interconnects PCOS and cancer. This hypothesis is based on two facts: a) in women with PCOS is found sympathetic hyperactivity and b) recent data showing a stimulatory effect of the sympathetic system on cancer initiation, progression, and development of metastases. If our hypothesis is correct, then new preventive approaches might be used to reduce cancer risk in women with PCOS.
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Affiliation(s)
- Boris Mravec
- Institute of Physiology, Faculty of Medicine, Comenius University in Bratislava, Slovakia; Biomedical Research Center, Institute of Experimental Endocrinology, Slovak Academy of Sciences, Bratislava, Slovakia.
| | - Miroslav Tibensky
- Institute of Physiology, Faculty of Medicine, Comenius University in Bratislava, Slovakia; Biomedical Research Center, Institute of Experimental Endocrinology, Slovak Academy of Sciences, Bratislava, Slovakia
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5
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Yang Q, Li Y, Zhang X, Chen D. Zac1/GPR39 phosphorylating CaMK-II contributes to the distinct roles of Pax3 and Pax7 in myogenic progression. Biochim Biophys Acta Mol Basis Dis 2018; 1864:407-419. [DOI: 10.1016/j.bbadis.2017.10.026] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2017] [Revised: 09/15/2017] [Accepted: 10/22/2017] [Indexed: 12/12/2022]
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Developmental and adult-specific processes contribute to de novo neuromuscular regeneration in the lizard tail. Dev Biol 2017; 433:287-296. [PMID: 29291978 DOI: 10.1016/j.ydbio.2017.10.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Revised: 10/01/2017] [Accepted: 10/05/2017] [Indexed: 12/12/2022]
Abstract
Peripheral nerves exhibit robust regenerative capabilities in response to selective injury among amniotes, but the regeneration of entire muscle groups following volumetric muscle loss is limited in birds and mammals. In contrast, lizards possess the remarkable ability to regenerate extensive de novo muscle after tail loss. However, the mechanisms underlying reformation of the entire neuromuscular system in the regenerating lizard tail are not completely understood. We have tested whether the regeneration of the peripheral nerve and neuromuscular junctions (NMJs) recapitulate processes observed during normal neuromuscular development in the green anole, Anolis carolinensis. Our data confirm robust axonal outgrowth during early stages of tail regeneration and subsequent NMJ formation within weeks of autotomy. Interestingly, NMJs are overproduced as evidenced by a persistent increase in NMJ density 120 and 250 days post autotomy (DPA). Substantial Myelin Basic Protein (MBP) expression could also be detected along regenerating nerves indicating that the ability of Schwann cells to myelinate newly formed axons remained intact. Overall, our data suggest that the mechanism of de novo nerve and NMJ reformation parallel, in part, those observed during neuromuscular development. However, the prolonged increase in NMJ number and aberrant muscle differentiation hint at processes specific to the adult response. An examination of the coordinated exchange between peripheral nerves, Schwann cells, and newly synthesized muscle of the regenerating neuromuscular system may assist in the identification of candidate molecules that promote neuromuscular recovery in organisms incapable of a robust regenerative response.
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Saifetiarova J, Liu X, Taylor AM, Li J, Bhat MA. Axonal domain disorganization in Caspr1 and Caspr2 mutant myelinated axons affects neuromuscular junction integrity, leading to muscle atrophy. J Neurosci Res 2017; 95:1373-1390. [PMID: 28370195 DOI: 10.1002/jnr.24052] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2017] [Revised: 02/14/2017] [Accepted: 02/24/2017] [Indexed: 12/19/2022]
Abstract
Bidirectional interactions between neurons and myelinating glial cells result in formation of axonal domains along myelinated fibers. Loss of axonal domains leads to detrimental consequences on nerve structure and function, resulting in reduced conductive properties and the diminished ability to reliably transmit signals to the targets they innervate. Thus, impairment of peripheral myelinated axons that project to the surface of muscle fibers and form neuromuscular junction (NMJ) synapses leads to muscle dysfunction. The goal of our studies was to determine how altered electrophysiological properties due to axonal domain disorganization lead to muscle pathology, which is relevant to a variety of peripheral neuropathies, demyelinating diseases, and neurodegenerative disorders. Using conventional Contactin-Associated Protein 1 (Caspr1) and Caspr2 single or double mutants with disrupted paranodal, juxtaparanodal, or both regions, respectively, in peripheral myelinated axons, we correlated defects in NMJ integrity and muscle pathology. Our data show that loss of axonal domains in Caspr1 and Caspr2 single and double mutants primarily alters distal myelinated fibers together with presynaptic terminals, eventually leading to NMJ denervation and reduction in postsynaptic endplate areas. Moreover, reduction in conductive properties of peripheral myelinated fibers together with NMJ disintegration leads to muscle atrophy in Caspr1 mutants or muscle fiber degeneration accompanied by mitochondrial dysfunction in Caspr1/Caspr2 double mutants. Together, our data indicate that proper organization of axonal domains in myelinated fibers is critical for optimal propagation of electrical signals, NMJ integrity, and muscle health, and provide insights into a wide range of pathologies that result in reduced nerve conduction leading to muscle atrophy. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Julia Saifetiarova
- Department of Cellular and Integrative Physiology, Center for Biomedical Neuroscience, School of Medicine, University of Texas Health Science Center, San Antonio, Texas
| | - Xi Liu
- Department of Cellular and Integrative Physiology, Center for Biomedical Neuroscience, School of Medicine, University of Texas Health Science Center, San Antonio, Texas.,Xiangya School of Medicine, Central South University, Changsha, China
| | - Anna M Taylor
- Department of Cellular and Integrative Physiology, Center for Biomedical Neuroscience, School of Medicine, University of Texas Health Science Center, San Antonio, Texas
| | - Jie Li
- Department of Cellular and Integrative Physiology, Center for Biomedical Neuroscience, School of Medicine, University of Texas Health Science Center, San Antonio, Texas
| | - Manzoor A Bhat
- Department of Cellular and Integrative Physiology, Center for Biomedical Neuroscience, School of Medicine, University of Texas Health Science Center, San Antonio, Texas
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Arai K, Takahashi K, Yasuda A, Kanno N, Kohara Y, Michishita M, Harada Y, Hara Y. Denervation-Associated Change in the Palatinus and Levator Veli Palatini Muscles of Dogs with Elongated Soft Palate. J Comp Pathol 2016; 155:199-206. [PMID: 27426002 DOI: 10.1016/j.jcpa.2016.06.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Revised: 06/08/2016] [Accepted: 06/21/2016] [Indexed: 11/28/2022]
Abstract
Muscle lesions and decreased numbers of peripheral nerve branches have been reported in the soft palates of dogs presenting with brachycephalic airway obstruction syndrome (BAOS). Myosin adenosine triphosphatase staining was employed to investigate whether muscle lesions in the elongated soft palate (ESP) of dogs with BAOS reflect the presence of denervation. Soft palates were collected from nine brachycephalic dogs during surgical intervention for BAOS and from five healthy beagle dogs as controls. In the control soft palates, myofibres with relatively uniform diameters and a random mosaic pattern of type I and II myofibres were observed in the palatinus muscle (PM), while almost all of the myofibres in the levator veli palatini muscle (LVPM) were of type II. In the ESPs, small group atrophy, large group atrophy and angular-shaped atrophy were observed in myofibres of the PM and rarely in the LVPM. Fibre type grouping and an increase in type IIC myofibres were found only in the PM. Morphometric analysis of ESPs revealed a significant increase in the number of type I and II myofibres in the PM showing atrophy or hypertrophy compared with controls. A significant increase in atrophic type II myofibres was found in the LVPM of affected dogs. Myopathy consistent with denervation was observed in the PM, but rarely in the LVPM, of ESP specimens. The results suggest that the myopathy seen in dogs with ESP may partly reflect atrophy of myofibres resulting from damage to peripheral nerve branches, with subsequent reinnervation of myofibres.
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Affiliation(s)
- K Arai
- Laboratory of Veterinary Surgery, Japan; Laboratory of Veterinary Pathology, Japan.
| | | | | | - N Kanno
- Laboratory of Veterinary Surgery, Japan
| | - Y Kohara
- Laboratory of Veterinary Anatomy, Nippon Veterinary and Life Science University, 1-7-1 Kyounan-cho, Musashino, Tokyo, Japan
| | | | - Y Harada
- Laboratory of Veterinary Surgery, Japan
| | - Y Hara
- Laboratory of Veterinary Surgery, Japan
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Massimino ML, Peggion C, Loro F, Stella R, Megighian A, Scorzeto M, Blaauw B, Toniolo L, Sorgato MC, Reggiani C, Bertoli A. Age-dependent neuromuscular impairment in prion protein knockout mice. Muscle Nerve 2015; 53:269-79. [DOI: 10.1002/mus.24708] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/13/2015] [Indexed: 12/26/2022]
Affiliation(s)
| | - Caterina Peggion
- Department of Biomedical Sciences; University of Padova; Via U. Bassi 58/B 35131 Padova Italy
| | - Federica Loro
- Department of Biomedical Sciences; University of Padova; Via U. Bassi 58/B 35131 Padova Italy
| | - Roberto Stella
- Department of Biomedical Sciences; University of Padova; Via U. Bassi 58/B 35131 Padova Italy
| | - Aram Megighian
- Department of Biomedical Sciences; University of Padova; Via U. Bassi 58/B 35131 Padova Italy
| | - Michele Scorzeto
- Department of Biomedical Sciences; University of Padova; Via U. Bassi 58/B 35131 Padova Italy
| | - Bert Blaauw
- Department of Biomedical Sciences; University of Padova; Via U. Bassi 58/B 35131 Padova Italy
| | - Luana Toniolo
- Department of Biomedical Sciences; University of Padova; Via U. Bassi 58/B 35131 Padova Italy
| | - Maria Catia Sorgato
- CNR Neuroscience Institute, University of Padova
- Department of Biomedical Sciences; University of Padova; Via U. Bassi 58/B 35131 Padova Italy
| | - Carlo Reggiani
- CNR Neuroscience Institute, University of Padova
- Department of Biomedical Sciences; University of Padova; Via U. Bassi 58/B 35131 Padova Italy
| | - Alessandro Bertoli
- Department of Biomedical Sciences; University of Padova; Via U. Bassi 58/B 35131 Padova Italy
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Fiber type composition of the human quadratus plantae muscle: a comparison of the lateral and medial heads. J Foot Ankle Res 2014; 7:54. [PMID: 25530807 PMCID: PMC4271414 DOI: 10.1186/s13047-014-0054-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/11/2014] [Accepted: 11/27/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The human quadratus plantae muscle has been attributed a variety of functions, however no consensus has been reached on its significance to foot functioning. The architecture of the human quadratus plantae consists of an evolutionarily conserved lateral head, and a medial head thought to be unique to Man. Surveys of human anatomy have demonstrated the absence of either the medial or lateral head in 20% of the population, which may have implications for foot functioning if each muscle head performs a discrete function. METHODS We investigated the quadratus plantae from eleven formalin-embalmed specimens with a mean age of 84 ± 9 years. Immunohistochemical methods were used to determine the percentage of Type I and Type II muscle fibers in the medial and lateral heads of the quadratus plantae from these specimens. RESULTS Results showed striking homogeneity in fiber type composition within an individual, with an average difference in Type I fiber content of 4.1% between lateral and medial heads. Between individuals, however, the ratio of fiber types within the quadratus plantae was highly variable, with Type I fiber percentages ranging from 19.1% to 91.6% in the lateral head, and 20.4% to 97.0% within the medial head. CONCLUSIONS Our finding of similar fiber type composition of lateral and medial heads within an individual supports the hypothesis that the two heads have a singular function.
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Long-term analyses of innervation and neuromuscular integrity in the Trembler-J mouse model of Charcot-Marie-Tooth disease. J Neuropathol Exp Neurol 2013; 72:942-54. [PMID: 24042197 DOI: 10.1097/nen.0b013e3182a5f96e] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
A large fraction of hereditary demyelinating neuropathies, classified as Charcot-Marie-Tooth disease type 1A, is associated with misexpression of peripheral myelin protein 22. In this study, we characterized morphologic and biochemical changes that occur with diseaseprogression in neuromuscular tissue of Trembler-J mice, a spontaneous rodent model of Charcot-Marie-Tooth disease type 1A. Using age-matched, 2- and 10-month-old, wild-type and Trembler-J mice, we observed neuromuscular deficits that progress from distal to proximal regions. The impairments in motor performance are underlined by degenerative events at distal nerve segments and structural alterations at nerve-muscle synapses. Furthermore, skeletal muscle of affected mice showed reduced myofiber diameter, increased expression of the muscle atrophy marker muscle ring-finger protein 1, and fiber type switching. A dietary intervention of intermittent fasting attenuated these progressive changes and supported distal nerve myelination and neuromuscular junction integrity. In addition to the well-characterized demyelination aspects of this model, our investigations identified distinct degenerative events in distal nerves and muscle of affected neuropathic mice. Therefore, therapeutic studies aimed at slowing or reversing the neuropathic features of these disorders should include the examination of muscle tissue, as well as neuromuscular contact sites.
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Laser capture microdissection of metachromatically stained skeletal muscle allows quantification of fiber type specific gene expression. Mol Cell Biochem 2012. [PMID: 23196635 DOI: 10.1007/s11010-012-1538-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Skeletal muscle contains various myofiber types closely associated with satellite stem cells, vasculature, and neurons, thus making it difficult to perform genetic or proteomic expression analysis with sufficient cellular specificity to resolve differences at the individual cell or myofiber type level. Here, we describe the combination of a simple histochemical method capable of simultaneously identifying Type I, IIA, IIB, and IIC myofibers followed by laser capture micro-dissection (LCM) to compare the expression profiles of individual fiber types, myonuclear domains, and satellite cells in frozen muscle sections of control and atrophied muscle. Quantitative RT-PCR (qPCR) was used to verify the integrity of the cell-specific RNAs harvested after histologic staining, while qPCR for specific genes of interest was used to quantify atrophy-associated changes in mRNA. Our data demonstrate that the differential myofiber atrophy previously described by histologic means is related to differential expression of atrophy-related genes, such as MuRF1 and MAFbx (a.k.a. Atrogin-1), within different myofiber type populations. This spatially resolved molecular pathology (SRMP) technique allowed quantitation of atrophy-related gene products within individual fiber types that could not be resolved by expression analysis of the whole muscle. The present study demonstrates the importance of fiber type specific expression profiling in understanding skeletal muscle biology especially during muscle atrophy and provides a practical method of performing such research.
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Abstract
Neuromuscular disorders that are diagnosed in the intensive care unit (ICU) usually cause substantial limb weakness and contribute to ventilatory dysfunction. Although some lead to ICU admission, ICU-acquired disorders, mainly critical illness myopathy (CIM) and critical illness polyneuropathy (CIP), are more frequent and are associated with considerable morbidity. Approximately 25% to 45% of patients admitted to the ICU develop CIM, CIP, or both. Their clinical features often overlap; therefore, nerve conduction studies and electromyography are particularly helpful diagnostically, and more sophisticated electrodiagnostic studies and histopathologic evaluation are required in some circumstances. A number of prospective studies have identified risk factors for CIP and CIM, but their limitations often include the inability to separate CIM from CIP. Animal models reveal evidence of a channelopathy in both CIM and CIP, and human studies also identified axonal degeneration in CIP and myosin loss in CIM. Outcomes are variable. They tend to be better with CIM, and some patients have longstanding disabilities. Future studies of well-characterized patients with CIP and CIM should refine our understanding of risk factors, outcomes, and pathogenic mechanisms, leading to better interventions.
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Affiliation(s)
- David Lacomis
- Department of Neurology and Pathology (Neuropathology), University of Pittsburgh School of Medicine, PA, USA.
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