Invited Review the Cytoskeleton in Skeletal, Cardiac and Smooth

Total Page:16

File Type:pdf, Size:1020Kb

Invited Review the Cytoskeleton in Skeletal, Cardiac and Smooth Histol Histopathol (1998) 13: 283-291 Histology and 001: 10.14670/HH-13.283 Histopathology http://www.hh.um.es From Cell Biology to Tissue Engineering Invited Review The cytoskeleton in skeletal, cardiac and smooth muscle cells M.H. Stromer Department of Animal Science, Iowa State University, Ames, lA, USA Summary. The muscle cell cytoskeleton consists of cell that maintain the overall structural order of proteins or structures whose primary function is to link, components inside the muscle cell but that do not anchor or tether structural components inside the cell. actually participate in contraction per se. Unfortunately Two important attributes of the cytoskeleton are strength this has sometimes evoked the concept that the of the various attachments and flexibility to accommo­ cytoskeleton of muscle cells is relatively static and less date the changes in cell geometry that occur during interesting than the contractile machinery. The well­ contraction. In striated muscle cells, extramyofibrillar documented observations that skeletal muscle maintains and intramyofibrillar domains of the cytoskeleton have a remarkably constant cell volume during contraction by been identified, Evidence of the extramyofibrillar simultaneously increasing cell diameter as cell length cytoskeleton is seen at the cytoplasmic face of the decreases and that smooth muscle cells can contract to sarcolemma in striated muscle where vinculin- and 60% of rest length and can return to rest length with dystrophin-rich costameres adjacent to sarcomeric Z their internal structure relatively intact suggest that the lines anchor intermediate filaments that span from cytoskeleton must be highly adaptable to cell shape peripheral myofibrils to the sarcolemma. Intermediate changes. How this adaptation occurs is generally filaments also link Z lines of adjacent myofibrils and unknown. For this review, a muscle cell cytoskeletal may, in some muscles, link successive Z lines within a component is defined as a protein or structure whose myofibril at the surface of the myofibril. The intramyo­ primary role is usually considered to be that of a linker, fibrillar cytoskeletal domain includes elastic titin a n anchor or tether that connects two structural filaments from adjacent sarcomeres that are anchored in components. In striated muscle, two compartments of the Z line and continue through the M line at the center the cytoskeleton will be discussed, the extramyofibrillar of the sarcomere; inelastic nebulin filaments also and the intramyofibrillar. The principal proteins that anchored in the Z line and co-extensible with thin constitute the thick and the thin sarcomeric filaments filaments; the Z line, which also anchors thin filaments will not be considered as part of the muscle cell from adjacent sarcomeres; and the M line, which forms cytoskeleton. This definition is consistent with that bridges between the centers of adjacent thick filaments, proposed by Walsh (1997). For reviews on the muscle In smooth muscle, the cytoskeleton includes adherens cell cytoskeleton, see Small et al. (1992) and Stromer junctions at the cytoplasmic face of the sarcolemma, (1995). The existence in muscle of multiple isoforms of which a nchor B-actin filaments and intermediate actin, however, complicate the classification system. filaments of the cytoskeleton, and dense bodies in the Early embryonic and some cultured skeletal muscle cells cytoplasm, which also anchor actin filaments and express mainly cardiac a-sarcomeric actin and intermediate filaments and which may be the interface cytoplasmic or nonmuscle 13- and y-actin isoforms between cytoskeletal and contractile elements. (Vandekerckhove et aI., 1986; Otey et aI., 1988). In adult skeletal muscle, the skeletal a-sarcomeric isoform Key words: Cytoskeleton, Muscle, Skeletal, Cardiac, predominates but the cytoplasmic 13- and y-isoforms are Smooth also present and apparently are not completely segregated from the a-isoform. Otey et al. (1988) used immunofluorescence to demonstrate that isolated Introduction myofibrils from mature skeletal muscle contained mainly a-actin but also contained lesser amounts of y­ The muscle cell cytoskeleton has frequently been cytoplasmic actin, Immunogold labeling of L6 cells considered to include those components of the muscle showed that y-cytoplasmic actin predominated in cortical actin filaments, skeletal a-actin predominated in nascent Offprint requests to: Dr. Marvin H. Stromer, 3116 Molecular Biology myofibrils and both actin isoforms existed at each of Building, Iowa State University, Ames, IA 50011 -3260, USA these locations (Otey et aI., 1988). Smooth muscle cells 284 The muscle cell cytoskeleton in th e adult ve rtebrate vascul ar and di gestive systems th e sarcolemm a by f3-d ys troglyca n, a 43 kDa trans­ contain up to 30% of the total ac tin in th e 13 - and y­ membrane subunit of dystroglycan, a glyco pro tein th at cy topl asmi c isoform s and th e remain der in a - and y­ also contain s a -d ys troglycan, a 156 kD a extracellul ar contrac til e isoform s (Small , 1995). A furthe r laminin-binding subunit (Henry and Camp be ll , 1996). complicating factor is that there is a possibility th at some The biological fun cti ons of the dystroglyca n compl ex in protein s such as titin, nebulin ~ n d myosin binding stri ated muscl e and in other ti ss ues have been rev iewed protein C (MyBP-C), usuall y considered as cy toskeletal by Matsumura et al. ( 1997). The amino-terminal domain pro teins, may modul ate th e acti on of contrac til e protein s of dys trophin contains an ac tin binding domain and is in thi c k and in thin fil ame nt s. A n example is th e th ought to link y-actin fil ament s to th e sarcolemm a. inhibition of in vitro motility of F-actin or reconstituted Although the first three domains of dystrophin ex hi bit thin fil aments when titin was bound to th ese fil ament s sequence homology with actin cross-linking proteins (Kell erm ayer and Granzier, 1996). These exampl es point such as a -actinin and spec trin , Rybakova et al. (1996) out both the complex ity of the muscle ce ll cy toskeleton found that a dystrophin-glycoprotein complex could not and why thi s is an exciting area of research. cross-link F-actin fil ament s. Instea d, Rybakova et al. (1996) identified an additional actin binding sit e near th e Striated muscle ce nter of th e dystrophin rod domain and observed th at when the dystro phin-glycoprotein compl ex was bound to The extramyofibrillar cytoskeleton: Connections between F- actin, th e depolymeri zati on of F- ac tin was slowed. the sarcolemma and peripheral myofibrils These observa tions suggest th at dystrophin may interact with up to 24 actin monomers and may bind along th e The locali za ti on, by immunoflu o rescence, o f side of actin fil aments instead of, or in addition to, the vin culin, a 116 kDa protein , in rib-like bands call ed end . In ra t cardi ac myocytes, dys trophin is not prese nt in costameres th at are located opposit e Z lines at th e a costameri c pattern , but in stead is uni fo rml y distributed cy topl asmi c face of the sarcolemm a in ca rdiac mu scl e at the cytopl asmic fa ce of non-interca lated di sk regions (Pardo et aI. , 1983a) and in skeletal muscl e (Pardo et aI. , of the sarcolemma (Stevenso n et aI. , 1997). Su bce llular 1983b) and at intercalated di sks of ca rdiac mu scle fractionati on of rabbit ventricles demonstra ted th at about (Pardo et aI. , 1983a) suggested th at fil ament attachm ent 55 % of dystrophin was recovered with the sa rcolemm a sit es ex isted at th e sarcole mma. This provided an and 35 % of dystrophin was associa te d with the ex pl anati on for how the fil aments obse rved by Pi erobon­ myo fibrill ar fracti on (Meng et aI. , 1996). Immu nogold Bormi oli ( 198 1) in th e s pace betwee n Z lines of labeling of th ese myofibrils showed that Z lin es were peripheral myofibrils and th e sarcolemm a of skeletal preferentiall y labeled. Additional expe riments will be mu scl e could be anchored at th e membrane. Myo­ needed to dete rmine th e s ig ni f icance o f th e two tendinous and neuromuscular junctions in av ian anteri or subsa rcolemm al distributio ns of dystrophin in skeletal lati ssimus dorsi (ALD) and posteri or lati ss imus dorsi and ca rdiac mu scle and of the presence of dystrophin at (PLD) twitch fibers, and subsa rcoJemm al de nse patches the Z line. over th e I bands in tonic ALD fi be rs, all contain vinculin The inte rcala ted di sk in ca rdi ac mu scle is a (S hea r and Bl ock, 1985). The colocali zati on of y-actin, speciali zed cell-cell cont act th at consists of three intermedi ate filament pro teins and spectrin with vinculin morphologica ll y identifiable regions. The nex us or ga p at costa me res (Craig a nd Pardo, 1983) prov id ed juncti on is para ll el to th e myofib ril ax is, th e mac ul a additional ev id ence that costameres are sit es where adh erens or desmosome is import ant for ce ll-ce ll cytoskeletal fil aments are attached to the sarcolemm a. adh esion and also serv es as an anchor for desmi n­ Both Pierobon-Bormioli (198 1) and Pardo et al.
Recommended publications
  • 1933.Full.Pdf
    0270.6474/84/0408-1933$02.00/O The Journal of Neuroscience Copyright 0 Society for Neuroscience Vol. 4, No. 8, pp. 1933-1943 Printed in U.S.A. August 1984 PARTIAL PURIFICATION AND FUNCTIONAL IDENTIFICATION OF A CALMODULIN-ACTIVATED, ADENOSINE 5’-TRIPHOSPHATE-DEPENDENT CALCIUM PUMP FROM SYNAPTIC PLASMA MEMBRANES1 DIANE M. PAPAZIAN,* HANNAH RAHAMIMOFF,$ AND STANLEY M. GOLDIN§’ Departments of *Biological Chemistry and $Pharmacology, Harvard Medical School, Boston, Massachusetts 02115 and *Department of Biochemistry, Hadassah Medical School, Hebrew University, Jerusalem, Israel Received July 18, 1983; Revised February 27, 1984; Accepted February 28, 1984 Abstract Synaptic plasma membranes isolated from rat brain contain a calmodulin-activated Ca2+ pump. It has been purified 80- to 160-fold by solubilization with Triton X-100 and affinity chromatography on a calmodulin- Sepharose 4B column. After reconstitution into phospholipid vesicles, the affinity-purified pump efficiently catalyzed ATP dependent Ca2+ transport, which was activated 7- to g-fold by calmodulin. The major protein component of the affinity-purified preparation had a M, = 140,000; it was virtually the only band visualized on a Coomassie blue-stained SDS polyacrylamide gel. It has been identified as the Ca”’ pump by two functional criteria. First, it was phosphorylated by [y-““P]ATP in a Ca’+-dependent manner; the phosphorylated protein had the chemical reactivity of an acyl phosphate, characteristic of the phosphorylated intermediates of ion-transporting ATPases. Second, the protein was enriched by transport-specific fractiona- tion, a density gradient procedure which uses the transport properties of the reconstituted Ca2+ pump as a physical tool for its purification.
    [Show full text]
  • Microanatomy of Muscles
    Microanatomy of Muscles Anatomy & Physiology Class Three Main Muscle Types Objectives: By the end of this presentation you will have the information to: 1. Describe the 3 main types of muscles. 2. Detail the functions of the muscle system. 3. Correctly label the parts of a myocyte (muscle cell) 4. Identify the levels of organization in a skeletal muscle from organ to myosin. 5. Explain how a muscle contracts utilizing the correct terminology of the sliding filament theory. 6. Contrast and compare cardiac and smooth muscle with skeletal muscle. Major Functions: Muscle System 1. Moving the skeletal system and posture. 2. Passing food through the digestive system & constriction of other internal organs. 3. Production of body heat. 4. Pumping the blood throughout the body. 5. Communication - writing and verbal Specialized Cells (Myocytes) ~ Contractile Cells Can shorten along one or more planes because of specialized cell membrane (sarcolemma) and specialized cytoskeleton. Specialized Structures found in Myocytes Sarcolemma: The cell membrane of a muscle cell Transverse tubule: a tubular invagination of the sarcolemma of skeletal or cardiac muscle fibers that surrounds myofibrils; involved in transmitting the action potential from the sarcolemma to the interior of the myofibril. Sarcoplasmic Reticulum: The special type of smooth endoplasmic Myofibrils: reticulum found in smooth and a contractile fibril of skeletal muscle, composed striated muscle fibers whose function mainly of actin and myosin is to store and release calcium ions. Multiple Nuclei (skeletal) & many mitochondria Skeletal Muscle - Microscopic Anatomy A whole skeletal muscle (such as the biceps brachii) is considered an organ of the muscular system. Each organ consists of skeletal muscle tissue, connective tissue, nerve tissue, and blood or vascular tissue.
    [Show full text]
  • VIEW Open Access Muscle Spindle Function in Healthy and Diseased Muscle Stephan Kröger* and Bridgette Watkins
    Kröger and Watkins Skeletal Muscle (2021) 11:3 https://doi.org/10.1186/s13395-020-00258-x REVIEW Open Access Muscle spindle function in healthy and diseased muscle Stephan Kröger* and Bridgette Watkins Abstract Almost every muscle contains muscle spindles. These delicate sensory receptors inform the central nervous system (CNS) about changes in the length of individual muscles and the speed of stretching. With this information, the CNS computes the position and movement of our extremities in space, which is a requirement for motor control, for maintaining posture and for a stable gait. Many neuromuscular diseases affect muscle spindle function contributing, among others, to an unstable gait, frequent falls and ataxic behavior in the affected patients. Nevertheless, muscle spindles are usually ignored during examination and analysis of muscle function and when designing therapeutic strategies for neuromuscular diseases. This review summarizes the development and function of muscle spindles and the changes observed under pathological conditions, in particular in the various forms of muscular dystrophies. Keywords: Mechanotransduction, Sensory physiology, Proprioception, Neuromuscular diseases, Intrafusal fibers, Muscular dystrophy In its original sense, the term proprioception refers to development of head control and walking, an early im- sensory information arising in our own musculoskeletal pairment of fine motor skills, sensory ataxia with un- system itself [1–4]. Proprioceptive information informs steady gait, increased stride-to-stride variability in force us about the contractile state and movement of muscles, and step length, an inability to maintain balance with about muscle force, heaviness, stiffness, viscosity and ef- eyes closed (Romberg’s sign), a severely reduced ability fort and, thus, is required for any coordinated move- to identify the direction of joint movements, and an ab- ment, normal gait and for the maintenance of a stable sence of tendon reflexes [6–12].
    [Show full text]
  • The Role of Z-Disc Proteins in Myopathy and Cardiomyopathy
    International Journal of Molecular Sciences Review The Role of Z-disc Proteins in Myopathy and Cardiomyopathy Kirsty Wadmore 1,†, Amar J. Azad 1,† and Katja Gehmlich 1,2,* 1 Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham B15 2TT, UK; [email protected] (K.W.); [email protected] (A.J.A.) 2 Division of Cardiovascular Medicine, Radcliffe Department of Medicine and British Heart Foundation Centre of Research Excellence Oxford, University of Oxford, Oxford OX3 9DU, UK * Correspondence: [email protected]; Tel.: +44-121-414-8259 † These authors contributed equally. Abstract: The Z-disc acts as a protein-rich structure to tether thin filament in the contractile units, the sarcomeres, of striated muscle cells. Proteins found in the Z-disc are integral for maintaining the architecture of the sarcomere. They also enable it to function as a (bio-mechanical) signalling hub. Numerous proteins interact in the Z-disc to facilitate force transduction and intracellular signalling in both cardiac and skeletal muscle. This review will focus on six key Z-disc proteins: α-actinin 2, filamin C, myopalladin, myotilin, telethonin and Z-disc alternatively spliced PDZ-motif (ZASP), which have all been linked to myopathies and cardiomyopathies. We will summarise pathogenic variants identified in the six genes coding for these proteins and look at their involvement in myopathy and cardiomyopathy. Listing the Minor Allele Frequency (MAF) of these variants in the Genome Aggregation Database (GnomAD) version 3.1 will help to critically re-evaluate pathogenicity based on variant frequency in normal population cohorts.
    [Show full text]
  • Genetic Mutations and Mechanisms in Dilated Cardiomyopathy
    Genetic mutations and mechanisms in dilated cardiomyopathy Elizabeth M. McNally, … , Jessica R. Golbus, Megan J. Puckelwartz J Clin Invest. 2013;123(1):19-26. https://doi.org/10.1172/JCI62862. Review Series Genetic mutations account for a significant percentage of cardiomyopathies, which are a leading cause of congestive heart failure. In hypertrophic cardiomyopathy (HCM), cardiac output is limited by the thickened myocardium through impaired filling and outflow. Mutations in the genes encoding the thick filament components myosin heavy chain and myosin binding protein C (MYH7 and MYBPC3) together explain 75% of inherited HCMs, leading to the observation that HCM is a disease of the sarcomere. Many mutations are “private” or rare variants, often unique to families. In contrast, dilated cardiomyopathy (DCM) is far more genetically heterogeneous, with mutations in genes encoding cytoskeletal, nucleoskeletal, mitochondrial, and calcium-handling proteins. DCM is characterized by enlarged ventricular dimensions and impaired systolic and diastolic function. Private mutations account for most DCMs, with few hotspots or recurring mutations. More than 50 single genes are linked to inherited DCM, including many genes that also link to HCM. Relatively few clinical clues guide the diagnosis of inherited DCM, but emerging evidence supports the use of genetic testing to identify those patients at risk for faster disease progression, congestive heart failure, and arrhythmia. Find the latest version: https://jci.me/62862/pdf Review series Genetic mutations and mechanisms in dilated cardiomyopathy Elizabeth M. McNally, Jessica R. Golbus, and Megan J. Puckelwartz Department of Human Genetics, University of Chicago, Chicago, Illinois, USA. Genetic mutations account for a significant percentage of cardiomyopathies, which are a leading cause of conges- tive heart failure.
    [Show full text]
  • Vocabulario De Morfoloxía, Anatomía E Citoloxía Veterinaria
    Vocabulario de Morfoloxía, anatomía e citoloxía veterinaria (galego-español-inglés) Servizo de Normalización Lingüística Universidade de Santiago de Compostela COLECCIÓN VOCABULARIOS TEMÁTICOS N.º 4 SERVIZO DE NORMALIZACIÓN LINGÜÍSTICA Vocabulario de Morfoloxía, anatomía e citoloxía veterinaria (galego-español-inglés) 2008 UNIVERSIDADE DE SANTIAGO DE COMPOSTELA VOCABULARIO de morfoloxía, anatomía e citoloxía veterinaria : (galego-español- inglés) / coordinador Xusto A. Rodríguez Río, Servizo de Normalización Lingüística ; autores Matilde Lombardero Fernández ... [et al.]. – Santiago de Compostela : Universidade de Santiago de Compostela, Servizo de Publicacións e Intercambio Científico, 2008. – 369 p. ; 21 cm. – (Vocabularios temáticos ; 4). - D.L. C 2458-2008. – ISBN 978-84-9887-018-3 1.Medicina �������������������������������������������������������������������������veterinaria-Diccionarios�������������������������������������������������. 2.Galego (Lingua)-Glosarios, vocabularios, etc. políglotas. I.Lombardero Fernández, Matilde. II.Rodríguez Rio, Xusto A. coord. III. Universidade de Santiago de Compostela. Servizo de Normalización Lingüística, coord. IV.Universidade de Santiago de Compostela. Servizo de Publicacións e Intercambio Científico, ed. V.Serie. 591.4(038)=699=60=20 Coordinador Xusto A. Rodríguez Río (Área de Terminoloxía. Servizo de Normalización Lingüística. Universidade de Santiago de Compostela) Autoras/res Matilde Lombardero Fernández (doutora en Veterinaria e profesora do Departamento de Anatomía e Produción Animal.
    [Show full text]
  • Influence of Nebulin on the Assembly Mechanics Of
    INFLUENCE OF NEBULIN ON THE ASSEMBLY MECHANICS OF DESMIN An Undergraduate Research Scholars Thesis by MARC ADRIAN CARAGEA Submitted to Honors and Undergraduate Research Texas A&M University In partial fulfillment of the requirements for the designation as UNDERGRADUATE RESEARCH SCHOLAR Approved by Research Adviser: Gloria M. Conover, Ph.D. May 2014 Major: Biomedical Sciences TABLE OF CONTENTS Page ABSTRACT ............................................................................................................................... 1 ACKNOWLEDGMENTS ........................................................................................................... 2 NOMENCLATURE .................................................................................................................... 3 CHAPTER I INTRODUCTION ............................................................................................... 4 II MATERIALS AND METHODS ......................................................................... 8 Affinity purification of WT and mutant desmin proteins from bacteria ................ 8 Affinity purification of recombinant Nebulin M160 – 164 ................................... 9 Assembly protocol for desmin precursors into filaments in vitro ...................... 11 Sample preparation for atomic force microscopy ............................................... 11 Single desmin filament length acquisition and analysis ..................................... 13 Determination of Young’s modulus for desmin filament networks ...................
    [Show full text]
  • Muscle Histology
    Muscle Histology Dr. Heba Kalbouneh Functions of muscle tissue ▪ Movement ▪ Maintenance of posture ▪ Joint stabilization ▪ Heat generation Types of Muscle Tissue ▪ Skeletal muscle ▪ Cardiac muscle ▪ Smooth muscle Types of Muscle Tissue Skeletal •Attach to and move skeleton •40% of body weight •Fibers = multinucleate cells (embryonic cells fuse) •Cells with obvious striations •Contractions are voluntary Cardiac: only in the wall of the heart •Cells are striated •Contractions are involuntary (not voluntary) Smooth: walls of hollow organs •Lack striations •Contractions are involuntary (not voluntary) Similarities… ▪ Their cells are called fibers because they are elongated ▪ Contraction depends on myofilaments ▪ Actin ▪ Myosin ▪ Plasma membrane is called sarcolemma ▪ Sarcos = flesh ▪ Lemma = sheath SKELETAL MUSCLES Epimysium: surrounds whole muscle Endomysium is around each muscle fiber Perimysium is around fascicle = muscle cell= myofiber Skeletal muscle This big cylinder is a fiber: a cell ▪ Fibers (each is one cell) have striations ▪ Myofibrils are organelles of the cell: these are made -an organelle up of myofilaments ▪ Sarcomere ▪ Basic unit of contraction ▪ Myofibrils are long rows of repeating sarcomeres ▪ Boundaries: Z discs (or lines) Sarcomere M line provides an attachment to myosin filaments Z line provides an attachment to actin filaments A band is the darker band of the myofibril containing myosin filaments H band is the lighter section in the middle of the A band where only myosin is present I band is the lighter band containing
    [Show full text]
  • (7E) Powerpoint Lecture Outline Chapter 8: Control of Movement
    Carlson (7e) PowerPoint Lecture Outline Chapter 8: Control of Movement This multimedia product and its contents are protected under copyright law. The following are prohibited by law: •any public performance or display, including transmission of any image over a network; •preparation of any derivative work, including extraction, in whole or in part, of any images; •any rental, lease, or lending of the program. Copyright 2001 by Allyn & Bacon Skeletal Muscle n Movements of our body are accomplished by contraction of the skeletal muscles l Flexion: contraction of a flexor muscle draws in a limb l Extension: contraction of extensor muscle n Skeletal muscle fibers have a striated appearance n Skeletal muscle is composed of two fiber types: l Extrafusal: innervated by alpha-motoneurons from the spinal cord: exert force l Intrafusal: sensory fibers that detect stretch of the muscle u Afferent fibers: report length of intrafusal: when stretched, the fibers stimulate the alpha-neuron that innervates the muscle fiber: maintains muscle tone u Efferent fibers: contraction adjusts sensitivity of afferent fibers. 8.2 Copyright 2001 by Allyn & Bacon Skeletal Muscle Anatomy n Each muscle fiber consists of a bundle of myofibrils l Each myofibril is made up of overlapping strands of actin and myosin l During a muscle twitch, the myosin filaments move relative to the actin filaments, thereby shortening the muscle fiber 8.3 Copyright 2001 by Allyn & Bacon Neuromuscular Junction n The neuromuscular junction is the synapse formed between an alpha motor neuron
    [Show full text]
  • Back-To-Basics: the Intricacies of Muscle Contraction
    Back-to- MIOTA Basics: The CONFERENCE OCTOBER 11, Intricacies 2019 CHERI RAMIREZ, MS, of Muscle OTRL Contraction OBJECTIVES: 1.Review the anatomical structure of a skeletal muscle. 2.Review and understand the process and relationship between skeletal muscle contraction with the vital components of the nervous system, endocrine system, and skeletal system. 3.Review the basic similarities and differences between skeletal muscle tissue, smooth muscle tissue, and cardiac muscle tissue. 4.Review the names, locations, origins, and insertions of the skeletal muscles found in the human body. 5.Apply the information learned to enhance clinical practice and understanding of the intricacies and complexity of the skeletal muscle system. 6.Apply the information learned to further educate clients on the importance of skeletal muscle movement, posture, and coordination in the process of rehabilitation, healing, and functional return. 1. Epithelial Four Basic Tissue Categories 2. Muscle 3. Nervous 4. Connective A. Loose Connective B. Bone C. Cartilage D. Blood Introduction There are 3 types of muscle tissue in the muscular system: . Skeletal muscle: Attached to bones of skeleton. Voluntary. Striated. Tubular shape. Cardiac muscle: Makes up most of the wall of the heart. Involuntary. Striated with intercalated discs. Branched shape. Smooth muscle: Found in walls of internal organs and walls of vascular system. Involuntary. Non-striated. Spindle shape. 4 Structure of a Skeletal Muscle Skeletal Muscles: Skeletal muscles are composed of: • Skeletal muscle tissue • Nervous tissue • Blood • Connective tissues 5 Connective Tissue Coverings Connective tissue coverings over skeletal muscles: .Fascia .Tendons .Aponeuroses 6 Fascia: Definition: Layers of dense connective tissue that separates muscle from adjacent muscles, by surrounding each muscle belly.
    [Show full text]
  • Troponin Variants in Congenital Myopathies: How They Affect Skeletal Muscle Mechanics
    International Journal of Molecular Sciences Review Troponin Variants in Congenital Myopathies: How They Affect Skeletal Muscle Mechanics Martijn van de Locht , Tamara C. Borsboom, Josine M. Winter and Coen A. C. Ottenheijm * Department of Physiology, Amsterdam Cardiovascular Sciences, Amsterdam UMC, Location VUmc, 1081 HZ Amsterdam, The Netherlands; [email protected] (M.v.d.L.); [email protected] (T.C.B.); [email protected] (J.M.W.) * Correspondence: [email protected]; Tel.: +31-(0)-20-444-8123 Abstract: The troponin complex is a key regulator of muscle contraction. Multiple variants in skeletal troponin encoding genes result in congenital myopathies. TNNC2 has been implicated in a novel congenital myopathy, TNNI2 and TNNT3 in distal arthrogryposis (DA), and TNNT1 and TNNT3 in nemaline myopathy (NEM). Variants in skeletal troponin encoding genes compromise sarcomere function, e.g., by altering the Ca2+ sensitivity of force or by inducing atrophy. Several potential therapeutic strategies are available to counter the effects of variants, such as troponin activators, introduction of wild-type protein through AAV gene therapy, and myosin modulation to improve muscle contraction. The mechanisms underlying the pathophysiological effects of the variants in skeletal troponin encoding genes are incompletely understood. Furthermore, limited knowledge is available on the structure of skeletal troponin. This review focusses on the physiology of slow and fast skeletal troponin and the pathophysiology of reported variants in skeletal troponin encoding genes. A better understanding of the pathophysiological effects of these variants, together with enhanced knowledge regarding the structure of slow and fast skeletal troponin, will direct the development of Citation: van de Locht, M.; treatment strategies.
    [Show full text]
  • CAP2 Deficiency Delays Myofibril Actin Cytoskeleton Differentiation and Disturbs Skeletal Muscle Architecture and Function
    CAP2 deficiency delays myofibril actin cytoskeleton differentiation and disturbs skeletal muscle architecture and function Lara-Jane Kepsera, Fidan Damara, Teresa De Ciccob, Christine Chaponnierc, Tomasz J. Prószynski b, Axel Pagenstecherd, and Marco B. Rusta,e,f,1 aMolecular Neurobiology Group, Institute of Physiological Chemistry, University of Marburg, 35032 Marburg, Germany; bLaboratory of Synaptogenesis, Nencki Institute of Experimental Biology PAS, 02-093 Warsaw, Poland; cDepartment of Pathology and Immunology, University of Geneva, 1211 Geneva, Switzerland; dInstitute of Neuropathology, University of Marburg, 35032 Marburg, Germany; eCenter for Mind, Brain and Behavior, Research Campus of Central Hessen, 35032 Marburg, Germany; and fDFG Research Training Group “Membrane Plasticity in Tissue Development and Remodeling,” GRK 2213, University of Marburg, 35032 Marburg, Germany Edited by Yale E. Goldman, University of Pennsylvania/PMI, Philadelphia, PA, and approved March 14, 2019 (received for review August 7, 2018) Actin filaments (F-actin) are key components of sarcomeres, the have acquired specific functions. While previous analyses of mu- basic contractile units of skeletal muscle myofibrils. A crucial step tant mice demonstrated a role of CAP2 in neuron morphology and during myofibril differentiation is the sequential exchange of heart physiology (13–15), its function in skeletal muscles has not α-actin isoforms from smooth muscle (α-SMA) and cardiac (α-CAA) been investigated, yet. to skeletal muscle α-actin (α-SKA) that, in mice, occurs during early We here report a function for CAP2 in skeletal muscle de- postnatal life. This “α-actin switch” requires the coordinated activ- velopment. We found that CAP2 controls the exchange of ity of actin regulators because it is vital that sarcomere structure α-actin isoforms during myofibril differentiation.
    [Show full text]