Phenotypic expression of 2b myosin heavy chain isoform: a comparative study among species and different muscles (original) (raw)
Related papers
1999
Because complex structural dierences in adult extraocular muscles may have physiological and pathophysiological signi®cance, the three-dimensional pattern of myosin heavy chain (MHC) isoform expression within the orbital and global layers of the muscle bellies compared with the distal tendon ends was quantitatively assessed. Three of the six extraocular muscles of adult rabbits were examined for immunohistologic expression of all fast, fast IIA/X, slow, neonatal and developmental MHC isoforms. The percentages of myo®bers positive for each of these 5 myosin isoforms were determined in the orbital and global layers. There were relatively similar patterns of fast and slow MHC expression in the orbital and global layers of each of the three muscles examined. There were high levels of developmental MHC in the orbital layers, but signi®cantly fewer developmental MHC positive myo®bers in the global layer. The most variable expression was found with the neonatal MHC. There were signi®cant dierences between the longitudinal expression of the various isoforms in the middle of each muscle compared with the tendon end. In the orbital layer of all three muscles examined, the large numbers of ®bers positive for fast MHC in the middle of the muscle dramatically decreased at the tendon end, with a concomitant increase in expression of slow myosin. There was a greater number of developmental MHC-positive myo®bers at the tendon end than in the middle of the muscle in all three muscles examined. In the global layer, the IIA/X-positive myo®bers comprised only half of the total number of fast-positive myo®bers whereas in the orbital layer they comprised all or almost all of the fast positive myo®bers. The con®guration of the extraocular muscles is more complex than might be indicated by previous studies. The lateral rectus muscle had the most individual pattern of MHC expression when compared with the inferior rectus and inferior oblique muscles. Together with dramatic cross-sectional MHC ®ber type dierences between the orbital and global layers of the muscles, there are pronounced longitudinal dierences in the proportions of myo®bers expressing these ®ve MHC isoforms in the middle region of the muscles and those in the distal tendon ends. This longitudinal progression appears to occur both within single myo®bers, as well as within the series of myo®bers that comprise the length of the muscle. We also con®rm that the number of myo®bers is reduced at the tendonous end while the cross-sectional area of each of the remaining myo®bers is proportionally increased with regard to those in the muscle belly. Future studies may yet require two additional schemes for anatomic classi®cation of the named extraocular muscles. One will be based on immunohistochemical features of their constituent myo®bers as a supplement to classi®cations based on their electron microscopic appearance, innervation patterns or relative position with regard to the globe and orbit. Another will be based on the proportional length and longitudinal position of individual myo®bers within an individual extraocular muscle.
Journal of muscle research and cell motility, 1999
Because complex structural differences in adult extraocular muscles may have physiological and pathophysiological significance, the three-dimensional pattern of myosin heavy chain (MHC) isoform expression within the orbital and global layers of the muscle bellies compared with the distal tendon ends was quantitatively assessed. Three of the six extraocular muscles of adult rabbits were examined for immunohistologic expression of all fast, fast IIA/X, slow, neonatal and developmental MHC isoforms. The percentages of myofibers positive for each of these 5 myosin isoforms were determined in the orbital and global layers. There were relatively similar patterns of fast and slow MHC expression in the orbital and global layers of each of the three muscles examined. There were high levels of developmental MHC in the orbital layers, but significantly fewer developmental MHC positive myofibers in the global layer. The most variable expression was found with the neonatal MHC. There were signif...
Fibre types in extraocular muscles: a new myosin isoform in the fast fibres
Journal of Muscle Research and Cell Motility, 1987
We report on the existence of a myosin heavy chain (MHC) isoform with unique structural properties in extraocular (EO) muscles. Differences in MHC composition are apparent using a polyclonal antibody prepared against myosin isolated from bovine EO muscle myosin. In enzyme immunoassays and western blotting experiments, this anti-EO myosin antibody reacted specifically with the heavy chains of EO muscle myosin and not with the heavy chains of other myosins. The distribution of this new MHC isoform in the globe rotating muscles from different mammalian species was analysed using a panel of specific anti-myosin antibodies and comparing the histochemical myosin ATPase profile of muscle fibres with their isomyosin content. Most fibres which display a type 2 ATPase reaction pattern were selectively labelled by anti-EO antibodies. A few type 2 fibres were found to react with both anti-EO and anti-2A myosin antibodies and others, located almost exclusively in the orbital layers, reacted with anfi-foetals as well as anti-EO antibodies.
European journal of histochemistry : EJH, 2004
Myosin heavy chain isoforms (MHC) of adult skeletal muscles are codified by four genes named: slow, or type 1, and fast types 2A, 2X and 2B. The slow, 2A and 2X isoforms have been found expressed in all mammalian species studied so far whereas there is a large inter-species variability in the expression of MHC-2B. In this study histochemistry (m-ATPase), immunohistochemistry with the use of specific monoclonal antibodies and RT-PCR were combined together to assess whether the MHC-2B gene is expressed in bovine muscles. ATPase staining and RT-PCR experiments showed that three MHC isoforms (1, 2A, 2X) were expressed in trunk and limb muscles. Slow or type 1 expression was confirmed using a specific antibody (BA-F8) whereas the detection of fast MHC isoforms were validate by means of BF-35 antibody although not by the SC-71 antibody. MHC-2B was absent in limb and trunk muscles, but was present in specialized eye muscles (rectus lateralis and retractor bulbi) as consistently showed by R...
Distinct Myosin Heavy Chain Isoform Transitions in Developing Slow and Fast Cat Hindlimb Muscles
Cells Tissues Organs, 2000
The expression of myosin heavy chain (MHC) isoforms leading to adult fiber phenotypes in the tibialis anterior (TA) and soleus muscles of the cat were investigated from embryonic day 35 to 1 year after birth. Electrophoresis and immunoblotting of myofibrils demonstrated the expression of 5 different MHC isoforms, i.e. I, IIa, IIx, embryonic, and neonatal, during development. Based on electrophoresis, the adult-like MHC composition of the soleus and TA were not observed until postnatal day 40 (P40) and 120 (P120), respectively. In contrast, immunohistochemical analyses revealed that the adult-like fiber phenotype composition was attained much later (P120) in the soleus. The existence of multiple MHC isoforms in individual fibers suggested that transitions occurred until P120 in both muscles. Adult type I fibers were first observed at P1. Adult IIA fibers were first observed at P30 in the TA and P40 in the soleus. IIX fibers were not identified until P40 in the TA. The transition to the predominantly slow phenotype of the soleus involved a gradual loss of embryonic and fast isoforms accompanied by an accumulation of slow MHC. In contrast, the expression of slow and fast MHC in the fast TA muscle was relatively unchanged throughout development. These results show that the establishment of a given MHC-based fiber phenotype varies significantly between slow and fast muscles in the kitten.
Fiber types in canine muscles: myosin isoform expression and functional characterization
AJP: Cell Physiology, 2006
This study was aimed to achieve a definitive and unambiguous identification of fiber types in canine skeletal muscles and of myosin isoforms that are expressed therein. Correspondence of canine myosin isoforms with orthologs in other species as assessed by base sequence comparison was the basis for primer preparation and for expression analysis with RT-PCR. Expression was confirmed at protein level with histochemistry, immunohistochemistry, and SDS-PAGE combined together and showed that limb and trunk muscles of the dog express myosin heavy chain (MHC) type 1, 2A, and 2X isoforms and the so-called “type 2dog” fibers express the MHC-2X isoform. MHC-2A was found to be the most abundant isoform in the trunk and limb muscle. MHC-2X was expressed in most but not all muscles and more frequently in hybrid 2A-2X fibers than in pure 2X fibers. MHC-2B was restricted to specialized extraocular and laryngeal muscles, although 2B mRNA, but not 2B protein, was occasionally detected in the semimem...
Postnatal Changes in the Developing Rat Extraocular Muscles
Investigative Ophthalmology & Visual Science, 2011
PURPOSE. To examine the distribution and timing of expression of nonmuscle myosin IIB (nmMyH IIB) and the extraocular muscle (EOM)-specific myosin (EO-MyHC) during postnatal development of the rat extraocular muscles. METHODS. Whole orbits were collected from postnatal development day (P) 1 through P30 from Sprague-Dawley rats. Samples were analyzed by immunofluorescence microscopy and Western blot to examine the distribution and abundance of nmMyH IIB and EO-MyHC compared with other myosin isoforms and sarcomeric ␣-actinin. Polyclonal antibodies were produced to specifically detect EO-MyHC. Postnatal limb muscles were used as control. RESULTS. Analysis of EOM morphology in the developing orbits indicates that the global and orbital layers are not evident until day P15. The distribution of nmMyH IIB changes between days P10 and P15 from a subsarcolemma distribution to an intrafiber distribution in the global layer. EO-MyHC appears by day p15, primarily in the orbital layer of the EOMs. Sarcomeric ␣-actinin was equally abundant in the EOMs at all stages. Fetal MyHC was the predominant isoform at day P1 but slowly diminished in abundance with age in a layer-specific manner. CONCLUSIONS. These data demonstrate that significant changes occur in the EOMs from P10 to P15 and suggest that visual stimulation may play a role in the signals that regulate both nmMyH IIB and EO-MyHC developmental transitions. The pronounced distinctions of the orbital and global layers occurring by P15 establish the adult morphologic phenotype of the muscle.
International Journal of Primatology, 2011
The supraspinatus muscle is a key component of the soft tissues of the shoulder. In pronograde primates, its main function, in combination with the other rotator cuff muscles (subscapularis, infraspinatus, and teres minor), is to stabilize the glenohumeral joint, whereas in orthograde primates it functions together with the deltoid, to elevate the upper extremity in the scapular plane. To determine whether these functional differences are also reflected in the molecular biochemistry of the supraspinatus muscles involved in these different locomotor modes, we used realtime polymerase chain reaction (RT-PCR) to analyze the expression of the myosin heavy chain (MHC) isoforms in supraspinatus muscles from modern humans and 12 species of pronograde and orthograde primates. The MHC expression pattern in the supraspinatus muscle of pronograde primates was consistent with its function as a tonic and postural muscle, whereas the MHC expression pattern observed in the supraspinatus muscle of nonhuman orthograde primates was that of a muscle that emphasizes speed, strength, and less resistance to fatigue. These findings are Int J Primatol (2011) 32:931-944 consistent with the role of the supraspinatus in the posture and locomotor modes of these groups of nonhuman primates. The humans included in the study had an expression pattern similar to that of the nonhuman orthograde primates. In conclusion, molecular analysis of skeletal muscles via RT-PCR can contribute to a better understanding of the morphological and functional characteristics of the primate musculoskeletal system.