Dimerization specificity of adult and neonatal chicken skeletal muscle myosin heavy chain rods.

The dimerization specificity of the recombinantly expressed and purified rod domain of adult and neonatal chicken myosin heavy chain was analyzed using metal chelation chromatography. Our results indicate that full-length adult and neonatal rods preferentially formed homodimers when renatured from an equimolar mixture of the two isoforms denatured in guanidine hydrochloride. The contribution made toward the dimerization specificity by subdomains of the rod has been addressed by making a chimeric protein consisting of the subfragment 2 (S2) region of the adult isoform and the light meromyosin region of the neonatal isoform.

Myonuclear domain size varies along the lengths of maturing skeletal muscle fibers.

In a skeletal muscle fiber, each myonucleus is responsible for gene expression in its surrounding cytoplasm. The region of cytoplasm associated with an individual myonucleus is termed myonuclear domain. However, little is known about domain size variation within individual muscle fibers.

Evolutionary significance of myosin heavy chain heterogeneity in birds.

This article reviews the complexity, expression, genetics, regulation, function, and evolution of the avian myosin heavy chain (MyHC). The majority of pertinent studies thus far published have focussed on domestic chicken and, to a much lesser extent, Japanese quail. Where possible, information available about wild species has also been incorporated into this review.

Repression of myosin isoforms in developing and denervated skeletal muscle fibers originates near motor endplates.

During development of chicken pectoralis muscle, a neonatal myosin heavy-chain isoform is supplanted progressively by an adult isoform. This expression is under neuronal control. In this study we test the hypothesis that developmental myosin transformations are initiated near the motor endplate of each muscle fiber, thereafter progressing toward the fiber ends.

Persistent expression of developmental myosin heavy chain isoforms in the tapered ends of adult pigeon pectoralis muscle fibres.

We have shown previously that in addition to the adult myosin heavy chain (MyHC) isoform present throughout the length of each fast-twitch glycolytic muscle fibre within the pectoralis of the mature chicken, the neonatal isoform is retained in the tapered ends of these fibres. This work, however, has been the only published report of this phenomenon. Here, we tested the hypothesis that similar to the chicken, the ends of mature pigeon pectoralis muscle fibres contain developmental MyHC isoform(s).

Regulation of alpha-helical coiled-coil dimerization in chicken skeletal muscle light meromyosin.

The dimerization specificity of the light meromyosin (LMM) domain of chicken neonatal and adult myosin isoforms was analyzed by metal chelation chromatography. Our results show that neonatal and adult LMMs associate preferentially, although not exclusively, as homodimeric coiled-coils. Using chimeric LMM constructs combining neonatal and adult sequences, we observed that a stretch of 183 amino acids of sequence identity at the N terminus of the LMM was sufficient to allow the adult LMM to dimerize in a non-selective manner.

Functional properties of myosin isoforms in avian muscle.

Sarcomeric myosin is the major skeletal muscle protein and is encoded by a large and complex multigene family whose members are differentially expressed in developing and adult muscle cells. The structure and function of sarcomeric myosins have been extensively analyzed and many myosin genes have now been cloned and sequenced. This manuscript reviews the broad spectrum of myosin research with emphasis on studies in avian systems and discusses how advances in myosin isoform analysis have contributed to muscle and meat science.

Expression of myosin heavy chain isoforms during development of domestic pigeon pectoralis muscle.

The pectoralis muscle of birds provides virtually all the power for the downstroke of the wing during flight. In adults it consists almost entirely of FOG (fast-twitch oxidative-glycolytic) and/or FG (fast-twitch glycolytic) fiber types. The aims of this study are to contrast MyHC (myosin heavy chain) transitions occurring within avian FG and FOG fibers during development, and to test the hypothesis that the pectoralis matures before the acquisition of flight.

The role of interhelical ionic interactions in myosin rod assembly.

Interhelical electrostatic interactions at specific heptad positions can regulate dimerization specificity of alpha-helical coiled-coils. We have analyzed 20 vertebrate myosin sequences from a variety of organisms and tissues in order to determine if interhelical ionic interactions correlate with the observed myosin dimerization specificity. We find that the sites for potential interhelical ion pairing are identical in virtually all sarcomeric myosins whether they form homo- or heterodimers.

Cloning, nucleotide sequence and characterization of a full-length cDNA encoding the myosin heavy chain from adult chicken pectoralis major muscle.

Four cDNA clones, encoding the chicken adult sarcomeric MyHC, have been isolated from a pectoralis major muscle cDNA library using gene-specific DNA probes. These clones were sequenced and then subcloned into a full-length, 6-kb, chicken adult sarcomeric MyHC cDNA. The entire cDNA consists of 5873 nucleotides with 19 bp 5'-untranslated region and 34 bp 3'-untranslated region.

Identification of a genomic locus containing three slow myosin heavy chain genes in the chicken.

Two unique cDNA clones containing chicken slow myosin heavy chain (MyHC) inserts have been isolated from an expression library. Immunochemical analyses of the expressed proteins using different slow MyHC specific monoclonal antibodies were consistent with the two clones encoding slow MyHC 1 (SM1) and slow MyHC 2 (SM2) protein sequences. Northern blot analyses showed that the clones hybridized with 6-kb mRNAs that are differentially expressed in developing and adult slow muscles, further supporting the conclusion that these two clones represent SM1 and SM2 cDNAs.

Expression of fast myosin heavy chain transcripts in developing and dystrophic chicken skeletal muscle.

The expression of fast myosin heavy chain (MyHC) genes was examined in vivo during fast skeletal muscle development in the inbred White Leghorn chicken (line 03) and in adult muscles from the genetically related dystrophic White Leghorn chicken (line 433). RNA dotblot and northern hybridization was employed to monitor MyHC transcript levels utilizing specific oligonucleotide probes. The developmental pattern of MyHC gene expression in the pectoralis major (PM) and the gastrocnemius muscles was similar during embryonic development with three embryonic MyHC isoform genes, Cemb1, Cemb2, and Cemb3, sequentially expressed.

Innervation regulates myosin heavy chain isoform expression in developing skeletal muscle fibers.

The influence of innervation on primary and secondary myogenesis and its relation to fiber type diversity were investigated in two specific wing muscles of quail embryo, the posterior (PLD) and anterior latissimus dorsi (ALD). In the adult, these muscles are composed almost exclusively of pure populations of fast and slow fibers, respectively. When slow ALD and fast PLD muscles developed in ovo in an aneurogenic environment induced after neural tube ablation, the cardiac ventricular myosin heavy chain (MHC) isoform was not expressed.

Heterogeneity of myosin heavy-chain expression in fast-twitch fiber types of mature avian pectoralis muscle.

The aims of this study are to investigate the diversity of myosin heavy-chain (MyHC) expression among avian fast-twitch fibers, and to test the hypothesis that dissimilar MyHC isoforms are found in each of the principal avian fast-twitch fiber types. MyHCs within the muscle fibers of the pectoralis of 31 species of bird are characterized using immunocytochemical methods. A library of 11 monoclonal antibodies previously produced against chicken MyHCs is used.

Myosin heavy chain expression within the tapered ends of skeletal muscle fibers.

Background: The pectoralis muscle of the chicken contains fast-twitch glycolytic fibers, which during development undergo a transformation in their myosin heavy chain (MyHC) content from embryonic to a neonatal to an adult isoform (Bandman et al., 1990). Little, however, is known of MyHC expression within the ends of these or other muscle fibers.

Tough calls: making ethical decisions in the care of older patients.

Medicine is a moral endeavor concerned with the good of treating those who are ill. An ethical decision is the justifiable response to a "should" question, with consequences of good or harm. Three conditions are necessary for a patient to share in making an ethical decision: competence, voluntariness, and knowledge related to the condition of illness.

The evolution of the chicken sarcomeric myosin heavy chain multigene family.

This manuscript describes the chicken sarcomeric myosin heavy chain (MyHC) multigene family and how it differs from the sarcomeric MyHC multigene families of other vertebrates. Data is discussed that suggests the chicken fast MyHC multigene family has undergone recent expansion subsequent to the divergence of avians and mammals, and has been subjected to multiple gene conversion-like events. Similar to human and rodent MyHC multigene families, the chicken multigene family contains sarcomeric MyHC genes that are differentially regulated in developing embryonic, fetal, and neonatal muscles.

The evolutionary relationship of avian and mammalian myosin heavy-chain genes.

Sequence comparisons of avian and mammalian skeletal and cardiac myosin heavy-chain isoforms are used to examine the evolutionary relationships of sarcomeric myosin multigene families. Mammalian fast-myosin heavy-chain isoforms from different species, with comparable developmental expression, are more similar to each other than they are to other fast isoforms within the same genome. In contrast, the developmentally regulated chicken fast isoforms are more similar to each other than they are to myosin heavy-chain isoforms in other species.

Contractile protein isoforms in muscle development.

The contractile proteins of skeletal muscle are often represented by families of very similar isoforms. Protein isoforms can result from the differential expression of multigene families or from multiple transcripts from a single gene via alternative splicing. In many cases the regulatory mechanisms that determine the accumulation of specific isoforms via alternative splicing or differential gene expression are being unraveled.

Skeletal muscle satellite cells appear during late chicken embryogenesis.

The emergence of avian satellite cells during development has been studied using markers that distinguish adult from fetal cells. Previous studies by us have shown that myogenic cultures from fetal (Embryonic Day 10) and adult 12-16 weeks) chicken pectoralis muscle (PM) each regulate expression of the embryonic isoform of fast myosin heavy chain (MHC) differently. In fetal cultures, embryonic MHC is coexpressed with a ventricular MHC in both myocytes (differentiated myoblasts) and myotubes.

Developmental modulation of myosin expression by thyroid hormone in avian skeletal muscle.

It is well established that a rise in circulating thyroid hormone during the second half of chick embryo development significantly influences muscle weight gain and bone growth. We studied thyroid influence on differentiation in slow anterior latissimus dorsi (ALD) and fast posterior latissimus dorsi (PLD) muscles of embryos rendered hypothyroid by hypophysectomy or administration of an anti-thyroid drug. The expression of native myosins and myosin light chains (MLCs) was studied by electrophoretic analysis, and the myosin heavy chain (MHC) was characterized by immunohistochemistry.

Analysis of the chicken fast myosin heavy chain family. Localization of isoform-specific antibody epitopes and regions of divergence.

cDNAs encoding the rod region of four different fast myosin heavy chains (MYCHs) in the chicken were identified, using anti-MYCH monoclonal antibodies, in two expression libraries prepared from 19-day embryonic and adult chicken muscle. These clones were used to determine the amino acid sequences that encompass the epitopes of five anti-MYHC monoclonal antibodies. Additionally, the amino acid sequences were compared to each other and to a full length embryonic MYHC.

Gene conversions within the skeletal myosin multigene family.

Comparisons of the nucleotide sequences of the light meromyosin (LMM) region of developmentally regulated fast chicken myosin heavy chain (MHC) isoforms indicates that chicken MHC isoforms are more similar to each other than to MHC isoforms in other species. The sequence data provide evidence that gene conversion events have occurred recently among the isoforms. An embryonic (Cemb1) isoform and neonatal isoform have the most extensive regions of sequence identity.

Myoblasts from fetal and adult skeletal muscle regulate myosin expression differently.

We compared the expression of myosin heavy chains in myogenic cultures prepared from fetal (embryonic Day 10) and adult (12-16 weeks) chicken pectoralis muscle using immunofluorescence with isoform-specific monoclonal antibodies. We found that the majority of fetal myocytes (differentiated myoblasts) and myotubes coexpressed ventricular and embryonic myosin heavy chains in culture. Also, when fetal cells were plated at a clonal density most clones coexpressed both ventricular and embryonic isoforms.