Myosin, parvalbumin and myofibril expression in barbel (Barbus barbus L.) lateral white muscle during development

Developmental, physiologic and phylogenetic perspectives on the expression and regulation of myosin heavy chains in mammalian skeletal muscles

The kinetics of myosin controls the speed and power of muscle contraction. Mammalian skeletal muscles express twelve kinetically different myosin heavy chain (MyHC) genes which provides a wide range of muscle speeds to meet different functional demands. Myogenic progenitors from diverse craniofacial and somitic mesoderm specify muscle allotypes with different repertoires for MyHC expression. This review provides a brief synopsis on the historical and current views on how cell lineage, neural impulse patterns, and thyroid hormone influence MyHC gene expression in muscles of the limb allotype during development and in adult life and the molecular mechanisms thereof. During somitic myogenesis, embryonic and foetal myoblast lineages form slow and fast primary and secondary myotube ontotypes which respond differently to postnatal neural and thyroidal influences to generate fully differentiated fibre phenotypes. Fibres of a given phenotype may arise from myotubes of different ontotypes which retain their capacity to respond differently to neural and thyroidal influences during postnatal life. This gives muscles physiological plasticity to adapt to fluctuations in thyroid hormone levels and patterns of use. The kinetics of MyHC isoforms vary inversely with animal body mass. Fast 2b fibres are specifically absent in muscles involved in elastic energy saving in hopping marsupials and generally absent in large eutherian mammals. Changes in MyHC expression are viewed in the context of the physiology of the whole animal. The roles of myoblast lineage and thyroid hormone in regulating MyHC gene expression are phylogenetically the most ancient while that of neural impulse patterns the most recent.

Biomechanics of swimming in developing larval fish

Most larvae of bony fish are able to swim almost immediately after hatching. Their locomotory system supports several vital functions: fish larvae make fast manoeuvres to escape from predators, aim accurately during suction feeding and may migrate towards suitable future habitats. Owing to their small size and low swimming speed, larval fish operate in the intermediate hydrodynamic regime, which connects the viscous and inertial flow regimes. They experience relatively strong viscous effects at low swimming speeds, and relatively strong inertial effects at their highest speeds. As the larvae grow and increase swimming speed, a shift occurs towards the inertial flow regime. To compensate for size-related limitations on swimming speed, fish larvae exploit high tail beat frequencies at their highest speeds, made possible by their low body inertia and fast neuromuscular system. The shifts in flow regime and body inertia lead to changing functional demands on the locomotory system during larval growth. To reach the reproductive adult stage, the developing larvae need to adjust to and perform the functions necessary for survival. Just after hatching, many fish larvae rely on yolk and need to develop their feeding systems before the yolk is exhausted. Furthermore, the larvae need to develop and continuously adjust their sensory, neural and muscular systems to catch prey and avoid predation. This Review discusses the hydrodynamics of swimming in the intermediate flow regime, the changing functional demands on the locomotory system of the growing and developing larval fish, and the solutions that have evolved to accommodate these demands.

Development of the ultrastructure of sonic muscles: a kind of neoteny?

Background

Drumming muscles of some sound-producing fish are ‘champions’ of contraction speed, their rate setting the fundamental frequency. In the piranha, contraction of these muscles at 150 Hz drives a sound at the same frequency. Drumming muscles of different not closely related species show evolutionary convergences. Interestingly, some characters of sonic muscles can also be found in the trunk muscles of newly hatched larvae that are able to maintain tail beat frequencies up to 100 Hz. The aim of this work was to study the development of sound production and sonic and epaxial muscles simultaneously in the red bellied piranhas (Pygocentrus nattereri) to seek for possible common characteristics.

Results

Call, pulse and period durations increased significantly with the fish size, but the call dominant frequencies decreased, and the number of pulses and the call amplitude formed a bell curve. In epaxial muscles, the fibre diameters of younger fish are first positioned in the graphical slope corresponding to sonic muscles, before diverging. The fibre diameter of older fish trunk muscles was bigger, and the area of the myofibrils was larger than in sonic muscles. Moreover, in two of the biggest fish, the sonic muscles were invaded by fat cells and the sonic muscle ultrastructure was similar to the epaxial one. These two fish were also unable to produce any sound, meaning they lost their ability to contract quickly.

Conclusions

The volume occupied by myofibrils determines the force of contraction, the volume of sarcoplasmic reticulum sets the contraction frequency, and the volume of mitochondria sets the level of sustained performance. The functional outcomes in muscles are all attributable to shifts in the proportions of those structures. A single delay in the development restricts the quantity of myofibrils, maintains a high proportion of space in the sarcoplasm and develops sarcoplasmic reticulum. High-speed sonic muscles could thus be skeletal muscles with delayed development. This hypothesis has the advantage that it could easily explain why high-speed sonic muscles have evolved so many times in different lineages.

Comparative study of GH-transgenic and non-transgenic amago salmon (Oncorhynchus masou ishikawae) allergenicity and proteomic analysis of amago salmon allergens

Genetically modified (GM) foods are beneficial from the standpoint of ensuring a constant supply of foodstuffs, but they must be tested for safety before being released on the market, including by allergenicity tests to ensure that they do not contain new allergens or higher concentrations of known allergens than the same non-GM foods. In this study we used GM-amago salmon into which a growth hormone gene had been introduced and compared the allergens contained in the GM and the non-GM-amago salmons. We used a combination of Western blotting with allergen-specific antibodies and a proteomic analysis of their allergens with patients' sera, a so-called allergenome analysis, to analyze allergens. Western blotting with specific antibodies showed no increase in the content of the known allergens fish parvalbumin and fish type-I collagen in GM-amago salmon, in comparison with their content in non-GM-amago salmon. The allergenome analysis of two fish-allergic patients allowed us to identify several IgE-binding proteins in amago salmon, including parvalbumin, triose-phosphate isomerase, fructose-bisphosphate aldolase A, and serum albumin, and there were no qualitative differences in these proteins between GM and non-GM-amago salmons. These results indicate that amago salmon endogenous allergen expression does not seem to be altered by genetic modification.

Long-term culture of muscle explants from Sparus aurata

Although there are mammalian myoblast cell lines, no fish myoblast cell line has been developed so far. The aim of this study was to develop a culture system of muscle explants for fish, as explants provide an approximation of the in vivo conditions for cell proliferation and differentiation, and enable a close comparison with events in muscle regenerating in vivo. Here we describe the main features of a long-term in vitro culture system for muscle explants from Sparus aurata fry. At the time of sampling, the original fibres were damaged and subsequently degenerated as shown by the loss of parvalbumin (PV) and presence of apoptotic nuclei. This mechanical damage provoked a myogenic response by activation of myogenic precursor cells. After a few days, new mononucleate cells aligned with the original fibres were seen in the explants, some with proliferating cell nuclear antigen (PCNA-) and Myf-5-positive nuclei, indicating proliferation and their myogenic fate. By 1 week, multinucleate cells with desmin immunoreactivity but PCNA- and Myf5-negative nuclei were present, equivalent to differentiated, postmitotic myotubes. Some of these myotubes were also immunoreactive for PV and insulin-like growth factors (IGFs). By 11 days, many of the myotubes were also immunoreactive for myostatin (MSTN). By 23 days, many of the myotubes had increased in diameter, were packed with myofibrils, and were strongly PV-positive and immunoreactive for MSTN, IGF-I and IGF-I receptor. This study shows that a proliferative process occurs in the explants despite the death of the original muscle fibres, and new muscle fibres expressing growth regulators are formed by regeneration from myogenic precursors present in the explants at the time of sampling.

Detecting fish parvalbumin with commercial mouse monoclonal anti-frog parvalbumin IgG

Parvalbumin is a calcium-binding muscle protein that is highly conserved across fish species and amphibians. It is the major cross-reactive allergen associated with both fish and frog allergy. We used two-dimensional electrophoretic and immunoblotting techniques to investigate the utility of a commercial monoclonal anti-frog parvalbumin IgG for detecting parvalbumin present in some commonly consumed fish species. The 2D electrophoresis and immunoblots revealed species-specific differences in proteins that appear to represent various numbers of isoforms of parvalbumin in carp (5), catfish (3), cod (1) and tilapia (2). No parvalbumin was detected in yellowfin tuna. Based on minor differences in relative intensities of protein staining and immunodetection, parvalbumin isoforms may have slight differences in the epitope region recognized by the anti-frog parvalbumin antibody. These results suggest that the frog anti-parvalbumin antibody can be used as a valuable tool to detect parvalbumins from the fish tested in this study, except yellowfin tuna.

Characterization of the primary sonic muscles in Carapus acus (Carapidae): a multidisciplinary approach

Sound production in carapid fishes results from the action of extrinsic muscles that insert into the swim bladder. Biochemical, histochemical and morphological techniques were used to examine the sonic muscles and compare them with epaxial muscles in Carapus acus. Sonic fibres are thicker than red and thinner than white epaxial fibres, and sonic fibres and myofibrils exhibit an unusual helicoidal organization: the myofibrils of the centre are in a straight line whereas they are more and more twisted towards the periphery. Sonic muscles have both features of red (numerous mitochondria, high glycogen content) and white (alkali-stable ATPase) fibres. They differ also in the isoforms of the light chain (LC3) and heavy chain (HC), in having T tubules at both the Z-line and the A-I junction and in a unique parvalbumin isoform (PAI) that may aid relaxation. All these features lead to the expression of two assumptions about sound generation: the sonic muscle should be able to perform fast and powerful contractions that provoke the forward movement of the forepart of the swim bladder and the stretching and "flapping" of the swim bladder fenestra; the helicoidal organization allows progressive drawing of the swim bladder fenestra which emits a sound when rapidly released in a spring-like manner.

Expression of myofibrillar proteins and parvalbumin isoforms during the development of a flatfish, the common sole Solea solea: comparison with the turbot Scophthalmus maximus

Developmental changes in myofibrillar protein and parvalbumin isoform composition were investigated in the myotomal muscle of the flatfish Solea solea, characterized by a very brief metamorphic stage. Results were compared with previously obtained data on another pleuronectiform teleost, the turbot (Scophthalmus maximus), displaying prolonged metamorphosis. Electrophoretically measurable changes in myofibrillar proteins and parvalbumins were detected late in the sole, after completion of metamorphosis. In the course of development, muscles showed the usual sequential synthesis of isoforms of the myofibrillar proteins myosin light chain LC2, troponin-T, and troponin-I. An adult parvalbumin isoform (PA III) was found to predominate during sole growth. The two flatfish were characterized by highly species-specific parvalbumin isoforms. Compared with turbot, the profiles of the myofibrillar subunits and parvalbumin isoforms varied little in the course of sole development. The early appearance of adult traits might be correlated with the brevity of metamorphosis of this fish.

Immunological study of muscle parvalbumin isotypes in three African catfish during development

Eleven parvalbumin isotypes expressed during the development of clariids Heterobranchus longifilis and Clarias gariepinus and claroteid Chrysichthys auratus were purified and electrophoresed on sodium-dodecyl-sulfate polyacrylamide gels. Immunochemical cross-reactions among these proteins were investigated by immunoblotting, using purified antibodies raised against three isotypes chosen at different stages of fish development. Antibodies raised against H. longifilis PA I (larval-juvenile isotype) and against C. gariepinus PA IIIa (juvenile-adult isotype) cross-reacted to a rather similar extent despite a weaker cross-reaction of anti-PA IIIa with larval-juvenile isotypes. On the other hand, antibodies raised against H. longifilis PA IV (an exclusively adult isotype) recognized markedly only H. longifilis PA IV and C. gariepinus PA IIIb. These two adult isotypes most likely belong to the alpha lineage, and all the others to the beta lineage. These results show that parvalbumin isotypes synthesized at different stages of fish growth differ structurally, and that the most marked difference is between larval-juvenile and adult clariid isotypes.

Isoform distribution of parvalbumins and of some myofibrillar proteins in adult and developing Chrysichthys auratus (Geoffroy St. Hilaire, 1808) (Pisces, Claroteidae)

Polyacrylamide gel electrophoresis was used to analyse the distribution of parvalbumin, myosin light chain, and troponin I isoforms in white muscles of larval, juvenile, and adult Chrysichthys auratus (catfish, siluriforms) and to study the kinetics of their synthesis. Parvalbumin isoform PA II was first detected from day 5 post-hatching and was the main "larval" isoform in this species. PA III appeared at the beginning of the juvenile stage but always remained the minor isoform, even in adult fish. Young mature specimens (approximately 12 cm long) displayed the highest total parvalbumin content. Adult-type myosin light chains were detected from day 8. Densitometric analysis confirmed the light-chain distribution typical of fish muscles, with a relatively high amount of LC3 and a low amount of LC1. We evidenced a "larval" form of troponin-I and its progressive replacement by an "adult" form.

Cloning of a trout fast skeletal myosin heavy chain expressed both in embryo and adult muscles and in myotubes neoformed in vitro

In fish, little is known about the isoforms of myosin heavy chain in developing muscle. Two cDNA libraries from whole skeletal muscle of embryo (eyed stage) (A) and from white muscle of 300 g body weight immature trout (B) were constructed. Three cDNA clones were isolated and characterised as encoding for a fast skeletal myosin heavy chain. Two cDNA clones A1 (1534 bp) and B6 (2203 bp) which were extracted from the two different libraries had the same nucleotide sequence including the 3' untranslated region. The third cDNA B8 (1606 bp) shared 98% identity with the others. The latter could possibly be an allelic isoform of the B6. Northern blot analysis revealed that the fast skeletal MyoHC transcripts were expressed throughout development from myotube appearance to the white muscle present at older stages (adult). These results suggest that this myosin heavy chain is present throughout muscle development in fish and are consistent with the hyperplastic growth of fish muscle. The amino acid sequence of the trout myosin heavy chain diverged from its mammalian and avain counterpart with respect to a higher level of glycine which could be related to an environmental adaptation by increasing thermal instability of the molecule.

The characterisation of the 5' regulatory region of a temperature-induced myosin-heavy-chain gene associated with myotomal muscle growth in the carp

We have isolated and characterised the 5' region of a member of the carp myosin heavy chain gene family. Expression of this gene has previously been shown to be induced by an increase in environmental temperature and is restricted to the small-diameter white myotomal muscle fibres which are associated with growth. The whole isoform gene, including potential regulatory sequence 5' to the transcription start site and the 3' untranslated region was cloned in a lambda2001 bacteriophage vector. Studies of the structure of the 5'-end of the gene revealed high amino acid sequence similarity with translated exons 3-7 of mammalian myosin heavy chain genes indicating identical exon/intron boundaries. The overall length of the gene was however only about one half of that in mammals and birds due to shorter introns. The region 5' to the transcription unit was sequenced and revealed the presence of putative TATA and CCAAAT boxes. In order to study the regulation of expression, a series of endonuclease-generated fragments from the 5' flanking sequence were spliced to chloramphenicol acetyltransferase reporter vectors and used in cell transfection assays or direct gene injection into carp skeletal muscle. The 5' flanking region, which contains a consensus sequence known as an E-box (CANNTG) and a MEF2 binding site, was shown to improve the expression of the reporter gene in fish acclimated at 18 degrees C or 28 degrees C. Unlike the coding region, there was little similarity between the 5'-upstream sequence (promoter region) when compared with sequences flanking the 5'-end of the other myosin heavy chain genes in mammals or chicken.

Differentiation and growth of muscle in the fish Sparus aurata (L): I. Myosin expression and organization of fibre types in lateral muscle from hatching to adult

Post-hatching development of lateral muscle in a teleost fish, Sparus aurata (L) was examined. At hatching only two fibre types were present, several layers of mitochondria-poor, myofibril-rich deep muscle fibres surrounded the notochord and were covered by a superficial monolayer of mitochondria-rich, myofibril-poor A third ultrastructurally distinct fibre type first appeared as one or two fibres located just under the lateral line at 6 days post-hatching. This type, which gradually increased in number during larval life, contained a slow isoform of myosin, identified by mATPase staining and immunostaining with myosin isoform-specific antibodies. Deep muscle fibres--the presumptive fast-white type--contained a fast myosin, and superficial monolayer fibres an isoform similar but not identical to that in adult pink muscle fibres. The only fibres present during larval life which showed a clear change in myosin expression were the superficial monolayer fibres, which gradually transformed into the slow type post-larvally. Pink muscle fibres first appeared near the end of larval life. Both slow and pink muscle fibres remained concentrated around the horizontal septum under the lateral line during larval life, expanding outwards towards the apices of the myotomes only after metamorphosis. Between 60 and 90 days very small diameter fibres with a distinct mATPase profile appeared scattered throughout the deep, fast-white muscle layer, giving it a 'mosaic' appearance, which persisted into adult life. A marked expansion in the slow muscle layer began at the same time, partly by transformation of superficial monolayer fibres, but mainly by addition of new fibres both on the deep surface of the superficial monolayer and close to the lateral line. The order of appearance of these fibre types, their myosin composition, and the significance of the superficial monolayer layer are discussed and compared to muscle fibre type development in higher vertebrates.