Characterisation of red and white muscle myosin heavy chain gene coding sequences from antarctic and tropical fish

Characterization of myosin heavy chain (MYH) genes and their differential expression in white and red muscles of Chinese perch, Siniperca chuatsi

Fish skeletal muscle is composed of two anatomically and functionally different fiber layers, white or fast and red or slow muscles. Myosin, the major structural protein of fish skeletal muscle, contains multiple myosin heavy chain (MYH) isoforms involved in the high plasticity of muscle in response to varying functional demands and/or environmental changes. In this study, we comparatively assayed the cellular and ultrastructural feature of white and red skeletal muscles. Then, a total of 28 class II myosin heavy chain genes were identified in by searching the Chinese perch genome database. Among them, 14 genes code for the fast-muscle-type myosin heavy chain, and 7 genes code for the slow-muscle-type myosin heavy chain. Further, the different isoform gene structures, function domains, phylogenetic relations, and muscle-fiber type-specific expression were characterized. This is the first systematic work on the molecular characterization of class II myosin heavy chain isoforms and the differential analysis of their expression in red and white muscle tissues in Chinese perch Siniperca chuatsi. Our work provided valuable information for a better understanding of myh genes and their molecular characteristics, and the correlations of multiple myosin isoforms with potential functions in response to varying functional demands and/or environmental changes.

Determination and quantification of γ-glutamyl-valyl-glycine in commercial fish sauces

It was recently reported that kokumi substances such as glutathione are perceived through the calcium-sensing receptor (CaSR). In addition, screening by the CaSR assay and sensory evaluation revealed that γ-glutamyl-valyl-glycine (γ-Glu-Val-Gly) was a potent kokumi peptide. In this study, the quantities of γ-Glu-Val-Gly in various commercial fish sauces originating from Vietnam (Nuoc Mum), Thailand (Nampra), China (Yu-lu), Korea, Japan (Shottsuru and Ikanago-shoyu), and Italy (Garum) were investigated using a LC/MS/MS method followed by derivatization with 6-aminoquinoyl-N-hydroxysuccinimidyl-carbamate (AQC). The analyses revealed γ-Glu-Val-Gly at concentrations ranging from 0.04 to 1.26 mg/dL, indicating that γ-Glu-Val-Gly is widely distributed among various commercial fish sauces.

EST-based identification of genes expressed in skeletal muscle of the mandarin fish (Siniperca chuatsi)

To enrich the genomic information of the commercially important fish species, we obtained 5,063 high-quality expressed sequence tags (ESTs) from the muscle cDNA database of the mandarin fish (Siniperca chuatsi). Clustering analysis yielded 1,625 unique sequences including 443 contigs (from 3,881 EST sequences) and 1,182 singletons. BLASTX searches showed that 959 unique sequences shared homology to proteins in the NCBI non-redundant database. A total of 740 unique sequences were functionally annotated using Gene Ontology. The 1,625 unique sequences were assigned to Kyoto Encyclopedia of Genes and Genomes reference pathways, and the results indicated that transcripts participating in nucleotide metabolism and amino acid metabolism are relatively abundant in S. chuatsi. Meanwhile, we identified 15 genes to be abundantly expressed in muscle of the mandarin fish. These genes are involved in muscle structural formation and regulation of muscle differentiation and development. The most remarkable gene in S. chuatsi is nuclease diphosphate kinase B, which is represented by 449 EST sequences accounting for 8.86% of the total EST sequences. Our work provides a transcript profile expressed in the white muscle of the mandarin fish, laying down a foundation in better understanding of fish genomics.

Three embryonic myosin heavy chain genes encoding different motor domain structures from common carp show distinct expression patterns in cranial muscles

Three embryonic myosin heavy chain (MYH) genes >> (MYHs) including MYH(emb1), MYH(emb2) and MYH(emb3) and encoding a C-terminal part of MYH were previously cloned and demonstrated to be expressed transiently in this order during development of common carp Cyprinus carpio embryos. The present study determined the full-length cDNA nucleotide sequences encoding the motor domain of the three MYHs, suggesting the implication of loop 1 and loop 2 sequences for the differences in the motor functions. Phylogenetic analysis based on the full-length amino acid sequences showed that MYH(emb1) and MYH(emb2) both belong to the fast types, though clearly differ from fast-type MYHs expressed in adult fast muscle previously reported. In contrast, MYH(emb3) was in a clade containing slow/cardiac type. Whole-mount immunostaining and in situ hybridization showed that the transcripts of the three embryonic MYHs are localized in the same or different cranial muscles of common carp larvae, suggesting that the three MYHs function cooperatively or individually in various cranial muscles.

Structural differences in the motor domain of temperature-associated myosin heavy chain isoforms from grass carp fast skeletal muscle

We determined coding sequences for three types of grass carp myosin subfragment-1 (S1) heavy chain by extending 5'-regions of the three known genes encoding light meromyosin isoforms (10 degrees C, intermediate and 30 degrees C types). The primary structures of these three S1 heavy chain isoforms showed 81.4%, 81.2%, and 97.8% identities between the 10 degrees C and intermediate types, between the 10 degrees C and 30 degrees C types, and between the intermediate and 30 degrees C types, respectively. Isoform-specific differences were clearly observed between the 10 degrees C type and the other two types in 97 amino acid residues. Furthermore, among these amino acid mutations, 51 mutations occurred at the conserved residue sites of S1 heavy chain from fish and homoiotherm. Additionally, the 10 degrees C type showed striking differences compared with the other two types in the two surface loops, loop 1 located near the ATP-binding pocket and loop 2, which is one of the actin-binding sites, suggesting that such structural differences possibly affect their motor functions. Interestingly, this 10 degrees C-type myosin heavy chain isolated from adult grass carp skeletal muscle was surprisingly similar to the embryonic fast-type myosin heavy chain from juvenile silver carp in the structure of S1 heavy chain, indicating that it may also function as embryonic fast-type myosin heavy chain in juvenile stage.

Fish muscle: the exceptional case of Notothenioids

Fish skeletal muscle is an excellent model for studying muscle structure and function, since it has a very well-structured arrangement with different fiber types segregated in the axial and pectoral fin muscles. The morphological and physiological characteristics of the different muscle fiber types have been studied in several teleost species. In fish muscle, fiber number and size varies with the species considered, limiting fish maximum final length due to constraints in metabolites and oxygen diffusion. In this work, we analyze some special characteristics of the skeletal muscle of the suborder Notothenioidei. They experienced an impressive radiation inside Antarctic waters, a stable and cold environment that could account for some of their special characteristics. The number of muscle fibers is very low, 12,700-164,000, in comparison to 550,000-1,200,000 in Salmo salar of similar sizes. The size of the fibers is very large, reaching 600 microm in diameter, while for example Salmo salar of similar sizes have fibers of 220 microm maximum diameter. Evolutionary adjustment in cell cycle length for working at low temperature has been shown in Harpagifer antarcticus (111 h at 0 degrees C), when compared to the closely related sub-Antarctic species Harpagifer bispinis (150 h at 5 degrees C). Maximum muscle fiber number decreases towards the more derived notothenioids, a trend that is more related to phylogeny than to geographical distribution (and hence water temperature), with values as low as 3,600 in Harpagifer bispinis. Mitochondria volume density in slow muscles of notothenioids is very high (reaching 0.56) and since maximal rates of substrate oxidation by mitochondria is not enhanced, at least in demersal notothenioids, volume density is the only means of overcoming thermal constraints on oxidative capacity. In brief, some characteristics of the muscles of notothenioids have an apparent phylogenetic component while others seem to be adaptations to low temperature.

Comparative sequence analysis of myosin heavy chain proteins from congeneric shallow- and deep-living rattail fish (genus Coryphaenoides)

The evolutionary adaptations of functional genes to life at high pressure are not well understood. To elucidate the mechanisms of protein adaptation to high pressure, we cloned the myosin heavy chain (MyHC) cDNA from skeletal muscle of two deep-sea fishes, Coryphaenoides yaquinae and C. armatus, and two non-deep-sea fishes, C. acrolepis and C. cinereus. The MyHCs of deep-sea fishes have a unique structure in two loop regions, loop-1 and loop-2, in comparison with those of non-deep-sea fishes. The loop-1 region of deep-sea fishes has a Pro residue and the loop-2 region, which is an actin-binding site, is shorter than the same region in non-deep-sea fishes. The amino acid substitution in the loop-1 region is expected to be mainly involved in ATPase activity, whereas the deletion in the loop-2 region affects the association of MyHC with actin filaments at high pressure. In addition, the MyHC of deep-sea fishes has biased amino acid substitutions at core positions in the coiled-coil structure of the rod region. These amino acid substitutions are likely to decrease the cavities in the coiled-coil structure and consequently make the structure more compact and unaffected by high pressure. Together, these results indicate that amino acid substitutions can adaptively alter the pressure sensitivity of a protein even if they do not directly influence core structure.

Divergent evolution of the myosin heavy chain gene family in fish and tetrapods: evidence from comparative genomic analysis

Myosin heavy chain genes (MYHs) are the most important functional domains of myosins, which are highly conserved throughout evolution. The human genome contains 15 MYHs, whereas the corresponding number in teleost appears to be much higher. Although teleosts comprise more than one-half of all vertebrate species, our knowledge of MYHs in teleosts is rather limited. A comprehensive analysis of the torafugu (Takifugu rubripes) genome database enabled us to detect at least 28 MYHs, almost twice as many as in humans. RT-PCR revealed that at least 16 torafugu MYH representatives (5 fast skeletal, 3 cardiac, 2 slow skeletal, 1 superfast, 2 smooth, and 3 nonmuscle types) are actually transcribed. Among these, MYH(M743-2) and MYH(M5) of fast and slow skeletal types, respectively, are expressed during development of torafugu embryos. Syntenic analysis reveals that torafugu fast skeletal MYHs are distributed across five genomic regions, three of which form clusters. Interestingly, while human fast skeletal MYHs form one cluster, its syntenic region in torafugu is duplicated, although each locus contains just a single MYH in torafugu. The results of the syntenic analysis were further confirmed by corresponding analysis of MYHs based on databases from Tetraodon, zebrafish, and medaka genomes. Phylogenetic analysis suggests that fast skeletal MYHs evolved independently in teleosts and tetrapods after fast skeletal MYHs had diverged from four ancestral MYHs.

Stress-related genomic responses during the course of heat acclimation and its association with ischemic-reperfusion cross-tolerance

Acclimation to heat is a biphasic process involving a transient perturbed phase followed by a long lasting period during which acclimatory homeostasis is developed. In this investigation, we used cDNA stress microarray (Clontech Laboratory) to characterize the stress-related genomic response during the course of heat acclimation and to test the hypotheses that 1) heat acclimation influences the threshold of activation of protective molecular signaling, and 2) heat-acclimation-mediated ischemic-reperfusion (I/R) protection is coupled with reprogrammed gene expression leading to altered capacity or responsiveness of protective-signaling pathways shared by heat and I/R cytoprotective systems. Rats were acclimated at 34°C for 0, 2, and 30 days.32P-labeled RNA samples prepared from the left ventricles of rats before and after subjection to heat stress (HS; 2 h, 41°C) or after I/R insult (ischemia: 75%, 45 min; reperfusion: 30 min) were hybridized onto the array membranes. Confirmatory RT-PCR of selected genes conducted on samples taken at 0, 30, and 60 min after HS or total ischemia was used to assess the promptness of the transcriptional response. Cluster analysis of the expressed genes indicated that acclimation involves a “two-tier” defense strategy: an immediate transient response peaking at the initial acclimating phase to maintain DNA and cellular integrity, and a sustained response, correlated with slowly developed adaptive, long-lasting cytoprotective signaling networks involving genes encoding proteins that are essential for the heat-shock response, antiapoptosis, and antioxidation. Gene activation was stress specific. Faster activation and suppression of signaling pathways shared by HS and I/R stressors probably contribute to heat-acclimation I/R cross-tolerance.

Myosin heavy chain expression in cranial, pectoral fin, and tail muscle regions of zebrafish embryos

To investigate whether different myosin heavy chain (MHC) isoforms may constitute myofibrils in the trunk and tail musculature and if their respective expression may be regulated by spadetail (spt) and no tail (brachyury), we identified and characterized mRNA expression patterns of an embryonic- and tail muscle-specific MHC gene (named myhz2) during zebrafish development in wild type, spt, and ntl mutant embryos. The identified myhz2 MHC gene encodes a polypeptide containing 1,935 amino acids. Deduced amino acid comparisons showed that myhz2 MHC shared 92.6% sequence identity with that of carp fast skeletal MHC. Temporal and spatial myhz2 MHC mRNA expression patterns were analyzed by quantitative RT-PCR and whole-mount in situ hybridization using primer pairs and probes designed from the 3'-untranslated region (UTR). Temporally myhz2 MHC mRNA appears in pharyngula embryos and peaks in protruding-mouth larvae. The expression level decreased in 7-day-old hatching larvae, and mRNA expression was not detectable in adult fish. Spatially in pharyngula embryos, mRNA was localized only in the tail somite region, while in long-pec embryos, transcripts were also expressed in the two cranial muscle elements of the adductor mandibulae and medial rectus, as well as in pectoral fin muscles and the tail muscle region. Myhz2 MHC mRNA was expressed in most cranial muscle elements, pectoral fin muscles, and the tail muscle region of 3-day-old hatching larvae. In contrast, no expression of myhz2 MHC mRNA could be observed in spt prim-15 mutant embryos. In spt long-pec mutant embryos, transcripts were expressed in two cranial muscle elements and the tail muscle region, but not in pectoral fin muscles, while only trace amounts of myhz2 MHC mRNA were expressed in the remaining tail muscle region of 38 hpf and long-pec ntl mutant embryos.

Primary structure of myosin heavy chain from fast skeletal muscle of Chum salmon Oncorhynchus keta

The nucleotide sequence of the cDNA encoding myosin heavy chain of chum salmon Oncorhynchus keta fast skeletal muscle was determined. The sequence consists of 5,994 bp, including 5,814 bp of translated region deducing an amino acid sequence of 1,937 residues. The deduced sequence showed 79% homology to that of rabbit fast skeletal myosin and 84-87% homology to those of fast skeletal myosins from walleye pollack, white croaker and carp. The putative binding-sites for ATP, actin and regulatory light-chains in the subfragment-1 region of the salmon myosin showed high homology with the fish myosins (78-100% homology). However, the Loop-1 and Loop-2 showed considerably low homology (31-60%). On the other hand, the deduced sequences of subfragment-2 (533 residues) and light meromyosin (564 residues) showed 88-93% homology to the corresponding regions of the fish myosins. It becomes obvious that several specific residues of the rabbit LMM are substituted to Gly in the salmon LMM as well as the other fish LMMs. This may be involved in the structural instability of the fish myosin tail region.

Physiological basis of temperature-dependent biogeography: trade-offs in muscle design and performance in polar ectotherms

Polar, especially Antarctic, oceans host ectothermic fish and invertebrates characterized by low-to-moderate levels of motor activity; maximum performance is reduced compared with that in warmer habitats. The present review attempts to identify the trade-offs involved in adaptation to cold in the light of progress in the physiology of thermal tolerance. Recent evidence suggests that oxygen limitations and a decrease in aerobic scope are the first indications of tolerance limits at both low and high temperature extremes. The cold-induced reduction in aerobic capacity is compensated for at the cellular level by elevated mitochondrial densities, accompanied by molecular and membrane adjustments for the maintenance of muscle function. Particularly in the muscle of pelagic Antarctic fish, among notothenioids, the mitochondrial volume densities are among the highest known for vertebrates and are associated with cold compensation of aerobic metabolic pathways, a reduction in anaerobic scope, rapid recovery from exhaustive exercise and enhanced lipid stores as well as a preference for lipid catabolism characterized by high energy efficiency at high levels of ambient oxygen supply. Significant anaerobic capacity is still found at the very low end of the activity spectrum, e.g. among benthic eelpout (Zoarcideae).

In contrast to the cold-adapted eurytherms of the Arctic, polar (especially Antarctic) stenotherms minimize standard metabolic rate and, as a precondition, the aerobic capacity per milligram of mitochondrial protein,thereby minimizing oxygen demand. Cost reductions are supported by the downregulation of the cost and flexibility of acid—base regulation. At maintained factorial scopes, the reduction in standard metabolic rate will cause net aerobic scope to be lower than in temperate species. Loss of contractile myofilaments and, thereby, force results from space constraints due to excessive mitochondrial proliferation. On a continuum between low and moderately high levels of muscular activity, polar fish have developed characteristics of aerobic metabolism equivalent to those of high-performance swimmers in warmer waters. However, they only reach low performance levels despite taking aerobic design to an extreme.