Myosin heavy chain expression in the red, white, and ventricular muscle of juvenile stages of rainbow trout

Thermal acclimation of rainbow trout myotomal muscle, can trout acclimate to a warming environment?

Climate change is a looming threat to the planet. Cold-water aquatic species will face significant physiological challenges due to elevated summer temperatures. Salmonids, such as rainbow trout (Oncorhynchus mykiss) maintain fidelity to native streams, limiting their ability to mitigate the impact of climate change through migration. We examined how rainbow trout swimming performance and muscle function were shaped by the thermal environment. We hypothesized that trout would show slower muscle contractile properties and slower swimming performance with long-term exposure to warmer water. For fish held at either 10 °C or 20 °C, maximum steady swimming speed (U_crit) was determined, and contractile properties of both fast-twitch (white) and slow-twitch (red) myotomal muscle were examined. In addition, immunohistochemistry and quantitative PCR were used to assess changes in myosin content of the myotomal muscle in response to holding temperature. Rainbow trout exposed to warm water for six weeks displayed relatively limited thermal acclimation response. When tested at a common temperature (10 °C), 20 °C acclimated fish had modestly slower muscle performance compared to 10 °C acclimated fish. Significant differences in swimming performance and muscle contractile properties were primarily at colder test temperatures (e.g. 2 °C for muscle mechanics). Shifts in myosin heavy chain protein composition and myosin heavy chain gene expression in the swimming muscle were observed in white but not red muscle. Our results suggest that rainbow trout will have a limited ability to mitigate elevated environmental temperature through thermal acclimation of their myotomal or swimming muscle.

Moderate and sustained exercise modulates muscle proteolytic and myogenic markers in gilthead sea bream (Sparus aurata)

Swimming activity primarily accelerates growth in fish by increasing protein synthesis and energy efficiency. The role of muscle in this process is remarkable and especially important in teleosts, where muscle represents a high percentage of body weight and because many fish species present continuous growth. The aim of this work was to characterize the effects of 5 wk of moderate and sustained swimming in gene and protein expression of myogenic regulatory factors, proliferation markers, and proteolytic molecules in two muscle regions (anterior and caudal) of gilthead sea bream fingerlings. Western blot results showed an increase in the proliferation marker proliferating cell nuclear antigen (PCNA), proteolytic system members calpain 1 and cathepsin D, as well as vascular endothelial growth factor protein expression. Moreover, quantitative real-time PCR data showed that exercise increased the gene expression of proteases (calpains, cathepsins, and members of the ubiquitin-proteasome system in the anterior muscle region) and the gene expression of the proliferation marker PCNA and the myogenic factor MyoD in the caudal area compared with control fish. Overall, these data suggest a differential response of the two muscle regions during swimming adaptation, with tissue remodeling and new vessel formation occurring in the anterior muscle and enhanced cell proliferation and differentiation occurring in the caudal area. In summary, the present study contributes to improving the knowledge of the role of proteolytic molecules and other myogenic factors in the adaptation of muscle to moderate sustained swimming in gilthead sea bream.

Expression of MyHC genes, composition of muscle fiber type and their association with intramuscular fat, tenderness in skeletal muscle of Simmental hybrids

In adult bovine skeletal muscle, it expressed four isoforms of Myosin heavy chain (MyHC) gene, MyHC-I, MyHC-IIa, MyHC-IIb, and MyHC-IIx that are translated into different structural protein myofibrils, and then further form different types of muscle fiber. In the studies, our objective is to reveal the expression patterns of MyHC genes in longissimus dorsi (Ld), semitendinosus (Se) and soleus (Sol) of Simmental hybrids cattle, and their association with intramuscular fat (IMF) content and meat shearing force (MSF). The muscle tissue of Ld, Se and Sol were collected from 6, 12 and 36-month old Simmental hybrids respectively, then the expression levels of MyHCs were examined by real-time PCR, at the same time, IMF, MSF and muscle type were measured with chemical assessment, shearing force measurer and immunostaining respectively. Our results showed that t Ld, Se, and Sol expressed MyHC-I, MyHC-IIa and MyHC-IIx isoforms but not MyHC-IIb, furthermore MyHC-I, MyHC-IIa and MyHC-IIx had different expression patterns in different skeletal muscle. The expression of MyHC-I in Se and Sol, MyHC-IIa in Ld, Se, and Sol, and MyHC-IIx in Sol was decreased with increasing age. The highest expression of MyHC-I in Ld, and MyHC-IIx in Ld and Se was observed in 12-month-old animals. The percentage of type-IIa fiber approximately occupied 70-80 % among various muscle fiber of Ld, Se and Sol. The percentage of different type fiber was not related to IMF content and MSF, but the expression levels of MyHC-I and MyHC-IIa were negatively related to IMF content (r = -0.724, and -0.681, respectively) and MSF (r = -0.672, and -0.641, respectively). The expression level of MyHC-IIx was also negatively related to MSF (r = -0.655). In conclusion, MyHC gene might be considered as a negative factor in genetic selection of IMF content and MSF.

Myosin heavy chain and parvalbumin expression in swimming and feeding muscles of centrarchid fishes: the molecular basis of the scaling of contractile properties

In centrarchid fishes, such as bluegill (Lepomis macrochirus, Rafinesque) and largemouth bass (Micropterus salmoides, Lacepède), the contractile properties of feeding and swimming muscles show different scaling patterns. While the maximum shortening velocity (V(max)) and rate of relaxation from tetanus of swimming or myotomal muscle slow with growth, the feeding muscle shows distinctive scaling patterns. Cranial epaxial muscle, which is used to elevate the head during feeding strikes, retains fast contractile properties across a range of fish sizes in both species. In bass, the sternohyoideous muscle, which depresses the floor of the mouth during feeding strikes, shows faster contractile properties with growth. The objective of this study was to determine the molecular basis of these different scaling patterns. We examined the expression of two muscle proteins, myosin heavy chain (MyHC) and parvalbumin (PV), that affect contractile properties. We hypothesized that the relative contribution of slow and fast MyHC isoforms will modulate V(max) in these fishes, while the presence of PV in muscle will enhance rates of muscle relaxation. Myotomal muscle displays an increase in sMyHC expression with growth, in agreement with its physiological properties. Feeding muscles such as epaxial and sternohyoideus show no change or a decrease in sMyHC expression with growth, again as predicted from contractile properties. PV expression in myotomal muscle decreases with growth in both species, as has been seen in other fishes. The feeding muscles again show no change or an increase in PV expression with growth, contributing to faster contractile properties in these fishes. Both MyHC and PV appear to play important roles in modulating muscle contractile properties of swimming and feeding muscles in centrarchid fishes.

Identification and analysis of muscle-related protein isoforms expressed in the white muscle of the mandarin fish (Siniperca chuatsi)

To identify muscle-related protein isoforms expressed in the white muscle of the mandarin fish Siniperca chuatsi, we analyzed 5,063 high-quality expressed sequence tags (ESTs) from white muscle cDNA library and predicted the integrity of the clusters annotated to these genes and the physiochemical properties of the putative polypeptides with full length. Up to about 33% of total ESTs were annotated to muscle-related proteins: myosin, actin, tropomyosin/troponin complex, parvalbumin, and Sarcoplasmic/endoplasmic reticulum calcium ATPase (SERCa). Thirty-two isoforms were identified and more than one isoform existed in each of these proteins. Among these isoforms, 14 putative polypeptides were with full length. In addition, about 2% of total ESTs were significantly homologous to "glue" molecules such as alpha-actinins, myosin-binding proteins, myomesin, tropomodulin, cofilin, profilin, twinfilins, coronin-1, and nebulin, which were required for the integrity and maintenance of the muscle sarcomere. The results demonstrated that multiple isoforms of major muscle-related proteins were expressed in S. chuatsi white muscle. The analysis on these isoforms and other proteins sequences will greatly aid our systematic understanding of the high flexibility of mandarin fish white muscle at molecular level and expand the utility of fish systems as models for the muscle genetic control and function.

Molecular cloning and mRNA expression analysis of carp embryonic, slow and cardiac myosin heavy chain isoforms

Three embryonic class II myosin heavy chains (MYHs) were cloned from the common carp (Cyprinus carpio L.), MYHemb1, MYHemb2 and MYHemb3. MYH DNA clones were also isolated from the slow muscle of adult carp acclimated to 10 degrees C (MYHS10) and 30 degrees C (MYHS30). Phylogenetic analysis demonstrated that MYHemb1 and MYHemb2 belonged to the fast skeletal muscle MYH clade. By contrast, the sequence of MYHemb3 was similar to the adult slow muscle isoforms, MYHS10 and MYHS30. MYHemb1 and MYHemb2 transcripts were first detected by northern blot analysis in embryos 61 h post-fertilization (h.p.f.) at the heartbeat stage, with peak expression occurring in 1-month-old juveniles. MYHemb1 continued to be expressed at low levels in 7-month-old juveniles when MYHemb2 was not detectable. MYHemb3 transcripts appeared at almost the same stage as MYHemb1 transcripts did (61 h.p.f.), and these genes showed a similar pattern of expression. Whole mount in situ hybridization analysis revealed that the transcripts of MYHemb1 and MYHemb2 were expressed in the inner part of myotome, whereas MYHemb3 was expressed in the superficial compartment. MYHS10 and MYHS30 mRNAs were first detected at hatching. In adult stages, the expression of slow muscle MYH mRNAs was dependent on acclimation temperature. MYHS10 mRNA was expressed at an acclimation temperature of 10 and 20 degrees C, but not at 30 degrees C. In contrast, MYHS30 mRNA was strongly expressed at all acclimation temperatures. The predominant MYH transcripts found in adult slow muscle and in embryos at hatching were expressed in adult fast muscle at some acclimation temperatures but not others. A MYH DNA clone was isolated from the cardiac muscle of 10 degrees C-acclimated adult fish (MYHcard). MYHcard mRNA was first detected at 61 h.p.f., but strong signals were only observed in the adult myocardium. The present study has therefore revealed a complex pattern of expression of MYH genes in relation to developmental stage, muscle type and acclimation temperature. None of the skeletal muscle MYHs identified so far was strongly expressed during the late juvenile stage, indicating further developmentally regulated members of the MYH II gene family remain to be discovered.

Transgenic salmon overexpressing growth hormone exhibit decreased myostatin transcript and protein expression

To characterize the role of myostatin (MSTN) in fast growing animals and to examine the relationship between MSTN and growth hormone (GH), MSTN transcript and protein expression were measured in coho salmon overexpressing GH and in wild-type coho salmon. Quantitative real-time RT-PCR and western analysis were used to measure RNA expression of the two salmonid MSTN genes (1 and 2) and levels of MSTN immunoreactive protein (MIP) in developing embryos and adult coho salmon tissues. In transgenic and control coho embryos, MSTN1 and MSTN2 RNA expression were initially observed at about the time of eying, and a 42 kDa MIP was just detected prior to hatching. Expression of the MSTN1 transcript in transgenic salmon was not different from that in wild-type adult coho salmon muscle and brain tissue. However, expression of the MSTN2 transcript was less in white muscle, and greater in red muscle, from transgenic fish compared to wild-type salmon of the same size. Northern analysis revealed that expression of the MSTN2 transcript was less in white muscle from wild-type, age-matched salmon than in transgenic fish. In addition, there was less presumed bioactive MIP in muscle taken from adult transgenic fish compared to controls and evidence of differential protein processing. Decreased MSTN expression in faster growing fish suggests that MSTN does act as a negative regulator of muscle growth in fish, as it does in mammals. The results of this study also suggest that the anabolic effects of GH could be mediated through MSTN.