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Parvalbumins (PVALBs) are particularly abundant in the fast-contracting muscles and correlate positively with muscle relaxation speed in amphibians and fishes. MiRNAs play important roles in diverse biologic processes via binding to the 3’ untranslated region (3’UTR) of the target mRNAs. In the study, four PVALB isoforms, named as PVALB1, 2, 3, and 4, were identified in the mandarin fish ( Siniperca chuatsi ) fast muscle and PVALB4 exhibited the highest expression level among them. By bioinformatics analysis, a putative miR-181a binding site in PVALB4 was detected and the direct interaction between miR-181a and PVALB4 was confirmed with the luciferase reporter assay. Further, when miR-181a was inhibited, it substantially increased PVALB4 mRNA expression level and the muscle relaxation rate in vivo . Taken together, the obtained results suggest that miRNA-181a/PVALB4 is an evolutionarily conserved miRNAtarget pair and their interaction is correlated with muscle relaxation rate in the mandarin fish. Therefore, the study revealed a novel molecular mechanism in the regulation of skeletal muscle relaxation in fish.

Follistatin-related protein (FSRP), which belongs to a member of the follistatin family, has been postulated to be a new negative regulator of myostatin (MSTN) and is involved in muscle development. In this study, we cloned the complete cDNA sequence of FSRP-1 from Chinese perch muscle. FSRP-1 mRNA was highly expressed in the fast muscle and brain tissue of adult fish. The expression of FSRP-1 rapidly increased at 90 days post hatching (dph) in the fast muscle of Chinese perch. Furthermore, to investigate the roles of FSRP-1 in muscle growth, we constructed a FSRP- 1 expression vector and isolated FSRP-1 fusion protein. The purified FSRP-1 fusion protein was injected into the muscle tissues of the Chinese perch (90 dph). The results showed that the number of muscle fibers and the satellite cell activation frequency were increased in the FSRP-1 treatment group. In addition, the myostatin (MSTN) expression was significantly decreased upon the FSRP-1 treatment. Collectively, the results suggest a possible mechanism of the FSRP-1 for inhibiting MSTN activity and enhancing muscle growth and renewal in vivo, and it may provide an applicable implication for the defected muscle repairing and regeneration.

The fast and slow skeletal muscle fibers in fish are separated to a much greater degree than in mammals. MyoD is required for the maintenance of normal fiber type balance in muscles. So far, the upstream regulatory factors of MyoD in terms of controlling muscle phenotype are poorly understood. In the present study, we used Siniperca chuatsi as a model system and demonstrated that miR-143 expression was negatively correlated with MyoD expression in the fast and slow muscles of S. chuatsi. The luciferase reporter assay further verified the direct interaction between the miR-143 and MyoD. The miR-143 suppression also led to the significant increase in MyoD and fast myosin heavy chain gene expression in vivo. Taken together, our studies indicated that miRNA participates in controlling the performance of different muscle fiber types in vertebrates.

Sinipercids are a group of freshwater perciform fish endemic in East Asia with the majority of species recorded in China. In the present study, we analyzed the organizations of complete mitogenomes of the six sinipercid fish populations from the Yangtze River and the Pearl River systems in China. The proportion of G was relatively low just at 16.2%-16.5% among the fish populations analyzed. The similarity and divergence analysis showed that the populations from different drainages have more sequence similarities than those from different species in the same drainages. The rate of point mutation was 0.39% and a total of 422 variable sites were identified in the 12 protein-coding genes (excluding the ND6) among the four S. scherzeri populations. The analysis of evolutionary relationship showed that the four S. scherzeri populations can be divided into two groups of Yangtze River system and the Pearl River. Overall the data provide significant information for the genetic and evolutionary status of sinipercids upon adapting to different environments, and for genetic conservation and selective breeding of these fish species in fishery and aquaculture.

MicroRNAs (miRNAs) participate in the regulation of myogenesis and muscle physiological function. Most skeletal muscles in vertebrates contain a mixture of fibertypes. So far, the regulatory mechanism of the miRNA in terms of controlling muscle phenotype is poorly understood. In the present study, we use Siniperca chuatsi as a model system and demonstrate that miRNAs are involved in regulating the physiological processes and metabolism of different muscle fibers in vertebrates. The miRNA transcriptomes of the white muscle, red muscle, and five other tissues from Siniperca chuatsi were profiled using Solexa deep sequencing. We characterized 186 conserved miRNAs and 3 novel miRNAs from the two small RNA libraries of white and red muscles. Among the 155 miRNAs overlapped between the two libraries, we identified 60 significantly expressed miRNAs between the two types of muscle fibers. Using integrative miRNA target-prediction and network-analysis approaches, an interaction network of differentially expressed and muscle-related miRNAs and their putative targets were constructed. Sch-miR-181a-5p that could act to control the performance of the different muscle fiber types by targeting the myostatin gene was identified.