Growth and the regulation of myotomal muscle mass in teleost fish

Abstract

SummaryTeleost muscle first arises in early embryonic life and its development is driven by molecules present in the egg yolk and modulated by environmental stimuli including temperature and oxygen. Several populations of myogenic precursor cells reside in the embryonic somite and external cell layer and contribute to muscle fibres in embryo, larval, juvenile and adult stages. Many signalling proteins and transcription factors essential for these events are known. In all cases, myogenesis involves myoblast proliferation, migration, fusion and terminal differentiation. Maturation of the embryonic muscle is associated with motor innervation and the development of a scaffold of connective tissue and complex myotomal architecture needed to generate swimming behaviour. Adult muscle is a heterogeneous tissue composed of several cell types that interact to affect growth patterns. The development of capillary and lymphatic circulations and extramuscular organs -notably the gastrointestinal, endocrine, neuroendocrine and immune systems -serves to increase information exchange between tissues and with the external environment, adding to the complexity of growth regulation. Teleosts often exhibit an indeterminate growth pattern, with body size and muscle mass increasing until mortality or senescence occurs. The dramatic increase in myotomal muscle mass between embryo and adult requires the continuous production of muscle fibres until 40-50% of the maximum body length is reached. Sarcomeric proteins can be mobilised as a source of amino acids for energy metabolism by other tissues and for gonad generation, requiring the dynamic regulation of muscle mass throughout the life cycle. The metabolic and contractile phenotypes of muscle fibres also show significant plasticity with respect to environmental conditions, migration and spawning. Many genes regulating muscle growth are found as multiple copies as a result of paralogue retention following whole-genome duplication events in teleost lineages. The extent to which indeterminate growth, ectothermy and paralogue preservation have resulted in modifications of the genetic pathways regulating muscle growth in teleosts compared to mammals largely remains unknown. This review describes the use of compensatory growth models, transgenesis and tissue culture to explore the mechanisms of muscle growth in teleosts and provides some perspectives on future research directions.

Molecular basis and genetic improvement of economically important traits in aquaculture animals

“…Since growth hormone (GH) gene was identified, many important growth-related genes have been demonstrated to play critical roles in growth regulation of vertebrates. Numerous candidate genes are correlated with growth, including main growth-related genes within the somatotropic axis, such as GH, growth hormone receptor (GHR), insulin-like growth factors (IGF-I and -II), growth hormone-releasing hormone (GHRH), Leptin, and growth hormone inhibiting hormone (GHIH or somatostatin), important transforming growth factor genes expressed in muscle tissues, such as myostatin (MSTN) and myogenic regulatory factors (MRFs), and other possible candidate genes have been recommended in fish through reviewing the livestock and fish literatures [93], and the regulative mechanisms of muscle growth have been explored by introducing different growth models including compensatory growth, genetic manipulation and in vitro tissue culture [94].…”

Is There a Trade-Off between Radiation-Stimulated Growth and Metabolic Efficiency?

“…Calabrese (13) has speculated that radiation may induce an overcompensation effect which may be analogous to compensatory growth observed after fasting-refeeding experiments (14). Alternate mechanisms include inactivation of inhibitory pathways (15) or even radiation as a direct input of energy (16).…”

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“…Two processes are characteristic for muscle growth and development -hyperplasia and hypertrophy. In myogenesis two types of hyperplasia can be distinguished: stratified hyperplasia (SH), and mosaic hyperplasia (MH) (Johnston et al, 2011). SH, the step of myogenesis occurring after myoblast fusion is observed during embryogenesis, and shortly after hatching (Steinbacher, Haslett, Sänger & Stoiber, 2006;Valente et al, 2013).…”

“…SH, the step of myogenesis occurring after myoblast fusion is observed during embryogenesis, and shortly after hatching (Steinbacher, Haslett, Sänger & Stoiber, 2006;Valente et al, 2013). MH, a step following SH, is characterized by presence of muscle fibers of various sizes (Rescan, 2005;Johnston et al, 2011). Proliferation of somatic cells, including MPCs, can be detected using antibodies directed against proliferating cell nuclear antigen (PCNA).…”