Temperature and the expression of seven muscle-specific protein genes during embryogenesis in the Atlantic codGadus morhuaL.

Abstract

SUMMARYSeven cDNA clones coding for different muscle-specific proteins (MSPs) were isolated from the fast muscle tissue of Atlantic cod Gadus morhua L. In situ hybridization using cRNA probes was used to characterize the temporal and spatial patterns of gene expression with respect to somite stage in embryos incubated at 4°C, 7°C and 10°C. MyoDtranscripts were first observed in the presomitic mesoderm prior to somite formation, and in the lateral compartment of the forming somites. MyoD expression was not observed in the adaxial cells that give rise to the slow muscle layer, and expression was undetectable by in situhybridization in the lateral somitic mesoderm after the 35-somite stage,during development of the final ∼15 somites. RT-PCR analysis, however,confirmed the presence of low levels of the transcript during these later stages. A phylogenetic comparison of the deduced aminoacid sequences of the full-length MyoD cDNA clone and those from other teleosts, and inference from the in situ expression pattern suggested homology with a second paralogue (MyoD2) recently isolated from the gilthead seabream Sparus aurata. Following MyoD expression,α-actin was the first structural gene to be switched on at the 16-somite stage, followed by myosin heavy chain, troponin T, troponin I and muscle creatine kinase. The final mRNA in the series to be expressed was troponin C. All genes were switched on prior to myofibril assembly. The troponin C sequence was unusual in that it showed the greatest sequence identity with the rainbow trout Oncorhynchus mykiss cardiac/slow form, but was expressed in the fast myotomal muscle and not in the heart. In addition, the third TnC calcium binding site showed a lower level of sequence conservation than the rest of the sequence. No differences were seen in the timing of appearance or rate of posterior progression (relative to somite stage) of any MSP transcripts between embryos raised at the different temperatures. It was concluded that myofibrillar genes are activated asynchronously in a distinct temporal order prior to myofibrillar assembly and that this process was highly canalized over the temperature range studied.

In situhybridisation of a large repertoire of muscle-specific transcripts in fish larvae: the new superficial slow-twitch fibres exhibit characteristics of fast-twitch differentiation

“…The specification of the different muscle cell identities depends upon distinct levels of activity of the morphogens of the hedgehog family (Du et al, 1997;Blagden et al, 1997;Wolff et al, 2003). The early differentiation of embryonic muscle fibres in fish embryos involves a complex temporal sequence of gene activations (Xu et al, 2000;Hall et al, 2003) including transient expression of fast Bryson-Richardson et al, 2005) as well as slow muscle isoforms in superficial slow fibres and deep fast fibres, respectively. Following embryonic myogenesis, an expansion of the myotome occurs in fish larvae involving the recruitment of new muscle fibres in germinal zones (Veggetti et al, 1990;Johnston et al, 1998;Galloway et al, 1999;Rowlerson and Veggetti, 2001).…”

Molecular characterization of three muscle alpha actin genes in mud loach (Misgurnus mizolepis; Cypriniformes)

“…During embryonic development, the onset expression of ACTA1 mRNAs was faintly detected by RT-qPCR at late gastrula stage (8 HPF; characterized by 70% epiboly cover). The expression was gradually increased with the progress of somitogenesis until 24 HPF (corresponding to pre-hatching stage exhibiting more than 30 somites), suggesting the essential roles of ACTA1 in embryonic myogenesis in mud loach embryos (Hall et al 2003;Xu et al 2000;Moutou et al 2001). Afterward, the transcript level of ACTA1 in mud loach embryos was sharply increased until hatch-out and further rigorously until 2 DPH.…”

“…Muscle growth in teleosts is signified by the combined contribution of a long-lasting hyperplasia (increase in fiber number) as well as the hypertrophy (increase in fiber size), which is hardly observable in many other higher vertebrates (Kiessling et al 2006;Johnston et al 2011). Furthermore, metabolic and contractile characteristics of teleost muscles also represent significant plasticity and flexibility with regard to not only environmental conditions (e.g., temperature (Hall et al 2003;Johnston et al 2008;Stickland et al 1988;Johnston 2006)) but also reproductive status (e.g., gonad maturation (Johnston et al 2011;Mathana et al 2012)). …”

The effect of temperature and thermal acclimation on the sustainable performance of swimming scup

“…Only the coldacclimated nervous system working at 108C differs from this default. This modification may be crucial during long migrations at cold temperatures (Neville & Talbot 1964) and may represent the expression of a different set of genes (Goldspink et al 1992;Cole & Johnston 2001;Hall et al 2003) …”