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Troponin T isoform expression is modulated during Atlantic halibut metamorphosis.

Campinho MA, Silva N, Nowell MA, Llewellyn L, Sweeney GE, Power DM - BMC Dev. Biol. (2007)

Bottom Line: In contrast, expression of red muscle specific genes, AfTnT and sTnT2, did not change during natural metamorphosis or after T4 treatment.Muscle organisation in halibut remains symmetrical even after metamorphosis suggesting TH driven changes are associated with molecular adaptations.We hypothesize that species specific differences in TnT gene expression in teleosts underlies different larval muscle developmental programs which better adapts them to the specific ecological constraints.

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Affiliation: CCMAR, FERN, Universidade do Algarve, Campus de Gambelas, Faro, Portugal. macampin@ualg.pt <macampin@ualg.pt>

ABSTRACT

Background: Flatfish metamorphosis is a thyroid hormone (TH) driven process which leads to a dramatic change from a symmetrical larva to an asymmetrical juvenile. The effect of THs on muscle and in particular muscle sarcomer protein genes is largely unexplored in fish. The change in Troponin T (TnT), a pivotal protein in the assembly of skeletal muscles sarcomeres and a modulator of calcium driven muscle contraction, during flatfish metamophosis is studied.

Results: In the present study five cDNAs for halibut TnT genes were cloned; three were splice variants arising from a single fast TnT (fTnT) gene; a fourth encoded a novel teleost specific fTnT-like cDNA (AfTnT) expressed exclusively in slow muscle and the fifth encoded the teleost specific sTnT2. THs modified the expression of halibut fTnT isoforms which changed from predominantly basic to acidic isoforms during natural and T4 induced metamorphosis. In contrast, expression of red muscle specific genes, AfTnT and sTnT2, did not change during natural metamorphosis or after T4 treatment. Prior to and after metamorphosis no change in the dorso-ventral symmetry or temporal-spatial expression pattern of TnT genes and muscle fibre organization occurred in halibut musculature.

Conclusion: Muscle organisation in halibut remains symmetrical even after metamorphosis suggesting TH driven changes are associated with molecular adaptations. We hypothesize that species specific differences in TnT gene expression in teleosts underlies different larval muscle developmental programs which better adapts them to the specific ecological constraints.

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Halibut TnT genes tissue specific expression; (A) Northern blot analysis of the expression of halibut fTnThh, AfTnThh and sTnT2hh genes in adult white muscle (W), red muscle (R), heart (H) and liver (L). All images represent 48 hour exposures. Ethidium bromide gel image is shown to give an indication of the quantity of total RNA loaded per sample. (B) RT-PCR analysis of expression of fTnThh, AfTnThh and sTnT2hh in halibut adult white (WM) and red (RM) muscle and heart (H). The 18s rRNA is shown and was used for normalisation. The graphs on the right of the fTnThh and AfTnThh gels represent, respectively, expression of the different fTnThh or AfTnThh isoforms relative to 18s rRNA.
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Figure 3: Halibut TnT genes tissue specific expression; (A) Northern blot analysis of the expression of halibut fTnThh, AfTnThh and sTnT2hh genes in adult white muscle (W), red muscle (R), heart (H) and liver (L). All images represent 48 hour exposures. Ethidium bromide gel image is shown to give an indication of the quantity of total RNA loaded per sample. (B) RT-PCR analysis of expression of fTnThh, AfTnThh and sTnT2hh in halibut adult white (WM) and red (RM) muscle and heart (H). The 18s rRNA is shown and was used for normalisation. The graphs on the right of the fTnThh and AfTnThh gels represent, respectively, expression of the different fTnThh or AfTnThh isoforms relative to 18s rRNA.

Mentions: Northern blot and RT-PCR analysis were carried out in order to determine tissue specificity of the halibut TnT genes isolated. The northern blot results (Fig. 3A) show that fTnThh, as expected, is expressed in adult halibut white (fast) muscle and is absent from red muscle, cardiac muscle and liver. However, the more sensitive RT-PCR technique revealed that fTnThh is also expressed in halibut adult red muscle (Fig. 3B). The tBLASTx and phylogenetic analysis of AfTnThh classified this cDNA as the product of a fast TnT gene, although its expression is red (slow) muscle specific (Fig. 3A) and it is not detected in adult white (fast) muscle, cardiac muscle or liver. The halibut sTnT2 gene is exclusively expressed in halibut adult red muscle (Fig. 3A). The red muscle tissue specificity of AfTnThh and sTnT2hh was further confirmed by RT-PCR (Fig. 3B).


Troponin T isoform expression is modulated during Atlantic halibut metamorphosis.

Campinho MA, Silva N, Nowell MA, Llewellyn L, Sweeney GE, Power DM - BMC Dev. Biol. (2007)

Halibut TnT genes tissue specific expression; (A) Northern blot analysis of the expression of halibut fTnThh, AfTnThh and sTnT2hh genes in adult white muscle (W), red muscle (R), heart (H) and liver (L). All images represent 48 hour exposures. Ethidium bromide gel image is shown to give an indication of the quantity of total RNA loaded per sample. (B) RT-PCR analysis of expression of fTnThh, AfTnThh and sTnT2hh in halibut adult white (WM) and red (RM) muscle and heart (H). The 18s rRNA is shown and was used for normalisation. The graphs on the right of the fTnThh and AfTnThh gels represent, respectively, expression of the different fTnThh or AfTnThh isoforms relative to 18s rRNA.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC1919359&req=5

Figure 3: Halibut TnT genes tissue specific expression; (A) Northern blot analysis of the expression of halibut fTnThh, AfTnThh and sTnT2hh genes in adult white muscle (W), red muscle (R), heart (H) and liver (L). All images represent 48 hour exposures. Ethidium bromide gel image is shown to give an indication of the quantity of total RNA loaded per sample. (B) RT-PCR analysis of expression of fTnThh, AfTnThh and sTnT2hh in halibut adult white (WM) and red (RM) muscle and heart (H). The 18s rRNA is shown and was used for normalisation. The graphs on the right of the fTnThh and AfTnThh gels represent, respectively, expression of the different fTnThh or AfTnThh isoforms relative to 18s rRNA.
Mentions: Northern blot and RT-PCR analysis were carried out in order to determine tissue specificity of the halibut TnT genes isolated. The northern blot results (Fig. 3A) show that fTnThh, as expected, is expressed in adult halibut white (fast) muscle and is absent from red muscle, cardiac muscle and liver. However, the more sensitive RT-PCR technique revealed that fTnThh is also expressed in halibut adult red muscle (Fig. 3B). The tBLASTx and phylogenetic analysis of AfTnThh classified this cDNA as the product of a fast TnT gene, although its expression is red (slow) muscle specific (Fig. 3A) and it is not detected in adult white (fast) muscle, cardiac muscle or liver. The halibut sTnT2 gene is exclusively expressed in halibut adult red muscle (Fig. 3A). The red muscle tissue specificity of AfTnThh and sTnT2hh was further confirmed by RT-PCR (Fig. 3B).

Bottom Line: In contrast, expression of red muscle specific genes, AfTnT and sTnT2, did not change during natural metamorphosis or after T4 treatment.Muscle organisation in halibut remains symmetrical even after metamorphosis suggesting TH driven changes are associated with molecular adaptations.We hypothesize that species specific differences in TnT gene expression in teleosts underlies different larval muscle developmental programs which better adapts them to the specific ecological constraints.

View Article: PubMed Central - HTML - PubMed

Affiliation: CCMAR, FERN, Universidade do Algarve, Campus de Gambelas, Faro, Portugal. macampin@ualg.pt <macampin@ualg.pt>

ABSTRACT

Background: Flatfish metamorphosis is a thyroid hormone (TH) driven process which leads to a dramatic change from a symmetrical larva to an asymmetrical juvenile. The effect of THs on muscle and in particular muscle sarcomer protein genes is largely unexplored in fish. The change in Troponin T (TnT), a pivotal protein in the assembly of skeletal muscles sarcomeres and a modulator of calcium driven muscle contraction, during flatfish metamophosis is studied.

Results: In the present study five cDNAs for halibut TnT genes were cloned; three were splice variants arising from a single fast TnT (fTnT) gene; a fourth encoded a novel teleost specific fTnT-like cDNA (AfTnT) expressed exclusively in slow muscle and the fifth encoded the teleost specific sTnT2. THs modified the expression of halibut fTnT isoforms which changed from predominantly basic to acidic isoforms during natural and T4 induced metamorphosis. In contrast, expression of red muscle specific genes, AfTnT and sTnT2, did not change during natural metamorphosis or after T4 treatment. Prior to and after metamorphosis no change in the dorso-ventral symmetry or temporal-spatial expression pattern of TnT genes and muscle fibre organization occurred in halibut musculature.

Conclusion: Muscle organisation in halibut remains symmetrical even after metamorphosis suggesting TH driven changes are associated with molecular adaptations. We hypothesize that species specific differences in TnT gene expression in teleosts underlies different larval muscle developmental programs which better adapts them to the specific ecological constraints.

Show MeSH
Related in: MedlinePlus