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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.

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.

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In situ expression of halibut TnT genes during metamorphosis; Temporal and spatial expression of halibut embryonic/larval fTnT exon (A-D), General 3'UTR-fTnT probe (E-H), AfTnT (I-L) and sTnT2 (M-P) in transversal sections of halibut larvae, by in situ hybridization using DIG labelled riboprobes. Pre-metamorphic stg 5 larvae: A, E, I, M; pre-metamorphic stg 6 larvae: B, F, J and N; larvae at the beginning of metamorphic climax (stg 8): C, G, K and O; larvae at metamorphic climax (stg 9): D; postmetamorphic juveniles (stg 10): H, L and P. In C arrows depict efTnThh expression in putative myogenic satellite cells. In L arrows depicts AfTnT expression. In P arrows depict sTnT2 expression. Scale bars, 50 μm.
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Figure 9: In situ expression of halibut TnT genes during metamorphosis; Temporal and spatial expression of halibut embryonic/larval fTnT exon (A-D), General 3'UTR-fTnT probe (E-H), AfTnT (I-L) and sTnT2 (M-P) in transversal sections of halibut larvae, by in situ hybridization using DIG labelled riboprobes. Pre-metamorphic stg 5 larvae: A, E, I, M; pre-metamorphic stg 6 larvae: B, F, J and N; larvae at the beginning of metamorphic climax (stg 8): C, G, K and O; larvae at metamorphic climax (stg 9): D; postmetamorphic juveniles (stg 10): H, L and P. In C arrows depict efTnThh expression in putative myogenic satellite cells. In L arrows depicts AfTnT expression. In P arrows depict sTnT2 expression. Scale bars, 50 μm.

Mentions: Halibut embryonic/larval fTnT exon expression in pre-metamorphic halibut larvae (Stg5 and 6; Fig. 8 and Fig. 9A and 9B) is restricted to white muscle, in the lateral and apical germinal zones of the myotome. As the halibut larvae approach metamorphic climax (Stg8; Fig. 8 and Fig. 9C) the efTnThh expression is significantly downregulated and confined to very small fibres and to presumptive satellite cells (arrows in Fig. 8 and Fig. 9C). From climax of metamorphosis (stg 9; Fig. 8 and 9D) onwards no efTnThh expression is detected. The 3'UTR fTnT probe reveals the general fTnThh expression pattern in stage 5 (Fig. 8 and Fig. 9E) and stage 6 larvae (Fig. 8 and Fig. 9F) which is similar to that observed with the embryonic/larval fTnT exon probe. At stage 8 (Fig. 8 and Fig. 9G) fTnT is uniformly distributed in the white muscle. As the animals reach post-metamorphic juvenile stage 10 (Fig. 8 and Fig. 9H) fTnThh expression looses its uniformity and although still expressed in the entire myotome, the signal is more intense in cells close to the myosepta (Fig. 8).


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)

In situ expression of halibut TnT genes during metamorphosis; Temporal and spatial expression of halibut embryonic/larval fTnT exon (A-D), General 3'UTR-fTnT probe (E-H), AfTnT (I-L) and sTnT2 (M-P) in transversal sections of halibut larvae, by in situ hybridization using DIG labelled riboprobes. Pre-metamorphic stg 5 larvae: A, E, I, M; pre-metamorphic stg 6 larvae: B, F, J and N; larvae at the beginning of metamorphic climax (stg 8): C, G, K and O; larvae at metamorphic climax (stg 9): D; postmetamorphic juveniles (stg 10): H, L and P. In C arrows depict efTnThh expression in putative myogenic satellite cells. In L arrows depicts AfTnT expression. In P arrows depict sTnT2 expression. Scale bars, 50 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 9: In situ expression of halibut TnT genes during metamorphosis; Temporal and spatial expression of halibut embryonic/larval fTnT exon (A-D), General 3'UTR-fTnT probe (E-H), AfTnT (I-L) and sTnT2 (M-P) in transversal sections of halibut larvae, by in situ hybridization using DIG labelled riboprobes. Pre-metamorphic stg 5 larvae: A, E, I, M; pre-metamorphic stg 6 larvae: B, F, J and N; larvae at the beginning of metamorphic climax (stg 8): C, G, K and O; larvae at metamorphic climax (stg 9): D; postmetamorphic juveniles (stg 10): H, L and P. In C arrows depict efTnThh expression in putative myogenic satellite cells. In L arrows depicts AfTnT expression. In P arrows depict sTnT2 expression. Scale bars, 50 μm.
Mentions: Halibut embryonic/larval fTnT exon expression in pre-metamorphic halibut larvae (Stg5 and 6; Fig. 8 and Fig. 9A and 9B) is restricted to white muscle, in the lateral and apical germinal zones of the myotome. As the halibut larvae approach metamorphic climax (Stg8; Fig. 8 and Fig. 9C) the efTnThh expression is significantly downregulated and confined to very small fibres and to presumptive satellite cells (arrows in Fig. 8 and Fig. 9C). From climax of metamorphosis (stg 9; Fig. 8 and 9D) onwards no efTnThh expression is detected. The 3'UTR fTnT probe reveals the general fTnThh expression pattern in stage 5 (Fig. 8 and Fig. 9E) and stage 6 larvae (Fig. 8 and Fig. 9F) which is similar to that observed with the embryonic/larval fTnT exon probe. At stage 8 (Fig. 8 and Fig. 9G) fTnT is uniformly distributed in the white muscle. As the animals reach post-metamorphic juvenile stage 10 (Fig. 8 and Fig. 9H) fTnThh expression looses its uniformity and although still expressed in the entire myotome, the signal is more intense in cells close to the myosepta (Fig. 8).

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