Troponin T isoform expression is modulated during Atlantic Halibut metamorphosis

<p>Abstract</p> <p>Background</p> <p>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 <it>Troponin T </it>(<it>TnT</it>), a pivotal protein in the assembly of skeletal muscles sarcomeres and a modulator of calcium driven muscle contraction, during flatfish metamophosis is studied.</p> <p>Results</p> <p>In the present study five cDNAs for halibut <it>TnT </it>genes were cloned; three were splice variants arising from a single <it>fast TnT </it>(<it>fTnT</it>) gene; a fourth encoded a novel teleost specific fTnT-like cDNA (<it>AfTnT</it>) expressed exclusively in slow muscle and the fifth encoded the teleost specific <it>sTnT2</it>. THs modified the expression of halibut <it>fTnT </it>isoforms which changed from predominantly basic to acidic isoforms during natural and T4 induced metamorphosis. In contrast, expression of red muscle specific genes, <it>AfTnT </it>and <it>sTnT2</it>, 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 <it>TnT </it>genes and muscle fibre organization occurred in halibut musculature.</p> <p>Conclusion</p> <p>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 <it>TnT </it>gene expression in teleosts underlies different larval muscle developmental programs which better adapts them to the specific ecological constraints.</p

Thyroid hormone receptor expression during metamorphosis of Atlantic halibut (Hippoglossus hippoglossus)

Flatfish such as the Atlantic halibut (Hippoglossus hippoglossus) undergo a dramatic metamorphosis that transforms the pelagic, symmetric larva into a benthic, cranially asymmetric juvenile. In common with amphibian metamorphosis, flatfish metamorphosis is under endocrine control with thyroid hormones being particularly important. In this report we confirm that tri-iodothyronine (T3) levels peak at metamorphic climax during halibut metamorphosis. Moreover we have isolated cDNA clones of TR and TR genes and confirmed the presence in halibut of two TR isoforms (representing the products of distinct genes) and two TR isoforms (generated from a single gene by alternative splicing). Real time PCR was used to assess expression of these genes during metamorphosis. TR shows the most dramatic expression profile, with a peak occurring during metamorphic climax.This work has been carried out within the project “Arrested development: The Molecular and Endocrine Basis of Flatfish Metamorphosis” (Q5RS-2002-01192) with financial support from the Commission of the European Communities. However, it does not necessarily reflect the Commission’s views and in no way anticipates its future policy in this area. We thank Heiddis Smáradóttir (Fiskeldi Eyjafjarðar, IS-600 Akureyri, Iceland) for collecting and providing the Atlantic halibut samples, and Karin Pittman and Øystein Sæle (both from the Department of Biology, University of Bergen, Norway) for analysing samples to determine developmental stage. We are also grateful to Marco Campinho for preparing the RNA used in the study

Cloning of the Atlantic salmon (Salmo salar) estrogen receptor-α gene

A cDNA clone encoding most of an Atlantic salmon (Salmo salar) estrogen receptor (ER) was obtained from a liver cDNA library and the remainder of the coding sequence from the gene was isolated from a genomic library. Sequence comparisons showed that the cloned gene represents ER-α. Expression of the ER-α gene in male and female salmon parr was analysed by RT-PCR. Highest expression was found in brain and liver, with lower levels of ER-α mRNA present in all other tissues tested. There was little difference in expression of ER-α between male and female

Expression of thyroid hormone receptor during early development of the sea bream (Sparus aurata)

The thyroid hormones thyroxine (T4) and triiodothyronine (T3) are crucial to many aspects of vertebrate growth, development, and metabolism. They act through intracellular receptor proteins which act directly on target genes. Although the role of thyroid hormones in fish, especially in early development, is not well understood, thyroid hormones are passed to eggs by broodfish during spawning and are implicated in fish development.1,2 Sea bream (Sparus aurata) aquaculture has grown rapidly in importance in the European Community, particularly in southern Portugal. However, its further development is hindered by the high larval mortality rate and incidence of malformations. This work investigates the significance of thyroid hormones in sea bream development by cloning the thyroid hormone receptor (TR) and analyzing its expression during larval development

Cloning, characterisation and expression of the apolipoprotein A-I gene in the sea bream (Sparus aurata)

A full length cDNA clone representing apolipoprotein A-I was isolated from a sea bream (Sparus aurata) liver library. The clone encodes a 261 amino acid protein which shows highest amino acid identity (38%) with salmon apolipoprotein A-I. Northern blot analysis showed strong expression of a 1.4 kb transcript in liver with lower expression in intestine. Expression of apolipoprotein A-I in intestine was markedly reduced by treatment with triiodothyronine (T3). ß 1998 Elsevier Science B.V. All rights reserved.European Union AI

Cloning and unusual expression profile of the aldolase B gene from Atlantic salmon

A full-length clone of the aldolase B gene has been isolated from a cDNA library constructed from liver of Atlantic salmon (Salmo salar). Sequencing showed that the clone encodes a typical aldolase B, possessing a number of amino acid residues which are seen in aldolase B, but not in other aldolase isoforms. RT-PCR analysis showed that the gene is expressed in liver, kidney and intestine as expected. However, in contrast to mammalian and avian aldolase B, expression was also found in a number of other tissues. Levels of aldolase B mRNA in liver and kidney were not significantly altered during smoltification, the transformation of freshwater-dwelling salmon (parr) into saltwater-adapted salmon (smolts)

Cloning and characterisation of a fish aldolase B gene

E.C. (contract No. AIR2-CT93-1483).A full length cDNA clone representing an aldolase mRNA was isolated from a sea bream (Sparus aurutu) liver cDNA library. Sequencing of this clone revealed it to encode a 364 amino acid protein with 74% amino acid identity to human aldolase B and slightly lower similarity to human aldolase A and C. In view of the sequence data and of Northern blot analysis showing strong expression of a 1.6 kb transcript in liver it was concluded that the cloned gene represents aldolase B. This clone represents the first aldolase gene to be sequenced from any fish species thus providing new data on the evolution of the vertebrate aldolase gene family

Cloning and sequencing of a full-length sea bream (Sparus aurata) beta-actin cDNA

A full-length cDNA clone encoding beta-actin (b-actin) was isolated from a sea bream (Sparus aurata) liver cDNA library. Sequencing of this clone reveals an open reading frame encoding a 375 amino acid protein that shares a high degree of conservation to other known actins. The sea breamb-actin sequence showed 98% identity to carp and human b-actin and 95% and 94% identity to sea squirt and Dictyostelium cytoplasmic actins, respectively.The sea bream sequence is available from EMBL/GenBank Data Libraries under the accession number X89920. This work was supported by an EC Grant (AIR2-CT93 1483). Cecilia R. A. Santos was funded by JNICT (Programa Ciencia/BD/2632/IG/93)

Analysis of the Sox gene family in the European sea bass (Dicentrarchus labrax)

Sox (SRY-related genes containing a HMG box) genes encode a family of transcription factors that are involved in a variety of developmental processes including sex determination. Twenty Sox genes are present in the genomes of humans and mice, but far less is known about the Sox gene family in other vertebrate types. We have obtained clones representing the HMG boxes of twelve Sox genes from European sea bass (Dicentrarchus labrax), a fish species whose farming is complicated by a heavily skewed sex ratio, with between 70% and 99% of offspring typically being male. The cloned Sox genes are members of the SoxB, SoxC, SoxE and SoxF groups. Sequence analysis shows that some of the clones represent genes duplicated in sea bass with respect to the mammalian Sox gene family.This research has been carried out with the financial support of the Commission of the European Union, Quality of Life and Management of Living Resources specific RTD programme (Q5RS-2000-31365)

Analysis of the Sox gene family in the European sea bass (Dicentrarchus labrax)

Sox (SRY-related genes containing a HMG box) genes encode a family of transcription factors that are involved in a variety of developmental processes including sex determination. Twenty Sox genes are present in the genomes of humans and mice, but far less is known about the Sox gene family in other vertebrate types. We have obtained clones representing the HMG boxes of twelve Sox genes from European sea bass (Dicentrarchus labrax), a fish species whose farming is complicated by a heavily skewed sex ratio, with between 70% and 99% of offspring typically being male. The cloned Sox genes are members of the SoxB, SoxC, SoxE and SoxF groups. Sequence analysis shows that some of the clones represent genes duplicated in sea bass with respect to the mammalian Sox gene family