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- Molecular and cellular changes in skin and muscle during metamorphosis of Atlantic halibut (Hippoglossus hippoglossus) are accompanied by changes in deiodinases expressionPublication . Campinho, Marco António; Galay-Burgos, M.; Silva, Nádia; Costa, R. A.; Alves, Ricardo N.; Sweeney, Glen E.; Power, DeborahFlatfish metamorphosis is the most dramatic postnatal developmental event in teleosts. Thyroid hormones (TH), thyroxine (T4) and 3,3′-5′-triiodothyronine (T3) are the necessary and sufficient factors that induce and regulate flatfish metamorphosis. Most of the cellular and molecular action of TH is directed through the binding of T3 to thyroid nuclear receptors bound to promoters with consequent changes in the expression of target genes. The conversion of T4 to T3 and nuclear availability of T3 depends on the expression and activity of a family of 3 selenocysteine deiodinases that activate T4 into T3 or degrade T4 and T3.
- The molecular and endocrine basis of flatfish metamorphosisPublication . Power, Deborah; Einarsdóttir, Ingibjörg E.; Pittman, Karin; Sweeney, Glen E.; Hildahl, Jon; Campinho, Marco António; Silva, Nadia; Saele, Oystein; Galay-Burgos, M.; Smaàradóttir, Heiddis; Björnsson, Björn ThrandurA significant component of aquaculture is the production of good quality larvae, and, in the case of flatfish, this is tied up with the change from a symmetric larva to an asymmetric juvenile. Despite the pioneering work carried out on the metamorphosis of the Japanese flounder (Paralichthys olivaceus) and summer flounder (Paralichthys dentatus), the underlying molecular basis of flatfish metamorphosis is still relatively poorly characterized. It is a thyroid hormone (TH) driven process, and the role of other hormones in the regulation of the process along with the interplay of abiotic factors are still relatively poorly characterized as is the extent of tissue and organ remodeling, which underlie the profound structural and functional modifications that accompany the larval/juvenile transition. The isolation of genes for hormones, receptors, binding proteins, and other accessory factors has provided powerful tools with which to pursue this question. The application of molecular methodologies such as candidate gene approaches and microarray analysis coupled to functional genomics has started to contribute to understanding the complexity of tissue and organ modifications that accompany flatfish metamorphosis. A better understanding of the biology of normal metamorphosis is essential to identify factors contributing to abnormal metamorphosis.
- Coordination of deiodinase and thyroid hormone receptor expression during the larval to juvenile transition in sea bream (Sparus aurata, Linnaeus)Publication . Campinho, Marco António; Galay-Burgos, M.; Sweeney, Glen E.; Power, DeborahTo test the hypothesis that THs play an important role in the larval to juvenile transition in the marine teleost model, sea bream (Sparus auratus), key elements of the thyroid axis were analysed during development. Specific RT-PCR and Taqman quantitative RT-PCR were established and used to measure sea bream iodothyronine deiodinases and thyroid hormone receptor (TR) genes, respectively. Expression of deiodinases genes (D1 and D2) which encode enzymes producing T3, TRs and T4 levels start to increase at 20–30 days post-hatch (dph; beginning of metamorphosis), peak at about 45 dph (climax) and decline to early larval levels after 90–100 dph (end of metamorphosis) when fish are fully formed juveniles. The profile of these different TH elements during sea bream development is strikingly similar to that observed during the TH driven metamorphosis of flatfish and suggests that THs play an analogous role in the larval to juvenile transition in this species and probably also in other pelagic teleosts. However, the effect of T3 treatment on deiodinases and TR transcript abundance in sea bream is not as clear cut as in larval flatfish and tadpoles indicating divergence in the responsiveness of TH axis elements and highlighting the need for further studies of this axis during development of fish.