Identification of thyroid hormone receptor homologs in the fluke Opisthorchis felineus (Platyhelminthes)

• There are two genes of thyroid hormone receptors in the genome of Opisthorchis felineus.
• The maximal level of mRNA expression of thyroid receptors was observed in adult worms.
• There are DNA-binding and ligand-binding domains in the predicted thyroid hormone receptors.
• Triiodothyronine and thyroxine changed the expression of potential target genes in O. felineus.

The liver fluke, Opisthorchis felineus of the Opisthorchiidae family, is a well-known causative agent of opisthorchiasis in Russia and Europe. The aim of this work was to identify genes encoding thyroid hormone receptors in O. felineus, and to analyze the expression of possible target genes in response to treatment with exogenous thyroid hormones. We identified two genes encoding thyroid hormone receptors in the O. felineus genome, THRA and THRB. The genes were differentially expressed through the life cycle. The maximal level of mRNA expression of THRA1 and THRB was observed in adult worms. Treatment of the worms with triiodothyronine and thyroxine resulted in an increase in glucose 6-phosphatase mRNA expression and a decrease in malate dehydrogenase mRNA expression, potential gene targets of thyroid hormones. These data indicate that thyroid hormone receptors may perform essential roles in physiological processes in adult O. felineus.

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