Expression profiles of metamorphosis-related genes during natural transformations in tadpoles of wild Wood Frogs (Lithobates sylvaticus)

• Published in: Canadian journal of zoology Vol. 90; no. 9; pp. 1059 - 1071
• Main Authors: NAVARRO-MARTIN, Laia, LANCTOT, Chantal, EDGE, Christopher, HOULAHAN, Jeff, TRUDEAU, Vance L
• Format: Journal Article
• Language: English
• Published: Ottawa NRC Research Press 01.09.2012; National Research Council of Canada; Canadian Science Publishing NRC Research Press
• Subjects: Amphibians; amphibiens; axe thyroïdien; Biological and medical sciences; Development. Metamorphosis. Moult. Ageing; developmental gene expression profiles; Enzymes; Frogs; Fundamental and applied biological sciences. Psychology; Gene expression; Genetic aspects; grenouille des bois; Growth; Hormones; Lithobates sylvaticus; Metamorphosis; métamorphose; profils d’expression génique du développement; Rana sylvatica; Tadpoles; Thyroid; thyroid axis; Thyroid gland; têtards; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Wood Frog; Zoology; Canada; Vertebrata; Gene; Larva; Rana sylvatica; Amphibia; Development; Ranidae; Salientia; Gene expression; Metamorphosis
• ISSN: 1480-3283; 0008-4301; 1480-3283; 0008-4301
• DOI: 10.1139/z2012-074

Numerous studies using laboratory-reared tadpoles have shown the importance of thyroid hormones (TH), thyroid receptors (TR), and deiodinase (Dio) enzymes during anuran metamorphosis. Our study focuses on the analysis of thyroid-related genes in tadpoles of wild Wood Frogs (Lithobates sylvaticus (LeConte, 1825); also known as Rana sylvatica (Cope, 1889)) during metamorphosis. Results showed that, in concordance with laboratory-reared studies, thyroid receptor beta (trb) gene expression profiles presented the most marked changes. At climax and compared with premetamorphic stages, brains, tails, and gonad–mesonephros complex (GMC) tissues increased trb expression levels 5-, 21-, and 41-fold, respectively (p < 0.05). In addition, gene expression levels of brain deiodinase type II and III showed opposite trends, where 3-fold decrease and 10-fold increase were, respectively, found. This finding supports the idea that thyroid hormone, as it has been demonstrated in laboratory-reared tadpoles, is also involved in natural metamorphosis in wild tadpoles. Interestingly, and contrary to our predictions, we observed that whole brain corticotropin-releasing factor (crf) and crf receptor 1 (crfr1) gene expression levels significantly decrease through metamorphosis in wild L. sylvaticus tadpoles. Further analyses are required to determine if a role of TH in the timing of anuran gonadal development exists, as well as the importance of cell-specific and tissue-specific expression of crf and crfr1 to metamorphosis.