FERNANDINO Juan Ignacio
congresos y reuniones científicas
The role of triiodothyronine in sex reversal and delay of hatching in medaka embryos
CASTAÑEDA CORTÉS, D.C.; LANGLOIS, V.S.; FERNANDINO, J.I.
Conferencia; 3rd Biennial Conference of the North American Society for Comparative Endocrinology; 2015
North American Society for Comparative Endocrinology
Cumulative evidences show that thyroid hormones (THs) play an important role in many development process in mammalian and non-mammals species. Recent results suggest a more direct crossover between THs and androgen pathways. Initially we studied the crossover between THs and androgens with an in silico promoter analysis of several genes involved in the synthesis of THs and androgens in medaka (Oryzias latipes). We found thyroid response elements on androgen related genes; such as 5-alpha-reductases 1 (two TREs) and 11-beta hydroxysteroid dehydrogenase 2 (five TREs) genes, involved in the synthesis of 5-alpha-dihydrotestosterone and 11-Ketotestosterone, respectively. Then, to determine the biological effect of THs in the process of gonadal development have been reared medaka eggs from fertilization to hatching at different concentrations of triiodothyronine (T3; 0.05, 0.5 and 5 nM). The control without addition of T3 presented regular sex reversal of genetically males (XY) to phenotypically female (around 10%), observed by the development of ovary. The chronic exposed at low concentration of T3 increased the masculinization (development of testis) in genetically females (XX). This sex reversal was observed at all T3 treatment, with the concomitant reduction of female percentages. On the other hand, recently was observed in fish that Type 3 Iodothyronine Deiodinase (dio3) presents an important role in the regulation of hatching. The dio3 is the primary inactivating deiodinase, which terminate the TH action. When larvae of medaka were exposed to T3 the highest dose presented a severely delay of hatching of 4 days. These observations support the involvement of THs in different development processes of fish, as gonadal fate, and regulation of hatching during the transition of embryo to larvae stage.