INVESTIGADORES
SOMOZA Gustavo Manuel
congresos y reuniones científicas
Título:
Sex determination in teleost fish. Cortisol and androgens are involved in the masculinization process.
Autor/es:
GUSTAVO M. SOMOZA; JUAN I. FERNANDINO; RICARDO S. HATTORI; CARLOS A. STRÜSSMANN
Lugar:
Campinas
Reunión:
Congreso; V International Symposium on Animal Biology of Reproduction.; 2014
Institución organizadora:
Brazilian College of Animal Reproduction
Resumen:
In recent years, fish have been extensively studied because they present a variety of mechanisms of sex determination/differentiation. In vertebrates the sex is generally determined by two mechanisms: genetic (GSD) and environmental (ESD) sex determination. In those species with GSD, sex is genetically programmed at fertilization and follows the actions of specific gene(s) usually located in the sex chromosomes, whereas in ESD sex is determined by environmental factors. Different types of ESD inductors have been characterized: such a social interactions, hypoxia, pH and temperature. Among them temperature is the more studied factor defining the Temperature Sex Determination (TSD) system. The action of these environmental factors can be correlated to a male‐biased sex ratio and they can be seen as potential stressors. Our model species, the pejerrey Odontesthes bonariensis has a strong TSD where the exposure to high temperatures during a critical period early in life can produce all male populations. In this context we started to study the effects of cortisol, a stress‐related hormone, in the testicular differentiation process. Our recent results show that cortisol exposure during early development produces a male biased sex ration in pejerrey. In addition, larvae exposed to a male‐producing temperature showed increased whole‐body cortisol, developing as males. They also have high testosterone (T) and 11‐ketotestosterone (11‐KT) levels, suggesting a relation between cortisol and androgens during the masculinization process. This fact grabbed our attention because androgens are thought rather as consequences of the testicular differentiation than inductors of masculinization. It is known that 11β‐hydroxysteroid dehydrogenase (11β‐HSD) is one of enzymes shared by the glucocorticoid and androgen pathways, converting cortisol to cortisone and participating in the finals steps of the synthesis of the 11‐oxigenated androgens. In pejerrey exposed to warm temperatures during the critical period of sex determination, gene expression of the 11β‐HSD gene hsd11b2, glucocorticoid receptors gr1, and androgen receptors (ar1 and ar2) were shown to be increased and expressed in the gonads during masculinization. Similar results were obtained when cortisol was supplied to fish larvae raised at lower temperatures. These data suggest that the enzymatic machinery necessary for the local production of 11‐oxygenated steroids and the inactivation of cortisol are active in the undifferentiated gonads early in development, during the sex determination period. Also, gonadal explants incubated in the presence of cortisol showed an increase in the synthesis of 11‐KT showing that such a mechanism is present not only in larval stages but also in adults. Based on these results, and also from data taken from the literature, we are proposing that the masculinization induced by temperature is stressful and can be considered as a consequence of cortisol inactivation and the concomitant synthesis of 11‐KT. This is also possible for other types of environmental stressors. This work was supported by CONICET and ANPCyT (Argentina) and the Ministry of Education, Culture, Sports, Science and Technology of Japan.