Temperature influences the aromatase and estrogen receptor mRNA expression during the critic period of sex determination/differentiation in pejerrey fish (Odontesthes bonariensis) brain.

STROBL-MAZZULLA, P.H.; GUILGUR, L.G.; FERNANDINO, J.I.; MIRANDA, L.A.; SOMOZA, G.M.

Faro, Portugal.

Congreso; V Congresso Associação Ibérica de Endocrinologia Comparativa; 2005

Water temperature has big influence not only on gonadal sex differentiation of pejerrey fish (Odontesthes bonariensis), but also on the development of central neuroendocrine systems. Estrogens play an important role in the female differentiation in non-mammalian species. However, estrogen-forming (aromatase, CYP19b) and estrogen-target (estrogen receptors, ERalpha and beta) networks of glial cells and neurons are thought to be crucial also in teleost brain differentiation and maturation. In that context, semi-quantitative RT-PCR method was used in order to investigate the effects of temperature on the ontogeny expression of CYP19b and ERs in the developing brain of pejerrey fish. Temperature-induced sex differentiation in pejerrey larvae (19C all females and 28C all males) was applied during 5 weeks and then kept at 24C until the histological sex ratios could be determined. Every week 6 dissected heads were sampled during 7 weeks and individually processed for semi-quantitative analysis. CYP19b transcripts could be detected on day 14 post-hatching (dph) at both temperatures. However, between 14 to 28 dph aromatase expression was higher at male-forming temperature, reaching a peak on 21 dph. ERalpha and beta were firstly detected on day 7 at both temperatures. Between days 7 to 14 the ERalpha expression was higher a female-forming temperature, but at day 21 the expression reach a peak at male-forming temperature and was almost undetectable at female-forming temperature. After the day 21 CYP19b and ERbeta transcripts follow the same expression pattern in each temperature, suggesting an association between both genes. On the other hand, ERalpha was not affected by the temperature and mayor expression level was detected on day 28. All these data suggest that both CYP19b and ERbeta are regulated by the temperature during the critical period of sex determination, and the timing and level expression could be related with the brain sex-differentiation and the concomitant gonadal differentiation.