A NOVEL PEAK OF FUNCTIONAL NEUROSTEROIDOGENESIS AND ESTROGEN SIGNALLING IN THE EARLY BRAIN DEVELOPMENT OF ORANGE-SPOTTED GROUPER EPINEPHELUS COIOIDES

Abstract

Introduction: Despite neurosteroidogenic enzymes are playing important roles in the regulation of brain development and function, the potential link between brain and gonad by the action of steroid hormones during gondal sex differentiation is still matter of debate in teleosts [1]. In recent years, we focused on the early brain development in response to the synthesis of neurosteroids and receptor activation during gonadal sex differentiation in orangespotted grouper Epinephelus coioides (a mono-female sex development at the juvenile stage) and black porgy Acanthopagrus schlegeli (a mono-male sex development at the juvenile stage) [2,3]. The mechanism of brain sex differentiation and/or brain activation during early ages of female grouper fish is not fully understood yet. Moreover, there is an important lack of information regarding the expression of four key steroidogenic enzymes cyp11a1 (P450scc), hsd3b1, cyp17a1 and cyp19a1b in the early brain development and their potential links with gonadal sex differentiation. Hence, these phenomena support the selection of orange-spotted grouper as a model for neuroendocrine research, principally to understand the molecular mechanism of sex differentiation in female fish. Therefore, in the present study we aimed to test the hypothesis that 1) brain of orange-spotted grouper fish has the capability for de novo steroidogenesis and the production of these neurosteroids may have a correlation to the occurrence of gonadal sex differentiation and 2) we compared the expression of key genes and signalling in the protogynous grouper and protandrous black porgy in order to know whether this expression pattern has gender related event or not during gonadal sex differentiation. Here, we investigated the temporal expression pattern of the genes related to the neurosteroidogenesis and estrogen signaling in different days after hatching ages (dah) in the teleosts brain.