Abstract/Summary

Locally produced neuroestrogens are crucial in the development of sexually dimorphic brain regions and drive sex-typical social behaviours. These behaviours are due to the signalling of oestrogens via its receptors in a set of interconnected nuclei called the social behaviour network (SBN). This thesis investigated the molecular interactions between classical oestrogen receptor(s) (ERs) ERα and ERβ and novel member ER G-Protein-Coupled-Oestrogen-Receptor 1(GPER1) through investigation of localization and crosstalk of receptors within cell lines and the production and regulation of neurosteroids in the SBN of male mice. For the first time the subcellular localization of ERα, its variant ERα 36 and GPER1 was reported in mouse embryonic cells (mES) and mES derived motor neurons, although their functional roles remain to be investigated. Next, we treated a mouse embryonic hypothalamic neuronal cell (m-Hypo N42) with either vehicle (DSMO), E2, E2-BSA, G1 (GPER1 agonist), PPT (ERα agonist), or DPN (ERβ agonist) and measured aromatase expression through RT-qPCR. We also identified translocation of oestrogen receptors from the nucleus to the plasma membrane in two set of embryonic cell lines: mES and m-Hypo N42. For the first we demonstrate that ERβ and GPER1 may collaborate by signalling in the same pathway to rapidly increase aromatase expression in a mouse hypothalamic cell line. Using a novel ex vivo slice culture system, we show that the production of neuroestrogens - Estradiol (E2) and neurotestosterone- Testosterone (T) increases within 24 hours in all SBN nodes. Secretion of neurosteroids were measured by ELISA and RTqPCR and used to examine expression of steroidogenic enzymes and steroid receptors at various timepoints. Data presented in this thesis show that the expression of neurosteroids and steroidogenic enzymes are sexually dimorphic and increase with respect to time suggesting de novo synthesis. Lastly, we used the ex vivo slice culture system to examine the regulation of aromatase and subsequent oestrogen production in Medial Preoptic Area (MPOA) and Ventromedial Hypothalamus (VMH), two regions of the SBN associated with sexual and aggressive behaviour in male mice. However, the mechanism of action of aromatase regulation remains unclear. Collectively, these studies expand our knowledge of the function relevance of ERs in multiple systems and how they develop and maintenance the function of the SBN.