Localisation of oestrogen receptors in stem cells and in stem cell‐derived neurons of the mouse

Oestrogen receptors (ER) transduce the effects of the endogenous ligand, 17β‐estradiol in cells to regulate a number of important processes such as reproduction, neuroprotection, learning and memory and anxiety. The ERα or ERβ are classical intracellular nuclear hormone receptors while some of their variants or novel proteins such as the G‐protein coupled receptor (GPCR), GPER1/GPR30 are reported to localise in intracellular as well as plasma membrane locations. Although the brain is an important target for oestrogen with oestrogen receptors expressed differentially in various nuclei, subcellular organisation and crosstalk between these receptors is under‐explored. Using an adapted protocol that is rapid, we first generated neurons from mouse embryonic stem cells. Our immunocytochemistry approach shows that the full length ERα (ERα‐66) and for the first time, that an ERα variant, ERα‐36, as well as GPER1 is present in embryonic stem cells. In addition, these receptors typically decrease their nuclear localisation as neuronal maturation proceeds. Finally, although these ERs are present in many subcellular compartments such as the nucleus and plasma membrane, we show that they are specifically not colocalised with each other, suggesting that they initiate distinct signalling pathways. This study explores the localisation of oestrogen receptors (ERs) within organelles in two different cell types. In mES cells, there is low membrane localisation of ERs and high nuclear localisation. All receptors are present in the endoplasmic reticulum and the Golgi apparatus to a similar extent. Upon differentiation to neuronal cells, ERs (particularly the ERα variant, ERα‐36) increase localisation at the plasma membrane and at the endoplasmic reticulum. Regardless of cell type, ERs are not colocalised with each other in any organelle or cell compartment and appear to be separately distributed.