ESR1 and neurodegenerative disease: Nuclear-initiated estrogen signaling is mediated by classical estrogen receptors (ERs), α (ERα) and β (ERβ), which are transcription factors expressed by neurons, astrocytes and microglia [7,8] and are widely distributed in numerous brain regions, including those that are frequently involved in neurodegenerative diseases, such as the hippocampus, cerebral cortex and the striatum [7,8].