Localization of Retinoic Acid Receptor RARα in Adult Mouse Hippocampal Dentate Gyrus Neurons

Abstract

Retinoids (Vitamin A) play an important role in differentiation and patterning in the developing nervous system. Retinoids bind to specific nuclear receptors, retinoic acid receptors (RARs) and retinoid X receptors (RXRs), in order to mediate cellular effects. Three subtypes of RAR receptor, RARα, β and γ, have been identified. Evidence has emerged that retinoid signaling required for synaptic plasticity, learning and memory behaviors, and for adult neurogenesis. In this study, we investigated the expression pattern of RARα in adult mouse hippocampus. We hypothesized that the receptor may have a developmental‐dependent expression in the new neurons of the dentate gyrus. Co‐labeling experiments were performed with markers for immature and mature neurons (Doublecortin, Calretinin, NeuN) and for astrocytes/stem cells (nestin, GFAP). We found that RARα expression was located at several different areas in the mouse hippocampus, CA1‐CA3, the granule cell layer, hillus and granule cell layer of DG. RARα immunohistochemical stain was clearly visualized in cell cytoplasm, but not in nucleus. There was colocalization of RARα in DG with NeuN, but not with astrocyte/stem cell markers GFAP or Nestin. RARα immunohistochemical stain was not colocalized with immature granule cell markers doublecortin and calretinin. Our results provide the first evidence for identify RARα localized only in mature granular neurons of adult mouse dentate gyrus.