ApoE is required for maintenance of the dentate gyrus neural progenitor pool

Abstract

SUMMARYMany genes regulating adult neurogenesis have been identified and are known to play similar roles during early neuronal development. We recently identified apolipoprotein E (ApoE) as a gene the expression of which is essentially absent in early brain progenitors but becomes markedly upregulated in adult dentate gyrus stem/progenitor cells. Here, we demonstrate that ApoE deficiency impairs adult dentate gyrus development by affecting the neural progenitor pool over time. We utilized ApoEdeficient mice crossed to a nestin-GFP reporter to demonstrate that dentate gyrus progenitor cells proliferate more rapidly at early ages, which is subsequently accompanied by an overall decrease in neural progenitor cell number at later time points. This appears to be secondary to over-proliferation early in life and ultimate depletion of the Type 1 nestin-and GFAP-expressing neural stem cells. We also rescue the proliferation phenotype with an ApoE-expressing retrovirus, demonstrating that ApoE works directly in this regard. These data provide novel insight into late hippocampal development and suggest a possible role for ApoE in neurodegenerative diseases.

Detection and Phenotypic Characterization of Adult Neurogenesis

“…The best practice for identifying early markers of neural stem cells relies on a combination of otherwise more ubiquitous markers, along with consideration of immunoreactive cell location and morphology. For example, radial glial-like cells in the subgranular zone expressing GFAP and nestin, GFAP and Sox-2 or Pax-6, GFAP and brain lipid-binding protein (BLBP), or ApoE and BLBP appear to label multipotent cells (Stoykova and Gruss 1994; Komitova and Eriksson 2004;Nacher et al 2005;Baer et al 2007;Yang et al 2011). In fact, these combinations reflect a subset of radial glial-like astrocytes in both the subgranular and subventricular zone (AlvarezBuylla et al 2002).…”

Coupling Hippocampal Neurogenesis to Brain pH through Proneurogenic Small Molecules That Regulate Proton Sensing G Protein-Coupled Receptors

“…We used immunohistochemical localization and quantitative polymerase chain reaction (QPCR) to provide evidence of GPR68's functional importance through regulated expression in brain. We colocalized GPR68 (using a validated antibody) with Nestindriven green fluorescent protein (GFP) and glial fibrillary acid protein (GFAP) in the subgranular zone (SGZ) of adult Nestin-GFP transgenic mouse brain 21 ( Figure 2a, upper panels). Type 1-neural stem cells (NSCs) expressed GPR68, defined by triple (GPR68/Nestin-GFP/GFAP) colocalization and characteristic treelike neurite morphology (Figure 2a, upper panels, arrowheads).…”

“…21 Cell Culture and Immunocytochemistry. For primary cell cultures, DG was dissected from 600 μm coronal sections of 1 week Figure 7.…”

“…21 Nissl stained sections were used for DG volume quantification and estimated with Cavalier Estimator program as described. 21 Tamoxifen Treatment in Vivo. Tamoxifen (Sigma) was prepared as described previously.…”

“…Tamoxifen (Sigma) was prepared as described previously. 21 Briefly, tamoxifen was dissolved in sunflower oil (Sigma) and ethanol mixture (9:1) at a concentration of 6.7 mg/ mL and injected ip at a final concentration of 0.83 mg/kg twice a day for 2 consecutive days.…”