FGF2 modulates simultaneously the mode, the rate of division and the growth fraction in cultures of radial glia

Bexarotene drives the self-renewing proliferation of adult neural stem cells, promotes neuron-glial fate shift, and regulates late neuronal differentiation

Treatment with bexarotene, a selective retinoid X receptor (RXR) agonist, significantly improves behavioral dysfunctions in various neurodegenerative animal models. Additionally, it activates neurodevelopmental and plasticity pathways in the brains of adult mice. Our objective was to investigate the impact of RXR activation by bexarotene on adult neural stem cells (aNSC) and their cell lineages. To achieve this, we treated NSCs isolated from the subventricular zone (SVZ) of adult rat brains from the proliferative stage to the differentiated status. The results showed that bexarotene-treated aNSC exhibited increased BrdU incorporation, SOX2+ dividing cell pairs, and cell migration from neurospheres, revealing that the treatment promotes self-renewing proliferation and cell motility in SVZ-aNCS. Furthermore, bexarotene induced a cell fate shift characterized by a significant increase in GFAP+/S100B+ differentiated astrocytes, which uncovers the participation of activated-RXR in astrogenesis. In the neuronal lineage, the fate shift was counteracted by bexarotene-induced enhancement of NeuN+ nuclei together with neurite network outgrowth, indicating that the RXR agonist stimulates SVZ-aNCS neuronal differentiation at later stages. These findings establish new connections between RXR activation, astro- and neurogenesis in the adult brain, and contribute to the development of therapeutic strategies targeting nuclear receptors for neural repair.

The Symmetry of Neural Stem Cell and Progenitor Divisions in the Vertebrate Brain

Robust brain development requires the tight coordination between tissue growth, neuronal differentiation and stem cell maintenance. To achieve this, neural stem cells need to balance symmetric proliferative and terminal divisions with asymmetric divisions. In recent years, the unequal distribution of certain cellular components in mitosis has emerged as a key mechanism to regulate the symmetry of division, and the determination of equal and unequal sister cell fates. Examples of such components include polarity proteins, signaling components, and cellular structures such as endosomes and centrosomes. In several types of neural stem cells, these factors show specific patterns of inheritance that correlate to specific cell fates, albeit the underlying mechanism and the potential causal relationship is not always understood. Here, we review these examples of cellular neural stem and progenitor cell asymmetries and will discuss how they fit into our current understanding of neural stem cell function in neurogenesis in developing and adult brains. We will focus mainly on the vertebrate brain, though we will incorporate relevant examples from invertebrate organisms as well. In particular, we will highlight recent advances in our understanding of the complexities related cellular asymmetries in determining division mode outcomes, and how these mechanisms are spatiotemporally regulated to match the different needs for proliferation and differentiation as the brain forms.