(H-K) Overexpression of EphB2 inhibits astrocytic conversion of ependymal cells
(H-K) Overexpression of EphB2 inhibits astrocytic conversion of ependymal cells. market cell identity is definitely actively maintained and that market cells retain a high level of plasticity. Stem cell maintenance depends on cell intrinsic self-renewal capacity as well as the specific molecular environment produced by neighboring cells forming the stem cell market. Stem cell populations are safeguarded by, for example, a certain degree of lineage plasticity, with the possibility of dedifferentiation of progenitor cells to replace lost stem cells (Simon and Frisn, 2007). How niche cells are taken care of is largely unfamiliar, although this is likely to Rabbit Polyclonal to SLC39A7 be as important as intrinsic stem cell self-renewal capacity for cells homeostasis and regeneration. Several studies have shown altered morphology of the neural stem cell market in the lateral ventricle wall in adult rodents after experimental manipulations (Barnab-Heider et al., 2008;Carln et al., 2009;Conover et al., 2000;Kuo et al., 2006;Luo et al., 2008), providing a Tenacissoside G model system for the study of niche remodeling. The lateral ventricle is usually lined by a single layer of multiciliated ependymal cells. In the subventricular zone, located subjacent to the ependymal layer, there are both differentiated niche cells and cells of different maturational stages from a subpopulation of ventricle-contacting self-renewing astrocytes with characteristics of neural stem cells to neuroblasts which migrate to the olfactory bulb (Zhao et al., 2008). The main niche cells in the lateral ventricle wall are ependymal cells and astrocytes, which are tightly interconnected through adherence and gap junctions (Doetsch et al., 1997;Mirzadeh et al., 2008). Subventricular zone astrocytes can be divided into proliferating stem cells and non-proliferating niche cells, which are interconnected with each other as well as with ependymal cells to form a unique architectonic structure (Mirzadeh et al., 2008). Several studies have illustrated the importance of the niche and how damage or loss of ependymal cells impacts the maintenance and proliferation of stem/progenitor cells and the migration of neuroblasts (Barnab-Heider et al., 2008;Lim et al., 2000;Sawamoto et al., 2006). The ependymal layer was thought to be incapable of regeneration and that loss of this niche cell type would be permanent. This appears to be the case after loss of larger areas of ependymal cells (Carln et al., 2009;Kuo et al., 2006). However, two studies indicated that ependymal cells are replaced after minor lesions or during aging (Luo et al., 2006;Luo et al., 2008). These studies suggested that astrocytes give rise to new Tenacissoside G ependymal cells and also that some astrocytes relocate to the ependymal layer after a lesion or during aging (Luo et al., 2006;Luo et al., 2008). However, the origin of new ependymal cells or astrocytes in the ependymal layer has not been directly demonstrated and the molecular mechanisms of these restructuring processes have remained uncharacterized. Blocking of the ephrin-B/EphB conversation by infusion of soluble ectodomains of ligands or Tenacissoside G receptors into the lateral ventricles resuls in comparable remodeling of the niche as induced by a lesion or during aging (Conover et al., 2000), providing a first indication that this class of molecules may regulate niche cell plasticity. Eph tyrosine kinase receptors and their ephrin ligands control cell-cell interactions in many developing and adult tissues (Pasquale, 2008), and have been identified as important regulators of both proliferation, differentiation, survival and migration of stem/progenitor cells (Chumley et al., 2007;Depaepe et al., 2005;Genander and Frisn, 2010;Genander et al., 2009;Genander et al., 2010;Hara et al., 2010;Holmberg et al., 2005;Holmberg et al., 2006;Jiao et al., 2008;Qiu et al., 2008;Ricard et al., 2006). Here we report that EphB.