, 1997). FGF-2 loss also resulted in a decrease in the slow-dividing stem cell pool and less neurogenesis (Zheng et al., 2004). EGFR is primarily expressed on type C cells and a limited number of type B1 cells, and studies of the EGFR-expressing population www.selleckchem.com/products/BMS-777607.html have indicated that most neurospheres arise from the C cell population (Vescovi et al., 1993 and Doetsch et al., 2002). Exogenous stimulation of the EGFR by ventricular infusion of EGF has striking effects within the adult VZ-SVZ. First, an increased number of type B1 cells contacting the ventricle are visible by electron microscopy (Doetsch et al., 2002). Second,

VZ-SVZ cells exhibit increased proliferation, and generate progeny that invade the surrounding parenchyma (Craig et al., 1996, Doetsch et al., 2002, Aguirre et al., 2005, Aguirre et al., 2007 and Gonzalez-Perez et al., 2009). Elevated EGF signaling biases VZ-SVZ cells toward the oligodendrocytic lineage—rather than giving rise to neurons, labeled EGF-stimulated selleck screening library progenitors largely differentiate into oligodendrocytes or oligodendrocyte precursor cells (Gonzalez-Perez et al., 2009). The most likely endogenous ligand for this pathway is transforming growth factor-alpha (TGF-α). TGF-α-deficient mice exhibit decreased proliferation

within the adult VZ-SVZ, and these proliferation defects can be rescued in vitro by administration of EGF (Tropepe et al., 1997). More recently, TGF-α treatment has been suggested to decrease the percentage of highly motile neuroblasts within the RMS (Kim et al., 2009), but EGFR overexpression in NG2-positive progenitors has been reported to increase migration,

suggesting that this pathway may have different functions in distinct cell types (Aguirre et al., 2005). Intriguingly, the related receptor ErbB4 and its ligands, neuregulin 1 and 2, are also expressed in the adult VZ-SVZ and have been implicated in progenitor proliferation and the initiation of neuroblast migration (Ghashghaei et al., 2006). The platelet-derived growth factor (PDGF) signaling pathway also alters stem cell properties and through lineage decisions, although the endogenous source of ligand for this pathway is unknown. The PDGFRα is expressed by most GFAP-positive cells within the adult VZ-SVZ, and PDGF enhances in vitro neurosphere generation in cooperation with bFGF (Jackson et al., 2006). Infusion of PDGF, like EGF, induces elevated proliferation in VZ-SVZ cells, and many of these progenitors give rise to oligodendrocytes after ligand infusion has ended. However, PDGFRα staining and EGFR staining label separate populations of cells within the adult VZ-SVZ, suggesting that they affect stem and transit-amplifying populations respectively.