, 2006 and Toni et al., 2007). Such properties may also allow integrated Proteasome inhibitor adult-born neurons to make a unique contribution to information processing during this period. There are significant questions remaining. First, when
does the neuronal versus glial fate become fixed and how is it determined? Second, given the drastic changes in the local environment, are there any differences between embryonic and adult neurogenesis beyond the maturation tempo? Furthermore, are there any intrinsic differences between neural precursors or newborn neurons during development and in the adult? Do putative adult neural stem cells display a temporally segregated sequence of symmetric self-renewal, neurogenesis, and gliogenesis as occurs during embryonic cortical development (reviewed by Okano and Temple, 2009)? Third, we have limited knowledge about synaptic partners of newborn neurons and potentially dynamic nature of these synaptic interactions. Do embryonic-born and adult-born neurons have different synaptic partners? New technologies, such as optogenetics (reviewed by Zhang et al., 2010), transneuronal tracers (reviewed by Callaway, 2008), and in vivo imaging, will help to address these questions. Fourth, there are significant regional differences
Selleck HA 1077 in properties of neuronal precursor subtypes along dorso-ventral/rostro-caudal axes in the adult SGZ and SVZ (Merkle et al., 2007 and Snyder et al., 2009). How are development and properties of new neurons differentially regulated? First suggested from transplantation
studies of hematopoietic progenitors (Schofield, 1978), niches are defined as microenvironments that anatomically house stem cells and functionally control their development in vivo. In the past decades, significant progress has been made in describing stem cell niches at cellular, molecular, and functional levels in several model systems, including Drosophila germ line, mammalian skin, intestines, and bone marrow (reviewed by Li and Xie, 2005 and Morrison and Spradling, 2008). In the adult brain, the unique niche structure seems to restrict active neurogenesis to two discrete regions and much has been learned about cellular elements that form these neurogenic niches (reviewed Thiamine-diphosphate kinase by Riquelme et al., 2008 and Ihrie and Álvarez-Buylla, 2011 this issue). Endothelial cells, astrocytes, ependymal cells, microglia, mature neurons, and progeny of adult neural precursors are among major cellular components of the adult neurogenic niche (Figures 1B and 1C). Vascular cells play a prominent role in regulating proliferation of adult neural precursors. The initial suggestive evidence came from observations of increased neuronal differentiation of adult rat SVZ explants in coculture with endothelial cells (Leventhal et al., 1999).