Table 1. Summary of factors involved in the regulation of progenitor cell behavior and putative domains where they could act.

This table summarizes some of the known factors that affect progenitor behavior, although for many factors it is still unclear whether they act directly on NSCs, IPCs, or both. We here propose possible sites of action within the three proposed putative domains of B1 cells (Figure 1) and radial astrocytes (figure 2), the NSCs of V-SVZ and SGZ, respectively.

B1 cell compartment	Factor	Effect on progenitor cells	References
I. Proximal (apical)	Igf2 Noggin/LRP2 Noggin/Chordin Shh	Proliferacion ↑ Proliferation ↑ Oligodendrogenesis ↑ Ventral specification	Lehtinen et al., 2011 Lim et al., 2000, Peretto et al., 2004, Gajera et al., 2010 Colak et al., 2008, Jablonska et al., 2010 Ihrie et al., 2011
II. Intermediate	Notch GABA DBI Dopamine Serotonin	Maintenance Proliferation ↓ Proliferation ↑ Proliferation ↑ Proliferation/Neurogenesis ↑	Imayoshl et al., 2010, Aguirre et al., 2010, Chapouton, 2010 Liu et al., 2005, Fernando et al., 2011 Alfonso et al., 2012 Hoglinger et al., 2004, O'Keeffe et al., 2009, Kim et al., 2010 Banasr et al., 2004
III. Distal (basal)	SDF1 PEDF BTC	Recruitment to vasculature Proliferation ↑ Proliferation/Neurogenesis ↑	Shen et al., 2008 Ramirez-Castillejo et al., 2006, Andreu-Agullo et al., 2009 Gomez-Gaviro et al., 2011

Radial Astrocyte compartment	Factor	Effect on progenitor cells	References
I. Proximal	VEGF primary Cilium	Proliferation/Neurogenesis ↑ Proliferation ↑ Maintenance	Licht et al., 2011, Cao et al., 2004 Amador-Arjona et al., 2011 Breunig et al., 2008, Han et al., 2008
II. Intermediate	Notch Noggin/FXR2 BMPs long-term potentiation seizures	Maintenance Proliferation ↑ Quiescence Proliferation/Neurogenesis ↑ Proliferation/Neurogenesis ↑	Lugert et al., 2010, Ables et al., 2010, Ehm et al., 2010 Bonaguidi et al., 2008. Guo et al, 2011 Mira et al., 2010 Bruel-Jungerman et al., 2006 Parent et al., 1997, Ma et al., 2009
III. Distal	GABA Glutamate/NMDAR	Proliferation ↓ Differentation ↑ Differentation ↑	Wang et al., 2005, Tozuka et al., 2005 Deisseroth et al., 2004

Upper. Factors that may act on V-SVZ B1 cells. Domain I: Factors released from ependymal cells and present in the CSF. Domain II: Signaling between B1 cells and their progeny or neuronal terminals from other parts of the brain. Domain III: Blood-borne factors and those released from endothelial cells.

Lower. Factors that may act on SGZ radial astrocytes. Domain I: Vascular-derived factors and signaling acting through the primary cilium. Domain II: Factors that could facilitate interaction between radial astrocytes and surrounding cells. Domain III: Neuronal input within the IML.