Disruptions in this balance contribute to neurodevelopmental abnormalities that selleckchem can affect the gross size and organization of the nervous system (Pang et al., 2008) or impair cognitive and motor functions (Courchesne et al., 2007). An important step toward understanding the basis of these defects thus lies in defining the gene regulatory pathways that regulate NPC renewal. Throughout development, NPCs are organized in a polarized neuroepithelial sheet that surrounds the ventricles, termed the ventricular zone (VZ). This arrangement fosters progenitor-progenitor contacts that serve as a self-supporting

neural stem cell niche (Zhang et al., 2010). Within this compartment, NPCs exhibit a characteristic bipolar radial morphology mediated by two points of adhesion. At their apical pole, NPCs adhere

to the luminal surface of the ventricle through N-cadherin-based adherens junctions (AJs) formed between neighboring NPCs, while their basal end-feet are attached to the subpial extracellular matrix through integrin-laminin interactions (Meng and Takeichi, 2009). AJs maintain the radial morphology and self-renewal of NPCs by anchoring a variety of signaling proteins to the actin cytoskeleton. Some of the best studied of these factors include the following: (1) members of the catenin/armadillo protein family (α, δ, γ, and β-catenin, the latter of which also mediates the proliferative activity of the Wnt signaling pathway) (Farkas and Huttner, 2008, Meng and Takeichi, 2009 and Stepniak this website et al., 2009); (2) Par proteins, aPKC, and Cdc42, which control apical-basal polarity (Cappello et al., 2006, Manabe et al., 2002 and Sottocornola et al., 2010); and (3) Numb, an asymmetrically distributed regulator of Notch pathway activity and neuronal differentiation (Cayouette and Raff, 2002 and Rasin et al., 2007). Most studies of AJs in NPCs have focused

on how these signaling complexes are assembled to sustain Ribonucleotide reductase the neuroepithelial state. However, a less understood, but equally important aspect is the means by which AJs are disassembled to permit NPC differentiation and migration away from the VZ. This process must be tightly regulated, as blocking the expression or activity of AJ components causes NPCs to delaminate, resulting in widespread disruption of the neuroepithelium and deformation of the neural tube (Cappello et al., 2006, Chen et al., 2006, Ghosh et al., 2008, Imai et al., 2006, Kadowaki et al., 2007, Rasin et al., 2007, Zechner et al., 2003 and Zhang et al., 2010). To study this critical step in neurogenesis, we have focused on the formation of motor neurons (MNs) in the spinal cord. MN progenitors are specified at an early stage in development through the convergent actions of Sonic hedgehog and retinoic acid signaling, which direct a network of transcription factors centered around the bHLH protein Olig2 to promote MN differentiation (Briscoe and Novitch, 2008).