PAR3 acts as a molecular organizer to define the apical domain of chick neuroepithelial cells

Abstract

SummaryPAR3 acts as a molecular organizer to define the apical domain of chick neuroepithelial cells

Mitotic spindle orientation distinguishes stem cell and terminal modes of neuron production in the early spinal cord

“…The retention of a thin basal process composed of membrane and lacking microtubules as cells undergo mitosis at the apical surface confirms that cells maintain contact with both basal and apical surfaces throughout the cell cycle (see Afonso and Henrique, 2006). A similar membranous basal process has been observed in other neuroepithelia (Das et al, 2003;Miyata et al, 2001;Saito et al, 2003) and the relocation of eYFP-tubulin into this structure following mitosis is consistent with a microtubule-based mechanism mediating interkinetic nuclear migration movements (Messier and Auclair, 1974).…”

“…Prospective neurons with basally located nuclei retain this apical process (see Minaki et al, 2005) and may do so for many hours prior to the first morphological manifestation of neuronal differentiation; the release of this process from the apical surface. This step must thus involve loss of junctional complexes, including adherens junctions (see Afonso and Henrique, 2006), between the differentiating cell and its neighbours. A similar behaviour has also been reported prior to neuronal differentiation in the mammalian cortex, although here prospective neurons do not retain apical contact but migrate away and then form a new process that extends to the apical surface and is retracted on differentiation (Noctor et al, 2004).…”

Sonic Hedgehog Regulates Integrin Activity, Cadherin Contacts, and Cell Polarity to Orchestrate Neural Tube Morphogenesis

“…Last, matrix adhesion, cell-cell adhesion, and cell polarity are known to be coordinated within tissues. Integrin signaling regulates distribution and activity of N-cadherin during NC migration (Monier-Gavelle and Duband, 1997) and polarity regulators such as Par3 and Numb are required to maintain apical adherens junctions in NE cells (Afonso and Henrique, 2006) and control integrin endocytosis (Nishimura and Kaibuchi, 2007). Together, our observations strongly suggest that SHH acts first on conformation of ␤1 integrins, which, in turn, induces an increase in Cad6B, Daam1, and RhoB expression, resulting in strong cell-cell adhesion and polarity.…”

Adherens Junction: Molecular Architecture and Regulation

“…Some reports, on the other hand, suggest the AJs have a physical interaction with these polarity factors: Par3 and Par6, but not aPKC, coprecipitate with VE-cadherin, the endothelial-specific cadherin (Iden et al 2006). Par3/Bazooka colocalizes with cadherins in epithelial junctions (Harris and Peifer 2005;Afonso and Henrique 2006). These observations illustrate a possible pathway by which the apical membrane domain is primarily determined by those apical determinants, and, in turn, the AJ/ZA is recruited to this domain, possibly via interactions with the pre-existing Par complex.…”