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

Neural progenitors in the vertebrate nervous system are fully polarized epithelial cells, with intercellular junctions at the apical region. These progenitor cells remain within the neuroepithelium throughout neurogenesis, and will ultimately give rise to all the neurons in the mature nervous system. We have addressed the role of the PAR polarity complex in vertebrate neuroepithelial polarity and show that PAR3 functions as the initial scaffold to assemble and organize the PAR complex at the apical region of neuroepithelial cells, coordinating also the recruitment of additional polarity complexes and junction-associated proteins to the same region, while restricting other polarity proteins to the basolateral membrane. We propose that PAR3 acts as a molecular organizer to connect the acquisition of apico-basal polarity with the positioning and formation of junctional structures in neuroepithelial cells, a function of upmost importance for the morphogenesis of embryonic neural tissue and the process of neurogenesis.