Signaling-dependent control of apical membrane size and self-renewal in rosette-stage human neuroepithelial stem cells

In the early developing nervous system, self-renewing neural stem cells are polarized and maintain an apical domain facing a central lumen. The presence of apical membrane is thought to have a profound influence on maintaining the stem cell state. With the onset of neurogenesis cells lose their polarization and the concomitant loss of the apical domain coincides with a loss of the stem cell identity. Very little is known about the molecular signals controlling apical membrane size. Here we use two neuroepithelial cell systems, one derived from regenerating axolotl spinal cord and the other from human ESCs to identify a conserved molecular signalling pathway initiated by lysophosphatidic acid (LPA) that controls apical membrane size and consequently controls and maintains epithelial organization and lumen size in neuroepithelial rosettes. This apical domain size increase occurs independently of effects on proliferation and involves a SRF-dependent transcriptional induction of junctional and apical membrane components.