O26. Role of cell division during neural tube formation in the zebrafish

The vertebrate neural tube is a highly polarised tissue consisting of epithelial cells organised around a central lumen with their apical surfaces facing the lumen. In zebrafish the neural tube is generated by converting a soild neural rod into a tube. During rod stage, a polarised midline becomes established and eventually a small lumen opens in a roughly ventral to dorsal progression. The lumen inflates to become the ventricle later in development. We have previously suggested the transition from rod to tube is orchestrated by an unique mirror-symmetric cell division which deposits one daughter cell on either side of the future midline, and at the same time establishes the apical nature of the midline by depositing Par3 protein at the cleavage plane. To investigate the advantages of this novel division in establishment of apical-basal polarity and lumen formation we have inhibited cell division and examined the consequences on neural tube formation. We find that cells can still polarize when division is blocked, however polarization and cellular organization at the midline is more disorganized and lumen formation is disrupted. To better understand the roles of the mirror-symmetric division, we are using time-lapse microscopy to compare cell behaviour and polarization between wild-type and division-blocked embryos and we observe novel cell behaviours that are helping us understand the mechanisms that direct cell polarization and morphogenesis of the neural tube lumen.