During neural-tube (NT) formation in mammals and birds, newly formed neural folds bend inwards at dorsolateral hinge points (DLHPs) before fusing to close the NT. The mechanism of DLHP formation is not well understood, although it is known to require the zinc-finger transcription factor Zic2 and an apical actomyosin network. Now, Molly Nyholm and colleagues () investigate the role of zic genes during neurulation in zebrafish (in which DLHPs also form, albeit after NT closure). The authors create morphants of zic2a and zic5, and show that both proteins are required for DLHP formation; moreover, the ventral zic2a expression border predicts where DLHPs will form. zic2a and zic5, they show, are required for the apical localisation of actomyosin components (F-actin and active myosin II) and for the integrity of apical cell-cell junctions. They go on to demonstrate that canonical Wnt signalling (which activates zic gene transcription) is necessary for DLHP formation, localisation of active myosin II and junctional integrity. The authors conclude that zic genes act downstream of Wnt signalling to control cytoskeletal organisation during neurulation, and argue that zebrafish is a valuable model organism for studying mammalian NT formation.
