Basal epithelial tissue folding is mediated by differential regulation of microtubules

The folding of epithelial tissues is critical for development of three-dimensional structure and function. Understanding this process can assist in determining etiology of developmental disease and engineering of tissues for the future of regenerative medicine. Folding of epithelial tissues towards the apical surface has long been studied, while the molecular mechanisms that mediate epithelial folding towards the basal surface are just emerging. Here we utilize the zebrafish neuroepithelium to identify mechanisms that mediate basal tissue folding to form the highly conserved embryonic midbrain-hindbrain boundary. Live imaging revealed Wnt5b as a mediator of anisotropic epithelial cell shape, both apically and basally. In addition, we uncovered a Wnt5b mediated mechanism for specific regulation of basal anisotropic cell shape that is microtubule-dependent and likely to involve JNK signaling. We propose a model by which a single morphogen can differentially regulate apical versus basal cell shape during tissue morphogenesis.