Integrin-Mediated Focal Anchorage Drives Epithelial Zippering during Mouse Neural Tube Closure

Epithelial fusion is a key process of morphogenesis by which tissue connectivity is established between adjacent epithelial sheets. A striking and poorly understood feature of this process is “zippering,” whereby a fusion point moves directionally along an organ rudiment. Here, we uncover the molecular mechanism underlying zippering during mouse spinal neural tube closure. Fusion is initiated via local activation of integrin β1 and focal anchorage of surface ectoderm cells to a shared point of fibronectin-rich basement membrane, where the neural folds first contact each other. Surface ectoderm cells undergo proximal junction shortening, establishing a transitory semi-rosette-like structure at the zippering point that promotes juxtaposition of cells across the midline enabling fusion propagation. Tissue-specific ablation of integrin β1 abolishes the semi-rosette formation, preventing zippering and causing spina bifida. We propose integrin-mediated anchorage as an evolutionarily conserved mechanism of general relevance for zippering closure of epithelial gaps whose disturbance can produce clinically important birth defects. [Display omitted] •Surface ectoderm cells adhere at the fusion site via integrin β1 focal clustering•Integrins mediate junction shortening and formation of a semi-rosette structure•This configuration enables juxtaposition across the midline for fusion propagation•Tissue-specific ablation of integrin β1 prevents zippering, causing spina bifida Molè et al. show that integrin-mediated basal anchorage drives epithelial zippering during mouse spinal neural tube closure. This occurs via formation of a multicellular semi-rosette configuration that promotes juxtaposition between opposing surface ectoderm junctions. The loss of integrin halts zippering progression, causing failure of neural tube closure and open spina bifida.