Human mutations in the planar cell polarity component VANGL2 are associated with the neural tube defect spina bifida. Homozygous Vangl2 mutation in mice prevents initiation of neural tube closure, precluding analysis of its subsequent roles in neurulation. Spinal neurulation involves rostral-to-caudal ‘zippering’ until completion of closure is imminent, when a caudal-to-rostral closure point, ‘Closure 5’, arises at the caudal-most extremity of the posterior neuropore (PNP). Here, we used Grhl3Cre to delete Vangl2 in the surface ectoderm (SE) throughout neurulation and in an increasing proportion of PNP neuroepithelial cells at late neurulation stages. This deletion impaired PNP closure after the ∼25-somite stage and resulted in caudal spina bifida in 67% of Grhl3Cre/+Vangl2Fl/Fl embryos. In the dorsal SE, Vangl2 deletion diminished rostrocaudal cell body orientation, but not directional polarisation of cell divisions. In the PNP, Vangl2 disruption diminished mediolateral polarisation of apical neuroepithelial F-actin profiles and resulted in eversion of the caudal PNP. This eversion prevented elevation of the caudal PNP neural folds, which in control embryos is associated with formation of Closure 5 around the 25-somite stage. Closure 5 formation in control embryos is associated with a reduction in mechanical stress withstood at the main zippering point, as inferred from the magnitude of neural fold separation following zippering point laser ablation. This stress accommodation did not happen in Vangl2-disrupted embryos. Thus, disruption of Vangl2-dependent planar-polarised processes in the PNP neuroepithelium and SE preclude zippering point biomechanical accommodation associated with Closure 5 formation at the completion of PNP closure.

Highlights d Surface ectoderm cells adhere at the fusion site via integrin b1 focal clustering d Integrins mediate junction shortening and formation of a semi-rosette structure d This configuration enables juxtaposition across the midline for fusion propagation d Tissue-specific ablation of integrin b1 prevents zippering, causing spina bifida

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Protein quality and quantity influence the effect of dietary fat on weight gain and tissue partitioning via host-microbiota changes Graphical abstract Highlights d High dietary fat interacts with high casein and causes tissue expansion in mice d Changing the protein from casein to whey blunts tissue accruement d Alterations in gut microbiota are related to protein quality d Casein microbiota increases body size, and whey microbiota has the opposite effect