PT - JOURNAL ARTICLE AU - David Shook AU - Jason Wen AU - Ana Rolo AU - Brian Francica AU - Destiny Dobins AU - Paul Skoglund AU - Doug DeSimone AU - Rudolf Winklbauer AU - Ray Keller TI - Characterization of convergent thickening, a major convergence force producing morphogenic movement in amphibians AID - 10.1101/270892 DP - 2018 Jan 01 TA - bioRxiv PG - 270892 4099 - http://biorxiv.org/content/early/2018/02/27/270892.short 4100 - http://biorxiv.org/content/early/2018/02/27/270892.full AB - We characterize the morphogenic process of convergent thickening (CT), which occurs in the involuting marginal zone (IMZ) during gastrulation of Xenopus, the African clawed frog. CT was described previously as the tendency of explants of the ventral IMZ of Xenopus to converge their circumblastoporal dimension and thicken their radial dimension (Keller and Danilchik 1988). Here we show that CT occurs from the onset of gastrulation, initially throughout the pre-involution IMZ. We suggest that CT is driven by an increase in the interfacial tension between the deep IMZ and its epithelium, resulting in cells of the deep IMZ tending to minimize their surface area. In explants, this results in a progressive shortening (convergence) of the IMZ along its longer mediolateral axis and thickening in the orthogonal planes, and can generate tensile force (Shook et al. 2018). In vivo, convergence of the annular IMZ generates circumferential tension, closing the blastopore. These results provide the first clear example of a tensile morphogenic force from a Holtfreterian/Steinbergian change in tissue affinity.