Regulation of cell shape and movements during Xenopus morphogenesis

Morphogenesis, whereby embryos take shape during development, requires coordinated regulation of cell adhesion, polarity, morphology, and movements. During Xenopus gastrulation, cells from an entire embryo participate in morphogenetic movements and exhibit distinct behaviors depending on their locations in different embryonic regions. How cell behaviors are regulated at the molecular levels is not understood in detail. In this study, we show that reduction of apical surface in bottle-shaped cells that initiate tissue invagination during Xenopus gastrulation is controlled by a RhoGEF gene plekhg5, which regulates actomyosin dynamics. We demonstrate that bottle cells regain their surface areas at the end of gastrulation in a rapid process known as bottle cell respreading, which has been reported as a main contributor to elongation of embryonic gut (archenteron). Furthermore, we investigate how body axis elongation requires coordinated regulation by anterior-posterior patterning signals and planar cell polarity pathway to influence tissue convergence and extension. Together, our studies address the important knowledge gaps about molecular mechanisms governing gastrulation morphogenesis in Xenopus.