Dynamic and Polarized Muscle Cell Behaviors Accompany Tail Morphogenesis in the Ascidian Ciona intestinalis
Figure 8
Three-phase model of cell behavior operating during tail extension in Ciona.
High magnification photomicrographs of muscle cells expressing GPI GFP are shown in the left column. Schematics of wild type muscle cells are shown in the middle column, with the borders and projections of a single cell outlined in red. Schematics of muscle cells expressing Bix1 are shown in the right column. Muscle cells undergo their last division at the neurula stage. As they adopt their stereotypical relative positions they exhibit highly protrusive activity at the lateral plasma membranes. By the early tailbud stage, as cells have initiated elongation, protrusive activity has declined but has become polarized, with the majority of plasma membrane protrusions extending anteriorward. By the mid tailbud stage, elongation is underway and protrusive activity has ceased, with cells appearing almost quiescent. In sna>Bix embryos very few projections are observed in muscle cells and muscle elongation is impeded.