A digital image-based method for computational tissue fate mapping during early avian morphogenesis.

The early stages of vertebrate development, encompassing gastrulation, segmentation, and caudal axis formation, presumably involve large (finite) morphogenetic deformations; however, there are few quantitative biomechanical data available for describing such large-scale or tissue-level deformations in the embryo. In this study, we present a new method for automated computational "tissue fate mapping," by combining a recently developed high-resolution time-lapse digital microscopy system for whole-avian embryo imaging with particle image velocimetry (PIV), a well-established digital image correlation technique for measuring continuum deformations. Tissue fate mapping, as opposed to classical cell fate mapping or other cell tracking methods, is used to track the spatiotemporal trajectories of arbitrary (virtual) tissue material points in various layers of the embryo, which can then be used to calculate finite morphogenetic deformation or strain maps. To illustrate the method, we present representative tissue fate and strain mapping data for normal early-stage quail embryos. These data demonstrate, to our knowledge, for the first time, large tissue-level deformations that are shared between different germ layers in the embryo, suggesting a more global morphogenetic patterning mechanism than had been previously appreciated.