Dynamic Analysis of Vascular Morphogenesis Using Transgenic Quail Embryos
Figure 4
EC dynamics at the onset of vasculogenesis.
The overall narrowing of the embryo appears as a tissue drift towards the midline, discernible by particle imaging velocimetry (PIV) analysis of the DIC image sequence (a) Motion of H2B-eYFP+ (HH stage 7, 5ss embryo) nuclei are shown in a somite-attached reference system by projecting four consecutive frames (the first three in red and the last one in yellow). The prevalent medial EC movement mostly reflects tissue drift, as the superimposed, PIV-derived displacement vectors indicate. (b) DIC image of the same specimen, with tissue motion vectors superimposed. (c) After removing tissue motion from the image sequence, displacements of H2B-eYFP+ nuclei appear random, without a prevalent directionality. Area shown in panel (c) is outlined with dotted lines in panels (a) and (b). (d) Cell-autonomous movement of nuclei an hour later in the nascent lateral network, outlined with a dashed line in panel (c). Two consecutive frames, separated by 8 minutes, are shown — the first as red, the second as green. Motile activity is inhomogeneous within the population: some nuclei do not move (appear as yellow, some are marked with circles), while most cells move in a chain-migration fashion (indicated by arrows). At this stage of vasculogenesis movement directions scatter widely: cell groups can move in opposite directions even along the same vascular segment. Scale bar: 200 µm.