Multicellular rosette formation during cell ingression in the avian primitive streak
Laura J. Wagstaff, Gemma Bellett, Mette M. Mogensen, Andrea Münsterberg
Developmental Dynamics Volume 237, Issue 1, Pages 91-96
Where one can see differences in cytoskeletal organization (and cells’ organization as well) at the primitive streak of gastrulating chick embryos. Differences that some model failed to take in account ; oh dear, how fucking annoying, for the model…
Below the fold, my favorite, panel C of Figure 3 of the paper (and abstract):
C: Side view of a HH3 primitive streak anterior region, with microtubule staining in green and actin staining in red. Actin-rich parts are protruding towards the hypoblast. Scale bars = 20 mm.
Cell movements are a fundamental feature during the development of multi-cellular organisms. In amniote gastrulation, cells ingress through the primitive streak, which identifies the anterior-posterior axis of the embryo. We investigated the cytoskeletal architecture during these morphogenetic processes and characterized microtubule organisation in whole chick embryos. This revealed the distribution of cells with polarized and radial microtubule (MT) arrays across different regions of the embryo. Cells in the epiblast usually displayed radial MT-arrays, while the majority of cells in the primitive streak had polarized MT-arrays. Within the primitive streak, many cells organized into groups and were arranged in rosette-like structures with a distinct centre characterized by an accumulation of actin. Extended confocal microscopy and three-dimensional image reconstruction identified tips of polarized cells that were protruding from the plane of rosettes, usually from the centre. We propose that organization into higher order structures facilitates cell ingression during gastrulation.
Multicellular rosette formation… 
