The first movie shows germband extension at a more global level, while the second movie shows cell intercalation in more detail, highlighting T1 transitions driving the process (movies courtesy of Claudio Collinet and Thomas Lecuit). The third movie shows convergence and extension in zebrafish (movie courtesy Fengzhu Xiong and Sean Megason, Harvard Medical School).
Cell outlines are labelled with a fluorescent protein, Ecadherin::GFP ; cells can be seen to align along different rows across the AP axis and have been tracked and labelled with different colours. Cells labelled in cyan and magenta are not initially neighbours, they intercalate between cells labelled in yellow and become neighbours at the end of the process. Cell intercalation is polarised along the DV axis and drives tissue extension (see tissue patch outlines labelled in green) along the AP axis. Scale bar = 10 µm. Movie courtesy of Claudio Collinet and Thomas Lecuit.
This movie shows a maximum Z-projection of Ecadherin::GFP (magenta) and Myosin Regulatory Light Chain MRLC::mCherry. Three examples of T1 transitions are illustrated. ‘Vertical' junctions (labelled in red) shrink leading to a 4-way vertex configuration (labelled in yellow) which is then resolved by the growth of new ‘horizontal’ junctions (labelled in green). Scale bar = 5 µm. Movie courtesy Claudio Collinet and Thomas Lecuit.
Convergent extension is the key process of making body plans from 3 germ layers. This movie provides a single-cell resolution dorsal view of this process in a developing zebrafish embryo from 8.5 to 18.5 hours post fertilization (hpf). Movie is a continuous sequence of 300 images with time stamp (unit:hours and minutes post fertilization, YSL, yolk syncytial layer). Each image is a 3D projection of a Z-stack (71μm deep) of 2-photon slices (400μm in height and width, Scale bar: 20μm) at 2 minute time intervals. Cell membranes were labelled with membrane targeted yellow fluorescent protein (coloured cyan in the movie) and cell nucleus with histone2B tagged red fluorescent protein (coloured yellow in the movie). These markers are excited by 2 photon laser at 1020nm.This movie allows researchers to directly follow the cell divisions and movements, changes of cell shapes, as well as the formation of different tissues. Movie courtesy Fengzhu Xiong and Sean Megason (Harvard Medical School).