File:A-gene-trap-transposon-eliminates-haematopoietic-expression-of-zebrafish-Gfi1aa-but-does-not-mmc5.ogv

English: Movie 4 : flk1/kdrl: GFP/csl: Cer-double positive haemogenic endothelial cells give rise to blood cells that join the circulation. This movie provides supporting evidence related to Figure 1. It shows data from timelapse confocal microscopy on flk1/kdrl: gfp/csl: cer-double transgenic embryos starting from 48 hpf. Images of single 1.5 µm optical sections are shown with anterior to the left and dorsal up. Images were taken every 3 min. At 48 hpf, endothelial cells of the dorsal aorta co-express both reporter transgenes, while vein endothelial cells are only GFP-positive. During the course of the timelapse, different events were observed that are all highlighted with colored circles. The red circle marks a haemogenic endothelial cell as it underwent basal endothelial to haematopoietic transition. In the mesenchyme, the cell divided once and the daughter cells remained more or less stationary. As time went on, haematopoietic cells in the mesenchyme lost their green fluorescence faster than their blue fluorescence. Cells that entered the vein to join the circulation were clearly less brightly green than cells that had only just undergone EHT. Based on the residual intensity of their green fluorescence, it was obvious that cells remained in the mesenchyme for different periods of time before they entered the vein. They also entered the vein by different routes. One cell was seen to migrate around the vein before entering it through its ventral wall (blue circle). Another cell entered the vein through its dorsal wall (green circle) while several other cells got trapped in an endothelial pocket formed by venous endothelial cells (yellow circle). The cells eventually left the pocket to join the circulation.