Visualization of Endothelial Actin Cytoskeleton in the Mouse Retina

Angiogenesis requires coordinated changes in cell shape of
endothelial cells (ECs), orchestrated by the actin cytoskeleton.
The mechanisms that regulate this rearrangement in vivo are poorly
understood - largely because of the difficulty to visualize
filamentous actin (F-actin) structures with sufficient resolution.
Here, we use transgenic mice expressing Lifeact-EGFP to visualize
F-actin in ECs. We show that in the retina, Lifeact-EGFP expression
is largely restricted to ECs allowing detailed visualization of
F-actin in ECs in situ. Lifeact-EGFP labels actin associated with
cell-cell junctions, apical and basal membranes and highlights
actin-based structures such as filopodia and stress fiber-like
cytoplasmic bundles. We also show that in the skin and the skeletal
muscle, Lifeact-EGFP is highly expressed in vascular mural cells
(vMCs), enabling vMC imaging. In summary, our results indicate that
the Lifeact-EGFP transgenic mouse in combination with the postnatal
retinal angiogenic model constitutes an excellent system for
vascular cell biology research. Our approach is ideally suited to
address structural and mechanistic details of angiogenic processes,
such as endothelial tip cell migration and fusion, EC polarization
or lumen formation.