August 19, 2014

Think of life without tubes for a moment. Not only would our huge bodies cease to exist, but our homes’ plumbing would be a mess and my 5-year old’s marble run would be pretty boring. The formation of tubes during development is a fascinating topic. Today’s image is from a paper describing the role of endocytosis in seamless tube formation.

The trachea of the fruit fly is a simple tubular system that functions as the respiratory system of the fly. The star-shaped tracheal terminal cells form seamless tubes that extend the length of long cellular extensions. Schottenfeld-Roames and colleagues recently published a study investigating the mutations in the braided gene. Tracheal terminal cells in braided mutants have tubular cysts and fewer branches, as seen in the images above (top is wild-type; bottom is mutant). braided encodes Syntaxin7, a endocytosis protein that promotes fusion of vesicles to early endosomes. Schottenfeld-Roames and colleagues found that mutations in other early endosome proteins cause similar terminal cell tube defects. Additional data showing increased levels of the apical protein Crumbs in braided terminal cells suggests that early endocytosis regulates levels of Crumbs, which in turn affects tube formation through actin cytoskeleton modulation. The images above show the luminal membrane (green) and an apical protein (magenta) in tracheal tubes. The tubes in braided mutants are cystic and abnormal, and the tube tips are disorganized (higher magnified views of the boxed regions are on the left).

Schottenfeld-Roames, J., Rosa, J., & Ghabrial, A. (2014). Seamless Tube Shape Is Constrained by Endocytosis-Dependent Regulation of Active Moesin Current Biology, 24 (15), 1756-1764 DOI: 10.1016/j.cub.2014.06.029
Copyright ©2014 Elsevier Ltd. All rights reserved.

All the images were acquired by Dr. Jodi Schottenfeld-Roames.