May 13, 2013

Molecular motors are some of the raddest things in a cell.  They can walk along cytoskeletal elements such as microtubules and actin filaments, and the list of cellular events that they participate in is a long, long list.  Today’s image is from a paper showing a beautiful pattern of nonmuscle myosin II in epithelial cells.

Epithelial cells assemble junctions to adhere to one another, and the actin motor nonmuscle myosin II (NMII) is a major component of these epithelial apical junctions.  NMII helps the epithelial sheet respond to morphogenesis and changes in tissue homeostasis, and a recent paper describes how the network of NMII motors does so.  Ebrahim and colleagues have found that NMII in the apical junctional complex of epithelial cells assembles into precise muscle-like sarcomere units that form a belt around each cell.  The sarcomeres of neighboring cells are aligned, in turn assembling into a contractile network that can result in changes in cell shape.  In the images above, NMII (green) is seen in repeated sarcomere units around each cell (actin is in red).  NMII puncta are paired together in neighboring cells.  Arrows (middle) point to the junctions between three cells, seen at higher magnification on the right.

Ebrahim, S., Fujita, T., Millis, B., Kozin, E., Ma, X., Kawamoto, S., Baird, M., Davidson, M., Yonemura, S., Hisa, Y., Conti, M., Adelstein, R., Sakaguchi, H., & Kachar, B. (2013). NMII Forms a Contractile Transcellular Sarcomeric Network to Regulate Apical Cell Junctions and Tissue Geometry Current Biology, 23 (8), 731-736 DOI: 10.1016/j.cub.2013.03.039 
Copyright ©2013 Elsevier Ltd. All rights reserved.