“Our country is just so polarized these days,” I say as I shake my fist, then tell those pesky kids to get off of my lawn. “Polarized” doesn’t have to be a dirty word…in fact, if it weren’t for polarized epithelial cells we’d all be big puddles of cells lacking the ability to digest food, reproduce, circulate blood, or breathe. Today’s image is from a paper describing how septins guide microtubule organization in polarized epithelial cells.
Epithelial cells form sheets that line various organs throughout the body. These epithelial sheets are polarized, meaning the cells are not symmetrically organized. For example, our intestine is lined with a polarized epithelial sheet that must absorb nutrients from the intestine’s cavity in one side of the cell sheet, and then eventually guide those nutrients to blood vessels. A key step in the polarization of a cell is the organization of the microtubule cytoskeleton. Microtubules are organized in a radial array in rounded cells, while the microtubules in polarized epithelial cells are arranged along the lateral borders of the cells and in networks under the apical and basal membranes (top and bottom). A recent paper looks at the role of proteins called septins in guiding microtubule organization during the establishment of polarity. Septins are filamentous proteins known for their roles in cell polarity, but Bowen and colleagues were able to show a functional link between septins and microtubule organization. Specifically, two populations of septins allow microtubule growth, bundling, and capture in different regions of the cell. In the image above, thick septin filaments (left, green in merged) are seen colocalized with microtubules (middle, red in merged) in epithelial cells. Bottom images are higher magnification views of the boxed region.
Bowen, J., Hwang, D., Bai, X., Roy, D., & Spiliotis, E. (2011). Septin GTPases spatially guide microtubule organization and plus end dynamics in polarizing epithelia originally published in The Journal of Cell Biology, 194 (2), 187-197 DOI: 10.1083/jcb.201102076