Restless E-cadherin molecules might help confine Drosophila embryonic cells, preventing them from crossing into neighboring segments, Bulgakova et al. report.
E-cadherin fastens cells together by forming adherens junctions. In the epidermis of a fruit fly embryo, E-cadherin shows a striking pattern. The cells are rectangular, and the short sides (which form the dorsal and ventral borders) sport almost twice as much E-cadherin as the long sides (the anterior and posterior borders).
An epidermal cell carries two pools of E-cadherin, the researchers found. An immobile pool spreads around the periphery of the cell, but the dorsal and ventral borders teem with a peripatetic pool of E-cadherin that is continually entering and exiting the cell membrane and shifting around within it. This mobile E-cadherin links to the Bazooka/Par3 protein, which helps position E-cadherin–containing junctions.
Dynamic microtubules, which align along the dorsal–ventral axis of these cells, enable the mobile E-cadherin to amass at the cell membrane, Bulgakova et al. determined. The researchers think that the microtubules draw RhoGEF away from the dorsal–ventral cell borders, allowing mobile E-cadherin to accumulate at these membranes.
What is the function of the transient E-cadherin? In a Drosophila embryo, an epidermal cell typically remains within its segment, but it can occasionally stray into an adjoining one. Bulgakova et al.’s results suggest that the mobile E-cadherin prevents cells from crossing the boundary. The molecule might strengthen the dorsal and ventral attachments to adjoining cells or prevent the sides from associating with different neighbors.
Text by Mitch Leslie