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.
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Text by Mitch Leslie
