Thinner tubes

A switch that controls cell intercalation determines the diameter of fly embryo tracheal tubes, according to Carlos Ribeiro, Marc Neumann, and Markus Affolter (Biozentrum, Universität Basel, Switzerland). Other tube-like structures such as blood vessels may use similar sculpting techniques.

The direction of tracheal tube extension is defined by migration of interconnected precursors toward an FGF signal. But tube morphology is also affected by Dpp and Wnt signaling. The Swiss team wanted to know what cellular processes were being controlled by Dpp and Wnt.

They made movies of living fly embryos with labeled adherens junctions (AJs). The label showed cells that were initially paired, side-by-side, in wider tubes. But gradually individual cells reached around at one end until they made contact with themselves, and then started replacing their intercellular AJs with autocellular AJs....