A model for tube formation and branching in Cnidaria

Abstract

AbstractWhen all the cells of a tube are identical, they are unlikely to control how many of them are present in the circumference. However, when the circumference is subdivided into at least two regions of different cells, the tube diameter can be controlled via the width of these regions. We present a model and computer simulations for the formation of a tube which starts as a cone-like protrusion from a flat sheet of cells. Cells can exist in two alternative states. Cells of one state need signalling from those of the other state in order to maintain their state. Hence the cells of the two states arrange in stripes. A pattern-forming system, which defines where in this field of cells a tube will start to form, causes the stripes to become small at that very site. When four stripes originate at that point, and when the angle between the two borders of the stripes (as measured from the centre of the field) is less than 90°, the tissue is forced to protrude in the form of a cone. This model may help to understand the morphogenesis proper of buds of Cnidaria and of tubes, such as that of insect legs and the neural tube of vertebrates.