Figure 6. The importance of symmetry-breaking in generation of large-scale structures in organoids.

(a) shows a renal organoid made from a random mix of renogenic stem cells; there are red developing nephrons and many small green developing collecting duct treelets scattered throughout. (b) shows the more realistic anatomy (single ramifying collecting duct tree) that results from introducing collecting duct progenitors at one location only. (c) shows how introducing a second break of symmetry, a local source of the signalling molecule BMP4, introduces large-scale polarized organization with a ureter (orange) at one end and kidney-type anatomy (blue collecting duct, green nephrons) at the other. Image c is from one of our images in [32], cc-4.0 licence. Scale bar 100 µm.