The SCF/KIT pathway implements self-organised epithelial patterning by cell movement

SUMMARYHow individual cell behaviours lead to the emergence of global patterns is poorly understood. In the Xenopus embryonic epidermis, multiciliated cells (MCCs) are born in a random pattern within an inner mesenchymal layer, and subsequently intercalate at regular intervals into an outer epithelial layer. Using both experiments and mathematical modelling, we show that this transition from chaotic to ordered distribution relies on mutual repulsion among motile immature MCCs, and affinity towards outer-layer intercellular junctions. Consistently, ARP2/3-mediated actin remodelling is required for MCC pattern emergence. Using multiple functional approaches, we show that the Kit tyrosine kinase receptor, expressed in MCCs, and its ligand Scf, expressed in outer-layer cells, are both required for regular MCC distribution. While Scf behaves as a potent adhesive cue for MCCs, Kit expression is sufficient to confer order to a disordered heterologous cell population. Our work reveals how a single signalling system can implement self-organised large-scale patterning.Highlights- Immature multiciliated cells transit from a disordered to an ordered pattern- The transition is a self-organising process based on repulsive and affinity movements- ARP2/3-dependent actin remodelling is required for pattern emergence- The SCF/KIT pathway promotes both repulsion and affinity movementseTOC blurbIn developing Xenopus epidermis, immature multiciliated cells (MCCs), initially chaotically distributed within an inner layer, emerge in an orderly pattern among cells of the outer layer. This process involves MCC mutual repulsion and affinity towards outer-layer intercellular junctions. The SCF/KIT signalling pathway promotes both properties to allow regular MCC distribution.

Shedding patterns of Schistosoma mansoni and Ribeiroia marini cercariae from a mixed infection of Biomphalaria glabrata

ABSTRACTWhen the snail Biomphalaria glabrata is doubly infected by two species of trematode. Schistosoma mansoni and Ribeiroia marini, each species keeps its own cercarial shedding pattern. Emergence of S. mansoni cercariae occurs during the photophase while the R. marini cercariae are shed during the night. These results demonstrate the absence of interference between the machanisms responsible for the cercarial shedding of each species. The only difference noted concerns a two-hour shift in the peak emergence of S. mansoni as a consequence of the antagonism between the two parasites.