Fig. 4.

Models of the diverse molecular mechanisms of seven-transmembrane cadherins in neuronal interactions and connections. a Fmi/Celsr could act as pure adhesive molecules, without transmitting an intracellular signal. b Fmi/Celsr may be a receptor for an unknown ligand. c In mammals, Celsr2 and Celsr3 homotypic interactions trigger intracellular calcium increase, leading to opposite responses in dendritogenesis. d Fzd3 collaborates with Celsr3 in the formation of axonal tracts in mammals. The other PCP proteins Vangl2, Dvl, and Wnts are also involved in the guidance of commissural axons in the mice spinal cord. e In the fly visual system, synaptic-layer targeting in the medulla is mediated by asymmetric homophilic interaction, involving Fmi and Gogo in photoreceptors and Fmi in their target. Gogo interacts with the cytoskeleton via Adducin