Figure 7. Schematic of the model. Regulation of ribbon synapses by FGF22/calcium/CalN/MEF2D signaling. FGF22 signaling through its major receptor FGFE2b triggers an increase of intracellular Ca2+, which activates the CaN and its downstream factors, e.g. NFATc. Activated CaN subsequently suppresses MEF2D, the inhibitory effects of which on ribbon synapses are then released.