(A) Overexpression of FGF22 and FGF7 selectively promotes VGLUT1 or VGAT
clustering on the FGF-expressing hippocampal neurons (labeled with GFP) in culture. (B)
CA3 pyramidal neurons, by which FGF22 and FGF7 are expressed, receive excitatory inputs
from dentate granule cells (and CA3 and entorhinal cortical neurons) and inhibitory inputs
from GABAergic interneurons in CA3. (C) Impaired glutamatergic and GABAergic presynaptic
differentiation in CA3 of FGF22KO and FGF7KO mice, respectively. Glutamatergic and
GABAergic presynaptic differentiation was assessed by measuring the clustering of VGLUT1
or VGAT. Pictured areas correspond to the boxed area in (B). (D) Representative electron
microscopic pictures of asymmetric (excitatory) and symmetric (inhibitory) synapses in CA3
of wild-type (WT), FGF22KO and FGF7KO mice. Relative to WT synapses, excitatory synaptic
vesicles are more diffusely distributed in FGF22KO synapses, while less inhibitory
synaptic vesicles are observed in FGF7KO synapses. Adapted from Terauchi and others (2010). SV: synaptic vesicle, PSD: postsynaptic
density.