Mib1 expression in neurons of the adult brain. (A) X-gal-stained section of the adult mib1+/LacZ brain. X-gal reactivity was strong in the hippocampus and in the piriform cortex. Hip, hippocampus; Cor, cortex; Pir, piriform cortex; Tha, thalamus. Scale bar: 1 mm. (B) X-gal reactivity was high in the granule layers of the dentate gyrus (DG) and in the pyramidal layers of the CA1 and CA3 regions. Scale bar: 200 μm. (C) NeuN (left panel) and GFAP staining (right panel) on an X-gal-stained section of the adult mib1+/LacZ brain. X-gal-stained cells were merged with NeuN + neurons but not with GFAP + astrocytes in the hippocampal CA1 region. py, pyramidal neuron layer; s.r., stratum radiatum. Scale bars: 50 μm. (D) Distribution of Mib1 in subcellular fractions of adult rat brain. Note that Mib1 proteins were mainly detected in synaptic fractions, including P2 and LP1 and also in P3. Jagged1 (Jag1), one of candidate substrates of Mib1, was also detected in P2. PSD-95 and synaptophysin (SynPhy) were probed for comparison. H, homogenates; LP1, synaptosomal membranes; LP2, synaptic vesicle-enriched fraction; LS2, synaptosomal cytosol; P1, crude nuclear fraction; P3, light membranes; S3, cytosol.