Reduced Notch signaling in the hippocampus of mib1 cKO mice. (A) Mib1 deletion efficiency in mib1 cKO brains. Total RNA from 3-week-old, 6-week-old, and 8-week-old wild-type and mib1 cKO hippocampi were analyzed by quantitative real-time PCR for mib1 mRNA (left panel). Immunoblotting of Mib1 in the hippocampal lysates from 6-month-old wild-type and mib1 cKO mice (right panel). (B) Immunoblotting of activated Notch1 in the hippocampal lysates from 6-month-old wild-type and mib1 cKO mice. (C) Confocal images of NeuN and activated Notch1 coimmunoreactivity on the CA1 regions of 4-month-old wild-type and mib1 cKO hippocampi. py, pyramidal neuron layer; s.r., stratum radiatum. Scale bars: 50 μm. (D) Total RNA from the 4-month-old wild-type (n = 4) and mib1 cKO hippocampi (n = 4) were analyzed by semiquantitative RT-PCR for general Notch downstream genes, hes1, hes5, and nrarp (left panel). The same samples were also analyzed by quantitative RT-PCR (right panel). Error bars show standard deviation. *Significant difference; p < 0.001. **Significant difference; p < 0.02.