Morphological and functional abnormalities of hippocampus in APC 1638T/1638T mice

In the present study, we examined morphology and function of hippocampus in the APC mouse. Expression levels of the APC mRNA and protein were both identical in the hippocampus of the APC and APC mice. The dentate gyrus of the APC hippocampus was thicker, and has more densely-populated granule cells in the APC mouse hippocampus. Immunoelectron microscopy revealed co-localization of APC with alpha-amino-3- hydroxy-5-methyl- isoxazole-4-propionate receptor (AMPA-R) and with PSD-95 at post-synapse in the APC hippocampus, while APC1638T was co-localized with neither AMPA-R nor PSD-95 in the APC hippocampus. By immunoprecipitation assay, full-length APC expressed in the APC mouse was co-immunoprecipitated with AMPA-R and PSD-95. In contrast, APC1638T expressed in the APC mouse was not co-immunoprecipitated with AMPA-R and PSD-95. In the hippocampal CA1 region of the APC mouse, c-Fos expression after electric foot shock was decreased compared with the APC mouse. The present study showed some abnormalities on morphology of the hippocampus caused by a truncated APC (APC1638T). Also, our findings suggest that failure in APC binding to AMPA-R and PSD-95 may bring about less activities of hippocampal neurons in the APC mouse.