Therefore, to simplify subsequent breeding for in vivo analyses, we have chosen to focus our comparison primarily between APP+/− and APP−/− mice. We also noticed a reduction of dendritic complexity in culture hippocampal neurons from APP deficient mice. However, in cultured neurons, it is difficult to precisely define the apical vs. basal dendrites to quantify such changes in neuronal polarity. Therefore, the number of dendritic branch points within a radius of 150 μm from the neuron soma was assayed as a measure of dendritic complexity. We found that the average number of dendritic branch points was significantly reduced in APP−/− neurons compared to APP+/− (Fig. S3), indicating that both dendritic spine numbers and dendritic arborizations were diminished in the absence of APP in cultured hippocampal neurons.
