Figure 3.

Quantification of ER export sites in hippocampal neurons. Using our two-stage assay (supplemental Fig. 2, available at www.jneurosci.org), Sec23 vesicles were quantified in neurons at the designated DIV. A modification of the “centrifugal method” of dendritic branch ordering was used to describe the density of dendritic arborizations (Uylings and van Pelt, 2002). Our characterization was such that the dendrites emerging from the cell soma are called somatic for one soma diameter distance and then primary up to the point of bifurcation into second-order branches. Therefore, first branches are called secondary and so on, with increasing order until the tips are reached. For these experiments, the vesicles of dendrites from a minimum of five neurons, from at least three different experiments, at each time point were quantified. Values equal mean ± SEM.