PTPδ and IL1RAPL1 cis- interaction blocks the ability of IL1RAPL1 to regulate dendrite morphology. A, Hippocampal neurons were transfected at DIV 11 with GFP alone or with HA-IL1RAPL1, HA-PTPδ, HA-PTPδ ECTO, HA-PTPδ A−B−, and shRNA against PTPδ and IL1RAPL1 in combination with HA-PTPδ, HA-PTPδ ECTO, and HA-PTPδ A−B− and then fixed and stained at DIV 14–15 with anti-HA and anti-IL1RAPL1 antibodies. GFP signal (left) was used for the Sholl analysis. B, Quantification of branching points of neurons overexpressing the indicated constructs. Ten to 15 neurons analyzed for each construct in three independent experiments. All values represent mean ± SEM. *p < 0.05, ***p < 0.001 vs GFP, ANOVA followed by Dunnet's post hoc test. C, Quantification of branching points of neurons overexpressing the indicated combination of constructs plotted for distance from the soma (μm). All values represent mean of total branching points every 50 μm ± SEM. *p < 0.05, **p < 0.005 vs GFP ANOVA followed by Dunnet's post hoc test.