Figure 5. An Increase in Presynaptic Density, but Not Efficacy, Induces a Decrease of Postsynaptic Dendritic Arbor Extension.

(A) Reconstruction of a representative aCC arbor at 18 h AEL from a specimen in which faf was overexpressed in the presynaptic cholinergic neurons. Presynaptic sites on the arbor are indicated by coloration, with the colour code representing relative intensities of colocalised fluorescence signals. Scale bar indicates 5 μm.

(B) Quantification of the synaptic density (dendritic surface occupied by synapses divided by total dendritic length) on the aCC arbor in control (red), Cha::faf (cyan), and Ace mutant animals (magenta). The synaptic density on the postsynaptic dendritic arbor is increased when faf is overexpressed presynaptically but not in Ace mutants (controls: 0.22 ± 0.03, n = 12; Cha::faf : 0.54 ± 0.07, n = 10; Ace mutants: 0.18 ± 0.01, n = 8).

(C) Reconstruction of a representative aCC arbor of an Ace mutant animal. aCC arbors and the density of presynaptic cholinergic sites on these are comparable to controls. Scale bar indicates 5 μm.

(D) Quantification of total dendritic tree length in control (red), Cha::faf (cyan), and Ace mutant animals (magenta). Presynaptic overexpression of faf induces reduced growth of the arbor (94 ± 4 μm, n = 10) as compared to controls (115 ± 7 μm, n = 13; p = 0.02). aCC arbors in Ace mutants are not significantly different from control animals (124 μm ± 14 μm, n = 8; p > 0.05).

Box-plots show the median of the distribution (middle line), the 75th percentile (upper limit of box), and 25th percentile (lower limit of box). Whiskers indicate the highest and lowest value of each experimental group. Significance was assessed by unpaired, two-tailed t-test. A single asterisk (*) indicates p < 0.05; NS indicates p > 0.05.