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Fig. 2
Multi-day imaging of dendrite development and spine formation. (A,B) Native-orientation (dorsal view) maximum-projection images of the same PyrN at 4 dpf and 11 dpf. (C,D) Rotated sideview projections of the neuron in A,B. Three distinct dendritic stratifications are visible at each timepoint. Also note that the total length of the main dendritic process increases, most likely due to thickening of the tectal neuropil during this developmental period. (E-H) Higher magnification views of the SM-targeted apical dendrite of PyrN in A-D (region indicated by the yellow box in D). Sites where new branches are added are indicated by yellow arrowheads (before branch addition) and cyan arrowheads (after branch addition). Sites where branches were retracted are indicated by red arrowheads (before branch retraction) and open arrowheads (after branch retraction). Note that branches are added and retracted throughout this time window. Also note that from 4 to 11 dpf there is a gradual loss of long, filopodial protrusions and an increase in short, spine-like protrusions. (I) Neurite length measurements of PyrN SM dendrites between 4 and 10/11 dpf. Due to reduced survival at the 10 and 11 dpf timepoints, these groups were combined into one bin. (J) Retinotopic area measurements of PyrN SM dendrites between 4 and 10/11 dpf. (K) Spine density measurements of PyrN SM dendrites between 4 and 10/11 dpf. Number of neurons and larvae (indicated in parentheses) analyzed for each timepoint: 5 (5), 10 (10), 10 (10), 6 (6), 11 (11) and 7 (7). All graphs depict mean±s.d. Red diamonds indicate measurements obtained from PyrN dendrite in E-H. One-way ANOVA with Tukey's multiple comparisons test was used to determine significance, P-values for all pairwise comparisons in I, J and K were >0.05. Scale bars: 20 µm (A-D); 5 µm (E-H).