Fig. 3

Dynactin1a depletion leads to synapse instability at 2dpf, reduced synaptic density at 6dpf and ultrastructural changes. a Putative synapses are visualized with rab3-dendra2 labeling in single CaP cells at 6dpf. b Synaptic coverage in the arbors, determined by number, average area and total area, of putative synapses is reduced in 6dpf larvae in homozygous mutant embryos when compared with their wild-type siblings. c Synapse stability at 2dpf was assayed by imaging cell arbors over a period of 3 h, where comparison of the initial stack (t = 0) with the subsequent one (t = 3 h) for the same cell was used to determine the number of stable synapses. Examples of synapses added and lost are indicated in green and red arrows respectively. d Quantification is presented as fold-change and reduced in homozygous mutant embryos for number and total area, but not for mean area of putative synapses, when compared with their wild-type siblings. e Electron micrograph of a transverse section of the 6dpf NMJ, with close-up (dashed yellow box), showing active zones (center of yellow circle) in NMJ synapses of mok ^m632−/− larvae and their wild-type siblings. f No changes were detected in number of synaptic vesicles and average vesicle size when measured in the synaptic terminal. g Normal density and distribution of vesicles was also observed around the active zones (yellow circle perimeter), however the synaptic clefts were significantly wider at mok ^m632−/− larvae active zones. Data shown as b) d) average +/− SD, f) g) average +/− SEM. (c: n cells = 11,7; d: n cells = 17,15, f: n slices = 14, 14; g: n active zones = 34,22). Scale bar a) c) 50 μm; e) 500 nm