Figure 6

DFsn down-regulates the levels of the Wallenda/DLK kinase to restrain synaptic terminal growth. (a) Staining for endogenous Wallenda in central nervous system neuropil in ventral nerve cords of wild-type (WT), DFsn^f06595/Df [P(f06595)/Df(2R)7872], DFsn^f06595/Df-Res [presynaptic rescue: P(f06595)/Df(2R)7872; elav Gal4/UAS-GFP-DFsn] and DFsnf06595/Df; wnd¹/wnd³ third-instar larvae. Upper panels show Wallenda staining alone, and lower panels show co-staining of Wallenda (red) with the synaptic marker HRP (horseradish peroxidase) (blue). (b) Quantification of average Wallenda staining in the neuropil of third-instar larvae for the genotypes shown in (a). The Wallenda intensity was measured for each genotype and the background intensity measured for DFsnf06595/Df; wnd¹/wnd³ was subtracted. Wallenda staining in the DFsn^f06595/Df mutant was significantly higher than WT (p < 0.001). Presynaptic expression of a GFP-DFsn transgene rescues the increase of Wallenda level (p > 0.5 for DFsn^f06595/Df-Res versus WT). (c) Representative confocal images of muscle 4 synapses co-stained with DVGLUT (green) and FasII (red), in WT, DFsn^f06595/Df and DFsn^f06595/Df; wnd³ third instar larvae. (d-f) Quantification is shown for bouton number (d) and synaptic branch point number (e) and synaptic span (f) for WT, DFsn^f06595/Df and DFsn^f06595/Df; wnd³ (n = 23, 23, and 22 cells, respectively). The wallenda mutant fully suppresses the morphological defects in the DFsn^f06595/Df mutant (p > 0.1 for DFsn^f06595/Df; wnd³ versus WT in number of boutons and branch points; p < 0.001 for DFsn^f06595/Df; wnd³ versus DFsn^f06595/Df in synaptic span, number of boutons and branch points).