Fig. 1.

scat is a negative regulator of synaptic development at the larval NMJ. (A) scat loss-of-function causes defects in NMJ structure. Wandering third instar larvae from controls, scat¹ homozygotes, scat¹/Df(2L)Exel8022, and the scat¹/scat¹; scat-HA:scat/scat-HA:scat rescue (Res) lines were stained with antibodies targeting the postsynaptic density marker, Dlg (green) and the neuronal membrane marker, HRP (red). Images show maximum Z-projections. The NMJs innervating body wall muscles 6/7 in abdominal segment 3 (m6/7 in A3) were analyzed. scat mutants have an increased number of boutons and synaptic arbors in comparison to controls. Scale bar: 20 µm. (B) Total bouton number/MSA (normalized to control) and (C) synapse branch points are significantly increased in scat mutants. Both were quantified by counting manually and both phenotypes are rescued by the introduction of the scat-HA:scat transgenic construct. N=23, 21, 24 and 25. (D) scat loss-of-function causes defects in the size of both type 1b (arrowhead) and 1s boutons (arrows). Wandering third instar larvae from controls, scat¹ homozygotes, scat¹/Df(2L)Exel8022, and the scat¹/scat¹; scat-HA:scat/scat-HA:scat rescue lines were stained with an antibody targeting Dlg. Images shown are single focal planes through the equator of the type 1b boutons. scat¹ homozygotes have noticeably smaller boutons than controls. The NMJs innervating muscle 6/7 in body segment A3 were analyzed. Scale bar: 5 µm. (E) Total synaptic length/MSA (normalized to control) is significantly increased and (F) synaptic area per bouton is decreased in scat¹ homozygotes. Both features were quantified using the Morphometrics algorithm. N=23, 19, 24 and 25. Data are represented as the mean±s.e.m. All statistical analysis was done by Kruskal–Wallis followed by a Dunn's multiple comparison test. Unless otherwise indicated, all comparisons have been made to the control. *P<0.05, **P<0.01, ****P<0.0001.