Figure 2: DLG proteins regulate the number of active zones per bouton but only DLGS97 regulates the size of the glutamate receptors fields.

Confocal images of synaptic boutons labeled with antibodies against the active zone protein Bruchpilot (green) and antibodies against the constitutive subunit of the Glutamate receptor GLURIII (red). (A) WT and dlg mutants representative images. dlg^XI-2 and dlgS97 mutants show increased size of the GLUR-fields. (B) Quantification of the average size of the boutons (top-left), the average size of the active zones (top-right), the average number of active zones per bouton (bottom-left) and the average size of the GLUR-fields (bottom-right) in dlg mutants and dlg mutants over a deficiency covering the dlg region in the genome. (C) Representative images of motoneuron driver (GAL4-OK6) or the muscle driver (GAL4-C57) in the dlgS97⁵ mutant background with or without (genetic mutant control) expression of UAS-DLGS97. The size of the GLUR fields is rescued in dlgS97 mutant by the expression of DLGS97 in the muscle but not in the neuron. (D) Representative images of motoneuron driver (GAL4-OK6) or the muscle driver (GAL4-C57) in the dlgA^40.2 mutant background with or without (genetic mutant control) expression of UA-DLGA. (E) Quantification of the average size of the boutons (top-left), the average size of the active zones (top-right), the average number of active zones per bouton (bottom-left) and the average size of the GLUR-fields (bottom-right) in dlgS97⁵and dlgA^40.2mutants with or without the expression of DLGS97 or DLGA in the neuron and in the muscle. The size of the GLUR fields is only restored to a WT size in dlgS97 mutant by the expression of DLGS97 in the muscle but not in the neuron. The presynaptic expression of DLG is able to rescue the number of active zones per synaptic bouton, however only the expression of DLGA in the neuron is able to rescue the size of the active zones. Columns represent the average ± SEM n = 6. *p < 0.05, **p < 0.01 respect to the WT.