Figure 1. Activin/TGF-β pathway has no influence on synaptic growth at the NMJ.

(A) Expression of Activin/TGF-β-type ligands in the neuromuscular system: actβ-GAL4-driven ChRFP-Tubulin expression is found in the axons and axon terminals innervating the body-wall muscles, daw-GAL4 drives Cherry-Tubulin expression at high levels in muscle 6/7 and surface nerve wrapping glial cells. Lower expression is found in muscle 12&13. myo-GAL4 drives Cherry-Tubulin expression in all body wall muscles. (B) Flag-tagged Babo_b was expressed in muscle by Mef2-GAL4 or in motor neurons by OK6-GAL4. Immunohistochemistry using anti-Flag antibody reveals preferred localization of Babo_b(Flag) to NMJ both in the presynaptic and postsynaptic cells. (C) Representative images of the NMJ of wt, babo^fd4/df and smox^f4 animals from HRP staining. In this figure, babo^fd4/df and smox^f4 NMJs show concentrated distribution of synapses. (C’) Quantification of the NMJ size. The total number of synapses were counted and normalized to muscle surface area. There was no significant difference between the wild-type and babo or smox mutants. (D) Quantification of the NMJ size of the animals overexpressing constitutively-activated Babo either in the motor neuron or in the muscle. Overexpression of the activated Babo did not affect the NMJ size. Error bars represent SEM. Left scale bar in A is 80 µm; right scale bar in A is 16 µm; all others are 20 µm.