Different structural NMJ phenotypes in Drosophila embryos
Phenotypes at stage 16 (top row) and late stage 17 (bottom row; >>> explanatory scheme); N, nerv; Mn, motorneuron; Gc, growth cone; Ep, epidermis, M, muscle. B,C) Presynaptic specialisations differentiate even if neuromuscular contact is not established through absence of muscles (twist mutant or mesodermal expression of Notchintra, 24B::Nin) or upon misguidance of motoraxons (elav::eve). D) Many neuromuscular boutons form no neuromuscular contact if muscles are reduced in size in myoblast city (mbc). E) Neuromuscular terminals are reduced in kakapo/short stop mutant embryos (kak/shot). F) No neuromuscular contacts are formed if muscles fail to differentiate in embryos mutant for mesoderm enhancing factor (mef2). G) Neuromuscular adhesion is reduced if the extracellular matrix protein lamininA is absent (lamA).
___________________________________________________________________

Source: A,B,D,F modified from Prokop et al. (1996) Presynaptic development at the Drosophila neuromuscular junction: The assembly and localisation of presynaptic active zones. Neuron 17: 617-626.

(A-C) Light microscopical images of neuromuscular terminals (arrow head) on VL and VO muscles (>>> diagram of muscles) in wild type (wt), kakapo/short stop (kak) or myoblast city (mbc) mutant embryos.

(D-G) Ultrastructural images of neuromuscular junctions in wt, kak, lamininA (lamA) and mesoderm enhancing factor (mef2) mutant embryos; asterisk, presynaptic bouton; black arrow, synapse; mu, muscle, open arrow, extrasynaptic cell junction; open arrow head, basement membrane.

________________________________

Source: A-F modified from Prokop, A. (1999) Integrating bits and pieces - synapse formation in Drosophila embryos. Cell Tissue Res. 297(2): 169-186.