Null mutation in shaking-B eliminates electrical, but not chemical, synapses in the Drosophila giant fiber system: a structural study

J Comp Neurol. 1999 Feb 22;404(4):449-58.


Mutations in the Drosophila shaking-B gene perturb synaptic transmission and dye coupling in the giant fiber escape system. The GAL4 upstream activation sequence system was used to express a neuronal-synaptobrevin-green fluorescent protein (nsyb-GFP) construct in the giant fibers (GFs); nsyb-GFP was localized where the GFs contact the peripherally synapsing interneurons (PSIs) and the tergotrochanteral motorneurons (TTMns). Antibody to Shaking-B protein stained plaquelike structures in the same regions of the GFs, although not all plaques colocalized with nsyb-GFP. Electron microscopy showed that the GF-TTMn and GF-PSI contacts contained many chemical synaptic release sites. These sites were interposed with extensive regions of close membrane apposition (3.25 nm +/- 0.12 separation), with faint cross striations and a single-layered array of 41-nm vesicles on the GF side of the apposition. These contacts appeared similar to rectifying electrical synapses in the crayfish and were eliminated in shaking-B2 mutants. At mutant GF-TTMn and GF-PSI contacts, chemical synapses and small regions of close membrane apposition, more similar to vertebrate gap junctions, were not affected. Gap junctions with more vertebratelike separation of membranes (1.41 nm +/- 0.08) were abundant between peripheral perineurial glial processes; these were unaffected in the mutants.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Alleles
  • Animals
  • Connexins / biosynthesis*
  • Connexins / physiology*
  • Drosophila / physiology*
  • Drosophila Proteins*
  • Electrophysiology
  • Gap Junctions / physiology
  • Gap Junctions / ultrastructure
  • Green Fluorescent Proteins
  • Immunohistochemistry
  • Luminescent Proteins / metabolism
  • Membrane Proteins / metabolism
  • Microscopy, Electron
  • Motor Neurons / metabolism
  • Motor Neurons / physiology
  • Motor Neurons / ultrastructure
  • Mutation / physiology*
  • Nerve Fibers / metabolism*
  • Nerve Fibers / physiology*
  • Nerve Fibers / ultrastructure
  • Nerve Tissue Proteins / biosynthesis*
  • Nerve Tissue Proteins / metabolism
  • Nerve Tissue Proteins / physiology*
  • R-SNARE Proteins
  • Synapses / metabolism*
  • Synapses / physiology*


  • Connexins
  • Drosophila Proteins
  • Luminescent Proteins
  • Membrane Proteins
  • Nerve Tissue Proteins
  • R-SNARE Proteins
  • shakB protein, Drosophila
  • Green Fluorescent Proteins