A Drosophila kinesin required for synaptic bouton formation and synaptic vesicle transport

Nat Neurosci. 2007 Aug;10(8):980-9. doi: 10.1038/nn1936. Epub 2007 Jul 22.


The morphological transition of growth cones to synaptic boutons characterizes synaptogenesis. Here we have isolated mutations in immaculate connections (imac; CG8566), a previously uncharacterized Drosophila gene encoding a member of the Kinesin-3 family. Whereas earlier studies in Drosophila implicated Kinesin-1 in transporting synaptic vesicle precursors, we find that Imac is essential for this transport. An unexpected feature of imac mutants is the failure of synaptic boutons to form. Motor neurons lacking imac properly target to muscles but remain within target fields as thin processes, a structure that is distinct from either growth cones or mature terminals. Few active zones form at these endings. We show that the arrest of synaptogenesis is not a secondary consequence of the absence of transmission. Our data thus indicate that Imac transports components required for synaptic maturation and provide insight into presynaptic maturation as a process that can be differentiated from axon outgrowth and targeting.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Animals, Genetically Modified
  • Drosophila
  • Drosophila Proteins / genetics
  • Drosophila Proteins / physiology*
  • Gene Expression Regulation, Developmental / genetics
  • Gene Expression Regulation, Developmental / physiology
  • Green Fluorescent Proteins / genetics
  • Green Fluorescent Proteins / metabolism
  • Kinesin / genetics
  • Kinesin / physiology*
  • Microscopy, Electron, Transmission
  • Motor Neurons / cytology
  • Nerve Tissue Proteins / metabolism
  • Neuromuscular Junction / cytology
  • Neuromuscular Junction / physiology*
  • Photoreceptor Cells, Invertebrate / cytology
  • Presynaptic Terminals / physiology*
  • Presynaptic Terminals / ultrastructure
  • Protein Transport / physiology
  • Synaptic Vesicles / physiology*
  • Synaptic Vesicles / ultrastructure


  • Drosophila Proteins
  • Nerve Tissue Proteins
  • Green Fluorescent Proteins
  • Kinesin