Mutations in shaking-B prevent electrical synapse formation in the Drosophila giant fiber system.
The giant fiber system (GFS) is a simple network of neurons that mediates visually elicited escape behavior in Drosophila. The giant fiber (GF), the major component of the system, is a large, descending interneuron that relays visual stimuli to the motoneurons that innervate the tergotrochanteral jump muscle (TTM) and dorsal longitudinal flight muscles (DLMs). Mutations in the neural transcript from the shaking-B locus abolish the behavioral response by disrupting transmission at some electrical synapses in the GFS. This study focuses on the role of the gene in the development of the synaptic connections. Using an enhancer-trap line that expresses lacZ in the GFs, we show that the neurons develop during the first 30 hr of metamorphosis. Within the next 15 hr, they begin to form electrical synapses, as indicated by the transfer of intracellularly injected Lucifer yellow. The GFs dye-couple to the TTM motoneuron between 30 and 45 hr of metamorphosis, to the peripherally synapsing interneuron that drives the DLM motoneurons at approximately 48 hr, and to giant commissural interneurons in the brain at approximately 55 hr. Immunocytochemistry with shaking-B peptide antisera demonstrates that the expression of shaking-B protein in the region of GFS synapses coincides temporally with the onset of synaptogenesis; expression persists thereafter. The mutation shak-B2, which eliminates protein expression, prevents the establishment of dye coupling shaking-B, therefore, is essential for the assembly and/or maintenance of functional gap junctions at electrical synapses in the GFS.
Phelan
P
P
Sussex Centre for Neuroscience, School of Biological Sciences, University of Sussex, Brighton, United Kingdom.
Nakagawa
M
M
Wilkin
M B
MB
Moffat
K G
KG
O'Kane
C J
CJ
Davies
J A
JA
Bacon
J P
JP
D000595:Amino Acid Sequence; D000818:Animals; D030801:Animals, Genetically Modified; D017630:Connexins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000235:genetics / Q000254:growth & development / Q000502:physiology* / Q000648:ultrastructure; D004742:Enhancer Elements, Genetic; D004924:Escape Reaction / Q000502:physiology*; D017629:Gap Junctions / Q000502:physiology; D007395:Interneurons / Q000502:physiology* / Q000648:ultrastructure; D007814:Larva; D008675:Metamorphosis, Biological; D008969:Molecular Sequence Data; D009024:Morphogenesis / Q000235:genetics; D009046:Motor Neurons / Q000502:physiology; D009412:Nerve Fibers / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D011679:Pupa; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013569:Synapses / Q000502:physiology*; D014795:Visual Pathways / Q000378:metabolism / Q000502:physiology* / Q000648:ultrastructure
D017630:Connexins; D029721:Drosophila Proteins; D009419:Nerve Tissue Proteins; D011993:Recombinant Fusion Proteins; C079324:shakB protein, Drosophila