PUBLICATION

Synaptojanin1 is required for temporal fidelity of synaptic transmission in hair cells

Authors
Trapani, J.G., Obholzer, N., Mo, W., Brockerhoff, S.E., and Nicolson, T.
ID
ZDB-PUB-090511-26
Date
2009
Source
PLoS Genetics   5(5): e1000480 (Journal)
Registered Authors
Brockerhoff, Susan, Mo, Weike, Nicolson, Teresa, Obholzer, Nikolaus, Trapani, Josef
Keywords
Larvae, Vesicles, Action potentials, Synapses, Zebrafish, Cell membranes, Coated vesicles, Inner ear
MeSH Terms
  • Hair Cells, Vestibular/pathology
  • Hair Cells, Vestibular/physiology*
  • Evoked Potentials
  • Zebrafish/genetics
  • Zebrafish/growth & development
  • Zebrafish/physiology
  • Mutation
  • Phenotype
  • Physical Stimulation
  • Phosphoric Monoester Hydrolases/genetics*
  • Phosphoric Monoester Hydrolases/physiology*
  • Hair Cells, Auditory/pathology
  • Hair Cells, Auditory/physiology*
  • Zebrafish Proteins/genetics*
  • Zebrafish Proteins/physiology*
  • Animals
  • Calcium Channels, L-Type/genetics
  • Calcium Channels, L-Type/metabolism
  • Synaptic Transmission/genetics*
  • Synaptic Transmission/physiology*
  • Synaptic Vesicles/pathology
  • Synaptic Vesicles/physiology
  • Microscopy, Electron, Transmission
  • Alternative Splicing
(all 24)
PubMed
19424431 Full text @ PLoS Genet.
Abstract
To faithfully encode mechanosensory information, auditory/vestibular hair cells utilize graded synaptic vesicle (SV) release at specialized ribbon synapses. The molecular basis of SV release and consequent recycling of membrane in hair cells has not been fully explored. Here, we report that comet, a gene identified in an ENU mutagenesis screen for zebrafish larvae with vestibular defects, encodes the lipid phosphatase Synaptojanin 1 (Synj1). Examination of mutant synj1 hair cells revealed basal blebbing near ribbons that was dependent on Cav1.3 calcium channel activity but not mechanotransduction. Synaptojanin has been previously implicated in SV recycling; therefore, we tested synaptic transmission at hair-cell synapses. Recordings of post-synaptic activity in synj1 mutants showed relatively normal spike rates when hair cells were mechanically stimulated for a short period of time at 20 Hz. In contrast, a sharp decline in the rate of firing occurred during prolonged stimulation at 20 Hz or stimulation at a higher frequency of 60 Hz. The decline in spike rate suggested that fewer vesicles were available for release. Consistent with this result, we observed that stimulated mutant hair cells had decreased numbers of tethered and reserve-pool vesicles in comparison to wild-type hair cells. Furthermore, stimulation at 60 Hz impaired phase locking of the postsynaptic activity to the mechanical stimulus. Following prolonged stimulation at 60 Hz, we also found that mutant synj1 hair cells displayed a striking delay in the recovery of spontaneous activity. Collectively, the data suggest that Synj1 is critical for retrieval of membrane in order to maintain the quantity, timing of fusion, and spontaneous release properties of SVs at hair-cell ribbon synapses.
Genes / Markers
Figures
Figure Gallery (8 images)
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Expression
Phenotype
Mutations / Transgenics
Allele Construct Type Affected Genomic Region
nl1TgTransgenic Insertion
    s356tTgTransgenic Insertion
      tc323d
        Point Mutation
        tc1882ta
          Point Mutation
          tQ296X
            Point Mutation
            tW943X
              Point Mutation
              1 - 6 of 6
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              Human Disease / Model
              No data available
              Sequence Targeting Reagents
              Target Reagent Reagent Type
              cdh23MO1-cdh23MRPHLNO
              1 - 1 of 1
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              Fish
              Antibodies
              Name Type Antigen Genes Isotypes Host Organism
              Ab1-ctbp2lpolyclonalRabbit
              Ab1-slc17a8polyclonalRabbit
              1 - 2 of 2
              Show
              Orthology
              No data available
              Engineered Foreign Genes
              Marker Marker Type Name
              EGFPEFGEGFP
              GFPEFGGFP
              1 - 2 of 2
              Show
              Mapping
              No data available