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

Show all Figures

Expression

Gene	Fish	Conditions	Stage	Anatomy	Assay	Figure
synj1	WT	standard conditions	Day 5	brain	ISH	Fig. 1
synj1	WT	standard conditions	Day 5	hair cell	ISH	Fig. 1
synj1	WT	standard conditions	Day 5	inner ear	ISH	Fig. 1
synj1	WT	standard conditions	Day 4 to Day 5	neuromast hair cell	RTPCR	Fig. 1
synj1	WT	standard conditions	Day 5	retina	ISH	Fig. 1

1 - 5 of 5

Show

Phenotype

Fish	Conditions	Stage	Phenotype	Figure
cacna1da^{tc323d/tc323d}	standard conditions	Protruding-mouth to Days 21-29	neuromast hair cell plasma membrane shape, normal	Fig. 3
cacna1da^{tc323d/tc323d}; synj1^{tQ296X/tQ296X}	standard conditions	Protruding-mouth to Days 21-29	neuromast hair cell plasma membrane shape, normal	Fig. 3
synj1^{tQ296X/tQ296X}	standard conditions	Protruding-mouth to Days 21-29	neuromast hair cell plasma membrane protruding, abnormal	Fig. 3
synj1^{tQ296X/tQ296X}	standard conditions	Protruding-mouth to Days 21-29	neuromast hair cell synaptic vesicle amount, abnormal	Fig. 5
synj1^{tQ296X/tQ296X}	standard conditions	Day 5	chemical synaptic transmission disrupted, abnormal	Fig. 7
synj1^{tQ296X/tQ296X}	standard conditions	Day 5	chemical synaptic transmission disrupted, abnormal	Fig. 6
synj1^{tQ296X/tQ296X}	standard conditions	Day 5	vestibular reflex disrupted, abnormal	Fig. 1
synj1^{tQ296X/tQ296X}	standard conditions	Day 5	vestibular reflex disrupted, abnormal	Fig. 2
synj1^{tQ296X/tQ296X} + MO1-cdh23	standard conditions	Protruding-mouth to Days 21-29	neuromast hair cell plasma membrane protruding, abnormal	Fig. 3
synj1^{tQ296X/tQ296X}; s356tTg	standard conditions	Protruding-mouth to Days 21-29	neuromast hair cell plasma membrane protruding, abnormal	Fig. 3

1 - 10 of 10

Show

Mutations / Transgenics

Allele	Construct	Type	Affected Genomic Region
nl1Tg	TgBAC(neurod1:EGFP)	Transgenic Insertion
s356tTg	Tg(pou4f3:GAP-GFP)	Transgenic Insertion
tc323d		Point Mutation	cacna1da
tc1882ta		Point Mutation	synj1
tQ296X		Point Mutation	synj1
tW943X		Point Mutation	synj1

1 - 6 of 6

Show

Human Disease / Model

Sequence Targeting Reagents

Target	Reagent	Reagent Type
cdh23	MO1-cdh23	MRPHLNO

Fish

Fish
cacna1da^{tc323d/tc323d}
cacna1da^{tc323d/tc323d}; synj1^{tQ296X/tQ296X}
nl1Tg
s356tTg
synj1^{tc1882ta/tc1882ta}
synj1^{tQ296X/tQ296X}
synj1^{tQ296X/tQ296X} + MO1-cdh23
synj1^{tQ296X/tQ296X}; s356tTg
synj1^{tW943X/tW943X}
WT

1 - 10 of 10

Show

Antibodies

Name	Type	Antigen Genes	Isotypes	Host Organism
Ab1-ctbp2l	polyclonal	ctbp2l		Rabbit
Ab1-slc17a8	polyclonal	slc17a8		Rabbit

Orthology

Engineered Foreign Genes

Marker	Marker Type	Name
EGFP	EFG	EGFP
GFP	EFG	GFP

Mapping

Trapani et al., 2009 ZDB-PUB-090511-26 PMID:19424431

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

Trapani et al., 2009

ZDB-PUB-090511-26
PMID:19424431