Transcript TITLE or something

The Biochemistry of Visual Processing in the Retina:
Ribbon synapses at bipolar cell terminals
Kirigin Elstad
O’Day & Roberts labs
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Overview of the retina
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Ribbon Synapses: What do they do?
• Transmit sensory information
• Retina – photoreceptor and bipolar cell synaptic terminals.
• Cochlea – hair cells.
• Synaptic vesicles attach to the ribbon via short filaments.
• Ribbons maintain fast, prolonged neurotransmitter release.
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Ribbon Synapses: What are they made of?
• MANY different proteins, including:
– synapsin, cadherin, synaptotagmin, synaptobrevin,
synaptogyrin, syntaxin, clathrin, myo1c, and MORE!
– RIBEYE, Nok
•
How do these proteins control neurotransmitter release at
the synapse?
Can we understand ribbon synapses by
studying protein function?
• We need to measure some feature of the synapse
– typically done by making mutants and comparing mutants to
wildtype.
• Morphology, anatomy, microanatomy, biochemistry, physiology,
electrophysiology.
• The goal: find a way to make retinal slice recordings from
zebrafish axon terminals.
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Previous Research
www.sanger.ac.uk/
• Goldfish
• Giant danio
• Why zebrafish?
The Experiment
• Goal: design a way to make successful
electrophysiological recordings from zebrafish bipolar
synaptic terminals
The Setup
The zebrafish retina
Ganglion cell layer
Inner plexiform
layer
Inner nuclear layer
horizontal cells
bipolar cells
amacrine cells
Outer plexiform
layer
Outer nuclear layer
photoreceptors
Photoreceptors
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Future directions…
• Is there a phenotype for the absence of RIBEYE?
– Currently, Yvonne Bradford (Roberts lab) is working to create
morphlinos to block the synthesis of RIBEYE.
• What are morpholinos?
– A short sequence of fake nucleotides that can bind to mRNA or
pre-mRNA.
– Inject into zebrafish egg.
– Splice into mRNA  knocks out the protein due to steric
hindrance.
– Problem: It doesn’t replicate, so as the cell divides, you
continually cut the morpholino concentration.
– Advantage: You don’t have to mess with DNA/genetics.
Why RIBEYE?
• RIBEYE exists only at ribbon synapses.
• RIBEYE probably has catalytic activity that affects
vesicle formation.
• RIBEYE is composed of 2 domains:
• Unique A domain specific to ribbons.
• B domain identical with CtBP2, a lipid-chemistry
protein.
CtBP2
• CtBP2: catalytic activity converts
lysophosphatidic acid  phosphatidic acid.
• CtBP2 functionally converts big vesicles into smaller ones.
• Is RIBEYE involved in making vesicles whole again?
Nok
• Nok is a member of the membrane-associated guanylate
kinase (MAGUK) family.
•These proteins contain several protein-protein
interaction domains and work as scaffolding factors
that recruit signaling molecules to cell junctions and
synaptic terminals.
Acknowledgements…
• Peter O’Day
• Bill Roberts
• Mark Rutherford
• Rob Duncan
• Jerry Gleason
• SPUR Program
www.yamanashi-med.ac.jp/
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