Development of DA and 5HT neurons involved in rewardassociated behavior in zebrafish

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Development of DA and 5HT neurons involved in
reward-associated behavior in zebrafish
Su Guo, Ph.D.
University of california, San Francisco
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3-day old zebrafish labeled with anti-TH and 5HT
antibodies
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Questions

• Do zebrafish have reward-associated behavior?
• Experience-dependent morphine preference
• Do the basal forebrain DA/5HT neurons play a role
  in this behavior?
• The too few mutant
• How is the development of basal forebrain DA/5HT
  neurons regulated?
• The foggy mutant

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Zebrafish a vertebrate genetic model organism
Small-size
High fecundity
Rapid development
In vivo tracing of biological processes
Easy to maintain In large numbers
Optically transparent
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What is reward-associated behavior?

• A prior exposure to a substance elicits a
  preference behavior for the substance
• Spend more time in the substance-paired side
  (CPP)
• Self-administer the substance

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Studying reward-associated behavior in larval
zebrafish

• Larval zebrafish are amenable to genetic analysis
  and the study of cellular mechanisms
• Larval zebrafish are free-living (food hunting,
  escaping)
• The nervous system of larval zebrafish is more
  plastic than adult zebrafish.

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Choice chamber
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Larval zebrafish show experience-dependent
preference for morphine
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Morphine preference is dependent on opioid
receptors
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The too few mutant
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The basal forebrain DA/5HT neurons are required
for morphine preference behavior
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Functional analogy of zf basal FB to mammalian MB
DA neurons
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How is the development of basal FB DA and 5HT
neurons regulated?

• Will the mechanisms be homologous to mammalian FB
  or MB neurons?
• What are the genes and pathways involved in the
  development of these neurons?

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Mutagenesis screen
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Mutations affecting the development of basal FB
DA/5HT neurons

• too few
• motionless
• twin-of-motionless
• foggy

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The foggy mutant
WT
foggy
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foggy encodes a regulator of transcription
elongation
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The importance of regulating transcription
elongation during development
promoter
Transcription initiation
Transcription elongation
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foggy expression
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The foggy mutation selectively disrupts its
repressor activity
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Question

• What genes are de-repressed that leads to
  defects in DA/5HT neuron development?
• Micro-array study
• How is foggys repressor activity regulated
  during development?
• Focus on the function of the C-terminal domain,
  where the foggy mutation resides.

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Summary

• Zebrafish is an attractive genetic model organism
  to study
• the development of specific neuronal types.
• The developmental alteration that leads to
  abnormal reward-associated behavior.

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Acknowledgements
Reward-associated behavior in larval zebrafish
Sandrine Bretaud
Brent Lockwood
Foggy downstream tergets
Keerthi Krishnan
Foggy regulation
Jae-yeon Jeong
Arnon Rosenthal (Rinat Neuroscience)
Mark Fishman (Novartis)
Wolfgang Driever (University of Freiburg)