Presented by Juan Mo

Study Questions

• Why zebrafish transgenetic lines are very important for studying photoreceptor degeneration?

• The synapses in inner plexiform layer and in outer plexiform layer?

• ON bipolar cell & OFF bipolar cell?• What are the larval and adult phenotypes of pde6cw59 and Xops:mCFPq13 lines?

• Light and dark preference test?• How does morpholino injection knock down gene

expression?

• Contains red, green, blue and UV cone cells• Contains rods

Zebrafish: outstanding model studying photoreceptor degenerations

Advantages:•Ex utero rapid development•Optical transparency•Permeability to drugs•Ease of making transgenetic animal•The acute visual abilities of larvae

adult larvae

pde6cw59 transgenic line cone degeneration death of rod (larvae) rod persistence (juvenile and adult) Xops:mCFPq13 transgenic line rod degeneration loss of cone (mammanlian) cone unaffected (zebrafish)

Hypothesis

• Rod photoreceptors protects from cone degeneration-induced retinal remodeling and restore visual responses in zebrafish

http://what-when-how.com/neuroscience/visual-system-sensory-system-part-2/

K+

metabotropic glutamate receptor

ionotropicglutamate receptor

Na+

http://what-when-how.com/neuroscience/visual-system-sensory-system-part-2/

ON ON

OFF OFF

http://webvision.med.utah.edu/book/part-ii-anatomy-and-physiology-of-the-retina/oute-plexiform/

ribbon

M

A B

Confocal Microscopy

Result 1: development of ON bipolar cell contacts with rod and cone photoreceptors

cones rods

ON bipolar cell

OPL

Cone pedicle Rod spherule

dendrites

ON bipolar cell

conesrods

nyx:mYFPq16

Result 2: cone degeneration in pde6cw59 mutant larvae leads to ON bipolar cell remodeling

rods

cones

ON bipolar cell

ON bipolar cell

ON bipolar cell

ON bipolar cell

pde6cw59 transgenic

cone degeneration

Xops:mCFPq13 transgenic

rod degeneration

D6

D8

Result 2: cone degeneration in pde6cw59 mutant larvae leads to ON bipolar cell remodeling

pde6cw59 transgenic

cone degeneration

Xops:mCFPq13 transgenic

rod degeneration8 DPF

ON bipolar axon terminals

6 DPF

Result 3: postsynaptic glutamate receptor expression is altered in pde6cw59 larvae

OFF bipolar cell

ON bipolar cell

ON bipolar cell

horizontal cell

D6

D8

pde6cw59 transgenic

cone degeneration

Xops:mCFPq13 transgenic

rod degeneration

8 DPF

6 DPF

Result 4: synaptic structure is maintained in Xops:mCFPq13 and pde6cw59 adults

cones

ON bipolar cell

ON bipolar cell ON bipolar cell ON bipolar cell

cones cones

ON bipolar cell ON bipolar cell

Result 4: synaptic structure is maintained in Xops:mCFPq13 and pde6cw59 adults

photoreceptor terminals

horizontal cell

rod spheruleCone pedicle

photoreceptor terminals photoreceptor terminals

horizontal cellhorizontal cell

Result 5: visual responses are preserved in pde6cw59 mutant adults

diffuse white light

• Optokinetic response (OKR):

http://www.youtube.com/watch?v=mfstlvsW1IY

• WT and pde6cw59 adults display a robust OKR.

Result 5: visual responses are preserved in pde6cw59 mutant adults

Result 6: increased rod number protects the larval retina from cone degeneration-induced remodeling

rod

ON bipolar cell

nuclear

Morpholino: knock down gene translation

Conclusion

• Cone degeneration leads to ON bipolar cell remodeling in larvae.• Although the neural connectivity remains intact, the loss of the majority

of the presynaptic input leads to significant remodeling observed in cone degeneration adult.

• Visual responses are preserved in cone degeneration adult.• Increased rod number protects the larval retina from cone

degeneration-induced remodeling.

?Rod photoreceptors protects from cone degeneration-induced retinal remodeling and restore visual responses in zebrafish

Review Questions

• Why zebrafish transgenetic lines are very important for studying photoreceptor degeneration?

• The synapses in inner plexiform layer and in outer plexiform layer?

• ON bipolar cell & OFF bipolar cell?• What are the larval and adult phenotypes of pde6cw59 and Xops:mCFPq13 lines?

• Light and dark preference test?• How does morpholino injection knock down gene

expression?