Abstract
Purpose :
In the mouse retina there are 20+ different subtypes of retinal ganglion cells (RGCs) and these RGCs receive synaptic inputs from 40+ subtypes of amacrine cells (ACs) and 13 subtypes of bipolar cells (BCs). To identify the presynaptic cellular components of each subtype of RGCs, we use subtype specific transcellular tracers to label presynaptic ACs and BCs synapsed with three genetically identified subtypes of RGCs.
Methods :
Dual DNA recombinase transcellular labeling was used to label the presynaptic cells synapsed with BD, JamB and W3 RGCs. CreER-BD, CreER-JamB and Cre-W3 mice were crossed with RCE:FRT mice which harbor the R26R CAG-boosted EGFP (RCE) reporter allele with a FRT-flanked STOP cassette upstream of the enhanced green fluorescent protein (EGFP) gene. After an intravitreal injection of a Cre-dependent AAV2-EF1a-DIO mCherry-IRES-WGA-Flpo vector, transfected Cre-positive RGCs express a WGA (wheat germ agglutinin)-Flpo fusion protein. WGA-Flpo can be transported transcellularlly and cells containing WGA-Flpo are able to express EGFP. Therefore, RGC specific circuits in retina are illustrated based on EGFP expression.
Results :
(1) mCherry staining demonstrated that transfection of the viral vectors is Cre-positive RGC specific. (2) Most EGFP positive cells in retina contained WGA, indicating minimum non-specific EGFP expression, and WGA-Flpo fused protein transported into presynaptic neurons is functional to activate EGFP expression. (3) All major types of retinal neurons in INL and GCL, including RGCs, amacrine cells (ACs), bipolar cells (BCs), horizontal cells (HCs) are EGFP positive, indicating WGA-Flpo fused protein can be transported transcellularly into most presynaptic retinal neurons in the retina. (4) The three subtypes of RGCs seem to synapse with different populations of presynaptic ACs and BCs.
Conclusions :
We have developed a mouse model that allows us to label the retinal circuit based on a single subtype of RGCs. Using this model, we show that three subtypes of RGCs seem to synapse with different populations of presynaptic ACs and BCs.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.