Transgenic mouse retina engineered to express Enhanced Green Fluorescent Protein (EGFP)
On bipolar cells express mGluR6
ON bipolar cells detect glutamate released from photoreceptors with a metabotropic receptor called mGluR6. This receptor activates the G-protein Go1, which somehow closes unidentified cation channels. The main research goal of Dr. Vardi's lab is to identify the players in the mGluR6 cascade. This includes the effector for Go, the cation channel, and modulators of the cascade.

The picture to the right shows the retina of a transgenic mouse that was engineered to express Enhanced Green Fluorescent Protein (EGFP, green) under the control of a promotor for mGluR6. The section is immunostained for vesicular choline acetyl transferase (VAChT, purple) to show the OFF (top) and ON (bottom) sublaminas in the inner plexiform layer. EGFP is present only in cells that arborize in the ON sublamina, confirming their identity as ON bipolar cells.



The distribution of the Cl- transporters NKCC and KCC2 across the retinal layers

Chloride co-transporters contribute greatly to maintain chloride gradients in neurons
One class of chloride co-transporters (Na-K-Cl) normally accumulates chloride and is driven by the Na+ gradient, and another class (K-Cl) extrudes chloride and is driven by the K+ gradient. Chloride concentration is extremely important because it determines the equilibrium potential for chloride, and this in turn determines whether GABA, the main inhibitory transmitter in the brain, hyperpolarizes and thus inhibits or depolarizes and thus excites.

In the picture above, the left and middle panels show distributions across retinal layers of fluorescent antibodies against the two transporters. Right panel shows a control experiment where the KCC2 antibody was blocked by a peptide with sequence homology to KCC2.

For more information on projects related to "Chemical architecture in retinal circuits" consult Dr. Vardi's home page.