The function of wide-field amacrine cells in mammalian retina

University Of Texas Hlth Science Center, San Antonio TX

Investigators

Abstract

The trophoblast glycoprotein (TPBG, aka oncofaeto protein, 5T4) is restrictively expressed in adult retina in rod bipolar cell and the wide-field GABAergic ON/OFF amacrine cell, TH2-AC. Knocking out the Tpbg gene in mice does not alter scotopic or photopic ERG responses but photopic contrast sensitivity was enhanced, indicating that TPBG in TH2-AC participates in retinal information processing through unidentified mechanism. We have found that TH2-AC intrinsic excitability is enhanced in the absence of TPBG. We hypothesize that TPBG regulates TH2-AC excitability and that TH2-AC regulates retinal circuits responsible for contrast and/or motion encoding. Given that amacrine cell is the most diverse but lthe east understood retinal neuron thus far, studying TPBG in TH2-AC provides a rare opportunity to understand how wide-field amacrine cell works in the mammalian retina. We will use mouse genetics and electrophysiological approaches to 1) Use the DATIRESCre driver mouse line to manipulate TH2-AC to understand the molecular and cellular basis of the enhanced photopic contrast sensitivity phenotype of the Tpbg knockout animals (Aim-1) and 2) Genetically and/or virally ablate TH2-AC from retina to study how retinal contrast and motion encoding are affected at the behavioral level by OKR and at the cellular level in TH2-AC’s eight postsynaptic RGC partners (Aim-2). Completion of these independent aims will lead to a better understanding on how a wide-field amacrine cell works in a mammalian retina.