The function of wide-field amacrine cells in mammalian retina

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.