Rod bipolar cells (RBCs) are the first interneurons in the primary rod visual pathway. RBCs transmit light-driven signals from rods in the outer retina and contribute to retinal output through downstream amacrine cells (ACs) in the inner retina. This thesis presents my work identifying and characterizing trophoblast glycoprotein (TPBG), a leucine-rich repeat transmembrane protein recently identified in RBCs. Similar leucine-rich repeat proteins in RBCs are essential for synaptic targeting, correct localization of signal transduction proteins, and regulating the RBC light response across different light intensities