Abstract
Presentation Description :
The mammalian retina relies on bipolar cells to transfer visual information from photoreceptors to output ganglion cells. Typically, photoreceptor input is received at the dendrites of bipolar cells through glutamatergic ribbon synapses in the outer retina and the axon terminals of bipolar cells form output connections with amacrine cell interneurons and ganglion cell processes in the inner retina. Bipolar cell axon terminals also utilize glutamatergic ribbon synapses to connect with postsynaptic partners at specialized dyads. Ribbon output sites at bipolar cell terminals are flanked by inhibitory synapses that regulate information flow. The mechanisms that regulate the ultrastructural connectivity at bipolar cell dendrites and axon terminals remains underappreciated. Using serial electron microscopy and murine mutants deficient in inhibitory synaptic transmission, I will present our observations that reveal how inhibition across the axon terminals of bipolar cells can regulate the assembly of ribbon output sites and dyadic connections. I will also present our findings from primate retina serial electron microscopy across eccentricities, which demonstrates how the organization of photoreceptor->bipolar cell input connectivity in the outer retina is regulated in a region-specific manner. Taken together, our findings reveal new insights into the ultrastructural arrangement of bipolar cell connectivity in the inner and outer mammalian retina and unveil factors that regulate this organization.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.