Evolution of primate ganglion cells sensitive to short wavelengths (918.16)

Here, we propose an evolutionary scheme to account for the diversity of ganglion cells that respond to stimulation of short‐wavelength‐sensitive (S) cones in Old World anthropoids. The Therian common ancestor had monostratified S‐ON, S‐OFF and OFF brisk‐sustained ganglion cells. In the supra‐ordinal group Euarchontoglires, the monostratifed S‐ON ganglion cell was duplicated, giving rise to monostratified S‐ON and S‐OFF types, similar to those found in modern guinea pigs and rabbits. The monostratified S‐OFF ganglion cell became a bistratified S‐OFF cell like that observed in modern rabbits. If there is a homologous type in primates, it has not yet been described. In addition, the ancestral, monostratified S‐ON type became bistratified early in the primate lineage, and it later was duplicated to generate the large and small bistratified cells of modern primates. The ancestral OFF‐brisk sustained ganglion cell became smaller and, in Old World anthropoids, it receives excitatory input from S‐OFF midget bipolar cells. There have been many comparative studies of retinal neurons, but this is the first attempt to describe the evolution of cell types other than photoreceptors. There are two underlying processes: 1) duplication of a cell type followed by diversification and 2) transformation of a monostratified cell type into a bistratified type. These may also account for the diversity of cell types in primate brains.Grant Funding Source : NIH grant EY06472