Connecting the retina to the brain

Abstract

The visual system is beautifully crafted to transmit information of the external world to visual processing and cognitivecenters in the brain. For visual information to be relayed to the brain, a series of axon pathfinding events must take place toensure that the axons of retinal ganglion cells, the only neuronal cell type in the retina that sends axons out of the retina, findtheir way out of the eye to connect with targets in the brain. In the past few decades, the power of molecular and genetictools, including the generation of genetically manipulated mouse lines, have multiplied our knowledge about the molecularmechanisms involved in the sculpting of the visual system. Here, we review major advances in our understanding of themechanisms controlling the differentiation of RGCs, guidance of their axons from the retina to the primary visual centers,and the refinement processes essential for the establishment of topographic maps and eye-specific axon segregation. Humandisorders, such as albinism and achiasmia, that impair RGC axon growth and guidance and, thus, the establishment of a fullyfunctioning visual system will also be discussed.