Development and Degeneration of Retinal Ganglion Cell Axons in .

Neurons make long-distance connections via their axons, and the accuracy and stability of these connections are crucial for brain function. Research using various animal models showed that the molecular and cellular mechanisms underlying the assembly and maintenance of neuronal circuitry are highly conserved in vertebrates. Therefore, to gain a deeper understanding of brain development and maintenance, an efficient vertebrate model is required, where the axons of a defined neuronal cell type can be genetically manipulated and selectively visualized . Placental mammals pose an experimental challenge, as time-consuming breeding of genetically modified animals is required due to their development. , the most commonly used amphibian model, offers comparative advantages, since their embryos during which embryological manipulations can be performed. However, the tetraploidy of the genome makes them not ideal for genetic studies. Here, we use , a diploid amphibian species, to visualize axonal pathfinding and degeneration of a single central nervous system neuronal cell type, the retinal ganglion cell (RGC). First, we show that RGC axons follow the developmental trajectory previously described in with a slightly different timeline. Second, we demonstrate that co-electroporation of DNA and/or oligonucleotides enables the visualization of gene function-altered RGC axons in an intact brain. Finally, using this method, we show that the axon-autonomous, Sarm1-dependent axon destruction program operates in . Taken together, the present study demonstrates that the visual system of is a highly efficient model to identify new molecular mechanisms underlying axon guidance and survival.