Neurons of the central nervous system have a limited ability to survive and regenerate following axonal injury. Interventions to protect remaining cells and induce axonal regeneration have produced promising, yet ultimately unsatisfying, results, falling far short of recovery. To improve upon these results, it is imperative to determine why some neurons respond better than others. Retinal ganglion cells (RGCs), whose axons pass through the optic nerve, offer a tractable system to study these processes. Previously, our lab found that the progression of RGC degeneration following axonal damage (optic nerve crush, ONC) is not stochastic but instead is cell-type dependent. Further, axon regeneration was also cell-type restricted following two different interventions targeting the mTor pathway. These findings demonstrate that cell-intrinsic characteristics can have a strong influence on neuron degeneration and regeneration. However, this study only examined a few of the >30 RGC subtypes, and as such it was not possible to determine the characteristics that separate susceptible and resilient subtypes. In this study, I will determine the full cohort of RGCs that survive and regenerate following ONC, with or without different interventions. I will also examine the transcriptional differences between subtypes, which could underlie their differential responses. Two main approaches will be used to address these questions. First, I will use combinatorial immunohistochemistry in whole mount retinas to quantitatively track RGC subpopulations using established molecular and genetic tools. Second, I will perform massively-parallel single-cell mRNA sequencing on thousands of RGCs using DropSeq to characterize gene expression of all RGC populations in an unbiased manner. Together, these results will provide a comprehensive look into why RGC subtypes respond differently to axonal injury. This has important implications for understanding the different ways degeneration progresses in neurons and how therapeutic strategies could be sculpted to meet the needs of different populations.
Neurons in the central nervous system have a limited capacity to survive and regenerate following axonal injury. To understand why some neurons perform better than others, I will investigate the subtype-specific nature of retinal ganglion cell degeneration and regeneration following optic nerve crush.
