Central nervous system regeneration.

Neurons of the mammalian central nervous system fail to regenerate. Substantial progress has been made toward identifying the cellular and molecular mechanisms that underlie regenerative failure and how altering those pathways can promote cell survival and/or axon regeneration. Here, we summarize those findings while comparing the regenerative process in the central versus the peripheral nervous system. We also highlight studies that advance our understanding of the mechanisms underlying neural degeneration in response to injury, as many of these mechanisms represent primary targets for restoring functional neural circuits.