Schematic illustration depicting the spatiotemporal pattern of axon degeneration after cut and crush injury of a wild-type and a WldS peripheral nerve. Each yellow line represents an individual YFP positive axon in wild-type (A, B) and WldS (C, D) peripheral nerves. Accounting for wild-type peripheral nerves, firstly, both after transection (A) and crush injury (B) axonal fragmentation progresses as a localised wave quickly within a matter of few hours over the individual axon. Thereby, the abrupt shift between preserved and fragmented axon distances along partially fragmented axons represents the wave front. The processes differ only in direction with an anterograde course after cut and a retrograde course after crush lesion. Secondly, axonal fragmentation in the YFP positive axon population is asynchronous with some intact and others entirely or partially fragmented in one nerve at one time point. Thirdly, axonal breaks are dispersed homogenously along totally fragmented fibres. In contrast, in WldS peripheral nerves, firstly, both after transection (C) and crush (D) injury axonal degeneration progresses in anterograde direction with a velocity similar to that of slow axonal transport. Secondly, the gradients of axon degeneration are uniform with gradual decrease of degenerative changes along the axon from proximal to distal. Thirdly, degeneration happens broadly synchronously among the population of WldS axons. Fourthly, formation of end bulbs with subsequent swellings at the proximal ends of WldS axons can be observed especially after crush lesion but also occasionally after transection lesion.
Beirowski et al. BMC Neuroscience 2005 6:6 doi:10.1186/1471-2202-6-6