Caspase‐generated neoepitopes as markers of axonal degeneration in neural development and injury

Abstract

Neuronal death, axonal degeneration, and synapse loss are hallmarks of central nervous system development and injury. Commonly employed markers of apoptosis are TUNEL and immunohistochemistry for activated caspases, but these often fail to report axonal degeneration associated with somatic apoptosis. Axonal degeneration is classically detected by silver degeneration stains, but these have limitations (non‐selectivity, minimal reproducibility and incompatibility with co‐labeling). We demonstrate that antibodies to caspase‐cleaved protein substrates beta‐actin (cleaved by caspase 3 at D244) and alpha‐tubulin (cleaved by caspase 6 at D438) enable superior visualization of neurite degeneration. These antibodies label apoptotic cell bodies and neurites during embryonic and postnatal developmental pruning. In addition, they reveal injured neurons and neurites after induction of apoptosis in a mouse model of fetal alcohol syndrome and in sympathetic neuron cultures induced to undergo apoptosis after nerve growth factor withdrawal. Finally, the markers may have clinical utility, as they highlight degenerating neurites in neonatal hypoxic/ischemic injury and in adult patients with multiple sclerosis. Ongoing work aims to identify novel compartment‐specific neoepitopes that will allow monitoring of somatodendritic, axonal, and synaptic remodeling and degeneration. Supported by NS075869.