Hyperphosphorylation and cleavage at D421 enhance tau secretion.

It is well established that tau pathology propagates in a predictable manner in Alzheimer's disease (AD). Moreover, tau accumulates in the cerebrospinal fluid (CSF) of AD's patients. The mechanisms underlying the propagation of tau pathology and its accumulation in the CSF remain to be elucidated.

The formation of tau pathological phospho-epitopes in the axon is prevented by the dephosphorylation of selective sites in primary hippocampal neurons over-expressing human tau.

In tauopathies including Alzheimer's disease, the axonal microtubule-associated protein tau becomes hyperphosphorylated at pathological epitopes and accumulates in the somato-dendritic compartment. However, it remains unclear whether tau becomes phosphorylated at these epitopes in the somato-dendritic compartment and/or in the axon. In primary hippocampal neurons where human tau was over-expressed both in the somato-dendritic compartment and the axon, the pathological epitopes recognized by the antibodies AT8 (S199/S202/T205), AT100 (T212/S214/T217), and AT180 (T231/S235) were found in the somato-dendritic compartment but not in the axon where tau was either not phosphorylated (T205 and T217) or not simultaneously phosphorylated (T231 and S235) at sites included in the above epitopes.

Application of Rho antagonist to neuronal cell bodies promotes neurite growth in compartmented cultures and regeneration of retinal ganglion cell axons in the optic nerve of adult rats.

Inactivation of Rho promotes neurite growth on inhibitory substrates and axon regeneration in vivo. Here, we compared axon growth when neuronal cell bodies or injured axons were treated with a cell-permeable Rho antagonist (C3-07) in vitro and in vivo. In neurons plated in compartmented cultures, application of C3-07 to either cell bodies or distal axons promoted axonal growth on myelin-associated glycoprotein substrates.

Vaccination stimulates retinal ganglion cell regeneration in the adult optic nerve.

We examined whether vaccination of adult rats with spinal cord homogenate (SCH) can promote regeneration of retinal ganglion cells (RGCs) after microcrush lesion of the optic nerve. Injured animals vaccinated with SCH showed axon growth into the optic nerve and such regeneration was not observed in animals vaccinated with liver homogenate (LH). Regeneration was not a consequence of neuroprotection since our vaccine did not protect RGCs from axotomy-induced cell death.