Herpes simplex virus-mediated expression of the axonal protein tau in human model neurons (NT2-N cells)

The establishment of axonal-somatodendritic polarity is an important event during neuronal development. The analysis of the underlying molecular event s requires experimental models that display characteristic steps in the dev elopment of polarity and that are accessible for experimental manipulations . Here we show that human model neurons (NT2-N cells) can be efficiently in fected with an amplicon-based herpes simplex virus (HSV) system that expres ses the axonal microtubule-associated protein tau. We demonstrate that the neurons express a high level of exogenous tau, which persists for several d ays, thus allowing us to analyze the morphological effects of the expressed protein. The intracellular interactions of tau and the effects on the micr otubule structure of infected neurons, which were processed for immunocytoc hemistry, were determined using laser scanning microscopy (LSM). Exogenous tau expression does not result in an increased axon growth of the neurons b ut promotes neuronal microtubule assembly as indicated by an increased amou nt of total microtubule polymer as well as a labile, detyrosinated microtub ule subpopulation. In contrast, tau expression does not induce a significan t microtubule stabilization as judged from the quantitation of acetylated m icrotubule staining 24 hours after infection. The data demonstrate that HSV -mediated expression of proteins in human model neurons provides a useful s ystem for analysis of the effect of neuronal proteins on the morphology and cytoskeletal organization of terminally differentiated polar neurons. In a ddition, it suggests a role for tau as a factor which locally promotes tubu lin polymerization while the dynamics of axonal microtubules are preserved. (C) 2000 Wiley-Liss, Inc.