Digital quantification of neurite outgrowth and retraction by phase-contrast microscopy: A tau perspective.

The proper organization and function of the mammalian nervous system relies on neuronal processes or "neurites," extended morphological projections that include axons and dendrites. Tau is a structural microtubule-associated protein that is widely expressed in the nervous system that mediates the establishment of cell polarity, neurite outgrowth, and axonal transport. A useful model for studying the establishment and maintenance of these neuronal structures are rat neuronal PC12 cells, which can be induced to express tau and project neurites by treating the cells with nerve growth factor. Here, we present a simple method for continuously measuring the rate of neurite outgrowth and retraction over time by neurite length and neurite area analyses. This method uses freely available ImageJ software and widely available phase-contrast imaging.