Quantitative analysis of the effect of phosphorylated tau on cellular microfilament networks

The purpose of this study is to analyze the effect of site-specific tau phosphorylation on cellular microfilaments networks. We examined cell images to study tau's interaction with microfilaments in both wild type full-length (2N4R) tau and pathological human tau (PH-tau) when expressed in Chinese hamster ovarian fibroblasts (CHO). A custom ImageJ plugin was developed to provide quantitative analysis of the immunofluorescently labeled polymerized actin in cells expressing either of the above mentioned tau vectors. Using histograms of the pixel intensities of images, with userdefined thresholds, the code calculates the integrated densities and creates an output image to visualize the considered areas (those outside the thresholds are displayed as well). The data demonstrated the presence of an inverse correlation between the level of PH-tau expressed and the amount of total actin polymerization. Additionally, actin polymerization was not only interrupted by the presence of PH-tau but also punctate staining was also detected (as opposed to the normal fibril structure). These observations were not detected in cells expressing wild type tau. The visualization helped reveal some image acquisition anomalies such as varying levels of fluorescent staining as well as standardized image collection. The results should aid in a further understanding the mechanism of cellular degeneration induced by the hyperphosphorylation of MAP tau. Keywords: Microfilaments, Medical