Levels of Tau in HEK 293 expressing Tau cell line. A) Immunofluorescence analysis of both HEK 293 and HEK 293 expressing Tau cell lines using antibodies against β-tubulin, tau protein (Tau-5) and phalloidin to identifiy actin polymers. The results obtained for untransfected (left) and tau-transfected (right) cells are shown. In the presence of Tau, tubulin bundles were observed (see arrows). Inset shows a microtubule bundle inside HEK 293 tau expressing cells. B) RNA was isolated from previously mentioned cell lines as described in Materials and methods and a quantitative RT/PCR analysis using actin RNA, as internal control, was done. The size of the amplified DNA was determined by gel electrophoresis; Tau DNA, lanes 2 and 4 and actin DNA (lanes 3 and 5) are shown. In lane 1, are Hind III fragments of φ29 DNA used as electrophoretic markers. The quantitation of the ratio Tau/actin in arbitrary units is shown. C) Total protein extract from HEK 293 and HEK 293 expressing tau was obtained and Western blot analysis using an antibody against β-actin and an antibody (ab 7.51) against Tau, was done.