Sarkosyl-insoluble, urea-soluble fractions were extracted from the frontal and the temporal regions of control, FTLD-U and ALS brains as previously described23 (link). The samples before (−) and after (+) the treatment with lambda protein phosphatase (λPPase) were loaded on 10% SDS-PAGE. Proteins in the gel were then electrotransferred onto a polyvinylidene difluoride membrane (Millipore Corp., Bedford, MA). After blocking with 3% gelatin in Tris-buffered saline (20 mM Tris-HCl, pH 7.5, 500 mM NaCl), membranes were incubated overnight with the primary antibodies. Following incubation with an appropriate biotinylated secondary antibody, labeling was detected as previously described13 (link), 23 (link).