Tau and beyond for Alzheimer's disease.

One year ago on 22 September 2012, the Alzheimer’s disease (AD) field lost a pioneer—Inge Grundke-Iqbal—who passed away following a stroke. Together with her husband Khalid Iqbal, Inge discovered in the mid-1980s that the paired helical filaments of neurofibrillary tangles are made up of abnormally hyperphosphorylated tau. This seminal discovery opened a new major avenue for investigating neurodegeneration in AD and other tauopathies and attracted many neuroscientists to search for diagnostic tools and disease-modifying therapies for AD and related tauopathies based on tau pathology. The guest editors were introduced to the AD field by Inge and Khalid two decades ago. We were so privileged to be trained and inspired by them during our early careers. While we are still saddened by the loss of Inge, we feel that one of the best ways to remember her is to continue her research legacy by editing this special issue of the Journal of Alzheimer’s Disease. The contributors of this special issue are either Inge’s former collaborators/colleagues or trainees who are active investigators in the field of tau-associated neurodegeneration. After more than twenty years from the discovery of abnormally hyperphosphorylated tau as the major component of paired helical filaments, we know now that tau is crucial to neurodegeneration in AD. A lot more still needs to be done before we fully understand