Tau and Neuron Aging Jesus Avila 1, 2 ;Elena Gomez de Barreda 1, 2 ;Noemi Pallas-Bazarra 1, 2 ;Felix Hernandez 1, 2 ; 1 Centro de Biología Molecular Severo Ochoa, CSIC-UAM, 28049 Madrid, Spain. ; 2 Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain. ; Figure 1. Scheme of tau molecule. Upper part is showing the longest central nervous system human tau isoform. In gray, the presence of two exons 2 and 3 is indicated and, in black, that of the four similar, but not identical R1 to R4 tubulin binding regions. Lower part shows tau molecule divided in four parts. A Indicates the most variable parte of the molecule, when tau molecules from different organism are compared. B Shows a proline rich region that could be highly modified by phosphorylation. C Indicates the tubulin binding region. D Shows the C-terminal region that could be also modified by phosphorylation, at several residues. Inset shows the shortest and longest human tau isoforms. The first is mainly present in fetal F brain whereas the second is present in adult A brain. null,null,4(1),23-28. Doi:null