Irreversible modifications of chromatin and the nuclear lamina: A review inside the nuclear origin of Alzheimer's disease

Dementia is a public health problem with an extraordinary increase in recent years. Alzheimer's disease (AD) is the most common cause of dementia. This disease has been considered a consequence of cytoplasmic and extracellular accumulations of Tau protein and amyloid, respectively. Nevertheless, a nuclear origin of AD has recently emerged. Both Tau protein and the nuclear lamin protect the nuclear and chromatin organization for proper gene expression throughout neuronal life. Accumulation of DNA damage, mainly as a result of aging, drives post-mitotic neurons to initiate DNA repair by entering the cell cycle. The complexity of the nucleus-cytoskeleton prevents neurons from dividing and condemns them to a state of hyperdiploidy ending in neuronal death, after transiently prolonging their life. In AD, hippocampal neurons survive their fatal fate by triggering an aberrant structural and functional transformation of the nucleus. Lamin A expression and Tau protein transfer to the cytoplasm results in loss of the protector role of nuclear Tau and the subsequent global chromatin disorganization. Therefore, the cytoplasmic Tau protein accumulations that characterize AD are consequence of the attempted neuronal repair. Alzheimer's neurons with unstructured nuclei and aberrant cytoskeletons manage to survive by sacrificing their plasticity, which inexorably leads to dementia.

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