Abstract. Neural aging as a progressive loss of function involves central and peripheral postmitotic neurons and neural stem cells (NSCs). It promotes neurodegeneration, impairs neurogenesis, and can be considered a cause of cognitive impairment and sensory and motor deficits in the elderly. Age-related morphological atrophic changes and cellular alterations are addressed by neural aging mechanisms. Neurogenesis declines during aging through several mechanisms such as an increase in quiescence state, changes in lineage fate, telomerase dysfunction, the failure of the DNA repair system, increased apoptosis, and the impairment of self-renewal. The selfrenewal transcriptional factor Sox2 has been correlated with retrotransposon L1 and certain cellcycle-and epigenetic-related factors, which are sometimes considered age-related factors in NSC aging. As neurogenesis decreases, non-mitotic neurons undergo neurodegeneration by oxidative stress, sirtuin, insulin signaling and mTOR alteration, mitochondrial dysfunction, and protein misfolding and aggregation. As neurodegeneration and impaired neurogenesis promote the nervous system aging process, the identification of neuronal anti-aging is required to raise life expectancy. The role of melatonin in increasing neurogenesis and protecting against neurodegeneration has been investigated. Here, we review nervous system aging that is correlated with mechanisms of neurodegeneration and the impairment of neurogenesis and evaluate the effects of melatonin on these processes.

Sox2 is a component of the core transcriptional regulatory network which maintains the totipotency of the cells during embryonic preimplantation period, the pluripotency of embryonic stem cells, and the multipotency of neural stem cells. This maintenance is controlled by internal loops between Sox2 and other transcription factors of the core such as Oct4, Nanog, Dax1, and Klf4, downstream proteins of extracellular ligands, epigenetic modifiers, and miRNAs. As Sox2 plays an important role in the balance between stem cells maintenance and commitment to differentiated lineages throughout the lifetime, it is supposed that Sox2 could regulate stem cells aging processes. In this review, we provide an update concerning the involvement of Sox2 in neurogenesis during normal aging and discuss its possible role in Alzheimer's disease.

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