Presenilin mutations and their impact on neuronal differentiation in Alzheimer's disease.

The presenilin genes (PSEN1 and PSEN2) are mainly responsible for causing early-onset familial Alzheimer's disease, harboring ~300 causative mutations, and representing ~90% of all mutations associated with a very aggressive disease form. Presenilin 1 is the catalytic core of the γ-secretase complex that conducts the intramembranous proteolytic excision of multiple transmembrane proteins like the amyloid precursor protein, Notch-1, N- and E-cadherin, LRP, Syndecan, Delta, Jagged, CD44, ErbB4, and Nectin1a. Presenilin 1 plays an essential role in neural progenitor maintenance, neurogenesis, neurite outgrowth, synaptic function, neuronal function, myelination, and plasticity. Therefore, an imbalance caused by mutations in presenilin 1/γ-secretase might cause aberrant signaling, synaptic dysfunction, memory impairment, and increased Aβ42/Aβ40 ratio, contributing to neurodegeneration during the initial stages of Alzheimer's disease pathogenesis. This review focuses on the neuronal differentiation dysregulation mediated by PSEN1 mutations in Alzheimer's disease. Furthermore, we emphasize the importance of Alzheimer's disease-induced pluripotent stem cells models in analyzing PSEN1 mutations implication over the early stages of the Alzheimer's disease pathogenesis throughout neuronal differentiation impairment.