PSEN1 and Alzheimer disease: Taking into account that Presenilin is one of the causative genes for familial AD, showing altered Aβ processing and impaired synaptic function, which are characteristics of AD, and considering potential postmortem effects on tissue sphingolipid levels, a similar measurement was conducted on cell lysates from the following three groups (each comprising n = 8): iPS cells derived from AD patients (AD), iPS cells with inserted mutations in Presenilin 1 (PS), and control neurons.