TTR and Alzheimer disease: Next, we found that AD model neurons derived from human induced pluripotent stem cells carrying a mutant PSEN1(P117L) gene, exhibited mitochondrial dysfunction, accumulation of 8-oxoguanine and single-strand breaks in mtDNA, and impaired neuritogenesis with a decreased expression of transthyretin, which is known to be downregulated by oxidative stress.