Persistent epigenome anomalies in induced pluripotent stem cells from late-onset sporadic Alzheimer's disease cases [RNA-seq]
Reprogramming of adult somatic cells into induced pluripotent stem cells (iPSCs) resets the aging clock and is thought to erase other epigenomic marks. Here we show that iPSCs from late-onset sporadic Alzheimer's disease (AD) cases retain epigenomic anomalies that supersede developmental defects, genomic instability, and neurodegeneration. When compared to iPSCs from elderly controls, AD iPSCs display reduced BMI1 and KDM5A expression, a more relax heterochromatin, and an altered DNA methylome. AD neuroepithelial cells show lesser efficient neural induction and forebrain specification, together with perturbed WNT signaling. They also present a unique genomic instability phenotype characterized by replication stress and DNA damage at the nuclear envelope-associated heterochromatin. BMI1 knockdown in control neuroepithelial cells phenocopied the AD-related pathologies. Long-term AD neuronal cultures show a dedifferentiation and loss-of-cell identity phenotype resembling epigenome erosion. BMI1 overexpression in AD neurons mitigates amyloid accumulation, tau pathology, heterochromatin fragmentation and G4 DNA induction. These findings implicate persistent epigenomic anomalies or uncharacterized genetic alterations working in trans on the epigenome in AD iPSCs, which could have broader implications in our understanding of the disease origin and pathophysiological mechanisms. Overall design: CTL and AD samples were compared at multiple timepoint from iPSC to fully differentiated neurons