Expression Of Amyloidogenic Transthyretin Drives Hepatic Proteostasis Remodeling In An Induced Pluripotent Stem Cell Model Of Systemic Amyloid Disease

The systemic amyloidoses are diverse disorders in which misfolded proteins are secreted by effector organs and deposited as proteotoxic aggregates at downstream tissues. Although well-described clinically, the contribution of synthesizing organs to amyloid disease pathogenesis is unknown. Here, we utilize hereditary transthyretin amyloidosis (ATTR amyloidosis) induced pluripotent stem cells (iPSCs) to define the contribution of HLCs to the proteotoxicity of secreted TTR. To this end, we generated isogenic, patient-specific iPSCs expressing either amyloidogenic or wild-type TTR. We subsequently differentiated these lines into HLCs and performed single cell RNA sequencing (scRNAseq) via the Fluidigm C1 platform in an effort to identify a destabilized TTR-derived disease signature. Upon doing so, we identified a number of hepatic proteostasis factors (e.g. the unfolded protein response, UPR, as well as known and novel chaperone genes) whose expression correlates with the production destabilized TTR production. Single cell transcriptomic profiling of day 16 ATTR amyloidosis patient-specific iPSC-derived HLCs compared to syngeneic, isogenic control HLCs. Generation of isogenic "corrected" line was achieved via insertion of TTR-WT cDNA cassette at ATG-site of endogenous, mutant TTR allele via TALEN-mediated gene editing.