A dynamicin vitromodel of Down Syndrome neurogenesis with Trisomy 21 gene dosage correction

ABSTRACT/SUMMARY Excess gene dosage from human chromosome 21 (chr21) causes Down syndrome (DS), spanning developmental as well as acute phenotypes in terminal cell types. Which phenotypes remain amenable to intervention after development is unknown. To address this question in a model of DS neurogenesis, we generated trisomy 21 (T21) human induced pluripotent stem cells (hiPSCs) alongside otherwise isogenic euploid controls from mosaic DS fibroblasts, and integrated an inducible XIST transgene on one chr21 copy. Monoallelic chr21 silencing by XIST was near-complete and irreversible in hiPSCs. Differential expression reveals T21 neural lineages and T21 hiPSCs suppress similar translation and mitochondrial pathways, and activate cellular stress responses. When XIST is induced before the neural progenitor stage, T21 dosage correction mitigates a pronounced skew towards astrogenesis in differentiation. Because our transgene remained inducible in post-mitotic T21 neurons and astrocytes, we demonstrate XIST efficiently represses genes even after terminal differentiation, which will empower exploration of cell type-specific T21 phenotypes that remain responsive to chr21 dosage.