Chromosome silencing in vitro reveals trisomy 21 causes cell-autonomous deficits in angiogenesis and early dysregulation in Notch signaling

Despite the prevalence and clinical importance of Down syndrome, little is known as to the specific cell pathologies that underlie this multi-system disorder. To understand which cell types and pathways are more directly impacted by trisomy 21, we used an inducible-XIST system to silence the extra chromosome 21 in a panel of patient-derived iPSCs. Transcriptomic analysis showed significant dysregulation of potentially impacting programming of multiple cell-types as well as Notch. Analysis revealed prominent dysregulation in two major cell type processes: neurogenesis and angiogenesis. Angiogenesis is important for many systems impacted in Down syndrome but has been understudied. An in vitro assay for microvasculature formation used in a tightly controlled system reveals a novel cellular pathology that showed impairment in angiogenic response during tube formation. Results demonstrate that this is a cell-autonomous effect of trisomy 21 and transcriptomic analysis of differentiated endothelial cells shows deficits in known angiogenesis regulators. This study reveals a major unknown cell pathology caused by trisomy 21 and highlights the importance of endothelial cell function for Down syndrome pathologies, with wide reaching implications for development and disease progression. Overall design: Four trasgenic clones with an inducible XIST transgene, isogenic trisomic and disomic control cell lines (no XIST transgene) were grown with or without doxycycline (500 ng/ml). RNA was extracted and sequenced.