Endothelial defects unveil cardiovascular phenotype in iPSC-based disease modelling across three generations of a DiGeorge syndrome family.

DiGeorge syndrome (DGS) is caused by a microdeletion on chromosome 22, leading to variable disease phenotypes and severity and often involving congenital cardiovascular disease. In this work, we performed a detailed study of DGS patients with increasing severity within a family of three generations. Genetic analyses revealed no correlation between DGS severity and the size of the deletion or the number of overall genetic variants; however, we identified potentially high-impact variants, indicating a role for these genes in predisposition to the disease. For a phenotypic analysis, induced pluripotent stem cells (iPSCs) were generated and differentiated into functional cardiomyocytes and endothelial cells using blood cells from family members. In DGS patients, the iPSC-derived cardiomyocyte clusters during differentiation showed morphological differences in sarcomere arrangement along with lower cardiac connexin-43 expression. These findings indicate an impaired structural development due to an altered expression of gap junction proteins and cardiomyocyte-matrix connections as a basis of cardiovascular pathology. In endothelial cells differentiated from iPSCs of the DGS patients, we found an aberrant vascular phenotype. Vascular defects were observed in differentiation and migration, as well as in endothelial tubular morphology, accompanied by altered transcription patterns for angiogenesis and vascular integrity pathways. These results suggest that DGS-specific cell types differentiated from hiPSC show major alterations and may be used to uncover genotype-phenotype correlations with the potential to reveal the molecular basis of the clinical manifestations in DGS.