Lab Leader HUN-REN Research Centre for Natural Sciences Budapest, Hungary
Abstract: DiGeorge syndrome (DGS) is a microdeletion syndrome defined by the deletion of multiple genes, with a highly variable phenotype that does not correlate with deletion size. We hypothesized that various symptoms across organ systems could manifest as in vitro phenotypes. Our specific aims were: 1) to generate human induced pluripotent stem cells (hiPSCs) from blood cells of DGS patients, and 2) to assess whether differences in the in vitro phenotypic profiles of diseased and control hiPSCs and differentiated cell types reflect patient alterations. We studied a family with DGS, where disease severity increased across generations, providing a unique opportunity to explore phenotypic variability. The grandfather (with facial dimorphism) and mother (with vascular ring and hypocalcemia) exhibited milder symptoms, while the progeny presented severe symptoms, including tetralogy of Fallot, pulmonary atresia, and atrial septal defect, despite an identical deletion in all cases. We successfully reprogrammed peripheral blood cells from all family members: DGS patients and healthy controls (grandmother, father). hiPSC clones were characterized for pluripotency, spontaneous differentiation capacity, and genetic background. We investigated cardiovascular aspects of DGS using this hiPSC-based model. Functionally active cardiomyocytes (CMs) were generated from all cell lines, showing no differences in cardiomyocyte marker expression. However, morphological differences in hiPSC-CM clusters were noted in the mother and child compared to controls and the grandfather. Notably, Connexin43 (GJA1) expression was significantly lower in the child's CMs, suggesting that gap junction protein expression may contribute to cardiovascular symptoms. To model vascular symptoms, endothelial cells (ECs) were differentiated from iPSCs. The ECs from symptomatic patients (mother and child) exhibited significant morphological differences from other family members. Bulk RNA sequencing confirmed these cellular differences and revealed affected pathways; therefore, our results can help to explain the development of cardiovascular disorders and symptom exacerbation in DGS.
Funding Source: Hungarian Higher Education Institutional Excellence Programme and NKFIH Fund (RRF-2.3.1-21-2022-00003, TKP2021-EGA-23 and K128444), Intramural Research Program of the NIH, NIDCR, USA, NIH ZIA DE000748, and ZIC DC000086.
