Klinefelter syndrome derived hiPSCs show similar XCI behavior as female hPSCs

In this study, we reprogrammed fibroblasts from two azoospermic Klinefelter syndrome (KS) patients, and two healthy male and one healthy female donor with an efficient integration-free method using episomal plasmids and laminin-521 (LN521). Whole genome transcriptomics analysis showed differentially expressed genes between KS and healthy male donors with enrichment in gene ontology (GO) terms associated with fertility, cardiovascular development, ossification and brain development, for both KS hiPSCs and fibroblasts, correlating with the KS clinical phenotype. Thorough XCI analysis combining transcriptomics data, RNA FISH and H3K27me3 staining, revealed skewed XCI in one KS fibroblast line and variability in XCI state of KS hiPSCs similar to female hiPSCs, showing either XaXi or XaXe status. Furthermore, we found up-regulated X-linked genes involved in nervous system development, synaptic transmission as well as metabolic processes supporting the potential use of KS derived hiPSC as an in vitro model for KS.