Pseudoautosomal region 1 overdosage affects the global transcriptome in iPSCs from patients with Klinefelter syndrome and high-grade X chromosome aneuploidies

Klinefelter syndrome (KS) is the most prevalent aneuploidy in males and is characterized by one or more supernumerary X chromosomes. Here, using a paradigmatic cohort of KS-inducible pluripotent stem cells (iPSCs) carrying 49-XXXXY, 48-XXXY, and 47-XXY karyotypes, we identified genes within the pseudoautosomal region 1 (PAR1) region as the most susceptible to dosage-dependent transcriptional dysregulation and therefore potentially responsible for the progressively worsening phenotype in higher grade X aneuploidies. By contrast, biallelically expressed non-PAR escape genes displayed high interclonal and interpatient variability in iPSCs and differentiated derivatives, suggesting that these genes could be associated with variable KS traits. By interrogating KS-iPSCs at single-cell resolution, we showed that PAR1 and non-PAR escape genes were not only resilient to X-inactive specific transcript (XIST)-mediated inactivation but also that their transcriptional regulation was disjointed from the absolute XIST expression level. Finally, we explored the transcriptional effects of X chromosome overdosage on autosomes and identified the transcription factor nuclear respiratory factor 1 as the master regulator of zinc finger protein X-linked. Our findings provided the first evidence of an X-dosage-sensitive autosomal transcription factor regulating an X-linked gene in low- and high-grade X aneuploidies. Bulk transcriptomic profiles of iPSC derived from Klinefelter syndrome patients and controls. The cohort includes low and high grade KS clones. For each patient two or three independent clones have been generated and for each clone two or three independent RNA-Seq libraries have been processed