The sex of the samples was assessed using three metrics: (1) the heterozygosity rate of chromosome X genotype calls outside the pseudoautosomal regions. For this, we discarded variants with MAF < 5%. In male samples, a high heterozygosity rate can indicate sample contamination, sex mismatch, or chromosomal abnormalities like Klinefelter’s syndrome. (2) The read counts of OCRs adjacent to FIRRE and XIST, which are only, or predominantly, accessible in females51. (3) Read counts in OCRs on chromosome Y outside the pseudoautosomal region.
