Assessment of XCI skewing and demonstration of XCI escape region based on single-cell RNA sequencing: comparison between female Grave's disease and control

The reactivation and loss of mosaicism hypothesis due to X chromosome inactivation (XCI) skewing and escape could influence gender differences in autoimmune diseases. XCI selectively inactivates one of the two X chromosomes in females.

These results could aid in understanding the immunogenetics of gender differences in various autoimmune disease pathophysiologies.

To estimate XCI skewing and the occurrence of XCI escape, we conducted a normal female (NF) without a history of autoimmune thyroid disease (AITD) and a patient with Grave's disease (GD) based on a thyroid diagnosis. After single-cell RNA sequencing, heterozygous variants were converted and transformed. XCI skewing was calculated using the formula and the skewing degree was defined. NF/GD genes were compared using correction methods. Positions are heterozygous within a single cell as indicated by a unique barcode.

XCI skewing showed 45.8%/48.9% relatively random, 29.4%/27.0% skewing, 24.6%/23.7% severe skewing, and 0.2%/0.4% extreme severe skewing. 24.8%/24.1% in NF/GD exhibited severe skewing or higher. A total of 13 genes were significantly associated with XCI skewing ratios in NF/GD cells. In total, 371/250 nucleotide positions with only one barcode (representing a unique cell) were identified for XCI escape. A total of 143/52 nucleotide positions spanned 20/6 genes, and 12/1 genes were identified as XCI escapes. Conclusions: These results could aid in understanding the immunogenetics of gender differences in various autoimmune disease pathophysiologies.