A landscape of X-inactivation during human T cell development

Area of Science:

• Immunology
• Genetics
• Developmental Biology

Background:

• Females mount stronger immune responses than males, linked to X-linked immune gene expression.
• This contributes to higher autoimmune disease prevalence but better infection defense in females.

Purpose of the Study:

• To investigate the role of X-chromosome inactivation (XCI) in T cell development and sex differences in immunity.
• To create a detailed map of XCI escape during human T cell development.

Main Methods:

• Analysis of thymocytes from healthy males, females, a female with skewed XCI, and a female with Turner syndrome.
• Utilized whole exome sequencing, RNA sequencing, and DNA methylation profiling.
• Examined XIST lncRNA expression and gene expression from X-chromosomes.

Main Results:

• XCI remains transcriptionally and epigenetically stable throughout T cell development, irrespective of XIST.
• Identified genes escaping XCI that are expressed from only one X-chromosome in thymocytes.
• Demonstrated that a second X-chromosome is not essential for T cell development.

Conclusions:

• XCI is stable during human T cell development and independent of XIST.
• Provides a high-resolution map of XCI during human development.
• Suggests a re-evaluation of XCI's role in sex-based differences in T cell function is warranted.