---
title: "Lineage-specific XCI escape and skew drive sex-biased immune gene dosage and X-linked variant expo"
id: "biorxiv-11-lineage-specific-x-chromosome-inactivation-escape-and-skew-underlie-sex-biased"
canonical_url: "https://medichelpline.com/clinical-feed/biorxiv-11-lineage-specific-x-chromosome-inactivation-escape-and-skew-underlie-sex-biased"
content_type: "clinical_feed_article"
specialty: "General"
source_name: "bioRxiv (Biomedical Preprints)"
source_url: "https://www.biorxiv.org/content/10.64898/2026.08.26.739472v1?rss=1"
published_at: "2026-08-31T12:00:00.000Z"
evidence_level: "Verified Feed"
license: "CC-BY-NC-4.0 / Informational Use"
---
# Lineage-specific XCI escape and skew drive sex-biased immune gene dosage and X-linked variant expo
## Provenance & Clinical Metadata
- **Canonical URL:** https://medichelpline.com/clinical-feed/biorxiv-11-lineage-specific-x-chromosome-inactivation-escape-and-skew-underlie-sex-biased
- **Specialty:** [General](https://medichelpline.com/clinical-feed/general.md)
- **Primary Source:** bioRxiv (Biomedical Preprints)
- **Source URL:** [Original Journal Publication](https://www.biorxiv.org/content/10.64898/2026.08.26.739472v1?rss=1)
- **Published At:** 2026-08-31T12:00:00.000Z
- **Evidence Rating:** Verified Feed
## Executive GIST (TL;DR)
- The X chromosome is enriched for **immune genes** and contributes to sex differences in immune function and autoimmunity. X-chromosome inactivation (XCI) affects gene dosage through **XCI escape** and determines cellular exposure to heterozygous X-linked variants via **XCI skew**. - XCI creates a cellular mosaic in females, making lineage-specific escape and skew difficult to measure in individual donors without non-random XCI or large cohorts. - The authors developed scDaisyChain, a graph-based framework that reconstructs chromosome-scale X haplotypes from heterozygous SNPs and single-cell long-read transcriptomes, enabling patient-resolved measurement of XCI properties. - scDaisyChain showed near-ground-truth accuracy in highly polymorphic mouse hybrids and strong concordance with orthogonal long-read whole-genome phasing in human samples, according to the source. - In peripheral blood immune cells from healthy women, scDaisyChain revealed a **lineage-specific escape program**: lymphoid cells escape XCI more broadly than monocytes, with corresponding increases in inactive X chromatin accessibility and female-biased expression. - Lineage-specific **XCI skew** alters the fraction of cells expressing each heterozygous X-linked variant, a property the authors call **variant exposure**. - Predicted deleterious X-linked variants tend to be in low-exposure states; the paper gives an example of a splice-altering **TLR8** variant that is expressed in few cytotoxic T cells. - In rheumatoid arthritis (RA), monocytes—shown to have the lowest escape in healthy donors—exhibit reproducible inactive X dysregulation linked to a trained-immunity program, disease flare, and synovial macrophage activation, with elevated escape of **IL13RA1** and **HDAC8**. - The study positions lineage-specific escape, skew and variant exposure as measurable, patient-resolved determinants of sex-biased immune gene dosage and X-linked variant penetrance in health and autoimmune disease, addressing a previously inaccessible dimension of female biology.
## Clinical Analysis & Structured Key Points
The X chromosome carries an unusually high density of immune genes and is a major contributor to sex differences in immune function and autoimmune diseases. In females, X-chromosome inactivation (XCI) has two major functional consequences: it shapes X-linked gene dosage through XCI escape and determines the cellular exposure of heterozygous X-linked variants through XCI skew. Yet because XCI creates a mosaic of cells expressing different parental X chromosomes, these properties have remained largely inaccessible in individual women, becoming measurable only where XCI is non-random or after aggregation across large cohorts. Consequently, how X-linked variation contributes to sex-biased immunity and differs between individual women has remained unresolved. Here we present scDaisyChain, a graph-based framework that reconstructs chromosome-scale X haplotypes directly from heterozygous SNPs and single-cell long-read transcriptomes. scDaisyChain achieves near-ground-truth accuracy in highly polymorphic mouse hybrids and shows strong concordance with orthogonal long-read whole-genome phasing in human samples. Applied to peripheral blood immune cells from healthy women, it reveals a lineage-specific escape program in which lymphoid cells escape XCI more broadly than monocytes, with corresponding gains in the inactive X chromatin accessibility and female-biased expression. Lineage-specific skew further alters the proportion of cells expressing each heterozygous X-linked variant, a property we term variant exposure. Predicted deleterious variants are preferentially found in low-exposure states, exemplified by a splice-altering TLR8 variant expressed in few cytotoxic T cells. In rheumatoid arthritis (RA), the monocyte compartment - which has the lowest escape in health - shows reproducible inactive X dysregulation converging on a trained-immunity programme linked to disease flare and synovial macrophage activation, with elevated escape of IL13RA1 and HDAC8. These findings establish lineage-specific escape, skew and variant exposure as quantifiable, patient-resolved determinants of sex-biased immune gene dosage and X-linked variant penetrance in health and autoimmune disease, resolving a dimension of female biology that has been previously inaccessible in individual donors.
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