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Cutting Edge: CXCR3 Escapes X Chromosome Inactivation in T Cells during Infection: Potential Implications for Sex Differences in Immune Responses.

ABSTRACT: CXCR3, an X-linked gene, is subject to X chromosome inactivation (XCI), but it is unclear whether CXCR3 escapes XCI in immune cells. We determined whether CXCR3 escapes XCI in vivo, evaluated the contribution of allelic CXCR3 expression to the phenotypic properties of T cells during experimental infection with Leishmania, and examined the potential implications to sex differences in immune responses. We used a bicistronic CXCR3 dual-reporter mouse, with each CXCR3 allele linked to a green or red fluorescent reporter without affecting endogenous CXCR3 expression. Our results show that CXCR3 escapes XCI, biallelic CXCR3-expressing T cells produce more CXCR3 protein than monoallelic CXCR3-expressing cells, and biallelic CXCR3-expressing T cells produce more IFN-?, IL-2, and CD69 compared with T cells that express CXCR3 from one allele during Leishmania mexicana infection. These results demonstrate that XCI escape by CXCR3 potentially contributes to the sex-associated bias observed during infection.

SUBMITTER: Oghumu S

PROVIDER: S-EPMC6684832 | biostudies-literature | 2019 Aug

REPOSITORIES: biostudies-literature

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Cutting Edge: CXCR3 Escapes X Chromosome Inactivation in T Cells during Infection: Potential Implications for Sex Differences in Immune Responses.

Oghumu Steve S Varikuti Sanjay S Stock James C JC Volpedo Greta G Saljoughian Noushin N Terrazas Cesar A CA Satoskar Abhay R AR

Journal of immunology (Baltimore, Md. : 1950) 20190628 4

CXCR3, an X-linked gene, is subject to X chromosome inactivation (XCI), but it is unclear whether CXCR3 escapes XCI in immune cells. We determined whether CXCR3 escapes XCI in vivo, evaluated the contribution of allelic CXCR3 expression to the phenotypic properties of T cells during experimental infection with <i>Leishmania,</i> and examined the potential implications to sex differences in immune responses. We used a bicistronic CXCR3 dual-reporter mouse, with each CXCR3 allele linked to a green ...[more]

PMID: 31253729

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Project description:BackgroundHuman endosomal Toll-like receptors TLR7 and TLR8 recognize self and non-self RNA ligands, and are important mediators of innate immunity and autoimmune pathogenesis. TLR7 and TLR8 are, respectively, encoded by adjacent X-linked genes. We previously established that TLR7 evades X chromosome inactivation (XCI) in female immune cells. Whether TLR8 also evades XCI, however, has not yet been explored.MethodIn the current study, we used RNA fluorescence in situ hybridization (RNA FISH) to directly visualize, on a single-cell basis, primary transcripts of TLR7 and TLR8 relative to X chromosome territories in CD14+ monocytes and CD4+ T lymphocytes from women, Klinefelter syndrome (KS) men, and euploid men. To assign X chromosome territories in cells lacking robust expression of a XIST compartment, we designed probes specific for X-linked genes that do not escape XCI and therefore robustly label the active X chromosome. We also assessed whether XCI escape of TLR8 was associated with sexual dimorphism in TLR8 protein expression by western blot and flow cytometry.ResultsUsing RNA FISH, we show that TLR8, like TLR7, evades XCI in immune cells, and that cells harboring simultaneously TLR7 and TLR8 transcript foci are more frequent in women and KS men than in euploid men, resulting in a sevenfold difference in frequency. This transcriptional bias was again observable when comparing the single X of XY males with the active X of cells from females or KS males. Interestingly, TLR8 protein expression was significantly higher in female mononuclear blood cells, including all monocyte subsets, than in male cells.ConclusionsTLR8, mirroring TLR7, escapes XCI in human monocytes and CD4+ T cells. Co-dependent transcription from the active X chromosome and escape from XCI could both contribute to higher TLR8 protein abundance in female cells, which may have implications for the response to viruses and bacteria, and the risk of developing inflammatory and autoimmune diseases.

Project description:Aortic valve stenosis (AVS) is a sexually dimorphic disease, with women often presenting with sustained fibrosis and men with more extensive calcification. However, the intracellular molecular mechanisms that drive these clinically important sex differences remain under explored. Hydrogel scaffolds were designed to recapitulate key aspects of the valve tissue microenvironment and serve as a platform for culture of sex-specific valvular interstitial cells (VICs; precursors to pro-fibrotic myofibroblasts). The hydrogel culture system was used to interrogate intracellular pathways involved in sex-dependent VIC-to-myofibroblast activation and deactivation. RNA-seq was used to define pathways likely to be involved in driving sex-dependent activation. Interventions using small molecule inhibitors were performed to provide mechanistic insight into sex-specific cellular responses to microenvironmental cues, including matrix stiffness and exogenously delivered biochemical factors. In both healthy porcine and human aortic valves, female leaflets had higher baseline activation of the myofibroblast marker, α-smooth muscle actin (α-SMA), compared to male leaflets. When isolated and cultured, female VICs had higher levels of basal α-SMA stress fibers that further increased in response to the hydrogel matrix stiffness, both of which were higher than male VICs. A transcriptomic analysis of male and female porcine VICs revealed Rho-associated protein kinase (RhoA/ROCK) signaling as a potential driver of this sex-dependent myofibroblast activation. Further, we found that genes that escape X-chromosome inactivation, such as BMX and STS (encoding for Bmx non-receptor tyrosine kinase and steroid sulfatase, respectively) partially regulate the elevated female myofibroblast activation via RhoA/ROCK signaling. This finding was confirmed by treating male and female VICs with endothelin-1 and plasminogen activator inhibitor-1, factors that are secreted by endothelial cells and known to drive myofibroblast activation via RhoA/ROCK signaling. Together, in vivo and in vitro results confirm sex-dependencies in myofibroblast activation pathways, and transcriptome analyses and small molecule interventions implicate genes that escape X-chromosome inactivation in regulating sex differences in AVS progression. Our results underscore the importance of considering sex as a biological variable to understand the molecular mechanisms of AVS and help guide sex-based precision therapies.

Dataset Information

Cutting Edge: CXCR3 Escapes X Chromosome Inactivation in T Cells during Infection: Potential Implications for Sex Differences in Immune Responses.

Publications

Cutting Edge: CXCR3 Escapes X Chromosome Inactivation in T Cells during Infection: Potential Implications for Sex Differences in Immune Responses.

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