Maternal SMCHD1 controls both imprinted Xist expression and imprinted X chromosome inactivation

Embryonic development is dependent on the maternal supply of proteins through the oocyte, including factors setting up the adequate epigenetic patterning of the zygotic genome. We previously reported that one such factor is the epigenetic repressor SMCHD1, whose maternal supply controls autosomal imprinted expression in mouse preimplantation embryos and mid-gestation placenta. In mouse preimplantation embryos, X chromosome inactivation is also an imprinted process. Combining genomics and imaging, we show that maternal SMCHD1 is required not only for the imprinted expression of Xist in preimplantation embryos, but also for the efficient silencing of the inactive X in both the preimplantation embryo and mid-gestation placenta. These results expand the role of SMCHD1 in enforcing the silencing of Polycomb targets. The inability of zygotic SMCHD1 to fully restore imprinted X inactivation further points to maternal SMCHD1's role in setting up the appropriate chromatin environment during preimplantation development, a critical window of epigenetic remodelling.

Lack of Salivary Long Non-Coding RNA XIST Expression Is Associated with Increased Risk of Oral Squamous Cell Carcinoma: A Cross-Sectional Study

Studies have shown that there is a disparity between males and females in south-east Asia with regard to oral cancer morbidity. A previous study found that oral cancer tissue showed loss of heterozygosity of the X-linked lncRNA XIST gene. We suggest that XIST may play an important role in oral cancer morbidity when associated with sex. Saliva contains proteins and RNAs that are potential biomarkers for the diagnosis of diseases. This study investigated salivary XIST expression and the correlation to clinical–pathological data among oral squamous cell carcinoma patients. Salivary XIST expression was only observed in females, and a high proportion of females with OSCC lack salivary lncRNA XIST expression (88%). The expression showed no correlation with alcohol consumption, betel quid chewing, or cigarette smoking habits. People lacking salivary lncRNA XIST expression had a significantly increased odds ratio of suffering from OSCC (OR = 19.556, p < 0.001), particularly females (OR = 33.733, p < 0.001). The ROC curve showed that salivary lncRNA XIST expression has acceptable discrimination accuracy to predict the risk of OSCC (AUC = 0.73, p < 0.01). Lack of salivary lncRNA XIST expression was associated with an increased risk of OSCC. We provided an insight into the role of salivary lncRNA XIST as a biomarker to predict the morbidity of OSCC.

LncRNA XIST Relieves Hypoxia-Induced Damage in H9C2 Cells by Downregulating miR-429

This paper aimed to investigate LncRNA XIST relieving hypoxia-induced damage in H9C2 cells by downregulating miR-429. Rat H9C2 cell lines were selected and divided into a normal control group, a hypoxia group, a XIST expression group, a XIST blank expression group, a miR-429 interference group and a blank interference group. qPCR was adopted for detecting LncRNA XIST and miR-429 expression. Western blot (WB) was adopted for detecting the expression of AMPK, PDH, FAT, MCPT-1, Caspase-3, Bax and Bcl-2, ATP content, and levels of SOD, MDA and LDH. Dual luciferase reporter gene assay (DLRGA) and RNA pull-down were adopted for verifying the correlation of LncRNA XIST with miR-429. Hypoxia-induced H9C2 cells had low LncRNA XIST expression and high miR-429 expression. LncRNA XIST upregulation or miR-429 downregulation could inhibit AMPK, PDH, Caspase-3 and Bax, upregulate FAT, MCPT-1 and Bcl-2, and increase ATP content and SOD activity, as well as reduce MDA content and LDH activity. miR-429 was the target gene of LncRNA XIST. LncRNA XIST can relieve hypoxia-induced damage in H9C2 cells via binding to and downregulating miR-429

Tissue of Origin, but Not XCI State, Influences Germ Cell Differentiation from Human Pluripotent Stem Cells

Human pluripotent stem cells (hPSCs) are not only a promising tool to investigate differentiation to many cell types, including the germline, but are also a potential source of cells to use for regenerative medicine purposes in the future. However, current in vitro models to generate human primordial germ cell-like cells (hPGCLCs) have revealed high variability regarding differentiation efficiency depending on the hPSC lines used. Here, we investigated whether differences in X chromosome inactivation (XCI) in female hPSCs could contribute to the variability of hPGCLC differentiation efficiency during embryoid body (EB) formation. For this, we first characterized the XCI state in different hPSC lines by investigating the expression of XIST and H3K27me3, followed by differentiation and quantification of hPGCLCs. We observed that the XCI state did not influence the efficiency to differentiate to hPGCLCs; rather, hPSCs derived from cells isolated from urine showed an increased trend towards hPGCLCs differentiation compared to skin-derived hPSCs. In addition, we also characterized the XCI state in the generated hPGCLCs. Interestingly, we observed that independent of the XCI state of the hPSCs used, both hPGCLCs and soma cells in the EBs acquired XIST expression, indicative of an inactive X chromosome. In fact, culture conditions for EB formation seemed to promote XIST expression. Together, our results contribute to understanding how epigenetic properties of hPSCs influence differentiation and to optimize differentiation methods to obtain higher numbers of hPGCLCs, the first step to achieve human in vitro gametogenesis.

Linking Chromosomal Silencing With Xist Expression From Autosomal Integrated Transgenes

Xist is the master regulator of X-Chromosome Inactivation (XCI), the mammalian dosage compensation mechanism that silences one of the two X chromosomes in a female cell. XCI is established during early embryonic development. Xist transgene (Tg) integrated into an autosome can induce transcriptional silencing of flanking genes; however, the effect and mechanism of Xist RNA on autosomal sequence silencing remain elusive. In this study, we investigate an autosomal integration of Xist Tg that is compatible with mouse viability but causes male sterility in homozygous transgenic mice. We observed ectopic Xist expression in the transgenic male cells along with a transcriptional reduction of genes clustered in four segments on the mouse chromosome 1 (Chr 1). RNA/DNA Fluorescent in situ Hybridization (FISH) and chromosome painting confirmed that Xist Tg is associated with chromosome 1. To determine the spreading mechanism of autosomal silencing induced by Xist Tg on Chr 1, we analyzed the positions of the transcriptionally repressed chromosomal sequences relative to the Xist Tg location inside the cell nucleus. Our results show that the transcriptionally repressed chromosomal segments are closely proximal to Xist Tg in the three-dimensional nucleus space. Our findings therefore support a model that Xist directs and maintains long-range transcriptional silencing facilitated by the three-dimensional chromosome organization.

Prognostic Roles of LncRNA XIST and Its Potential Mechanisms in Human Cancers: A Pan-Cancer Analysis

Background: X-inactive specific transcript (XIST), it has been found, is abnormal expression in various neoplasms. This work aims to explore its potential molecular mechanisms and prognostic roles in types of malignancies. Methods: This research comprehensively investigated XIST transcription across cancers from Oncomine, TIMER 2.0 and GEPIA2. Correlations of XIST expression with prognosis, miRNAs, interacting protens, immune infiltrates, checkpoint markers and mutations of tumor-associated genes were also analyzed by public databases. Results: Compared to normal tissues, XIST was lower in BRCA, COAD, LUAD, lymphoma and OV in Oncomine; In TIMER 2.0, XIST was decreased in BRCA, KICH, THCA and UCEC, but increased in KIRC and PRAD; In GEPIA2, XIST was down-regulated in CESC, COAD, OV, READ, STAD, UCEC and UCS. Public databases also showed that XIST was a good indicator of prognosis in BRCA, CESC, COAD, STAD, OV and so on, but a bad one in KIRC, KIRP and so on. From starBase, we found 29 proteins interacting with XIST, and identified 4 miRNAs, including miR-103a-3p, miR-107, miR-130b-3p and miR-96-5p, which might be sponged by XIST in cancers. Furthermore, XIST was linked with immune infiltration, especially T cell CD4+, and was related to over 20 immune checkpoint markers. In addition, XIST was associated with several tumor-associated gene mutations in some cancers. Conclusion: In summary, abnormal expression of XIST influenced prognosis, miRNAs, immune cell infiltration and mutations of tumor-associated genes across cancers, especially BRCA and colorectal cancer. More efforts should be made to detect potential molecular mechanisms of XIST in the carcinogenesis.

Revisiting the consequences of deleting the X inactivation center

Mammalian cells equalize X-linked dosages between the male (XY) and female (XX) sexes by silencing one X chromosome in the female sex. This process, known as “X chromosome inactivation” (XCI), requires a master switch within the X inactivation center (Xic). The Xic spans several hundred kilobases in the mouse and includes a number of regulatory noncoding genes that produce functional transcripts. Over three decades, transgenic and deletional analyses have demonstrated both the necessity and sufficiency of the Xic to induce XCI, including the steps of X chromosome counting, choice, and initiation of whole-chromosome silencing. One recent study, however, reported that deleting the noncoding sequences of the Xic surprisingly had no effect for XCI and attributed a sufficiency to drive counting to the coding gene, Rnf12/Rlim. Here, we revisit the question by creating independent Xic deletion cell lines. Multiple independent clones carrying heterozygous deletions of the Xic display an inability to up-regulate Xist expression, consistent with a counting defect. This defect is rescued by a second site mutation in Tsix occurring in trans, bypassing the defect in counting. These findings reaffirm the essential nature of noncoding Xic elements for the initiation of XCI.

Kaempferol attenuates the effects of XIST/miR-130a/STAT3 on inflammation and extracellular matrix degradation in osteoarthritis

Aim: To investigate whether kaempferol exhibited protective effects on osteoarthritis chondrocytes by modulating the XIST/miR-130a/STAT3 axis. Methods: qRT-PCR and western blot assays were used for gene and protein determination. Dual luciferase reporter and RNA immunoprecipitation assays were employed to study the interaction between miRNA and lncRNA or genes. Results: Kaempferol decreased proinflammatory cytokine production and extracellular matrix degradation in C28/I2 cells. Additionally, kaempferol ameliorated XIST expression and enhanced miR-130a expression. XIST interacted with miR-130a, and STAT3 was identified as a target of miR-130a. Knockdown of XIST expression suppressed proinflammatory cytokine production and extracellular matrix degradation in C28/I2 cells. Overexpression of STAT3 rescued the effects of XIST knockdown. Conclusion: Kaempferol inhibited inflammation and extracellular matrix degradation by modulating the XIST/miR-130a/STAT3 axis in chondrocytes.

LncRNA XIST promotes liver cancer progression by acting as a molecular sponge of miR-200b-3p to regulate ZEB1/2 expression

Objective To evaluate the predictive value of long non-coding RNA (lncRNA) X-inactive specific transcript (XIST) for survival, and determine the involvement of miRNA(miR)-200b-3p and zinc finger E-box-binding homeobox (ZEB) 1/2 in the pro-tumor effect of lncRNA XIST in liver cancer. Methods We evaluated lncRNA XIST expression in liver cancer tissues and cell lines by quantitative reverse transcription polymerase chain reaction (RT-qPCR) and analyzed the correlation between its expression and overall survival of liver cancer patients by Kaplan–Meier analysis. Its effects on cell proliferation, migration, and invasion were analyzed by Cell-Counting Kit-8 and Transwell assays. The association between lncRNA XIST and miR-200b-3p, and the effects of lncRNA XIST on ZEB1/2 expression were explored using luciferase reporter assays, real-time PCR, and western blotting. Results The lncRNA XIST was significantly upregulated in liver cancer, and increased lncRNA XIST expression was associated with a poor prognosis. The lncRNA XIST promoted liver cancer cell proliferation, migration, and invasion in vitro, and acted as a molecular sponge for miR-200b-3p, and also regulated the expression of ZEB1/2 via miR-200b-3p. Conclusion The lncRNA XIST is an oncogenic lncRNA that promotes liver cancer metastasis, and its pro-metastatic phenotype can be partially attributed to the lncRNA XIST/miR-200b-3p/ZEB1/2 signaling axis.

Long Noncoding RNA X-Inactive-Specific Transcript Promotes the Secretion of Inflammatory Cytokines in LPS Stimulated Astrocyte Cell Via Sponging miR-29c-3p and Regulating Nuclear Factor of Activated T cell 5 Expression

BackgroundAstrocyte activation promotes glutamate accumulation and secretion of inflammatory factors, mainly responsible for epilepsy. Long noncoding RNA (lncRNA) X-inactive-specific transcript (XIST) regulates inflammation; however, the biological role and regulatory mechanism of XIST during astrocyte activation remain unclear.MethodsIn the present study, rat epilepsy model and lipopolysaccharide (LPS)-treated CTX-TNA2 were established. XIST and miR-29c-3p expression were evaluated using quantitative real-time polymerase chain reaction. Nuclear factor of activated T cells 5 (NFAT5) was measured using western blot analysis. Interleukin (IL)-1β, IL-6, tumor necrosis factor-α, and L-glutamate levels in the culture supernatants were assessed using enzyme-linked immunosorbent assay. The binding between XIST and miR-29c-3p and between miR-29c-3p and the 3′-UTR of NFAT5 was analyzed using dual-luciferase reporter, RNA-binding protein immunoprecipitation (RIP), and Biotin pull-down assay. The proliferation and apoptosis were evaluated using CCK8 and flow cytometry, respectively.ResultsXIST expression and NFAT5 protein level was increased, whereas miR-29c-3p expression was decreased in the epilepsy rat model and LPS-treated CTX-TNA2 cells. Silenced XIST expression, miR-29c-3p overexpression, or silenced NFAT5 expression inhibited the secretion of IL-1β, IL-6, and TNF-α and promoted glutamate transport in LPS-treated CTX-TNA2 cells. miR-29c-3p was the potential miRNA sponged by XIST. NFAT5 acted as a direct binding target of miR-29c-3p. Silenced miR-29c-3p expression or NFAT5 overexpression reversed the effect of silenced XIST expression on LPS-treated CTX-TNA2.XIST and miR-29c-3p treatment does not affect NFAT5 mRNA expression, but affects NFAT5 protein level. Furthermore, underexpressed XIST or overexpressed miR-29c-3p in LPS-stimulated CTX-TNA2 can attenuate neuronal apoptosis induced by LPS-stimulated CTX-TNA2.ConclusionLncRNA XIST promotes the secretion of inflammatory cytokines in LPS- treated CTX-TNA2 via sponging miR-29c-3p and regulating NFAT5 expression.