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Alternative splicing Hltf: intron retention-dependent activation of immune tolerance at the feto-maternal interface (RNA-Seq)

ABSTRACT: Purpose: we tested the hypothesis that Hltf deletion in placenta either caused or exacerbated neonatal hypoglycemia via Hif-1α regulation of nutrient transporters. Methods: Individual samples [1 term placenta/sample x 5 biological replicates for test and control littermate female mice = 10 total samples] were flash frozen and sent to Otogenetics Corp. (Norcross, GA) for RNA-seq assays. Paired-end 100 nucleotide reads were aligned to genomic assembly mm10 and analyzed using the platform provided by DNAnexus, Inc. (Mountain View, CA). Results: There was no measureable evidence of uteroplacental dysfunction or fetal compromise. Conclusion: Our study is the first to show only the truncated Hltf isoform is expressed in E18.5 term placenta, and we identified a functional link between alternative splicing of Hltf and immunosuppression at the feto-maternal interface.

ORGANISM(S): Mus musculus

PROVIDER: GSE114144 | GEO | 2018/12/14

REPOSITORIES: GEO

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Project description:The helicase-like transcription factor (HLTF) gene – a tumor suppressor in human colorectal cancer (CRC) - is regulated by alternative splicing and promoter hypermethylation. The detection of hypermethylated HLTF DNA in fecal occult blood tests is an indicator of disease recurrence and poor survival. Hltf-deficiency in the ApcMin/+ mouse strain increased the formation of intestinal adenocarcinoma with a high incidence of gross chromosomal instabilities. To investigate Hltf-deletion effects in CRC without cross-breeding into a tumorigenic strain, Hltf-deletion was studied in mice treated with the carcinogen azoxymethane (AOM) and the proinflammatory agent dextran sulfate (DSS). Hltf-deletion resulted in weight loss beginning at treatment week 6, and poor survival (Kaplan-Meier survival plot). Hltf-deletion increased tumor multiplicity compared to controls, and dramatically shifted the topographic distribution of lesions into the rectum. Differential isoform expression analysis of lesions from control mice revealed both the truncated isoform that lacks a DNA-repair domain and the full length isoform capable of DNA damage repair are present (3:1.8 ratio) during adenocarcinoma formation. iPathwayGuide identified 51 dynamically regulated genes of 10,967 total genes with measured expression. Oxidative Phosphorylation (Kegg: 00190), the top biological pathway (p=0.006; p value correction: Bonferroni) perturbed by Hltf-deletion, resulted from increased transcription of Atp5e, Cox7c, Uqcr11, Ndufa4 and Ndufb6 genes, concomitant with increased endogenous levels of ATP (p=0.0176). Upregulation of gene expression, as validated with qRT-PCR, was accompanied by a stable mtDNA/nDNA ratio. This is the first study to show Hltf-deletion in an inflammation-associated CRC model elevates mitochondrial bioenergetics. The distal shift in tumorigenesis indicates the detection of hypermethylated HLTF DNA in human stool samples might be a prognostic biomarker for distal (left-sided) colorectal cancer rather than proximal (right-sided) colon cancer.

Project description:Hypermethylation of helicase-like transcription factor (HLTF) in colorectal cancer (CRC) cells occurs more frequently in men than women. Progressive epigenetic silencing of HLTF in tumor cells is accompanied by negligible expression in the tumor microenvironment (TME). Cell line-derived xenografts were established in control (Hltf+/+) and Hltf-deleted male Rag2-/-IL2rg-/- mice by direct orthotopic microinjection of HLTF+/+HCT116 cells into the submucosa of the cecum. Combinatorial induction of IL6 and S100A8/A9 in the Hltf-deleted TME with ICAM-1 and IL8 in the primary tumor activated a positive feedback loop. The proinflammatory niche produced a major shift in CDX metastasis to peritoneal dissemination compared to controls. Inducible nitric oxide (iNOS) gene expression and transactivation of the iNOS-S100A8/A9 signaling complex in Hltf-deleted TME reprogrammed the human S-nitroso-proteome. S-nitroso (SNO) proteins POTEE, TRIM52 and UN45B are S-nitrosylated on the conserved I/L-X-C-X2-D/E motif indicative of iNOS-S100A8/A9-mediated S-nitrosylation. 2D-DIGE and protein identification by MALDI-TOF/TOF mass spectrometry authenticated S-nitrosylation of 53 individual cysteines in half-site motifs (I/L-X-C or C-X-X-D/E) in CDX tumors. POTEE-SNO in CDX tumors is both a general S-nitrosylation target and an iNOS-S100A8/A9 site-specific (Cys638) target in the Hltf-deleted TME. REL is an example of convergence of transcriptomic-S-nitroso-proteomic signaling. The gene is transcriptionally activated in CDX tumors with an Hltf-deleted TME, and REL-SNO (Cys143) is found in primary CDX tumors and all metastatic sites. Primary CDX tumors from Hltf-deleted TME shared 60% of their S-nitroso-proteome with all metastatic sites. Forty percent of SNO-proteins from primary CDX tumors were variably expressed at metastatic sites. Global S-nitrosylation of proteins in pathways related to cytoskeleton and motility is strongly implicated in the metastatic dissemination of CDX tumors. Hltf-deletion from the TME plays a major role in the pathogenesis of inflammation and links protein S-nitrosylation in primary CDX tumors with spatiotemporal continuity in metastatic progression even when the tumor cells express HLTF.

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Alternative splicing Hltf: intron retention-dependent activation of immune tolerance at the feto-maternal interface (RNA-Seq)

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