RNA Sequencing Analysis of Gene Expression by Electroacupuncture in Guinea Pig Gallstone Models

Background. Clinical studies have shown that electroacupuncture (EA) promotes gallbladder motility and alleviates gallstone. However, the mechanism underlying the effects of EA on gallstone is poorly understood. In this study, the mRNA transcriptome analysis was used to study the possible therapeutic targets of EA. Methods. Hartley SPF guinea pigs were employed for the gallstone models. Illumina NovaSeq 6000 platform was used for the RNA sequencing of guinea pig gallbladders in the normal group (Normal), gallstone model group (Model), and EA-treated group (EA). Differently expressed genes (DEGs) were examined separately in Model vs. Normal and EA vs. Model. DEGs reversed by EA were selected by comparing the DEGs of Model vs. Normal and EA vs. Model. Biological functions were enriched by gene ontology (GO) analysis. The protein-protein interaction (PPI) network was analyzed. Results. After 2 weeks of EA, 257 DEGs in Model vs. Normal and 1704 DEGs in EA vs. Model were identified. 94 DEGs reversed by EA were identified among these DEGs, including 28 reversed upregulated DEGs and 66 reversed downregulated DEGs. By PPI network analysis, 10 hub genes were found by Cytohubba plugin of Cytoscape. Quantitative real-time PCR (qRT-PCR) verified the changes. Conclusion. We identified a few GOs and genes that might play key roles in the treatment of gallstone. This study may help understand the therapeutic mechanism of EA for gallstone.

Understanding the source of METTL3-independent m6A in mRNA

N6-methyladenosine (m6A) is a highly prevalent mRNA modification which promotes degradation of transcripts encoding proteins that have roles in cell development, differentiation, and other pathways. METTL3 is the major methyltransferase that catalyzes the formation of m6A in mRNA. As 30—80% of m6A can remain in mRNA after METTL3 depletion by CRISPR/Cas9-based methods, other enzymes are thought to catalyze a sizable fraction of m6A. Here, we re-examined the source of m6A in the mRNA transcriptome. We characterized mouse embryonic stem cell lines which continue to have m6A in their mRNA after Mettl3 knockout. We show that these cells express alternatively spliced Mettl3 transcript isoforms that bypass the CRISPR/Cas9 mutations and produce functionally active methyltransferases. We similarly show that other reported METTL3 knockout cell lines express altered METTL3 proteins. We find that gene dependency datasets show that most cell lines fail to proliferate after METTL3 deletion, suggesting that reported METTL3 knockout cell lines express altered METTL3 proteins rather than have full knockout. Finally, we reassessed METTL3's role in synthesizing m6A using a genomic deletion of Mettl3, and found that METTL3 is responsible for >95% of m6A in mRNA. Overall, these studies suggest that METTL3 is responsible for the vast majority of m6A in the transcriptome, and that remaining m6A in putative METTL3 knockout cell lines is due to the expression of altered but functional METTL3 isoforms.

Hypoxia regulates overall mRNA homeostasis by inducing Met1-linked linear ubiquitination of AGO2 in cancer cells

Hypoxia is the most prominent feature in human solid tumors and induces activation of hypoxia-inducible factors and their downstream genes to promote cancer progression. However, whether and how hypoxia regulates overall mRNA homeostasis is unclear. Here we show that hypoxia inhibits global-mRNA decay in cancer cells. Mechanistically, hypoxia induces the interaction of AGO2 with LUBAC, the linear ubiquitin chain assembly complex, which co-localizes with miRNA-induced silencing complex and in turn catalyzes AGO2 occurring Met1-linked linear ubiquitination (M1-Ubi). A series of biochemical experiments reveal that M1-Ubi of AGO2 restrains miRNA-mediated gene silencing. Moreover, combination analyses of the AGO2-associated mRNA transcriptome by RIP-Seq and the mRNA transcriptome by RNA-Seq confirm that AGO2 M1-Ubi interferes miRNA-targeted mRNA recruiting to AGO2, and thereby facilitates accumulation of global mRNAs. By this mechanism, short-term hypoxia may protect overall mRNAs and enhances stress tolerance, whereas long-term hypoxia in tumor cells results in seriously changing the entire gene expression profile to drive cell malignant evolution.

A novel immune-related gene pair prognostic signature for predicting overall survival in bladder cancer

Background Bladder cancer (BC) is the ninth most common malignant tumor. We constructed a risk signature using immune-related gene pairs (IRGPs) to predict the prognosis of BC patients. Methods The mRNA transcriptome, simple nucleotide variation and clinical data of BC patients were downloaded from The Cancer Genome Atlas (TCGA) database (TCGA-BLCA). The mRNA transcriptome and clinical data were also extracted from Gene Expression Omnibus (GEO) datasets (GSE31684). A risk signature was built based on the IRGPs. The ability of the signature to predict prognosis was analyzed with survival curves and Cox regression. The relationships between immunological parameters [immune cell infiltration, immune checkpoints, tumor microenvironment (TME) and tumor mutation burden (TMB)] and the risk score were investigated. Finally, gene set enrichment analysis (GSEA) was used to explore molecular mechanisms underlying the risk score. Results The risk signature utilized 30 selected IRGPs. The prognosis of the high-risk group was significantly worse than that of the low-risk group. We used the GSE31684 dataset to validate the signature. Close relationships were found between the risk score and immunological parameters. Finally, GSEA showed that gene sets related to the extracellular matrix (ECM), stromal cells and epithelial-mesenchymal transition (EMT) were enriched in the high-risk group. In the low-risk group, we found a number of immune-related pathways in the enriched pathways and biofunctions. Conclusions We used a new tool, IRGPs, to build a risk signature to predict the prognosis of BC. By evaluating immune parameters and molecular mechanisms, we gained a better understanding of the mechanisms underlying the risk signature. This signature can also be used as a tool to predict the effect of immunotherapy in patients with BC.

P-523 Whole-chromosome aneuploidies revealed by transcriptome of trophectoderm biopsied from human pre-implantation blastocyst

Study question Whether mRNA transcriptome of biopsied trophectoderm (TE) in human pre-implantation blastocyst can predict embryo karyotype? Summary answer mRNA transcriptome of biopsied TE can precisely predict whole-chromosome aneuploidies but not mosaicism or segmental aneuploidies. What is known already Karyotype of human pre-implantation blastocyst is well recognized by PGT-A. However, genome can’t demonstrate gene expression level which might infer the development potential of euploidy. Transcriptome of blastocyst by singe-cell RNA-seq has revealed the lineage segregation of human pre-implantation blastocyst. It is not known whether transcriptome of biopsied TE used in PGT-A can infer the karyotype of human pre-implantation blastocyst. Study design, size, duration A total of 74 TE samples were biopsied from 26 blastocysts which were donated from patients who underwent PGT at our Reproductive Medicine Center. All of these embryos have been previously diagnosed as aneuploidies (n = 19) or euploidies (n = 7) with monogenic disorder. Participants/materials, setting, methods The DNA and mRNA of all biopsied TEs were separated independently using a modified oligo-dT bead capture, followed by PGT-A of DNA and smart2-sequencing of mRNA (G&T-seq). Karyotype of biopsied TEs were confirmed with PGT-A performed in MiSeq system (Illumina) in our PGT laboratory with the use of next-generation sequencing. Data of transcriptome was analyzed using Rstudio and R package InferCNV to predict aneuploidies by referring to euploidies which were inferred with corresponding PGT-A results. Main results and the role of chance In human pre-implantation blastocyst, all whole-chromosome aneuploidies could be inferred by transcriptome of biopsied TE, which were consistent with PGT-A result. But chromosomal mosaicism or segmental aneuploidies were hard to be predicted precisely by transcriptome of TE. Limitations, reasons for caution The main limitation of this study lies in the inability to retrieve the exact copy number variations from mRNA transcription. Gene expression is in a great imbalance in such an early development of human pre-implantation blastocyst. Wider implications of the findings Our data suggest that mRNA transcriptome is enough for prediction of whole-chromosome aneuploidies. The method and value for predicting mosaicism and segmental aneuploidies by transcriptome should be further investigated. Trial registration number not applicable

P–523 Whole-chromosome aneuploidies revealed by transcriptome of trophectoderm biopsied from human pre-implantation blastocyst

Study question Whether mRNA transcriptome of biopsied trophectoderm (TE) in human pre-implantation blastocyst can predict embryo karyotype? Summary answer mRNA transcriptome of biopsied TE can precisely predict whole-chromosome aneuploidies but not mosaicism or segmental aneuploidies. What is known already Karyotype of human pre-implantation blastocyst is well recognized by PGT-A. However, genome can’t demonstrate gene expression level which might infer the development potential of euploidy. Transcriptome of blastocyst by singe-cell RNA-seq has revealed the lineage segregation of human pre-implantation blastocyst. It is not known whether transcriptome of biopsied TE used in PGT-A can infer the karyotype of human pre-implantation blastocyst. Study design, size, duration A total of 74 TE samples were biopsied from 26 blastocysts which were donated from patients who underwent PGT at our Reproductive Medicine Center. All of these embryos have been previously diagnosed as aneuploidies (n = 19) or euploidies (n = 7) with monogenic disorder. Participants/materials, setting, methods The DNA and mRNA of all biopsied TEs were separated independently using a modified oligo-dT bead capture, followed by PGT-A of DNA and smart2-sequencing of mRNA (G&T-seq). Karyotype of biopsied TEs were confirmed with PGT-A performed in MiSeq system (Illumina) in our PGT laboratory with the use of next-generation sequencing. Data of transcriptome was analyzed using Rstudio and R package InferCNV to predict aneuploidies by referring to euploidies which were inferred with corresponding PGT-A results. Main results and the role of chance In human pre-implantation blastocyst, all whole-chromosome aneuploidies could be inferred by transcriptome of biopsied TE, which were consistent with PGT-A result. But chromosomal mosaicism or segmental aneuploidies were hard to be predicted precisely by transcriptome of TE. Limitations, reasons for caution The main limitation of this study lies in the inability to retrieve the exact copy number variations from mRNA transcription. Gene expression is in a great imbalance in such an early development of human pre-implantation blastocyst. Wider implications of the findings: Our data suggest that mRNA transcriptome is enough for prediction of whole-chromosome aneuploidies. The method and value for predicting mosaicism and segmental aneuploidies by transcriptome should be further investigated. Trial registration number Not applicable

A de novo Full-Length mRNA Transcriptome Generated From Hybrid-Corrected PacBio Long-Reads Improves the Transcript Annotation and Identifies Thousands of Novel Splice Variants in Atlantic Salmon

Atlantic salmon (Salmo salar) is a major species produced in world aquaculture and an important vertebrate model organism for studying the process of rediploidization following whole genome duplication events (Ss4R, 80 mya). The current Salmo salar transcriptome is largely generated from genome sequence based in silico predictions supported by ESTs and short-read sequencing data. However, recent progress in long-read sequencing technologies now allows for full-length transcript sequencing from single RNA-molecules. This study provides a de novo full-length mRNA transcriptome from liver, head-kidney and gill materials. A pipeline was developed based on Iso-seq sequencing of long-reads on the PacBio platform (HQ reads) followed by error-correction of the HQ reads by short-reads from the Illumina platform. The pipeline successfully processed more than 1.5 million long-reads and more than 900 million short-reads into error-corrected HQ reads. A surprisingly high percentage (32%) represented expressed interspersed repeats, while the remaining were processed into 71 461 full-length mRNAs from 23 071 loci. Each transcript was supported by several single-molecule long-read sequences and at least three short-reads, assuring a high sequence accuracy. On average, each gene was represented by three isoforms. Comparisons to the current Atlantic salmon transcripts in the RefSeq database showed that the long-read transcriptome validated 25% of all known transcripts, while the remaining full-length transcripts were novel isoforms, but few were transcripts from novel genes. A comparison to the current genome assembly indicates that the long-read transcriptome may aid in improving transcript annotation as well as provide long-read linkage information useful for improving the genome assembly. More than 80% of transcripts were assigned GO terms and thousands of transcripts were from genes or splice-variants expressed in an organ-specific manner demonstrating that hybrid error-corrected long-read transcriptomes may be applied to study genes and splice-variants expressed in certain organs or conditions (e.g., challenge materials). In conclusion, this is the single largest contribution of full-length mRNAs in Atlantic salmon. The results will be of great value to salmon genomics research, and the pipeline outlined may be applied to generate additional de novo transcriptomes in Atlantic Salmon or applied for similar projects in other species.