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LKB1 inactivation promotes epigenetic remodeling-induced lineage plasticity and antiandrogen resistance in prostate cancer.

Epigenetic regulation profoundly influences the fate of cancer cells and their capacity to switch between lineages by modulating essential gene expression, thereby shaping tumor heterogeneity and therapy response. In castration-resistant prostate cancer (CRPC), the intricacies behind androgen receptor (AR)-independent lineage plasticity remain unclear, leading to a scarcity of effective clinical treatments. Utilizing single-cell RNA sequencing on both human and mouse prostate cancer samples, combined with whole-genome bisulfite sequencing and multiple genetically engineered mouse models, we investigated the molecular mechanism of AR-independent lineage plasticity and uncovered a potential therapeutic strategy. Single-cell transcriptomic profiling of human prostate cancers, both pre- and post-androgen deprivation therapy, revealed an association between liver kinase B1 (LKB1) pathway inactivation and AR independence. LKB1 inactivation led to AR-independent lineage plasticity and global DNA hypomethylation during prostate cancer progression. Importantly, the pharmacological inhibition of TET enzymes and supplementation with S-adenosyl methionine were found to effectively suppress AR-independent prostate cancer growth. These insights shed light on the mechanism driving AR-independent lineage plasticity and propose a potential therapeutic strategy by targeting DNA hypomethylation in AR-independent CRPC.

Male↗

Transcript mapping with high-density oligonucleotide tiling arrays.

MOTIVATION: High-density DNA tiling microarrays are a powerful tool for the characterization of complete transcriptomes. The two major analytical challenges are the segmentation of the hybridization signal along genomic coordinates to accurately determine transcript boundaries and the adjustment of the sequence-dependent response of the oligonucleotide probes to achieve quantitative comparability of the signal between different probes. RESULTS: We describe a dynamic programming algorithm for finding a globally optimal fit of a piecewise constant expression profile along genomic coordinates. We developed a probe-specific background correction and scaling method that employs empirical probe response parameters determined from reference hybridizations with no need for paired mismatch probes. This combined analysis approach allows the accurate determination of dynamical changes in transcription architectures from hybridization data and will help to study the biological significance of complex transcriptional phenomena in eukaryotic genomes. AVAILABILITY: R package tilingArray at http://www.bioconductor.org.

Algorithms↗

Pervasive noise in human splice site selection.

RNA splicing has historically been thought to be highly efficient and accurate, with little opportunity for deviation from regulated alternative splicing decisions. This dogma has been challenged by recent observations that suggest that biological noise may contribute substantially to transcriptome diversity. However, quantitative understanding of stochastic variations in splicing is challenging because these transcripts are likely subject to rapid degradation. Here, we use ultra-deep sequencing across RNA compartments to track splicing intermediates in human cells and see abundant cryptic splicing associated with genomic features that promote splicing noise. We observe pervasive usage of low-fidelity splice sites, likely due to stochasticity in recruitment or binding of the spliceosome. These sites are most likely degraded in the nucleus rather than targeted by translation-dependent degradation processes, suggesting widespread surveillance and rapid quality control of non-productive RNA transcripts. Our findings provide unprecedented insights into the propensity for error in RNA processing mechanisms and the regulation of alternative splice sites across a gene.

Journal Article↗

Maximizing the efficacy of SAGE analysis identifies novel transcripts in Arabidopsis.

The efficacy of using Serial Analysis of Gene Expression (SAGE) to analyze the transcriptome of the model dicotyledonous plant Arabidopsis was assessed. We describe an iterative tag-to-gene matching process that exploits the availability of the whole genome sequence of Arabidopsis. The expression patterns of 98% of the annotated Arabidopsis genes could theoretically be evaluated through SAGE and using an iterative matching process 79% could be identified by a tag found at a unique site in the genome. A total of 145,170 reliable experimental tags from two Arabidopsis leaf tissue SAGE libraries were analyzed, of which 29,632 were distinct. The majority (93%) of the 12,988 experimental tags observed greater than once could be matched within the Arabidopsis genome. However, only 78% were matched to a single locus within the genome, reflecting the complexities associated with working in a highly duplicated genome. In addition to a comprehensive assessment of gene expression in Arabidopsis leaf tissue, we describe evidence of transcription from pseudo-genes as well as evidence of alternative mRNA processing and anti-sense transcription. This collection of experimental SAGE tags could be exploited to assist in the on-going annotation of the Arabidopsis genome.

Antisense Elements (Genetics)↗

The catheterized urinary tract selects for MRR1-mediated efflux and fluconazole resistance in Candida albicans biofilms.

Catheter-associated urinary tract infections (CAUTIs) are the most common nosocomial infection in developed countries, and Candida species are among the most frequently isolated organisms. Despite this, little is known about the biology, host-pathogen interactions, or outcomes of these infections, and this has led to uncertain guidelines for clinical management of Candida CAUTIs. Here, we develop the first physiologically relevant artificial urine medium (AUM) that supports fungal growth in a manner similar to, but more consistent than, human urine samples. We demonstrate that human catheter-associated (CA) clinical isolates of C. albicans exhibit environment-dependent fluconazole resistance: many isolates determined to be susceptible by standard CLSI testing in RPMI (MIC ≤ 2 µg/mL) were fully resistant (MIC ≥ 128 µg/mL) when grown in pooled human urine or AUM, complicating clinical management, which is based on catheter exchange and fluconazole treatment. Transcriptomic profiling of biofilms formed in AUM revealed a remarkably convergent upregulation of efflux and detoxification processes across clinical isolates with diverse biofilm phenotypes. Whole-genome sequencing of the CA isolates identified variant alleles of transcriptional regulators of drug efflux, including MRR1, that have been previously associated with antifungal resistance. A competition assay confirmed that Mrr1 provides a fitness advantage in urine and AUM in a urea-dependent manner. Thus, we show that the urinary environment promotes a unique biofilm differentiation program and selects for adaptations that increase drug resistance and would be predicted to render standard treatment regimens ineffective.IMPORTANCECatheter-associated urinary tract infections are the most common nosocomial infection in the United States, and Candida albicans is one of the most frequently isolated organisms from these infections. Despite this high prevalence, few molecular studies have examined C. albicans biology in the urinary environment, and recommendations for clinical management lack robust evidence. Here, we show that clinical catheter-associated isolates of C. albicans identified as susceptible to fluconazole by standard clinical microbiology testing were resistant when grown in human or artificial urine. We identified transcriptional responses intrinsic to the urinary environment that produce this environment-specific resistance phenotype. Biofilm growth in the urinary environment induces cellular processes for efflux and detoxification. These findings suggest that standard susceptibility testing may not predict fluconazole efficacy in the urinary tract and underscore the need for niche-informed approaches to antifungal management of these common infections.

Candida albicans↗

IGH::FENDRR and specific KRAS mutations define a novel B-ALL molecular subtype with poor chemotherapy response.

Large-scale sequencing efforts have defined up to 27 diagnostic subtypes in B-cell precursor acute lymphoblastic leukemia (B-ALL), leaving few samples unclassified. Extended genomic and transcriptomic profiling in routine diagnostics broadens the sample collection, enabling identification of novel subtypes. We analyzed 4857 patients with B-ALL from 3 cohorts and identified a group of 20 patients (age, 18-66 years; median, 34 years) characterized by a previously undescribed IGH::FENDRR rearrangement exclusive to this subtype (n = 17/20), KRAS p.A146T/V/P mutations (n = 17/20 vs n = 86/4857; P< .001), and distinct DNA methylation/gene expression profiles, including overexpression of the lncRNA FENDRR and the transcription factor FOXF1 (FOXF1/FENDRR) as well as JAK/STAT and RAS/MAPK signaling signatures. A gene expression machine learning classifier accurately identified FOXF1/FENDRR cases in 2 independent cohorts. Patients treated according to German Multicenter Study Group for Adult ALL (GMALL)/Group for Research in Adult ALL (GRAALL) protocols showed very poor chemotherapy response with 8 of 13 exhibiting induction failure or minimal residual disease (MRD) &#x2265;10-3 and 8 of 12 remaining MRD positive after first consolidation/salvage. Intensification including blinatumomab (n = 10) and/or allogeneic stem cell transplantation (n = 12) resulted in ongoing molecular remission in 13 of 16 patients. FOXF1/FENDRR represents a novel B-ALL subtype which might benefit from early immunotherapeutic treatment or targeted interventions.

Humans↗

Alternative splicing of mouse transcription factors affects their DNA-binding domain architecture and is tissue specific.

BACKGROUND: Analyzing proteins in the context of all available genome and transcript sequence data has the potential to reveal functional properties not accessible through protein sequence analysis alone. To analyze the impact of alternative splicing on transcription factor (TF) protein structure, we constructed a comprehensive database of splice variants in the mouse transcriptome, called MouSDB3 containing 461 TF loci. RESULTS: Our analysis revealed that 62% of these loci in MouSDB3 have variant exons, compared to 29% of all loci. These variant TF loci contain a total of 324 alternative exons, of which 23% are in-frame. When excluded, 80% of in-frame alternative exons alter the domain architecture of the protein as computed by SMART (simple modular architecture research tool). Sixty-eight % of these exons directly affect the coding regions of domains important for TF function. Seventy-five % of the domains affected are DNA-binding domains. Tissue distribution analyses of variant mouse TFs reveal that they have more alternatively spliced forms in 14 of the 18 tissues analyzed when compared to all the loci in MouSDB3. Further, TF isoforms are homogenous within a given single tissue and are heterogeneous across different tissues, indicating their tissue specificity. CONCLUSIONS: Our study provides quantitative evidence that alternative splicing preferentially adds or deletes domains important to the DNA-binding function of the TFs. Analyses described here reveal the presence of tissue-specific alternative splicing throughout the mouse transcriptome. Our findings provide significant biological insights into control of transcription and regulation of tissue-specific gene expression by alternative splicing via creation of tissue-specific TF isoforms.

Alternative Splicing↗

EGassembler: online bioinformatics service for large-scale processing, clustering and assembling ESTs and genomic DNA fragments.

Expressed sequence tag (EST) sequencing has proven to be an economically feasible alternative for gene discovery in species lacking a draft genome sequence. Ongoing large-scale EST sequencing projects feel the need for bioinformatics tools to facilitate uniform EST handling. This brings about a renewed importance for a universal tool for processing and functional annotation of large sets of ESTs. EGassembler (http://egassembler.hgc.jp/) is a web server, which provides an automated as well as a user-customized analysis tool for cleaning, repeat masking, vector trimming, organelle masking, clustering and assembling of ESTs and genomic fragments. The web server is publicly available and provides the community a unique all-in-one online application web service for large-scale ESTs and genomic DNA clustering and assembling. Running on a Sun Fire 15K supercomputer, a significantly large volume of data can be processed in a short period of time. The results can be used to functionally annotate genes, to facilitate splice alignment analysis, to link the transcripts to genetic and physical maps, design microarray chips, to perform transcriptome analysis and to map to KEGG metabolic pathways. The service provides an excellent bioinformatics tool to research groups in wet-lab as well as an all-in-one-tool for sequence handling to bioinformatics researchers.

Computational Biology↗

Smc01944, a secreted peroxidase induced by oxidative stresses in Sinorhizobium meliloti 1021.

Sequencing of the Sinorhizobium meliloti strain 1021 genome led to the detection of 6204 open reading frames, 41 % of which have no hypothetical function. To help annotate this genome, a transcriptome analysis was carried out with a dedicated microarray consisting of 146 genes belonging to three different classes: (i) no hypothetical function; (ii) potentially involved in oxidative stress responses; (iii) known to participate in oxidative stress responses (e.g. catalase and superoxide dismutase genes). This transcriptome analysis, together with biological experiments and in silico investigations, identified new genes induced by exogenous H(2)O(2). The smc01944 gene was the most strongly induced: quantitative PCR showed that the amount of smc01944 mRNA increased 50-fold following the addition of 10 mM H(2)O(2), whereas the amount of katA mRNA (encoding a catalase) only increased 10-fold. Smc01944 is a non-haem chloroperoxidase (Cpo). The only member of this family to have been so far characterized is encoded by prxC of Pseudomonas fluorescens. Unexpectedly, the NH(2)-terminus of Smc01944 includes a signal peptide and Smc01944 is secreted into the supernatant. Interestingly, smc01944 is preceded by smc01945, encoding an OhrR-like regulator (MarR family). Thus, Smc01944 is the first exported Cpo encoded by a gene possibly regulated by an OhrR regulator. It was also shown that smc01944 is induced by t-butyl and cumene hydroperoxides but only slightly by menadione. The study of Smc01944 described in this work showed that the oxidative stress response of S. meliloti seems to differ from that of other bacteria characterized to date.

Amino Acid Sequence↗

Quantitative analysis of the cardiac fibroblast transcriptome-implications for NO/cGMP signaling.

Cardiac fibroblasts regulate tissue repair and remodeling in the heart. To quantify transcript levels in these cells we performed a comprehensive gene expression study using serial analysis of gene expression (SAGE). Among 110,169 sequenced tags we could identify 30,507 unique transcripts. A comparison of SAGE data from cardiac fibroblasts with data derived from total mouse heart revealed a number of fibroblast-specific genes. Cardiac fibroblasts expressed a specific collection of collagens, matrix proteins and metalloproteinases, growth factors, and components of signaling pathways. The NO/cGMP signaling pathway was represented by the mRNAs for alpha(1) and beta(1) subunits of guanylyl cyclase, cGMP-dependent protein kinase type I (cGK I), and, interestingly, the G-kinase-anchoring protein GKAP42. The expression of cGK I was verified by RT-PCR and Western blot. To establish a functional role for cGK I in cardiac fibroblasts we studied its effect on cell proliferation. Selective activation of cGK I with a cGMP analog inhibited the proliferation of serum-stimulated cardiac fibroblasts, which express cGK I, but not higher passage fibroblasts, which contain no detectable cGK I. Currently, our data suggest that cGK I mediates the inhibitory effects of the NO/cGMP pathway on cardiac fibroblast growth. Furthermore the SAGE library of transcripts expressed in cardiac fibroblasts provides a basis for future investigations into the pathological regulatory mechanisms underlying cardiac fibrosis.

Adaptor Proteins, Signal Transducing↗

A transcript finishing initiative for closing gaps in the human transcriptome.

We report the results of a transcript finishing initiative, undertaken for the purpose of identifying and characterizing novel human transcripts, in which RT-PCR was used to bridge gaps between paired EST clusters, mapped against the genomic sequence. Each pair of EST clusters selected for experimental validation was designated a transcript finishing unit (TFU). A total of 489 TFUs were selected for validation, and an overall efficiency of 43.1% was achieved. We generated a total of 59,975 bp of transcribed sequences organized into 432 exons, contributing to the definition of the structure of 211 human transcripts. The structure of several transcripts reported here was confirmed during the course of this project, through the generation of their corresponding full-length cDNA sequences. Nevertheless, for 21% of the validated TFUs, a full-length cDNA sequence is not yet available in public databases, and the structure of 69.2% of these TFUs was not correctly predicted by computer programs. The TF strategy provides a significant contribution to the definition of the complete catalog of human genes and transcripts, because it appears to be particularly useful for identification of low abundance transcripts expressed in a restricted set of tissues as well as for the delineation of gene boundaries and alternatively spliced isoforms.

Alternative Splicing↗

Screening for glycosylphosphatidylinositol-anchored proteins in the Paracoccidioides brasiliensis transcriptome.

Open reading frames in the transcriptome of Paracoccidioides brasiliensis were screened for potential glycosylphosphatidylinositol (GPI)-anchored proteins, which are a functionally and structurally diverse family of post-translationally modified molecules found in a variety of eukaryotic cells. Numerous studies have demonstrated that various GPI anchor sequences can affect the localization of these proteins in the plasma membrane or the cell wall. The GPI anchor core is produced in the endoplasmic reticulum by sequential addition of monosaccharides and phospho-ethanolamine to phosphatidylinositol. The complete GPI anchor is post-translationally attached to the protein carboxyl-terminus by GPI transamidases. Removal of this GPI lipid moiety by phospholipases generates a soluble form of the protein. The identification of putative GPI-attached proteins in the P. brasiliensis transcriptome was based on the following criteria: the presence of an N-terminal signal peptide for secretion and a hydrophobic region in the C-terminus presenting the GPI-attachment site. The proteins that were identified were in several functional categories: i) eight proteins were predicted to be enzymes (Gel1, Gel2, Gel3, alpha-amylase, aspartic proteinase, Cu-Zn SOD, DFG5, PLB); ii) Ag2/PRA, ELI-Ag1 and Gel1 are probably surface antigens; iii) Crh-like and the GPI-anchored cell wall protein have a putative structural role; iv) ECM33 and Gels (1, 2 and 3) are possibly involved in cell wall biosynthesis, and v) extracellular matrix protein is considered to be an adhesion protein. In addition, eight deduced proteins were predicted to localize in the plasma membrane and six in the cell wall. We also identified proteins involved in the synthesis, attachment and cleaving of the GPI anchor in the P. brasiliensis transcriptome.

Cell Wall↗

A single-nucleus transcriptome atlas of soybean anthers.

Anther development is crucial for plant sexual reproduction. However, a high-resolution, cell-type-specific transcriptomic atlas of this process is lacking for the legume crop soybean (Glycine max). Here, we construct a comprehensive transcriptional atlas of developing soybean anthers using single-nucleus RNA sequencing (snRNA-seq). We identify and characterize nine distinct cell types spanning both somatic and reproductive lineages. Our analysis reveals robust transcriptional continuity across anther developmental stages and dynamic reprogramming during key transitions. Notably, the shift from diploid meiocytes to haploid unicellular microspores is marked by the induction of previously inactive genes, despite an overall reduction in transcript abundance. Subsequently, within bicellular microspores, generative and vegetative cell lineages exhibit sharply divergent transcriptional programs: generative cells specialize in mRNA export and turnover, whereas vegetative cells up-regulate translational machinery. Evolutionary analysis further indicates that generative-cell-specific genes are subject to more relaxed purifying selection compared to those specific to vegetative cells. Functional validation using mutants generated by CRISPR/Cas9-mediated genome editing and EMS mutagenesis reveals the essential roles of OSD1A and PKSA in pollen development and fertility. This high-resolution atlas provides fundamental insights into the transcriptional regulation of soybean anther development and serves as a valuable resource for manipulating male fertility to advance hybrid breeding programs. The data are available at https://databases.genedenovo.com/pollen.

Glycine max↗

Transcriptome-wide N6-methyladenosine modification profiling of long non-coding RNAs in patients with recurrent implantation failure.

N6-methyladenosine (m6A) is involved in most biological processes and actively participates in the regulation of reproduction. According to recent research, long non-coding RNAs (lncRNAs) and their m6A modifications are involved in reproductive diseases. In the present study, using m6A-modified RNA immunoprecipitation sequencing (m6A-seq), we established the m6A methylation transcription profiles in patients with recurrent implantation failure (RIF) for the first time. There were 1443 significantly upregulated m6A peaks and 425 significantly downregulated m6A peaks in RIF. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses revealed that genes associated with differentially methylated lncRNAs are involved in the p53 signalling pathway and amino acid metabolism. The competing endogenous RNA network revealed a regulatory relationship between lncRNAs, microRNAs and messenger RNAs. We verified the m6A methylation abundances of lncRNAs by using m6A-RNA immunoprecipitation (MeRIP)-real-time polymerase chain reaction. This study lays a foundation for further exploration of the potential role of m6A modification in the pathogenesis of RIF.

Humans↗

Identification of a new Schistosoma mansoni membrane-bound protein through bioinformatic analysis.

Progress in schistosome genome research has enabled investigators to move rapidly from genome sequences to vaccine development. Proteins bound to the surface of parasites are potential vaccine candidates, or they can be used for diagnosis. We analyzed 4342 proteins deduced from the Schistosoma mansoni transcriptome with bioinformatic computer programs. Thirty-four proteins had membrane-bound motifs. Within this group, we selected the Sm29 protein to be further characterized by in silico analysis. Sm29 was found to have a signal peptide made up of 26 amino acids, with a cleavage site between Ser26 and Val27. The glycosylation site search revealed three threonines (39, 132 and 133) with high probability of O-glycosylation and two asparagines (58 and 115) with high probability of N-glycosylation. Only one transmembrane helix was found in the C-terminal region of the protein from Leu169 to Lis191. The search for similarities and conserved motifs show that Sm29 is a protein with high identity to proteins present in S. japonicum (53, 52, 49, and 37% of identity) and it possesses disulfide-rich conserved domains. Apparently, Sm29 is a membrane bound protein, and it may be an important molecule in host-parasite interactions.

Amino Acid Sequence↗

Ten quick tips for spatial transcriptomics analysis.

Spatial transcriptomics (ST) enables genome-wide gene expression profiling while retaining spatial context within tissue sections. Since the foundational work by St&#xe5;hl et al. in 2016, the field has expanded rapidly, with diverse platforms now spanning sequencing-based (e.g., Visium, Visium HD, Slide-seq, Stereo-seq, and Seq-Scope) and imaging-based (e.g., MERFISH, Xenium, and CosMx SMI) approaches. The breadth of platforms, data structures, and computational tools, however, can be daunting for newcomers. Here, we present ten quick tips spanning the entire ST research workflow: whether ST suits a given biological question, how to select a platform aligned with study objectives, how to understand and process ST data, and which software tools to employ for analysis and visualization. We further discuss interpreting spatial patterns in biological context, integrating complementary modalities such as single-cell RNA sequencing and spatial proteomics, and leveraging public datasets and sharing results. Finally, we highlight current limitations of ST, particularly the challenge of reconstructing three-dimensional tissue architecture from serial tissue sections. This review provides biologists, bioinformaticians, and clinician-scientists with a concise, platform-neutral roadmap for incorporating ST into research, from experimental design to biological discovery.

Spatial Transcriptomics↗

Distinguishing protein-coding from non-coding RNAs through support vector machines.

RIKEN's FANTOM project has revealed many previously unknown coding sequences, as well as an unexpected degree of variation in transcripts resulting from alternative promoter usage and splicing. Ever more transcripts that do not code for proteins have been identified by transcriptome studies, in general. Increasing evidence points to the important cellular roles of such non-coding RNAs (ncRNAs). The distinction of protein-coding RNA transcripts from ncRNA transcripts is therefore an important problem in understanding the transcriptome and carrying out its annotation. Very few in silico methods have specifically addressed this problem. Here, we introduce CONC (for "coding or non-coding"), a novel method based on support vector machines that classifies transcripts according to features they would have if they were coding for proteins. These features include peptide length, amino acid composition, predicted secondary structure content, predicted percentage of exposed residues, compositional entropy, number of homologs from database searches, and alignment entropy. Nucleotide frequencies are also incorporated into the method. Confirmed coding cDNAs for eukaryotic proteins from the Swiss-Prot database constituted the set of true positives, ncRNAs from RNAdb and NONCODE the true negatives. Ten-fold cross-validation suggested that CONC distinguished coding RNAs from ncRNAs at about 97% specificity and 98% sensitivity. Applied to 102,801 mouse cDNAs from the FANTOM3 dataset, our method reliably identified over 14,000 ncRNAs and estimated the total number of ncRNAs to be about 28,000.

Animals↗