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Transcriptional regulatory network analysis of developing human erythroid progenitors reveals patterns of coregulation and potential transcriptional regulators.

Deciphering the molecular basis for human erythropoiesis should yield information benefiting studies of the hemoglobinopathies and other erythroid disorders. We used an in vitro erythroid differentiation system to study the developing red blood cell transcriptome derived from adult CD34+ hematopoietic progenitor cells. mRNA expression profiling was used to characterize developing erythroid cells at six time points during differentiation (days 1, 3, 5, 7, 9, and 11). Eleven thousand seven hundred sixty-three genes (20,963 Affymetrix probe sets) were expressed on day 1, and 1,504 genes, represented by 1,953 probe sets, were differentially expressed (DE) with 537 upregulated and 969 downregulated. A subset of the DE genes was validated using real-time RT-PCR. The DE probe sets were subjected to a cluster metric and could be divided into two, three, four, five, or six clusters of genes with different expression patterns in each cluster. Genes in these clusters were examined for shared transcription factor binding sites (TFBS) in their promoters by comparing enrichment of each TFBS relative to a reference set using transcriptional regulatory network analysis. The sets of TFBS enriched in genes up- and downregulated during erythropoiesis were distinct. This analysis identified transcriptional regulators critical to erythroid development, factors recently found to play a role, as well as a new list of potential candidates, including Evi-1, a potential silencer of genes upregulated during erythropoiesis. Thus this transcriptional regulatory network analysis has yielded a focused set of factors and their target genes whose role in differentiation of the hematopoietic stem cell into distinct blood cell lineages can be elucidated.

Antigens, CD34↗

IDH2 clonal hematopoiesis and IKAROS loss cooperate in a B-ALL subtype after lenalidomide therapy for multiple myeloma.

Lenalidomide, a maintenance treatment in multiple myeloma first-line therapy, increases the risk of secondary malignancies, including B-cell precursor acute lymphoblastic leukemia (B-ALL). We present a comprehensive molecular characterization of 57 patients with lenalidomide-associated B-ALL (LenB-ALL), revealing 3 mutational subgroups: (1) TP53mt (30%); (2) IDH2mt (p.R140Q) (23%); and (3) other, including NRAS/KRASmt. Remarkably, IDH2 R140Q mutations were highly enriched in LenB-ALL compared with those in primary B-ALL (P< .001). Furthermore, IKZF1 intragenic deletions, often subclonal and likely RAG recombinase-mediated, were observed in 54% (7/13) of IDH2mt patients with LenB-ALL. IDH2 mutations were not restricted to the leukemic clone: they persisted during measurable residual disease-negative remission and were identified in lymphoid as well as myeloid cell populations using fluorescence-activated cell sorting and single-cell RNA sequencing. This indicates a preleukemic origin of the IDH2 mutation within the context of clonal hematopoiesis. Transcriptomic and DNA methylation analyses revealed a distinct gene expression profile and a DNA hypermethylation phenotype in IDH2mt LenB-ALL, including IDH2mt-specific as well as lenalidomide-associated features. We propose that lenalidomide promotes the expansion of IDH2-mutated clonal hematopoiesis and, via IKAROS downregulation, induces a maturation arrest at the B-cell precursor stage. Subsequent genetic or epigenetic alterations render leukemogenesis independent of ongoing lenalidomide exposure. All these data define IDH2mt B-ALL as a distinct molecular subtype that is markedly overrepresented after lenalidomide treatment and highlight clonal hematopoiesis as a key contributing factor in the development of LenB-ALL.

Humans↗

Large-scale screening of genes responsible for silique length and seed size in Brassica Napus via pooled CRISPR library.

BACKGROUND: Enhancing rapeseed (Brassica napus, B. napus) yield is critical for ensuring global vegetable oil security. However, yield is heavily influenced by silique development and seed size, the enhancement of which is limited by scarce genetic resources. The CRISPR/Cas9 system has emerged as a powerful tool for constructing genome-wide mutant libraries, even in polyploid crops with complex genomes. RESULTS: The transcriptome-wide association study (TWAS) data, tissue-specific expression profiles data and reported genes were integrated to identify candidate genes regulating silique development and seed size. We constructed a sgRNA library targeting these genes and generated a CRISPR/Cas9 editing mutant library through genetic transformation. Specifically, 6124 sgRNAs were designed for 1739 candidate genes with &#x2266;&#x2009;4 orthologues. 681 T0 plants were obtained through genetic transformation, which harbor 453 sgRNAs. Of 408 T0 plants analyzed, 151 (37.00%) exhibited successful gene editing events, targeting 84 candidate genes. Ten homozygous mutant plants were isolated and preliminary phenotypic analysis was performed in mutants targeting the BnaHRDs. The results suggest that mutations in BnaHRD.A03 and BnaHRD.C03 may modulate plant height (PH), main inflorescence length (MIL), silique length (SL), effective silique number per plant (ENS), seed number per silique (SNPS), and thousand-seed weight (TSW). CONCLUSIONS: This study harnessed the CRISPR/Cas9 technology to establish a preliminary library of gene-edited mutants in B. napus, thereby laying a robust foundation for the future screening of candidate genes pertaining to silique development and seed size. Furthermore, this study provides a methodological framework for rapid functional gene discovery in B. napus through CRISPR-based approaches.

Brassica napus↗

Characterization and analysis of the full-length transcriptome of Frankliniella occidentalis (Thysanoptera: Thripidae).

BACKGROUND: Frankliniella occidentalis, an insect belonging to the order Thysanoptera, causes severe damage to agricultural and horticultural crops, resulting in significant economic losses worldwide. The development of molecular and sequencing technologies has helped elucidate the molecular mechanisms regulating its growth and development as well as its damaging activity. However, much remains to be explored. To further investigate the molecular complexity of this species, we sequenced the full-length transcriptome of mixed samples obtained from specimens at all developmental stages. RESULTS: Of all transcripts, 89.04% matched with the reference genome; additionally, 29,750 alternative splicing events, 2,342 genes with poly(A) sites, and 153 candidate fusion transcript events were identified, and 4,235 long noncoding RNAs were discovered. CONCLUSIONS: This is the first full-length transcriptome of F. occidentalis reported to date. This study greatly contributes to the understanding of the molecular complexity and diversity of this insect, providing a basis to develop specific molecular targets as well as resources for gene function studies in other insects.

Animals↗

Prediction of higher order functional networks from genomic data.

Post-genomics may be defined in different ways depending on how one views the challenges after the discovery of the genome. A traditional view is to follow the concept of the central dogma in molecular biology, namely from genome to transcriptome to proteome. Projects are ongoing to analyse gene expression profiles both at the mRNA and protein levels, and to catalogue protein 3D structure families, which will no doubt help the understanding of the information in the genome. However, once complete, such experimentally determined catalogues of genes, RNAs and proteins only tell us about the building blocks of life. They do not tell us much about how life operates as a system, such as higher order functional behaviours of the cell or the organism. Thus, an alternative view of post-genomics is to go up from the molecular level to the cellular level and eventually to still higher levels, i.e., the biological systems. Bioinformatics provides basic concepts as well as practical methods to integrate this view with the traditional view and to analyse complex interactions among building blocks and with dynamic environments.

Computational Biology↗

ZBTB16-associated NK cell alterations reveal shared immunometabolic signatures linking primary Sj&#xf6;gren's syndrome and type 1 diabetes mellitus.

BACKGROUND: Primary Sj&#xf6;gren's syndrome (pSS) and type 1 diabetes mellitus (T1DM) share immune-inflammatory features, yet conserved pathogenic signatures linking these autoimmune disorders remain incompletely understood. The present research sought to uncover common molecular markers and dissect the underlying immune-metabolic cross-talk underlying pSS and T1DM. METHODS: Gene expression profiles of patients with pSS and T1DM were retrieved from the Gene Expression Omnibus database, normalized, and corrected for batch effects prior to downstream analyses. Overlapping potential biomarkers were screened by integrating differential expression analysis, weighted gene co-expression network analysis and least absolute shrinkage and selection operator regression. Functional enrichment based on Gene Ontology and Kyoto Encyclopedia of Genes and Genomes databases was implemented to interpret gene biological properties, and a protein-protein interaction network was further established afterwards. Diagnostic performance was evaluated using receiver operating characteristic analysis. Experimental validation was conducted in non-obese diabetic (NOD) mice using quantitative PCR, immunohistochemistry, and flow cytometry. The CIBERSORT algorithm was adopted to quantify immune cell infiltration levels. RESULTS: ZBTB16 was identified as a shared hub biomarker in both pSS and T1DM and exhibited favorable diagnostic performance. Experimental validation confirmed significantly reduced ZBTB16 expression in peripheral blood mononuclear cells, salivary gland tissues, and pancreatic tissues of NOD mice. Gene Set Enrichment Analysis indicated that ZBTB16-associated signatures were enriched in mitochondrial-related processes, neuroactive ligand-receptor interactions, and ribosome-related pathways. Immune infiltration analysis revealed that resting natural killer (NK) cells were positively correlated with ZBTB16 expression in both diseases. Flow cytometric analysis further confirmed a reduced proportion of resting NK cells in peripheral blood of NOD mice, consistent with the CIBERSORT-based prediction. CONCLUSION: This study identifies ZBTB16 as a shared biomarker linking pSS and T1DM. Reduced resting NK-cell abundance was consistently observed in both computational and experimental analyses, and bioinformatic correlation analysis suggested a positive association with ZBTB16 expression. These findings provide evidence for shared molecular and immunological signatures underlying the two autoimmune disorders and support further investigation of the biological role and diagnostic value of ZBTB16 in pSS and T1DM.

Sjogren's Syndrome↗

Systematic mining and characterization of metal transporter families regulating zinc homeostasis provide insights into metal homeostasis in Camellia sinensis.

BACKGROUND AND AIMS: Zinc is essential for tea plant growth and quality formation, yet its homeostatic mechanisms remain poorly understood. This study identified metal transporter families regulating zinc homeostasis, analyzed their evolution, structure, and expression, and clarified zinc uptake, transport, detoxification networks, and their links to metabolism. METHODS: This study identified zinc homeostasis-related metal transporter families in the tea plant genome, characterized their structural features and expression profiles across tissues and developmental stages through integrative bioinformatics and transcriptomic analyses, and delineated the molecular mechanisms underlying zinc uptake, translocation, and detoxification by systematically integrating published evidence. RESULTS: This study identified 74 metal transporter genes from six families: 13 CsZIPs, 12 CsNRAMPs, 10 CsHMAs, 10 CsYSLs, 14 CsMTPs, and 15 CsCAXs in the 'Shuchazao2' genome, revealing closer affinity to woody species than to Arabidopsis. These proteins exhibit conserved domains, diverse subcellular localizations (cell membrane, vacuole, chloroplast, and Golgi apparatus), and tissue-specific expression with abundant stress/hormone-responsive cis-elements. At the plant-soil interface, tea plants mobilize rhizospheric zinc via proton and organic acid secretion; CsYSLs, CsNRAMPs, and CsZIPs mediate zinc uptake, aided by arbuscular mycorrhizal fungi (AMF) and plant growth-promoting rhizobacteria (PGPR) that expand root absorption zones. Xylem CsHMAs and phloem CsYSLs coordinate root-to-shoot zinc translocation, and vacuolar transporters (CsMTPs, CsCAXs), cell wall immobilization, and antioxidant systems alleviate high-zinc stress injury. CONCLUSIONS: These findings collectively delineate an integrated zinc "acquisition-distribution-buffering" network in tea plants, offering a repertoire of candidate genes with potential utility in zinc biofortification breeding and improving acid soil adaptation. Further experimental validation, including tea&#xa0;transgenesis, zinc-stress qRT-PCR, and heterologous functional complementation, is essential to substantiate their biological roles.

Camellia sinensis↗

Meta-Merging the Transcriptomes of Gastric Tumors Redefines the Connections among Molecular and Clinical Subtypes.

INTRODUCTION: The availability of a large number of cancer expression profiles presents an excellent opportunity to re-investigate various biological and clinical questions. While several expression profiles have been established for different cancers, merging them may provide a more powerful platform for extensively extrapolating molecular and clinical features across multiple cohorts. MATERIALS AND METHODS: In this study, five gastric tumor expression profiles from the Gene Expression Omnibus [GEO] and one in-house cohort comprising a total of 1,060 samples were merged. The batch effect was removed using non-parametric ComBat analysis, and the seamless merging of datasets was confirmed through various parameters. RESULTS: Extrapolation of ACRG [Asian Cancer Research Group] and TCGA [The Cancer Genome Atlas] molecular subtypes in the merged cohort of 1,060 gastric tumors revealed nine distinct clusters. Notably, the following patterns were observed: [i] mutual exclusivity between Epithelial to Mesenchymal Transition [EMT] and Microsatellite Instability [MSI] subtypes in 90% of tumors; [ii] overlapping occurrence of EMT and MSI subtypes in the remaining tumors; [iii] overlap between MSI and Epstein-Barr Virus [EBV] subtype tumors; [iv] both commonalities and differences between EMT and Genomically Stable [GS] subtypes; and [v] an association between EBV positivity and PI3K mutation. CONCLUSION: The current study demonstrates that compiling a larger expression profile is valuable for revisiting the molecular features and epidemiology associated with molecular subtypes, thereby aiding in the development of novel diagnostics and targeted therapeutics.

Humans↗

Global transcriptome analysis of the C57BL/6J mouse testis by SAGE: evidence for nonrandom gene order.

BACKGROUND: We generated the gene expression profile of the total testis from the adult C57BL/6J male mice using serial analysis of gene expression (SAGE). Two high-quality SAGE libraries containing a total of 76 854 tags were constructed. An extensive bioinformatic analysis and comparison of SAGE transcriptomes of the total testis, testicular somatic cells and other mouse tissues was performed and the theory of male-biased gene accumulation on the X chromosome was tested. RESULTS: We sorted out 829 genes predominantly expressed from the germinal part and 944 genes from the somatic part of the testis. The genes preferentially and specifically expressed in total testis and testicular somatic cells were identified by comparing the testis SAGE transcriptomes to the available transcriptomes of seven non-testis tissues. We uncovered chromosomal clusters of adjacent genes with preferential expression in total testis and testicular somatic cells by a genome-wide search and found that the clusters encompassed a significantly higher number of genes than expected by chance. We observed a significant 3.2-fold enrichment of the proportion of X-linked genes specific for testicular somatic cells, while the proportions of X-linked genes specific for total testis and for other tissues were comparable. In contrast to the tissue-specific genes, an under-representation of X-linked genes in the total testis transcriptome but not in the transcriptomes of testicular somatic cells and other tissues was detected. CONCLUSION: Our results provide new evidence in favor of the theory of male-biased genes accumulation on the X chromosome in testicular somatic cells and indicate the opposite action of the meiotic X-inactivation in testicular germ cells.

Animals↗

Identification and characterization of G protein-coupled receptors in the nocturnal halictid bee Megalopta genalis.

G protein-coupled receptors (GPCRs) are one of the largest families of membrane proteins in insects, regulating vision, neural signal transduction, and various physiological behaviors. Megalopta genalis exhibits a unique facultatively eusocial lifestyle and possesses adaptations for nocturnal activity; however, its GPCR family has not yet been systematically characterized. In this study, we performed genome-wide identification, phylogenetic analysis, and expression profiling of GPCRs in M. genalis by integrating genomic annotation and transcriptomic analysis. The results showed that a total of 99 GPCRs were identified in the genome of M. genalis, which were classified into four major families. Here, we show that M. genalis has undergone lineage-specific GPCR repertoire remodeling, marked by the expansion of novel orphan receptors and the systematic loss of multiple receptor subtypes, such as the neuropeptide receptors MIP-R and NPFR. Moreover, opsins have formed a diverse array of combinations and non-GPCR odorant receptors have undergone significant expansion via tandem duplication. Together, these features may represent part of the molecular repertoire associated with the adaptation of M. genalis to a nocturnal lifestyle. Furthermore, transcriptomic analysis revealed distinct spatiotemporal expression divergence within each of the Mth/Mthl and Fz GPCR families, suggesting functional specialization across development and adult tissues. This study provides the first systematic identification and initial functional characterization of GPCRs in M. genalis, revealing an evolutionary pattern characterized by the coexistence of contraction and expansion within the GPCR family. These findings lay a foundation for further studies aimed at elucidating the roles of these GPCRs in regulating M. genalis physiology and behavior.

Animals↗

Characterization of antirrhinum petal development and identification of target genes of the class B MADS box gene DEFICIENS.

The class B MADS box transcription factors DEFICIENS (DEF) and GLOBOSA (GLO) of Antirrhinum majus together control the organogenesis of petals and stamens. Toward an understanding of how the downstream molecular mechanisms controlled by DEF contribute to petal organogenesis, we conducted expression profiling experiments using macroarrays comprising >11,600 annotated Antirrhinum unigenes. First, four late petal developmental stages were compared with sepals. More than 500 ESTs were identified that comprise a large number of stage-specifically regulated genes and reveal a highly dynamic transcriptional regulation. For identification of DEF target genes that might be directly controlled by DEF, we took advantage of the temperature-sensitive def-101 mutant. To enhance the sensitivity of the profiling experiments, one petal developmental stage was selected, characterized by increased transcriptome changes that reflect the onset of cell elongation processes replacing cell division processes. Upon reduction of the DEF function, 49 upregulated and 52 downregulated petal target genes were recovered. Eight target genes were further characterized in detail by RT-PCR and in situ studies. Expression of genes responding rapidly toward an altered DEF activity is confined to different petal tissues, demonstrating the complexity of the DEF function regulating diverse basic processes throughout petal morphogenesis.

Antirrhinum↗

Transcriptional profiles of Microcystis reveal gene expression shifts that promote bloom persistence in in situ mesocosms.

Harmful algal blooms caused by cyanobacteria threaten aquatic ecosystems, the economy, and human health. Previous work has tried to identify the mechanisms that allow blooms to form, focusing on the role of nutrients. However, little is known about how introduced nutrients influence gene expression in situ. To address this knowledge gap, we used in situ mesocosms initiated with water experiencing a Microcystis bloom. We added pulses of nutrients that are commonly associated with anthropogenic sources to the mesocosms for 72 hours and collected samples for metatranscriptomics to examine how the physiological function of Microcystis and bloom status changed. The addition of nitrogen (N) as urea, but not the addition of PO4, resulted in conspicuous bloom persistence for at least 9 days after the final introduction of nutrients. The addition of urea initially resulted in the upregulation of photosynthesis machinery, as well as phosphate, carbon, and N transport and metabolism. Once Microcystis presumably became N-replete, upregulation of amino acid metabolism, microcystin biosynthesis, and other processes associated with biomass generation occurred. These capacities coincided with the upregulation of toxin-antitoxin systems, CRISPR-cas genes, and transposases suggesting that phage defense and genome rearrangement are critical in bloom persistence. Overall, our results show the stepwise transcriptional response of a Microcystis bloom to the introduction of nutrients, specifically urea, as it is sustained in a natural setting. The transcriptomic shifts observed herein may serve as markers of the longevity of blooms while providing insight into why Microcystis blooms over other cyanobacteria.IMPORTANCEHarmful algal blooms represent a threat to human health and ecosystems. Understanding why blooms persist may help us develop warning indicators of bloom persistence and create novel mitigation strategies. Using mesocosm experiments initiated with water with an active bloom, we measured the stepwise transcription changes of the toxin-producing cyanobacterium Microcystis in response to the addition of nutrients that are important in causing blooms. We found that nitrogen (N), but not phosphorus, promoted bloom longevity. The initial introduction of N resulted in the upregulation of genes involved in photosynthesis and N import. At later times in the bloom, upregulation of genes involved in biomass generation, phage protection, genomic rearrangement, and toxin production was observed. Our results suggest that Microcystis first fulfills nutritional requirements before investing energy in pathways associated with growth and protection against competitors, which allowed bloom persistence more than a week after the final addition of nutrients.

Microcystis↗

Defining the human macula transcriptome and candidate retinal disease genes using EyeSAGE.

PURPOSE: To develop large-scale, high-throughput annotation of the human macula transcriptome and to identify and prioritize candidate genes for inherited retinal dystrophies, based on ocular-expression profiles using serial analysis of gene expression (SAGE). METHODS: Two human retina and two retinal pigment epithelium (RPE)/choroid SAGE libraries made from matched macula or midperipheral retina and adjacent RPE/choroid of morphologically normal 28- to 66-year-old donors and a human central retina longSAGE library made from 41- to 66-year-old donors were generated. Their transcription profiles were entered into a relational database, EyeSAGE, including microarray expression profiles of retina and publicly available normal human tissue SAGE libraries. EyeSAGE was used to identify retina- and RPE-specific and -associated genes, and candidate genes for retina and RPE disease loci. Differential and/or cell-type specific expression was validated by quantitative and single-cell RT-PCR. RESULTS: Cone photoreceptor-associated gene expression was elevated in the macula transcription profiles. Analysis of the longSAGE retina tags enhanced tag-to-gene mapping and revealed alternatively spliced genes. Analysis of candidate gene expression tables for the identified Bardet-Biedl syndrome disease gene (BBS5) in the BBS5 disease region table yielded BBS5 as the top candidate. Compelling candidates for inherited retina diseases were identified. CONCLUSIONS: The EyeSAGE database, combining three different gene-profiling platforms including the authors' multidonor-derived retina/RPE SAGE libraries and existing single-donor retina/RPE libraries, is a powerful resource for definition of the retina and RPE transcriptomes. It can be used to identify retina-specific genes, including alternatively spliced transcripts and to prioritize candidate genes within mapped retinal disease regions.

Adult↗

Genome-wide identification and cold-stress-responsive expression analysis of the NOX gene family in Cucumis melo.

NADPH oxidases (NOXs) are crucial enzymes for reactive oxygen species (ROS) generation in plants and play vital roles in growth, development, and stress responses. To elucidate the sequence characteristics of the NOX gene family and its low-temperature response patterns in melon (Cucumis melo L.), this study conducted genome-wide identification and expression profiling of NOX family members using bioinformatics analysis, RNA-seq transcriptome sequencing, and real-time quantitative PCR (RT-qPCR). The results revealed that eight NOX members were identified in the melon genome, distributed across six chromosomes. All members harbored conserved domains including Ferric_reductase, FAD_binding_8, NAD_binding_6, and NADPH_Ox, and the encoded proteins were generally basic and hydrophilic. Phylogenetic analysis classified the NOX proteins into five subgroups. Synteny analysis indicated the presence of only one pair of intraspecific duplicated genes in melon, which was under purifying selection. The promoter regions contained multiple hormone- and stress-responsive cis-acting elements, with CmNOX2 and CmNOX4 harboring low-temperature responsive elements. Following treatment at 4&#x2103; for 24 h and 48 h, leaf relative electrolyte leakage (REL) increased from 28.33% to 42.67% and 52.67%, respectively; transcriptome analysis identified 5,633 and 6,882 differentially expressed genes (DEGs), respectively. Cold-responsive genes exhibited significant differential expression, with SLAC1 and CPK19 showing sustained upregulation. RT-qPCR results demonstrated that the expression of CmNOX2, CmNOX5, CmNOX6, and CmNOX7 was significantly downregulated after low-temperature treatment, whereas CmNOX4 expression was significantly upregulated at 48 h. Integrating promoter elements and expression characteristics, CmNOX4 may represent an important candidate gene involved in melon low-temperature response. This study systematically characterized the structure, evolution, and expression patterns of the melon NOX gene family, identified candidate genes responsive to low temperature, and provides a reference for further investigation into the mechanisms underlying melon cold adaptation.

Cucumis melo↗

Expression profile of the channel catfish spleen: analysis of genes involved in immune functions.

Both qualitative and quantitative patterns of tissue-specific gene expression can be determined using gene profiling. Expressed sequence tag (EST) analysis is an efficient approach not only for gene discovery and examining gene expression, but also for development of molecular resources useful for functional genomics. As part of an ongoing transcriptome analysis of channel catfish (Ictalurus punctatus), EST analysis was conducted for gene annotations and profiling using a complementary DNA library developed from messenger RNA of the spleen. A total of 1204 spleen cDNA clones were analyzed. Of the 1204 clones, 665 clones (55.2%) were identified as orthologs of known genes from other organisms by BLAST searches and 539 clones (44.8%) as unknown gene clones. In total 147 novel genes were identified, and annotations were made to 118 of them. In addition, 389 novel EST clusters were identified. Expression profile was analyzed in relation to metabolic functional groups. A total of 28 known genes were involved in immune functions, of which 10 were identified for the first time in channel catfish. Microsatellite-containing clones were also identified that may be potentially useful for genome mapping. This work contributed to the Catfish Gene Index, and toward a Unigene set useful for functional genomics research concerning spleen gene functions in relation to disease defenses.

Journal Article↗

Temporal gene expression profiling of dystrophin-deficient (mdx) mouse diaphragm identifies conserved and muscle group-specific mechanisms in the pathogenesis of muscular dystrophy.

Mutations in dystrophin are the proximate cause of Duchenne muscular dystrophy (DMD), but pathogenic mechanisms linking the absence of dystrophin from the sarcolemma to myofiber necrosis are not fully known. The muscular dystrophies also have properties not accounted for by current disease models, including the temporal delay to disease onset, broad species differences in severity, and diversity of skeletal muscle responses. To address the mechanisms underlying the differential targeting of muscular dystrophy, we characterized temporal expression profiles of the diaphragm in dystrophin-deficient (mdx) mice between postnatal days 7 and 112 using oligonucleotide microarrays and contrasted these data with published hindlimb muscle data. Although the diaphragm and hindlimb muscle groups differ in severity of response to dystrophin deficiency, and exhibited substantial divergence in some transcript categories including inflammation and muscle-specific genes, our data show that the general mechanisms operative in muscular dystrophy are highly conserved. The two muscle groups principally differed in expression levels of differentially regulated genes, as opposed to the non-conserved induced/repressed transcripts defining fundamentally distinct mechanisms. We also identified a postnatal divergence of the two wild-type muscle group expression profiles that temporally correlated with the onset and progression of the dystrophic process. These findings support the hypothesis that conserved disease mechanisms interacting with baseline differences in muscle group-specific transcriptomes underlie their differential responses to DMD. We further suggest that muscle group-specific transcriptional profiles contribute toward the muscle targeting and sparing patterns observed for a variety of metabolic and neuromuscular diseases.

Animals↗

A four-tiered transcriptional regulatory circuit controls flagellar biogenesis in Pseudomonas aeruginosa.

The single polar flagellum of Pseudomonas aeruginosa is an important virulence and colonization factor of this opportunistic pathogen. In this study, the annotation of the genes belonging to the fla regulon was updated and their organization was analysed in strains PAK and PAO1, representative type-a and type-b strains of P. aeruginosa respectively. The flagellar genes are clustered in three non-contiguous regions of the chromosome. A polymorphic locus flanked by flgJ and fleQ in Region I contains a glycosylation island in PAK. The expression and ordered assembly of the complex multicomponent flagellum is intricately regulated. Dedicated flagellar genes fleQ, fleS, fleR, fliA, flgM and fleN encode proteins that participate in the regulation of the flagellar transcriptional circuit. In addition, expression of the flagellum is coordinately regulated with other P. aeruginosa virulence factors by the alternative sigma factor sigma54, encoded by rpoN. In order to gain insight into the hierarchical regulation of flagellar genes, deletion mutations were constructed in fleQ, fleR, fliA and rpoN. The transcriptional impact of these mutations was examined by transcriptional profiling using a P. aeruginosa whole genome microarray. Analysis of the transcriptomes generated for each of these mutants indicates a four-tiered (Classes I-IV) hierarchy of transcriptional regulation. Class I genes are constitutively expressed and include the transcriptional regulator fleQ and the alternative sigma factor fliA (sigma28). Class II genes including fleSR, encoding a two-component regulatory system require FleQ and RpoN (sigma54) for their transcriptional activation. Class III genes are positively regulated by the activated response regulator FleR in concert with RpoN. The transcription of Class IV genes is dependent on the availability of free FliA following the export of the FliA specific antisigma factor FlgM through the basal body rod-hook structure (assembled from Class II and III gene products). Two previously uncharacterized genes, which are coordinately regulated with known flagellar genes have been identified by genome-wide analysis and their role in flagellar biogenesis was analysed.

Bacterial Proteins↗

Mechanisms of patulin toxicity under conditions that inhibit yeast growth.

Patulin, 4-hydroxy-4H-furo[3,2c]pyran-2(6H)-one, is one of the best characterized and most widely disseminated mycotoxins found in agricultural products. Nonetheless, the mechanisms by which patulin causes toxicity are not well understood. Thus, the cytotoxicity of patulin was characterized by analysis of the yeast transcriptome upon challenge with patulin. Interestingly, patulin-induced yeast gene expression profiles were found to be similar to gene expression patterns obtained after treatment with the antifungal agricultural chemicals thiuram, maneb, and zineb. Moreover, patulin treatment was found to activate protein degradation, especially proteasome activities, sulfur amino acid metabolism, and the defense system for oxidative stress. Damage to DNA by alkylation was also suggested, and this seemed to be repaired by recombinational and excision repair mechanisms. Furthermore, the results provide potential biomarker genes for the detection of patulin in agricultural products. The results suggest the possibility of applying the yeast transcriptome system for the evaluation of chemicals, especially for natural chemicals that are difficult to get by organic synthesis.

Amino Acids, Sulfur↗