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Transcriptomics and proteomics: advancing the understanding of genetic basis of fracture healing.

Fracture healing is a complex physiological post-natal process, which involves the coordination of several different cell types. Exploring the orchestration of events and the simultaneous activation of osteogenesis and chondrogenesis that recapitulates mammalian embryological skeletal development seems to be not only sophisticated but also challenging. A large number of genes involved in the above process are known, but many more remain to be discovered. The functional characterisation of these genes promises to elucidate the repair process as well as skeletal abnormalities and aging. We here review the current knowledge on early and late gene expression during fracture healing, the genes so far associated with osteoblast and osteoclast differentiation, the BMP antagonists, and the Wnts signalling pathway.

Bone Morphogenetic Proteins↗

Transcriptome profile within the mouse central nervous system and activation of myelin-reactive T cells following murine coronavirus infection.

Multiple sclerosis (MS) is an autoimmune disease associated with environmental factors, possibly including several viruses such as the coronaviruses. Indeed, murine coronavirus (MHV) infection provides a well-known experimental model for MS studies. Intracerebral infection of C57BL/6 mice with MHV-A59 revealed that viral replication was efficient and that clearance of infectious virus occurred as soon as 7 days post-infection. Using cDNA arrays, analysis of gene expression profile in the brain revealed a modulation of 80 different genes following infection, with at least 27 of these genes having previously been directly related to innate or acquired immune responses. Concordingly, an important activation of auto-reactive T cells specific to myelin basic protein was demonstrated. Altogether, these results indicate that an MHV infection of the central nervous system (CNS) leads to an important host genomic response implicating immunity-related genes and to the activation of myelin-reactive autoimmune T cells.

Animals↗

Integrated application of transcriptomics and metabonomics yields new insight into the toxicity due to paracetamol in the mouse.

Gene chip array (Affymetrix) data from liver tissue and high resolution 1H NMR spectra from intact liver tissue, tissue extracts and plasma have been analyzed to identify biochemical changes arising from hepatotoxicity in mice dosed with acetaminophen. These data sets have been co-interpreted in terms of common metabolic pathways. The principal metabolic changes comprised a decrease in hepatic glucose and glycogen in intact tissue, coupled with an increase in lipid content, with increases in the levels of glucose, pyruvate, acetate and lactate in plasma, and increases in alanine and lactate in the aqueous tissue extracts. Collectively these data provide evidence for an increased rate of hepatic glycolysis. The metabolic observations were consistent with the altered levels of gene expression relating to lipid and energy metabolism in liver which both preceded and were concurrent with the metabolic perturbations. The results show that these two technology platforms together offer a complementary view into cellular responses to toxic processes, providing new insight into the toxic consequences, even for well-studied therapeutic agents such as acetaminophen.

Acetaminophen↗

Assessment of representational difference analysis (RDA) to construct informative cDNA microarrays for gene expression analysis of species with limited transcriptome information, using red and green tomatoes as a model.

Microarray technology makes it feasible to analyse the expression of thousands of different gene elements in a single experiment. Most informative are 'whole genome' arrays, where all gene expression products of a single species or variety are represented. Such arrays are now available for a limited number of model species. However, for other, less well-documented species other routes are still necessary to obtain informative arrays. This includes the use of cDNA libraries. To enhance the amount of information that can be obtained from cDNA libraries, redundancy needs to be minimised, and the number of cDNAs relevant for the conditions of interest needs to be increased. Here, we used representational difference analysis (RDA), a mRNA subtraction procedure, as a tool to enhance the efficiency of cDNA libraries to be used to generate microarrays. Tomato was chosen as a model system for a less well-documented species. cDNA libraries for two distinct physiological conditions of tomato fruits, red and green, were made. The libraries were characterized by sequencing and hybridisation analysis. The RDA procedure was shown to be effective in selecting for genes of relevance for the physiological conditions under investigation, and against constitutively expressed genes. At the same time, redundancy was reduced, but complete normalisation was not obtained, and subsequent sequence analysis will be required to obtain non-redundant arrays. Further, known and putative ripening-related cDNAs were identified in hybridisation experiments on the basis of RNA populations as isolated from the green and red stage of ripening.

Fruit↗

Genome-wide profiling of segmental-regulated transcriptomes in human epididymis using oligo microarray.

Sperm maturation during passage through the epididymis depends on regionalized gene expression which maintains the progressively changing environment within the epididymal tubule. Towards defining the genes that drive the sequential maturation of spermatozoa, we profiled regionally regulated gene expression pattern in the epididymis of a fertile young male donor using Affymetrix human genome U133 plus 2.0 microarray representing approximately the whole human genome. Over 15000 transcripts, almost one-third of the total on the array were identified in whole epididymis. Among them, 65% were detected in all three regions of the epididymis, 410 or 2.6% were present only in one region and the remaining 32.4% were distributed in two regions. Region-specific transcripts observed in caput (264), corpus (61) and cauda (81) epididymides were further classified as empirically determined reported genes or ESTs. This study revealed for the first time, the expression in human epididymis of a number of region-specific genes. The original data will be made publicly available on the Shanghai Science and Technology Database (http://www.scbit.org/human_epididymis_transcriptomes).

Adult↗

Transcriptome of axenic liver stages of Plasmodium yoelii.

Plasmodium liver stages or early exo-eythrocytic forms (EEFs) contain antigens that are essential for achieving sterile, protective immunity against malaria. Yet, attempts at identifying these antigens have been hampered by the challenge of obtaining large numbers of purified EEFs, uncontaminated with hepatocyte material. Using a recently described system for producing axenically cultured EEFs from Plasmodium yoelii, we have constructed a cDNA library and generated 1453 expressed sequence tags (ESTs) resulting in 652 unique transcripts. Analysis of the library provides insight into processes required for the initiation and development of Plasmodium liver stages, such as protein degradation, cell cycle progression and nutrient transport. Analysis of the gene expression profile of liver stages, as revealed by this library, suggests that liver stages represent a shift from "sporozoite-like" to "blood-stage-like". This is the first study of the transcriptional repertoire of Plasmodium liver stages.

Animals↗

The transcriptomes of Trypanosoma brucei Lister 427 and TREU927 bloodstream and procyclic trypomastigotes.

We describe developmentally regulated genes in two strains of Trypanosoma brucei: the monomorphic strain Lister 427 and the pleomorphic strain TREU927. Expression patterns were obtained using an array of 24,567 genomic fragments. Probes were prepared from bloodstream-form or procyclic-form trypanosomes. Fourteen procyclic-specific and 77 bloodstream-specific signals were obtained from sequences matching variant surface glycoprotein or associated genes, and a further 17 regulated sequences were repetitive or transposable-element-related. Two hundred and eighty-six regulated spots corresponded to mRNAs from other protein-coding genes; these spots represent 191 different proteins. Regulation of 113 different genes (79 from procyclic forms, 34 from bloodstream-forms) was supported by at least two independent experiments or criteria; of these, about 60 were novel. Only two genes -- encoding HSP83 and an importin-related protein -- appeared to be regulated in the TREU927 strain only. Our results confirmed previous estimates that 2% of trypanosome genes show developmental regulation at the mRNA level.

Animals↗

Transcriptome analysis of Anopheles stephensi-Plasmodium berghei interactions.

Simultaneous microarray-based transcription analysis of 4987 Anopheles stephensi midgut and Plasmodium berghei infection stage specific cDNAs was done at seven successive time points: 6, 20 and 40h, and 4, 8, 14 and 20 days after ingestion of malaria infected blood. The study reveals the molecular components of several Anopheles processes relating to blood digestion, midgut expansion and response to Plasmodium-infected blood such as digestive enzymes, transporters, cytoskeletal and structural components and stress and immune responsive factors. In parallel, the analysis provide detailed expression patterns of Plasmodium genes encoding essential developmental and metabolic factors and proteins implicated in interaction with the mosquito vector and vertebrate host such as kinases, transcription and translational factors, cytoskeletal components and a variety of surface proteins, some of which are potent vaccine targets. Temporal correlation between transcription profiles of both organisms identifies putative gene clusters of interacting processes, such as Plasmodium invasion of the midgut epithelium, Anopheles immune responses to Plasmodium infection, and apoptosis and expulsion of invaded midgut cells from the epithelium. Intriguing transcription patterns for highly variable Plasmodium surface antigens may indicate parasite strategies to avoid recognition by the mosquito's immune surveillance system.

Animals↗

Analysis of the Leishmania donovani transcriptome reveals an ordered progression of transient and permanent changes in gene expression during differentiation.

Leishmania donovani is an intracellular protozoan parasite that causes kala-azar in humans. During infection the extracellular insect forms (promastigotes) undergo rapid differentiation to intracellular amastigotes that proliferates in phagolysosomes of mammalian macrophages. We used microarray-based expression profiling to investigate the time-course of changes in RNA abundance during promastigote-to-amastigote differentiation in a host-free system that mimics this process. These studies revealed that several hundred genes underwent an ordered progression of transient or permanent up- and down-regulation during differentiation. Genes that were permanently up-regulated in amastigotes were enriched for transporters and surface proteins, but under-represented in genes involved in protein and other metabolism. Most of these changes occurred late in the differentiation process, when morphological differentiation was essentially complete. Down-regulated genes were over-represented in those involved in cell motility, growth and/or maintenance, and these changes generally occurred earlier in the process. Genes that were transiently up- or down-regulated during differentiation included those encoding heat shock proteins, ubiquitin hydrolases, RNA binding proteins, protein kinases, a protein phosphatase, and a histone deacetylase. These results suggest that changes in mRNA abundance may be important in signal transduction, as well as protein and mRNA turnover, during differentiation. In addition to these mRNA changes, other transcripts including one or more rRNAs and snoRNAs, and non-coding RNAs from several telomeres, also showed substantial changes in abundance during the differentiation process. This paper provides the first genome-scale quantitative analysis of gene expression during the transition from promastigotes to amastigotes and demonstrates the utility of the host-free differentiation system.

Animals↗

Toward the computable transcriptome.

Applying a combination of innovative approaches to understanding neuronal gene regulation in C. elegans, an article in the latest Developmental Cell (Wenick and Hobert, 2004) gives hope that reading the genome's transcriptional regulatory code may one day be possible.

Animals↗

Silencing the transcriptome's dark matter: mechanisms for suppressing translation of intergenic transcripts.

Large portions of the genomes of higher eukaryotes are transcribed into RNA molecules that are never destined for translation into proteins. Although some of these transcripts have clearly defined biological roles other than protein coding, most arise from genomic regions devoid of functional genes and many are antisense to regions containing annotated genes. A variety of mechanisms exist to prevent adventitious production of proteins from these transcripts, ranging from degradation within the nucleus to translational silencing in the cytosol.

Animals↗

The dual specificity phosphatase transcriptome of the murine thymus.

Properly regulated mitogen-activated protein (MAP) kinase activity is critical for normal thymocyte development. MAP kinases are activated by phosphorylation of tyrosine and threonine, and dual specificity phosphatases (DUSPs) can inactivate MAP kinases by dephosphorylating both tyrosine and threonine. However, a role for DUSPs in thymocyte development has not been described. In this study, we have defined the subset of DUSP genes expressed in the murine thymus, and how their expression varies in different thymocyte subsets. Of the murine DUSP genes screened that could potentially dephosphorylate MAP kinases, we found 10 transcribed in the thymus. Seven of these 10 thymic DUSPs are true MAP kinase phosphatases based on the presence of a MAP kinase binding domain and demonstrated phosphatase activity against MAP kinases. Six of the seven thymic MAP kinase phosphatases have been shown to dephosphorylate extracellular regulated kinase (ERK). Quantitative PCR analysis of thymocyte populations isolated from different developmental stages revealed significant changes in DUSP expression as thymocytes progressed through development. Specifically, DUSPs 1, 4, and 5 significantly increase in expression as cells go from small, resting CD4/CD8 double positive cells to the CD4 single positive stage. Additionally, in vitro experiments showed that DUSPs could respond to TCR signaling, as anti-CD3 stimulation of thymocytes transiently increased transcription of six of the 10 thymic DUSP genes within 30 min. Notably, the ERK-specific phosphatase DUSP5 was upregulated 43-fold within 30 min, and returned to baseline within 24 h. Overall, we have identified a subset of DUSPs that could potentially regulate ERK activation in response to TCR signals in thymocytes.

Animals↗

Transcriptome response following administration of a live bacterial vaccine in Atlantic salmon (Salmo salar).

Antibacterial responses have been studied in Atlantic salmon following an acute intra peritoneal injection of a genetically attenuated (aroA(-)) strain of Aeromonas salmonicida known to elicit protective immunity. Three tissues were studied for transcriptional changes, the liver, head kidney and the gill. RNA was collected from fish 6, 12, 24 and 48 h following infection or at the same time points from fish injected with PBS as non-infected control. PCR-select cDNA subtraction libraries were constructed from pooled 24 and 48 h post infection RNA to identify up-regulated mRNAs. One thousand four hundred and eighty six cDNA clones were sequenced from enriched cDNA libraries, of which 71% had significant homologies to known functional proteins. Many of these clones have previously been un-characterised in Atlantic salmon. A salmonid cDNA microarray was used to further analyse the gene expression profile as the library construction in itself does not answer the dynamics of the response. The greatest increase in expression identified in the array analysis was a liver antibacterial peptide, hepcidin that was increased 11-fold following the challenge. A panel of clones were chosen for semiquantitative reverse transcriptase PCR from all time points sampled. These results indicated there were both temporal differences and tissue differences in the transcriptional response to bacterial exposure, potentially of relevance to the establishment of protection.

Aeromonas salmonicida↗

Identification of CD36 as a new surface marker of marginal zone B cells by transcriptomic analysis.

Follicular (FO) B cells and marginal zone (MZ) B cells belong to the mature B cell population in spleen of mice. To identify new surface markers of these mature B cell subsets, we compared gene expression profiles of FO and MZ B cells by DNA microarray using FACS-sorted mouse FO and MZ B cells. From 14,000 mouse genes, 27 membrane proteins were expressed mainly in MZ B cells while another 22 membrane proteins expressed largely in FO B cells. Using FACS analysis, we identified that CD36, CD68, and CD49e were expressed on MZ B cells but not on FO B cells. In addition, using semi-quantitative PCR, we found that the mRNA of CD131 were much more abundant in MZ B cells. These results revealed new phenotypic properties of MZ and FO B cells, and would facilitate further studies in the differentiation and functions of these mature B cells.

Animals↗

Transcriptome profiling reveals similarities and differences in plant responses to cadmium and lead.

We analyzed the influence of salts of two heavy metals--lead and cadmium (Pb2+ and Cd2+) on plants, including plant and root size, plant genome stability as well as global genome expression. Measurement of the metal uptake showed that there was a significantly higher incorporation of Cd than of Pb, 0.6 and 0.15 uM per gram of dry weight, respectively. The analysis of the root length and plant size showed a dose dependent decrease in plants exposed to cadmium. In contrast there was little difference in the size of plants exposed to lead, although there was nearly four-fold increase of the root length. Analysis of the genome stability revealed that cadmium led to a dose dependent increase of homologous recombination whereas lead had no effect. Analysis of the global genome expression of plants chronically exposed to 50 uM of Cd and Pb revealed 65 and 338 up- and down-regulated genes by Cd and 19 and 76 by Pb, respectively. Interestingly, half of the genes that changed their expression in Pb-treated plants also changed their expression in Cd-treated ones. The greater number of genes regulated by Cd reflects generally higher genome instability of plants as well as higher uptake as compared to Pb.

Arabidopsis↗

Transcriptome analysis in a rat model of L-DOPA-induced dyskinesia.

We have examined the pattern of striatal messenger RNA expression of over 8000 genes in a rat model of levodopa (L-DOPA)-induced dyskinesia and Parkinson disease (PD). 6-Hydroxydopamine (6-OHDA)-lesioned rats were treated with L-DOPA or physiological saline for 22 days and repeatedly tested for antiakinetic response to L-DOPA and the development of abnormal involuntary movements (AIMs). In a comparison of rats that developed a dyskinetic motor response to rats that did not, we found striking differences in gene expression patterns. In rats that developed dyskinesia, GABA neurons had an increased transcriptional activity, and genes involved in Ca2+ homeostasis, in Ca2+ -dependent signaling, and in structural and synaptic plasticity were upregulated. The gene expression patterns implied that the dyskinetic striatum had increased transcriptional, as well as synaptic activity, and decreased capacity for energy production. Some basic maintenance chores such as ribosome protein biosynthesis were downregulated, possibly a response to expended ATP levels.

Animals↗

Comparative transcriptome analysis of Yersinia pestis in response to hyperosmotic and high-salinity stress.

DNA microarray was used as a tool to investigate genome-wide transcriptional responses of Yersinia pestis to hyperosmotic and high-salinity stress. Hyperosmotic stress specifically upregulated genes responsible for ABC-type transport and the cytoplasmic accumulation of certain polysaccharides, while high-salinity stress induced the transcription of genes encoding partition proteins and several global transcriptional regulators. Genes whose transcription was enhanced by both kinds of stress comprised those encoding osmoprotectant transport systems and a set of virulence determinants. The number of genes downregulated by the two kinds of stress was much lower than that of upregulated genes, suggesting that neither kind of stress severely depresses cellular processes in general. Many differentially regulated genes still exist whose functions remain unknown. Y. pestis recognized high-salinity and hyperosmotic stress as different kinds of environmental stimuli, and different mechanisms enabled acclimation to these two kinds of stress, although Y. pestis still executed common mechanisms to accommodate both types of stress.

Gene Expression Regulation, Bacterial↗