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In silico toxicogenomics methods are resource- and time-efficient approaches for inferring chemical-protein-disease associations with potential mechanism information for exploring toxicological effects. However, current in silico toxicogenomics systems make inferences based on only chemical-protein interactions without considering tissue-specific gene/protein expressions. As a result, inferred diseases could be overpredicted with false positives. In this work, six tissue-specific expression datasets of genes and proteins were collected from the Expression Atlas. Genes were then categorized into high, medium, and low expression levels in a tissue- and dataset-specific manner. Subsequently, the tissue-specific expression datasets were incorporated into the chemical-protein-disease inference process of our ChemDIS system by filtering out relatively low-expressed genes. By incorporating tissue-specific gene/protein expression data, the enrichment rate for chemical-disease inference was largely improved with up to 62.26% improvement. A case study of melamine showed the ability of the proposed method to identify more specific disease terms that are consistent with the literature. A user-friendly user interface was implemented in the ChemDIS system. The methodology is expected to be useful for chemical-disease inference and can be implemented for other in silico toxicogenomics tools.

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The transforming growth factor-ß (TGF-ß) gene family is unique to animals and is involved in various important processes including tissue regeneration. Here, we identified 52 TGF-ß family genes based on genome sequences of the gecko (Gekko japonicus), compared TGF-ß genes between G. japonicus and other four reptilian species, and evaluated the expression of 14 randomly selected genes in muscle, kidney, liver, heart, and brain during tail regeneration to investigate whether their expression was tissue-dependent. We detected 23 conserved domains, 13 in the TGF-ß ligand subfamily, and 10 in the receptor subfamily. The pattern of higher genetic variation in the ligand subfamily than in the receptor subfamily in vertebrates might result from the precise localization of agonists and antagonists in the cell surface and intracellular compartment. TGF-ß genes were unevenly distributed across 15 chromosomes in G. japonicus, presumably resulting from gene losses and gains during evolution. Genes in the TGF-ß receptor subfamily (ACVR2A, ACVR2B, ACVR1, BMPR1A, ACVRL1, BMPR2 and TGFBR1) played a vital role in the TGF-ß signal pathway. The expression of all 14 randomly selected TGF-ß genes was tissue-specific. Our study supports the speculation that some TGF-ß family genes are involved in the early stages of tail regeneration.

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Age-related macular degeneration (AMD) is a leading cause of blindness, and elucidating its underlying disease mechanisms is vital to the development of appropriate therapeutics. We identified differentially expressed genes (DEGs) and differentially spliced genes (DSGs) across the clinical stages of AMD in disease-affected tissue, the macular retina pigment epithelium (RPE)/choroid and the macular neural retina within the same eye. We utilized 27 deeply phenotyped donor eyes (recovered within a 6 h postmortem interval time) from Caucasian donors (60-94 years) using a standardized published protocol. Significant findings were then validated in an independent set of well-characterized donor eyes (n = 85). There was limited overlap between DEGs and DSGs, suggesting distinct mechanisms at play in AMD pathophysiology. A greater number of previously reported AMD loci overlapped with DSGs compared to DEGs between disease states, and no DEG overlap with previously reported loci was found in the macular retina between disease states. Additionally, we explored allele-specific expression (ASE) in coding regions of previously reported AMD risk loci, uncovering a significant imbalance in C3 rs2230199 and CFH rs1061170 in the macular RPE/choroid for normal eyes and intermediate AMD (iAMD), and for CFH rs1061147 in the macular RPE/choroid for normal eyes and iAMD, and separately neovascular AMD (NEO). Only significant DEGs/DSGs from the macular RPE/choroid were found to overlap between disease states. STAT1, validated between the iAMD vs. normal comparison, and AGTPBP1, BBS5, CERKL, FGFBP2, KIFC3, RORα, and ZNF292, validated between the NEO vs. normal comparison, revealed an intricate regulatory network with transcription factors and miRNAs identifying potential upstream and downstream regulators. Findings regarding the complement genes C3 and CFH suggest that coding variants at these loci may influence AMD development via an imbalance of gene expression in a tissue-specific manner. Our study provides crucial insights into the multifaceted genomic underpinnings of AMD (i.e., tissue-specific gene expression changes, potential splice variation, and allelic imbalance), which may open new avenues for AMD diagnostics and therapies specific to iAMD and NEO.

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Multiple distal cis-regulatory elements (CREs) often cooperate to regulate gene expression, and the presence of multiple CREs for a gene has been proposed to provide redundancy and robustness to variation. However, we do not understand how attributes of a gene's distal CRE landscape-the CREs that contribute to its regulation-relate to its expression and function. Here, we integrate three-dimensional chromatin conformation and functional genomics data to quantify the CRE landscape composition genome-wide across ten human tissues and relate their attributes to the function, constraint, and expression patterns of genes. Within each tissue, we find that expressed genes have larger CRE landscapes than nonexpressed genes and that genes with tissue-specific CREs are more likely to have tissue-specific expression. Controlling for the association between expression level and CRE landscape size, we also find that CRE landscapes around genes under strong constraint (e.g., loss-of-function intolerant and housekeeping genes) are not significantly smaller than other expressed genes as previously proposed; however, they do have more evolutionarily conserved sequences than CREs of expressed genes overall. We also show that CRE landscape size does not associate with expression variability across individuals; nonetheless, genes with larger CRE landscapes have a relative depletion for variants that influence expression levels (expression quantitative trait loci). Overall, this work illustrates how differences in gene function, expression, and evolutionary constraint are reflected in features of CRE landscapes. Thus, considering the CRE landscape of a gene is vital for understanding gene expression dynamics across biological contexts and interpreting the effects of noncoding genetic variants.

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Introduction: Turner syndrome (TS) is a chromosomal disorder that affects phenotypic females who have one intact X chromosome and complete or partial absence of the second sex chromosome in association with one or more clinical manifestations. However, the immunological profile of TS with different X chromosome origins is incompletely understood. Methods: In this study, transcriptomic expression profiles of 26 TS (45,X) samples and 10 normal karyotype (46,XX) samples derived from GSE46687 cohort were employed. Differentially expressed immune-related genes (DEIRGs) between monosomy X TS patients with different X chromosome origins and normal females were investigated respectively. Subsequently, functional annotation, protein-protein interaction (PPI) network analysis, immunocyte infiltration evaluation, tissue-specific gene expression and Weighted gene co expression network analysis (WGCNA) were performed to explore the immunological characteristic in TS with different X chromosome origins. Results: 34 and 52 DEIRGs were respectively identified in 45,Xm and 45,Xp patients compared with normal individuals. The identified DEIRGs in Xm group were significantly enriched in pathways associated with cancer. In Xp TS patients, the most enriched signals were immune response-related. A majority of genes involved in the above pathways were downregulated. PPI analysis identified 4 (FLT3, IL3RA, CSF2RA, PIK3R3) and 6 (PDGFRB, CSF2, IL5, PRL, CCL17 and IL2)hub genes for Xm and Xp groups, respectively. CIBERSORT results showed that the proportion of Tregs in the Xm group and the naive B cells and resting NK cells in the Xp group significantly increased, respectively. Tissue-specific expression results indicated that BDCA4+_dentritic cells and CD19+ B cells were the prominent specific expressed tissues in Xp patients. Results of WGCNA support the above analysis. Conclusions: This study aims at studying the immunological characteristics of TS with different X chromosome origins. Pathways in cancer in Xm group and immune response in Xp group were suppressed. 4 and 6 hub IRGs were identified as biomarkers for Xm and Xp patients, respectively. B cells played important roles in Xp patients. Further studies are needed to draw more attention to the functional validation of these hub genes and the roles of B cells.

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Obesity is a complex medical condition that affects multiple organs in the body. However, the underlying mechanisms of obesity, as well as its treatment, are largely unexplored. The focus of this research was to use bioinformatics to discover possible treatment targets for obesity. To begin, the GSE133099 database was used to identify 364 differentially expressed genes (DEGs). Then, DEGs were subjected to tissue-specific analyses and enrichment analyses, followed by the creation of a protein-protein interaction (PPI) network and generation of a drug-gene interaction database to screen key genes and potential future drugs targeting obesity. Findings have illustrated that the tissue-specific expression of neurologic markers varied significantly (34.7%, 52/150). Among these genes, Lep, ApoE, Fyn, and FN1 were the key genes observed in the adipocyte samples from obese patients relative to the controls. Furthermore, nine potential therapeutic drugs (dasatinib, ocriplasmin, risperidone, gemfibrozil, ritonavir, fluvastatin, pravastatin, warfarin, atorvastatin) that target the key genes were also screened and selected. To conclude the key genes discovered (Lep, ApoE, Fyn, and FN1), as well as 9 candidate drugs, could be used as therapeutic targets in treating obesity.

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Urinary tract infection (UTI) is a common infectious disease. Urinary tract pathogenic Escherichia coli (UPEC) is the main cause of UTIs. At present, antibiotics are mainly used for the treatment of UTIs. However, with the increase of drug resistance, the course of the disease is prolonged. Therefore, identifying the receptors and signal pathways of host cells and tissues will further our understanding of the pathogenesis of UTIs and help in the development of new drug treatments. We used two public microarray datasets (GSE43790, GSE124917) in the Gene Expression Omnibus (GEO) database to identify differentially expressed genes (DEGs) between UTI and normal cell samples. A functional analysis based on Gene Ontology (GO) data, a pathway enrichment analysis based on Kyoto Encyclopedia of Genes and Genomes (KEGG) data and a protein-protein interaction analysis identified the main potential biomarkers and verified them in animal tissues. A total of 147 up-regulated genes and 40 down-regulated genes were identified. GO enrichment analysis showed that these functional changes relate to the terms response to lipopolysaccharide, regulation of cytokine production, and regulation of the inflammatory response. KEGG analysis indicated that urinary tract infections likely involve the TNF-αsignaling pathways. The 20 hub genes were selected from the protein-protein interaction network, and the highly significant hub genes were verified by animal experiments. Our findings provide potential targets for exploring new treatments for urinary tract infections. After a comprehensive analysis of the GEO database, these results may facilitate development of new diagnosis and treatment strategies for urinary tract infections.

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Despite their ecological and economical importance, conifers genomic resources are limited, mainly due to the large size and complexity of their genomes. Additionally, the available genomic resources lack complete structural and functional annotation. Transcriptomic resources have been commonly used to compensate for these deficiencies, though for most conifer species they are limited to a small number of tissues, or capture only a fraction of the genes present in the genome. Here we provide an atlas of gene expression patterns for conifer Pinus sylvestris across five tissues: embryo, megagametophyte, needle, phloem and vegetative bud. We used a wide range of tissues and focused our analyses on the expression profiles of genes at tissue level. We provide comprehensive information of the per-tissue normalized expression level, indication of tissue preferential upregulation and tissue-specificity of expression. We identified a total of 48,001 tissue preferentially upregulated and tissue specifically expressed genes, of which 28% have annotation in the Swiss-Prot database. Even though most of the putative genes identified do not have functional information in current biological databases, the tissue-specific patterns discovered provide valuable information about their potential functions for further studies, as for example in the areas of plant physiology, population genetics and genomics in general. As we provide information on tissue specificity at both diploid and haploid life stages, our data will also contribute to the understanding of evolutionary rates of different tissue types and ploidy levels.

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Neurodevelopmental and neurodegenerative disorders (NNDs) are a group of conditions with a broad range of core and co-morbidities, associated with dysfunction of the central nervous system. Improvements in high throughput sequencing have led to the detection of putative risk genetic loci for NNDs, however, quantitative neurogenetic approaches need to be further developed in order to establish causality and underlying molecular genetic mechanisms of pathogenesis. Here, we discuss an approach for prioritizing the contribution of genetic risk loci to complex-NND pathogenesis by estimating the possible impacts of these loci on gene regulation. Furthermore, we highlight the use of a tissue-specificity gene expression index and the application of artificial intelligence (AI) to improve the interpretation of the role of genetic risk elements in NND pathogenesis. Given that NND symptoms are associated with brain dysfunction, risk loci with direct, causative actions would comprise genes with essential functions in neural cells that are highly expressed in the brain. Indeed, NND risk genes implicated in brain dysfunction are disproportionately enriched in the brain compared with other tissues, which we refer to as brain-specific expressed genes. In addition, the tissue-specificity gene expression index can be used as a handle to identify non-brain contexts that are involved in NND pathogenesis. Lastly, we discuss how using an AI approach provides the opportunity to integrate the biological impacts of risk loci to identify those putative combinations of causative relationships through which genetic factors contribute to NND pathogenesis.

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Systemic lupus erythematosus (SLE) is a chronic autoimmune disease involving multiple organs. However, the underlying etiology and mechanisms remain unclear. This study was performed to identify potential therapeutic targets for SLE using bioinformatics methods. First, 584 differentially expressed genes were identified based on the GSE61635 dataset. Tissue-specific analyses, enrichment analyses, and Protein-Protein interaction network were successively conducted. Furthermore, ELISA was performed to confirm the expression levels of key genes in the control and SLE blood samples. The findings revealed that tissue-specific expression of markers of the hematological system (25.5%, 28/110) varied significantly. CCL2, MMP9, and RSAD2 expression was markedly increased in the SLE samples compared with controls. In conclusion, the identified key genes (CCL2, MMP9, and RSAD2) may act as possible therapeutic targets for the treatment of SLE.

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Acclimation of plants to adverse conditions requires the coordination of gene expression and signalling pathways between tissues and cell types. As the energy and carbon capturing organs, leaves are significantly affected by abiotic and biotic stresses. However, tissue- or cell type-specific analyses of stress responses have focussed on the Arabidopsis root. Here, we comparatively explore the transcriptomes of three leaf tissues (epidermis, mesophyll, vasculature) after induction of diverse stress pathways by chemical stimuli (antimycin A, 3-amino-1,2,4-triazole, methyl viologen, salicylic acid) and ultraviolet light in Arabidopsis using laser capture microdissection followed by RNA sequencing. Stimulation of stress pathways caused an overall reduction in the number of genes expressed in a tissue-specific manner, though a small subset gained or changed their tissue specificity. We find no evidence of a common stress response, with only a few genes consistently responsive to two or more treatments in the analysed tissues. However, differentially expressed genes overlap between tissues for individual treatments. A focussed analysis provided evidence for an interaction of auxin and ethylene that mediates retrograde signalling during mitochondrial dysfunction specifically in the epidermis, and a gene regulatory network defined the hierarchy of interactions. Taken together, we have generated an extensive reference dataset that will be valuable for future experiments analysing transcriptional responses on a tissue or single-cell level. Our results will enable the tailoring of the tissue-specific engineering of stress-tolerant plants.

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Long non-coding RNAs (lncRNAs) are a large class of gene transcripts that do not code proteins; however, their functions are largely unknown and many new lncRNAs are yet to be discovered. Taking advantage of our previously developed, super-fast, novel lncRNA discovery pipeline, UClncR, and rich resources of GTEx RNA-seq data, we performed systematic novel lincRNA discovery for over 8000 samples across 30 tissue types. We conducted novel detection for each major tissue type first and then consolidated the novel discoveries from all tissue types. These novel lincRNs were profiled and analyzed along with known genes to identify tissue-specific genes in 30 major human tissue types. Thirteen sub-brain regions were also analyzed in a similar manner. Our analysis revealed thousands to tens of thousands of novel lincRNAs for each tissue type. These lincRNAs could define each tissue type's identity and demonstrated their reliability and tissue-specific expression. Tissue-specific genes were identified for each major tissue type and sub-brain region. The tissue-specific genes clearly defined each respective tissue's unique function and could be used to expand the interpretation of non-coding SNPs from genome-wide association (GWAS) studies.

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The full length Andrographis paniculate 4-hydroxy 3-methyl 2-butenyl 4-diphosphate reductase (ApHDR) gene of MEP pathway was isolated for the first time. The ApHDR ORF with 1404 bp flanked by 100 bp 5'UTR and 235 bp 3'UTR encoding 467 amino acids (NCBI accession number: MK503970) and cloned in pET 102, transformed and expressed in E. coli BL21. The ApHDR protein physico-chemical properties, secondary and tertiary structure were analyzed. The Ramachandran plot showed 93.8% amino acids in the allowed regions, suggesting high reliability. The cluster of 16 ligands for binding site in ApHDR involved six amino acid residues having 5-8 ligands. The Fe-S cluster binding site was formed with three conserved residues of cysteine at positions C123, C214, C251 of ApHDR. The substrate HMBPP and inhibitors clomazone, paraquat, benzyl viologen's interactions with ApHDR were also assessed using docking. The affinity of Fe-S cluster binding to the cleft was found similar to HMBPP. The HPLC analysis of different type of tissue (plant parts) revealed highest andrographolide content in young leaves followed by mature leaves, stems and roots. The differential expression profile of ApHDR suggested a significant variation in the expression pattern among different tissues such as mature leaves, young leaves, stem and roots. A 16-fold higher expression of ApHDR was observed in the mature leaves of A. paniculata as compared to roots. The young leaves and stem showed 5.5 fold and fourfold higher expression than roots of A. paniculata. Our result generated new genomic information on ApHDR which may open up prospects of manipulation for enhanced diterpene lactone andrographolide production in A. paniculata. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s12298-021-00952-0.

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The Tg(Adipoq-cre)1Evdr mouse has become an important tool in adipose tissue biology. However, the exact genomic transgene integration site has not been established. Using Targeted Locus Amplification (TLA) we found the transgene had integrated on mouse chromosome 9 between exons 6 and 7 of Tbx18. We detected transgene-transgene fusion; therefore, we used droplet digital polymerase chain reaction to identify Cre copy number. In two separate experiments, we digested with BAMHI and with HindIII to separate potentially conjoined Cre sequences. We found one copy of intact Cre present in each experiment, indicating transgene-transgene fusion in other parts of the BAC that would not contribute to tissue-specific Cre expression. Cre copy number for Tg(Adipoq-cre)1Evdr mice can be potentially used to identify homozygous mice.

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Background: Turner syndrome (TS) is a sex chromosome aneuploidy with a variable spectrum of symptoms including short stature, ovarian failure and skeletal abnormalities. The etiology of TS is complex, and the mechanisms driving its pathogenesis remain unclear. Methods: In our study, we used the online Gene Expression Omnibus (GEO) microarray expression profiling dataset GSE46687 to identify differentially expressed genes (DEGs) between monosomy X TS patients and normal female individuals. The relevant data on 26 subjects with TS (45,XO) and 10 subjects with the normal karyotype (46,XX) was investigated. Then, tissue-specific gene expression, functional enrichment, and protein-protein interaction (PPI) network analyses were performed, and the key modules were identified. Results: In total, 25 upregulated and 60 downregulated genes were identified in the differential expression analysis. The tissue-specific gene expression analysis of the DEGs revealed that the system with the most highly enriched tissue-specific gene expression was the hematologic/immune system, followed by the skin/skeletal muscle and neurologic systems. The PPI network analysis, construction of key modules and manual screening of tissue-specific gene expression resulted in the identification of the following five genes of interest: CD99, CSF2RA, MYL9, MYLPF, and IGFBP2. CD99 and CSF2RA are involved in the hematologic/immune system, MYL9 and MYLPF are related to the circulatory system, and IGFBP2 is related to skeletal abnormalities. In addition, several genes of interest with possible roles in the pathogenesis of TS were identified as being associated with the hematologic/immune system or metabolism. Conclusion: This discovery-driven analysis may be a useful method for elucidating novel mechanisms underlying TS. However, more experiments are needed to further explore the relationships between these genes and TS in the future.

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It is known that long (200-300 nucleotides and longer) non-protein-coding RNAs (ncRNAs) tissue-specifically expressed from the regulatory regions of developmental genes can regulate the transcription of the mRNA of these genes. In this study, an attempt is made to identify differentially expressed ncRNAs in the extended promoter region of the fork head (fkh) gene of the fruit fly Drosophila melanogaster. We investigated four preparations of the total RNA: from embryos, from adult flies (separately from females and males), and from the S2 cell line of cultured Drosophila cells. In the total RNA preparations from embryos and adult flies, the levels of fkh expression differed substantially, whereas in S2 cells its expression is not detected at all (shown in this work). We perform classical Northern blot analysis of gel-separated RNAs hybridized to a series of radioactively labeled DNA fragments corresponding to the adjacent and partially overlapping regions of the promoter region of the fkh gene. Several previously unknown differentially expressed ncRNAs are detected, including those in the regions overlapping with the previously detected regulatory elements (TRE1 and salivary gland enhancer sgE) and the transcription start site of the fkh gene. The collected data complement and clarify the results of the previously conducted RNA-seq experiments, in particular, in terms of the length of the detected RNAs. These results may serve as a foundation for further studies of the mechanisms of tissue-specific regulation of the fkh gene expression.

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Hybridization and polyploidization are important evolutionary processes whose impacts range from the alteration of gene expression and phenotypic variation to the triggering of asexual reproduction. We investigated fishes of the Cobitis taenia-elongatoides hybrid complex, which allowed us to disentangle the direct effects of both processes, due to the co-occurrence of parental species with their diploid and triploid hybrids. Employing morphological, ecological, and RNAseq approaches, we investigated the molecular determinants of hybrid and polyploid forms. In contrast with other studies, hybridization and polyploidy induced relatively very little transgressivity. Instead, Cobitis hybrids appeared intermediate with a clear effect of genomic dosing when triploids expressed higher similarity to the parent contributing two genome sets. This dosage effect was symmetric in the germline (oocyte gene expression), interestingly though, we observed an overall bias toward C. taenia in somatic tissues and traits. At the level of individual genes, expression-level dominance vastly prevailed over additivity or transgressivity. Also, trans-regulation of gene expression was less efficient in diploid hybrids than in triploids, where the expression modulation of homoeologs derived from the "haploid" parent was stronger than those derived from the "diploid" parent. Our findings suggest that the apparent intermediacy of hybrid phenotypes results from the combination of individual genes with dominant expression rather than from simple additivity. The efficiency of cross-talk between trans-regulatory elements further appears dosage dependent. Important effects of polyploidization may thus stem from changes in relative concentrations of trans-regulatory elements and their binding sites between hybridizing genomes. Links between gene regulation and asexuality are discussed.

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BACKGROUND: Consideration of tissue-specific gene expression in reconstruction and analysis of molecular genetic networks is necessary for a proper description of the processes occurring in a specified tissue. Currently, there are a number of computer systems that allow the user to reconstruct molecular-genetic networks using the data automatically extracted from the texts of scientific publications. Examples of such systems are STRING, Pathway Commons, MetaCore and Ingenuity. The MetaCore and Ingenuity systems permit taking into account tissue-specific gene expression during the reconstruction of gene networks. Previously, we developed the ANDSystem tool, which also provides an automated extraction of knowledge from scientific texts and allows the reconstruction of gene networks. The main difference between our system and other tools is in the different types of interactions between objects, which makes the ANDSystem complementary to existing well-known systems. However, previous versions of the ANDSystem did not contain any information on tissue-specific expression. RESULTS: A new version of the ANDSystem has been developed. It offers the reconstruction of associative gene networks while taking into account the tissue-specific gene expression. The ANDSystem knowledge base features information on tissue-specific expression for 272 tissues. The system allows the reconstruction of combined gene networks, as well as performing the filtering of genes from such networks using the information on their tissue-specific expression. As an example of the application of such filtering, the gene network of the extrinsic apoptotic signaling pathway was analyzed. It was shown that considering different tissues can lead to changes in gene network structure, including changes in such indicators as betweenness centrality of vertices, clustering coefficient, network centralization, network density, etc. CONCLUSIONS: The consideration of tissue specificity can play an important role in the analysis of gene networks, in particular solving the problem of finding the most significant central genes. Thus, the new version of ANDSystem can be employed for a wide range of tasks related to biomedical studies of individual tissues. It is available at http://www-bionet.sscc.ru/and/cell /.

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Phosphoenolpyruvate carboxylase (PEPC) is an important regulatory enzyme situated at a key branch point of central plant metabolism. Plant genomes encode several plant-type PEPC (PTPC) isozymes, along with a distantly related bacterial-type PEPC (BTPC). BTPC is expressed at high levels in developing castor oil seeds where it tightly interacts with co-expressed PTPC polypeptides to form unusual hetero-octameric Class-2 PEPC complexes that are desensitized to allosteric inhibition by L-malate. Analysis of RNA-Seq and microarray transcriptome datasets revealed two distinct patterns of tissue-specific BTPC expression in vascular plants. Species such as Arabidopsis thaliana, strawberry, rice, maize, and poplar mainly exhibited pollen- or floral-specific BTPC expression. By contrast, BTPC transcripts were relatively abundant in developing castor, cotton, and soybean seeds, cassava tubers, as well as immature tomato, cucumber, grape, and avocado fruit. Immunoreactive 118 kDa BTPC polypeptides were detected on immunoblots of cucumber and tomato fruit extracts. Co-immunoprecipitation established that as in castor, BTPCs physically interact with endogenous PTPCs to form Class-2 PEPC complexes in tomato and cucumber fruit. We hypothesize that Class-2 PEPCs simultaneously maintain rapid anaplerotic PEP carboxylation and respiratory CO2 refixation in diverse, biosynthetically active sinks that accumulate high malate levels.

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Site-specific recombinases are potent tools to regulate gene expression. In particular, the Cre (cyclization recombination) and FLP (flipase) enzymes are widely used to either activate or inactivate genes in a precise spatiotemporal manner. Both recombinases work efficiently in the popular model organism Caenorhabditis elegans, but their use in this nematode is still only sporadic. To increase the utility of the FLP system in C. elegans, we have generated a series of single-copy transgenic strains that stably express an optimized version of FLP in specific tissues or by heat induction. We show that recombination efficiencies reach 100% in several cell types, such as muscles, intestine, and serotonin-producing neurons. Moreover, we demonstrate that most promoters drive recombination exclusively in the expected tissues. As examples of the potentials of the FLP lines, we describe novel tools for induced cell ablation by expression of the PEEL-1 toxin and a versatile FLP-out cassette for generation of GFP-tagged conditional knockout alleles. Together with other recombinase-based reagents created by the C. elegans community, this toolkit increases the possibilities for detailed analyses of specific biological processes at developmental stages inside intact animals.

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