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Identification of evolutionarily conserved gene networks mediating neurodegenerative dementia.

ABSTRACT: Identifying the mechanisms through which genetic risk causes dementia is an imperative for new therapeutic development. Here, we apply a multistage, systems biology approach to elucidate the disease mechanisms in frontotemporal dementia. We identify two gene coexpression modules that are preserved in mice harboring mutations in MAPT, GRN and other dementia mutations on diverse genetic backgrounds. We bridge the species divide via integration with proteomic and transcriptomic data from the human brain to identify evolutionarily conserved, disease-relevant networks. We find that overexpression of miR-203, a hub of a putative regulatory microRNA (miRNA) module, recapitulates mRNA coexpression patterns associated with disease state and induces neuronal cell death, establishing this miRNA as a regulator of neurodegeneration. Using a database of drug-mediated gene expression changes, we identify small molecules that can normalize the disease-associated modules and validate this experimentally. Our results highlight the utility of an integrative, cross-species network approach to drug discovery.

SUBMITTER: Swarup V

PROVIDER: S-EPMC6602064 | biostudies-literature | 2019 Jan

REPOSITORIES: biostudies-literature

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Project description:BACKGROUND: A co-ordinated tissue-independent gene expression profile associated with growth is present in rodent models and this is hypothesised to extend to all mammals. Growth in humans has similarities to other mammals but the return to active long bone growth in the pubertal growth spurt is a distinctly human growth event. The aim of this study was to describe gene expression and biological pathways associated with stages of growth in children and to assess tissue-independent expression patterns in relation to human growth. RESULTS: We conducted gene expression analysis on a library of datasets from normal children with age annotation, collated from the NCBI Gene Expression Omnibus (GEO) and EBI Arrayexpress databases. A primary data set was generated using cells of lymphoid origin from normal children; the expression of 688 genes (ANOVA false discovery rate modified p-value, q?<?0.1) was associated with age, and subsets of these genes formed clusters that correlated with the phases of growth--infancy, childhood, puberty and final height. Network analysis on these clusters identified evolutionarily conserved growth pathways (NOTCH, VEGF, TGFB, WNT and glucocorticoid receptor--Hyper-geometric test, q?<?0.05). The greatest degree of network 'connectivity' and hence functional significance was present in infancy (Wilcoxon test, p?<?0.05), which then decreased through to adulthood. These observations were confirmed in a separate validation data set from lymphoid tissue. Similar biological pathways were observed to be associated with development-related gene expression in other tissues (conjunctival epithelia, temporal lobe brain tissue and bone marrow) suggesting the existence of a tissue-independent genetic program for human growth and maturation. CONCLUSIONS: Similar evolutionarily conserved pathways have been associated with gene expression and child growth in multiple tissues. These expression profiles associate with the developmental phases of growth including the return to active long bone growth in puberty, a distinctly human event. These observations also have direct medical relevance to pathological changes that induce disease in children. Taking into account development-dependent gene expression profiles for normal children will be key to the appropriate selection of genes and pathways as potential biomarkers of disease or as drug targets.

Project description:Zebrafish (Danio rerio) is an excellent model organism for the study of vertebrate development including skeletogenesis. Studies of mammalian cartilage formation were greatly advanced through the use of a cartilage specific regulatory element of the Collagen type II alpha 1 (Col2a1) gene. In an effort to isolate such an element in zebrafish, we compared the expression of two col2a1 homologues and found that expression of col2a1b, a previously uncharacterized zebrafish homologue, only partially overlaps with col2a1a. We focused our analysis on col2a1a, as it is expressed in both the stacked chondrocytes and the perichondrium. By comparing the genomic sequence surrounding the predicted transcriptional start site of col2a1a among several species of teleosts we identified a small highly conserved sequence (R2) located 1.7 kb upstream of the presumptive transcriptional initiation site. Interestingly, neither the sequence nor location of this element is conserved between teleost and mammalian Col2a1. We generated transient and stable transgenic lines with just the R2 element or the entire 1.7 kb fragment 5' of the transcriptional initiation site. The identified regulatory elements enable the tracking of cellular development in various tissues by driving robust reporter expression in craniofacial cartilage, ear, notochord, floor plate, hypochord and fins in a pattern similar to the expression of endogenous col2a1a. Using a reporter gene driven by the R2 regulatory element, we analyzed the morphogenesis of the notochord sheath cells as they withdraw from the stack of initially uniform cells and encase the inflating vacuolated notochord cells. Finally, we show that like endogenous col2a1a, craniofacial expression of these reporter constructs depends on Sox9a transcription factor activity. At the same time, notochord expression is maintained after Sox9a knockdown, suggesting that other factors can activate expression through the identified regulatory element in this tissue.

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Identification of evolutionarily conserved gene networks mediating neurodegenerative dementia.

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