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Bone gene expression profiles in alpha-synuclein (Snca) knockout mice after ovariectomy

ABSTRACT: The peri- and postmenopausal periods in women are associated with decreases in circulating estrogen levels, marked acceleration of age-related bone loss and increased risk of fracture. However, despite the clinical importance of postmenopausal bone loss, our molecular understanding of this process is incomplete. Here, we used co-expression network analysis to gain novel insight into the molecular mechanisms mediating bone loss in ovariectomized (OVX) mice, a model of human menopause. Expression profiles from intact and OVX mice from a panel of inbred strains were used to generate a co-expression network consisting of 29 modules. Genes in network module 25 were decreased by OVX in all strains. Module 25 was enriched for genes involved in the response to oxidative stress, a process known to be an upstream causal factor for OVX-induced bone loss. It was also found that module 25 homologs were co-expressed in human bone marrow and were enriched for genes with evidence of genetic association with bone mineral density (BMD) in women. Alpha synuclein (Snca) was the most highly connected “hub” genes in module 25 and its in vivo knockout resulted in a 40% reduction in OVX-induced bone loss. Furthermore, protection was associated with the targeted alteration of genes in specific network modules, including module 10. Our results identify a gene module associated with OVX-induced bone loss and demonstrate that Snca regulates ovariectomy-induced bone loss by controlling bone network dynamics.

ORGANISM(S): Mus musculus

PROVIDER: GSE68302 | GEO | 2016/12/01

SECONDARY ACCESSION(S): PRJNA282406

REPOSITORIES: GEO

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Project description:Purpose: Using RNA-sequencing technology to screen the effect of moderate-intensity treadmill exercise on the key genes that affect bone mass in the peripheral blood mononuclear cells (PBMCs) of ovariectomized (OVX) rats. Methods: Three-month-old female Sprague–Dawley rats of Specific Pathogen Free (SPF) grade were randomly divided into the sham operation (SHAM) group, OVX group, and OVX combined exercise (OVX+EX) group. The OVX+EX group performed moderate-intensity treadmill exercise for 17 weeks. Upon completion of these exercises, the body composition and bone mineral density (BMD) were measured using dual-energy X-ray absorptiometry, and the bone microstructure of the femur was observed using micro-computed tomography scanning. PBMCs were collected from the abdominal aorta, and the differential genes were analyzed by transcriptome sequencing. The Metascape software was used for gene ontology and pathway enrichment analysis to further screen key genes. Results: 1. In the OVX group, the body weight and body fat content were significantly higher than in the SHAM group and the body muscle content and BMD were significantly lower. 2. The trabecular bone parameters in the OVX group were significantly lower than in the SHAM group, and they were significantly higher in the OVX+EX group than in the OVX group. When compared with the SHAM group, the microstructure of the distal femur trabecular in the OVX group was severely damaged, the trabecular bones were sparse, and there was a large gap between the trabecular bones. The number and continuity of the trabecular bones were higher in OVX+EX group than in the OVX group. 3. A Venn diagram showed that there were 58 common differential genes, with a fold change ≥2 and p value <0.05. and the differential genes were mainly enriched in the PI3K-Akt signaling pathway. Five key genes were screened including CCL2, Nos3, Tgfb3, ITGb4, and LpL. Conclusion: Moderate-intensity treadmill exercise may improve the body composition and bone mass of the OVX group by upregulating CCL2 and other genes of the PBMC. The results also showed that the PBMCs in the peripheral blood can be a useful tool for monitoring the effect of exercise on bone health in postmenopausal osteoporosis.

Project description:Genome-wide association studies (GWASs) for bone mineral density (BMD), one of the most significant predictors of osteoporotic fracture, have identified over 1100 independent associations; however, few of the causal genes have been identified. Recently, the “omnigenic” model of the genetic architecture of complex traits proposed two general categories of causal genes, core and peripheral. Core genes play a direct role in regulating traits; thus, their identification is key to revealing critical regulators and potential therapeutic targets. Here, we identified a co-expression module enriched for genes exhibiting properties consistent with core genes for BMD by analyzing GWAS data through the lens of a cell-type and timepoint-specific gene co-expression network for mineralizing osteoblasts. We identified multiple co-expression modules enriched for genes implicated by BMD GWAS and prioritized modules based on their enrichment for genes with core-like properties. Only one module, the purple module, was enriched for genes correlated with in vitro mineralization (r = 0.49; FDR = 0.012), with known roles in skeletal development (P <2.2 x 10-16), that when perturbed produce a bone phenotype in mice (OR = 4.1; P = 2.14 x 10-9), and are monogenic bone disease genes in humans (OR=21.3; P=6.94 x 10-9). Furthermore, the purple module contained genes from two distinct transcriptional profiles with regards to osteoblast differentiation, one of which, termed the late differentiation cluster (LDC), was more highly enriched for genes with core-like properties. Within the LDC, we found that the most highly connected genes were more likely to overlap a BMD GWAS association and associations that contained LDC genes overlapped enhancers and promoters in osteoblasts. Finally, we identified four LDC genes (B4GALNT3, CADM1, DOCK9, and GPR133) with colocalizing expression quantitative trait loci (eQTL) and altered BMD in mouse knockouts. Our network-based approach identified a “core” module for BMD and has provided a resource for expanding our understanding of the genetics of bone mass.

Project description:Background: Multiple regulatory mechanisms have been identified employing conventional hypothesis-driven approaches as contributing to allergen-specific immunotherapy outcomes, but understanding of how these integrate to maintain immunological homeostasis is incomplete. Objective: To explore the potential for unbiased systems-level gene co-expression network analysis to advance understanding of immunotherapy mechanisms. Methods: We profiled genome-wide allergen-induced Th-cell responses prospectively during 24 months subcutaneous immunotherapy (SCIT) in 25 rhinitis, documenting changes in immunoinflammatory pathways and associated co-expression networks and their relationships to symptom scores out to 36 months. Results: Prior to immunotherapy, mite-induced Th-cell response networks involved multiple discrete co-expression modules including those related to Th2-, type1 IFN-, inflammation- and FOXP3/IL2-associated signalling. A signature comprising 109 genes correlated with symptom scores, and these mapped to cytokine signalling/T-cell activation-associated pathways, with upstream drivers including hallmark Th1/Th2- and inflammation-associated genes. Reanalysis after 3.5 months SCIT updosing detected minimal changes to pathway/upstream regulator profiles despite 32.5% symptom reduction; however, network analysis revealed underlying merging of FOXP3/IL2-with inflammation-and Th2-associated modules. By 12 months SCIT, symptoms had reduced by 41% without further significant changes to pathway/upstream regulator or network profiles. Continuing SCIT to 24 months stabilized symptoms at 47% of baseline, accompanied by upregulation of the type1 IFN-associated network module and its merging into the Th2/FOXP3/IL2/inflammation module. Conclusions: Subcutaneous immunotherapy stimulates progressive integration of mite-induced Th cell-associated Th2-, FOXP3/IL2-, inflammation- and finally type1 IFN-signalling subnetworks, forming a single highly integrated co-expression network module, maximizing potential for stable homeostatic control of allergen-induced Th2 responses via cross-regulation. Th2-antagonistic type1 IFN signalling may play a key role in stabilizing clinical effects of SCIT.

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Bone gene expression profiles in alpha-synuclein (Snca) knockout mice after ovariectomy

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