SPTBN1 Prevents Primary Osteoporosis by Modulating Osteoblasts Proliferation and Differentiation and Blood Vessels Formation in Bone

Osteocyte Sptbn1 Deficiency Alters Cell Survival and Mechanotransduction Following Formation of Plasma Membrane Disruptions (PMD) from Mechanical Loading

We and others have shown that application of high-level mechanical loading promotes the formation of transient plasma membrane disruptions (PMD) which initiate mechanotransduction. We hypothesized that increasing osteocyte cell membrane fragility, by disrupting the cytoskeleton-associated protein β2-spectrin (Sptbn1), could alter osteocytic responses and bone adaptation to loading in a PMD-related fashion. In MLO-Y4 cells, treatment with the spectrin-disrupting agent diamide or knockdown of Sptbn1 via siRNA increased the number of PMD formed by fluid shear stress. Primary osteocytes from an osteocyte-targeted DMP1-Cre Sptbn1 conditional knockout (CKO) model mimicked trends seen with diamide and siRNA treatment and suggested the creation of larger PMD, which repaired more slowly, for a given level of stimulus. Post-wounding cell survival was impaired in all three models, and calcium signaling responses from the wounded osteocyte were mildly altered in Sptbn1 CKO cultures. Although Sptbn1 CKO mice did not demonstrate an altered skeletal phenotype as compared to WT littermates under baseline conditions, they showed a blunted increase in cortical thickness when subjected to an osteogenic tibial loading protocol as well as evidence of increased osteocyte death (increased lacunar vacancy) in the loaded limb after 2 weeks of loading. The impaired post-wounding cell viability and impaired bone adaptation seen with Sptbn1 disruption support the existence of an important role for Sptbn1, and PMD formation, in osteocyte mechanotransduction and bone adaptation to mechanical loading.

Inferring causal cell types of human diseases and risk variants from candidate regulatory elements

The heritability of human diseases is extremely enriched in candidate regulatory elements (cRE) from disease-relevant cell types. Critical next steps are to infer which and how many cell types are truly causal for a disease (after accounting for co-regulation across cell types), and to understand how individual variants impact disease risk through single or multiple causal cell types. Here, we propose CT-FM and CT-FM-SNP, two methods that leverage cell-type-specific cREs to fine-map causal cell types for a trait and for its candidate causal variants, respectively. We applied CT-FM to 63 GWAS summary statistics (average N = 417K) using nearly one thousand cRE annotations, primarily coming from ENCODE4. CT-FM inferred 81 causal cell types with corresponding SNP-annotations explaining a high fraction of trait SNP-heritability (~2/3 of the SNP-heritability explained by existing cREs), identified 16 traits with multiple causal cell types, highlighted cell-disease relationships consistent with known biology, and uncovered previously unexplored cellular mechanisms in psychiatric and immune-related diseases. Finally, we applied CT-FM-SNP to 39 UK Biobank traits and predicted high confidence causal cell types for 2,798 candidate causal non-coding SNPs. Our results suggest that most SNPs impact a phenotype through a single cell type, and that pleiotropic SNPs target different cell types depending on the phenotype context. Altogether, CT-FM and CT-FM-SNP shed light on how genetic variants act collectively and individually at the cellular level to impact disease risk.

Identification of bone mineral density associated genes with shared genetic architectures across multiple tissues: Functional insights for EPDR1, PKDCC, and SPTBN1

Recent studies suggest a shared genetic architecture between muscle and bone, yet the underlying molecular mechanisms remain elusive. This study aims to identify the functionally annotated genes with shared genetic architecture between muscle and bone using the most up-to-date genome-wide association study (GWAS) summary statistics from bone mineral density (BMD) and fracture-related genetic variants. We employed an advanced statistical functional mapping method to investigate shared genetic architecture between muscle and bone, focusing on genes highly expressed in muscle tissue. Our analysis identified three genes, EPDR1, PKDCC, and SPTBN1, which are highly expressed in muscle tissue and previously unlinked to bone metabolism. About 90% and 85% of filtered Single-Nucleotide Polymorphisms were in the intronic and intergenic regions for the threshold at P≤5×10-8 and P≤5×10-100, respectively. EPDR1 was highly expressed in multiple tissues, including muscles, adrenal glands, blood vessels, and the thyroid. SPTBN1 was highly expressed in all 30 tissue types except blood, while PKDCC was highly expressed in all 30 tissue types except the brain, pancreas, and skin. Our study provides a framework for using GWAS findings to highlight functional evidence of crosstalk between multiple tissues based on shared genetic architecture between muscle and bone. Further research should focus on functional validation, multi-omics data integration, gene-environment interactions, and clinical relevance in musculoskeletal disorders.

Revealing the Organ-Specific Expression of SPTBN1 using Single-Cell RNA Sequencing Analysis

Despite the recent technological advances in single-cell RNA sequencing, it is still unknown how three marker genes (SPTBN1, EPDR1, and PKDCC), which are associated with bone fractures and highly expressed in the muscle tissue, are contributing to the development of other tissues and organs at the cellular level. This study aims to analyze three marker genes at the single-cell level using 15 organ tissue types of adult human cell atlas (AHCA). The single-cell RNA sequencing analysis used three marker genes and a publicly available AHCA data set. AHCA data set contains more than 84,000 cells from 15 organ tissue types. Quality control filtering, dimensionality reduction, clustering for cells, and data visualization were performed using the Seurat package. A total of 15 organ types are included in the downloaded data sets: Bladder, Blood, Common Bile Duct, Esophagus, Heart, Liver, Lymph Node, Marrow, Muscle, Rectum, Skin, Small Intestine, Spleen, Stomach, and Trachea. In total, 84,363 cells and 228,508 genes were included in the integrated analysis. A marker gene of SPTBN1 is highly expressed across all 15 organ types, particularly in the Fibroblasts, Smooth muscle cells, and Tissue stem cells of the Bladder, Esophagus, Heart, Muscle, Rectum, Skin, and Trachea. In contrast, EPDR1 is highly expressed in the Muscle, Heart, and Trachea, and PKDCC is only expressed in Heart. In conclusion, SPTBN1 is an essential protein gene in physiological development and plays a critical role in the high expression of fibroblasts in multiple organ types. Targeting SPTBN1 may prove beneficial for fracture healing and drug discovery.

SPTBN1 attenuates rheumatoid arthritis synovial cell proliferation, invasion, migration and inflammatory response by binding to PIK3R2

BACKGROUND

As an autoimmune systemic disorder, rheumatoid arthritis (RA) features chronic inflammation as well as synovial infiltration of immune cells. This study was designed with the purpose of discussing the hidden mechanism of SPTBN1 and exploring favorable molecular-targeted therapies.

METHODS

With the application of RT-qPCR and western blot, the expressions of SPTBN1 and PIK3R2 before or after transfection were estimated. Besides, Cell Counting Kit-8, Edu, wound healing, transwell, enzyme-linked immunosorbent assay, and TUNEL were adopted for the evaluation of the viability, proliferation, migration, invasion, inflammatory response, and apoptosis of fibroblast-like synoviocyte (FLS). In addition, the interaction of SPTBN1 and PIK3R2 was testified by applying immunoprecipitation (IP) and western blot was utilized for the assessment of migration-, apoptosis-, and PI3K/AKT signal-related proteins.

RESULTS

It was discovered that SPTBN1 declined in RA synovial cells and its overexpression repressed the proliferation, migration, invasion, and inflammation of RA-FLSs but promoted apoptosis. IP confirmed that SPTBN1 could bind to PIK3R2 in FLSs. To further figure out the hidden mechanism of SPTBN1 in RA, a series of functional experiments were carried out and the results demonstrated that the reduced expressions of MMP2, MMP9, IL-8, IL-1β, IL-6, and Bcl2 as well as increased levels of Bax and cleaved caspase3 in SPTBN1-overexpressed RA-FLSs were reversed by PIK3R2 depletion, revealing that SPTBN1 repressed the migration and inflammation and promoted the apoptosis of RA-FLSs via binding to PIK3R2. Results obtained from western blot also revealed that PIK3R2 interference ascended the contents of p-PI3K and p-AKT in SPTBN1-overexpressed RA-FLSs, implying that SPTBN1 repressed PI3K/AKT signal in RA via PIK3R2.

DISCUSSION

SPTBN1 alleviated the proliferation, migration, invasion, and inflammation in RA via interacting with PIK3R2.

Exploring the Temporal Correlation of Sarcopenia with Bone Mineral Density and the Effects of Osteoblast-Derived Exosomes on Myoblasts through an Oxidative Stress-Related Gene

Sarcopenia is an age-related accelerated loss of muscle strength and mass. Bone and muscle are closely related as they are physically adjacent, and bone can influence muscle. However, the temporal association between bone mineral density (BMD) and muscle mass in different regions of the body after adjustment for potential indicators and the mechanisms by which bone influences muscle in sarcopenia remain unclear. Therefore, this study aimed to explore the temporal association between muscle mass and BMD in different regions of the body and mechanisms by which bone regulates muscle in sarcopenia. Here, cross-lagged models were utilized to analyze the temporal association between BMD and muscle mass. We found that low-density lipoprotein (LDL-C) positively predicted appendicular lean mass. Mean whole-body BMD (WBTOT BMD), lumbar spine BMD (LS BMD), and pelvic BMD (PELV BMD) temporally and positively predicted appendicular lean mass, and appendicular lean mass temporally and positively predicted WBTOT BMD, LS BMD, and PELV BMD. Moreover, this study revealed that primary mice femur osteoblasts, but not primary mice skull osteoblasts, induced differentiation of C2C12 myoblasts through exosomes. Furthermore, the level of long noncoding RNA (lncRNA) taurine upregulated 1 (TUG1) was decreased, and the level of lncRNA differentiation antagonizing nonprotein coding RNA (DANCR) was increased in skull osteoblast-derived exosomes, the opposite of femur osteoblast-secreted exosomes. In addition, lncRNA TUG1 enhanced and lncRNA DANCR suppressed the differentiation of myoblasts through regulating the transcription of oxidative stress-related myogenin (Myog) gene by modifying the binding of myogenic factor 5 (Myf5) to the Myog gene promoter via affecting the nuclear translocation of Myf5. The results of the present study may provide novel diagnostic biomarkers and therapeutic targets for sarcopenia.

Genome-Wide Association Study Identifies Genetic Loci Associated With Fat Cell Number and Overlap With Genetic Risk Loci for Type 2 Diabetes

Interindividual differences in generation of new fat cells determine body fat and type 2 diabetes risk. In the GENetics of Adipocyte Lipolysis (GENiAL) cohort, which consists of participants who have undergone abdominal adipose biopsy, we performed a genome-wide association study (GWAS) of fat cell number (n = 896). Candidate genes from the genetic study were knocked down by siRNA in human adipose-derived stem cells. We report 318 single nucleotide polymorphisms (SNPs) and 17 genetic loci displaying suggestive (P < 1 × 10-5) association with fat cell number. Two loci pass threshold for GWAS significance, on chromosomes 2 (lead SNP rs149660479-G) and 7 (rs147389390-deletion). We filtered for fat cell number-associated SNPs (P < 1.00 × 10-5) using evidence of genotype-specific expression. Where this was observed we selected genes for follow-up investigation and hereby identified SPATS2L and KCTD18 as regulators of cell proliferation consistent with the genetic data. Furthermore, 30 reported type 2 diabetes-associated SNPs displayed nominal and consistent associations with fat cell number. In functional follow-up of candidate genes, RPL8, HSD17B12, and PEPD were identified as displaying effects on cell proliferation consistent with genetic association and gene expression findings. In conclusion, findings presented herein identify SPATS2L, KCTD18, RPL8, HSD17B12, and PEPD of potential importance in controlling fat cell numbers (plasticity), the size of body fat, and diabetes risk.

Association of IL-6 and TGF-β Gene Polymorphisms with the Risk of Thoracolumbar Osteoporotic Vertebral Compression Fractures

Purpose

Osteoporotic vertebral compression fracture (OVCF) is a common disease in the elderly, and genetic factors play a key role in its occurrence. The present study was conducted to investigate the association between interleukin-6 (IL-6) and the transforming growth factor (TGF-β) gene polymorphisms and the occurrence of thoracolumbar OVCF.

Patients and Methods

This case–control study recruited 146 patients with OVCF and 144 osteoporosis patients as the control group. Genotypes of the IL-6 rs1800796 and TGF-β rs1982073 were analyzed by sequencing. Genotype distribution and allelic frequencies were investigated by the χ² test. Odds ratios (OR) and 95% confidence intervals (CI) evaluated the relationship of IL-6 or TGF-β polymorphism and OVCF susceptibility.

Results

Allele G and genotype GG of IL-6 rs1800796 was more frequent in patients with OVCF (40.07% vs.28.47%; 19.18% vs.7.64%) compared with controls. GG genotype (OR=3.394, 95% CI=1.560–7.385, P < 0.001) and G allele (OR=1.680, 95% CI=1.187–2.376, P < 0.001) of IL-6 rs1800796 was significantly associated with increased risk of OVCF. What is more, CT and TT genotypes (41.78 vs.51.39; 19.86 vs.26.39) and allele T (40.75 vs 52.08) of TGF-β rs1982073 were less frequent in OVCFs, more common in controls and protective against OVCF risk (OR=0.436, 95% CI=0.228–0.835, P = 0.012; OR=0.615, 95% CI=0.443–0.855, P = 0.004).

Conclusion

Our results suggest that the G allele and GG genotype of IL-6 rs1800796 may contribute to increased susceptibility to OVCF in elderly Chinese. In contrast, CT and TT genotypes and the T allele of TGF-β rs1982073 may contribute to lower susceptibility of OVCF.

The Progress of Nomenclature, Structure, Metabolism, and Bioactivities of Oat Novel Phytochemical: Avenanthramides

Oats are among the most commonly consumed whole grains and are widely grown worldwide, and they contain numerous nutrients, including proteins, lipids, vitamins, minerals, β-glucan, and unique phytochemical polyphenol avenanthramides (Avns). Recent studies have indicated that Avns play essential roles in mediating the health benefits of oats. This review systemically summarized the nomenclature and structures of Avns, effect of germination on promoting Avns production, and in vivo metabolites produced after Avns consumption. The classical functions and novel potential bioactivities of Avns were further elucidated. The classical functions of Avns in cancer prevention, antioxidative response, anti-inflammatory reaction, and maintaining muscle health were expounded, and the internal mechanisms of these functions were analyzed. The potential novel bioactivities of Avns in modulating gut microbiota, alleviating obesity, and preventing chronic diseases, such as atherosclerosis and osteoporosis, were further revealed. This review may provide new prospects and directions for the development and utilization of oat Avns.