Project description:Single-cell sorted cells from the osteocytic cell line Ocy454 were screened for high- and low-Sost/sclerostin expression to see changes in other gene expressions related to Sost/sclerostin.
Project description:Osteogenesis imperfecta (OI) is a rare bone disease that is associated with fractures and low bone mass. Sclerostin inhibition is being evaluated as a potential approach to increase bone mass in OI. We had previously found that in Col1a1Jrt/+ mice, a model of severe OI, treatment with an anti-sclerostin antibody had a minor effect on the skeletal phenotype. In the present study, we assessed the effect of genetic sclerostin inactivation in the Col1a1Jrt/+ mouse. We crossed Col1a1Jrt/+ mice with Sost knockout mice to generate Sost-deficient Col1a1Jrt/+ mice and assessed differences between Col1a1Jrt/+ mice with homozygous Sost deficiency and Col1a1Jrt/+ mice with heterozygous Sost deficiency. We found that Col1a1Jrt/+ mice with homozygous Sost deficiency had higher body mass, femur length, trabecular bone volume, cortical thickness and periosteal diameter as well as increased biomechanical parameters of bone strength. Differences between genotypes were larger at the age of 14 weeks than at 8 weeks of age. Transcriptome analysis of RNA extracted from the tibial diaphysis revealed only 5 differentially regulated genes. Thus, genetic inactivation of Sost increased bone mass and strength in the Col1a1Jrt/+ mouse. It appears from these observations that the degree of Sost suppression that is required for eliciting a beneficial response can vary with the genetic cause of OI.
Project description:Trisomy 21 (T21), a recurrent aneuploidy occurring in 1:800 births, predisposes to congenital heart disease (CHD) and multiple extra-cardiac phenotypes. Despite a definitive genetic etiology, the mechanisms by which T21 perturbs development and maintenance remains poorly understood. We compared the transcriptome of CHD tissues from 49 T21 and 226 euploid (eCHD) patients. We resolved cell lineages that mis-expressed T21 transcripts by cardiac single-nucleus RNA-sequencing and RNA in situ hybridization. Compared to eCHD, T21 had increased chr21 gene expression, 11-fold greater levels (p=1.2E-8) of SOST (chr17), encoding the Wnt-inhibitor sclerostin, and 1.4-fold higher levels (p=8.7E-8) of the SOST transcriptional activator ZNF467 (chr7). Cardiac endothelial cells co-expressed SOST and ZNF467. T21 endothelial cells had 6.9-fold higher SOST (p=2.7E-27) with downregulation of Wnt pathway genes. Within the chr21 CHD critical region, the expression of DSCAM was correlated with SOST (p=1.9E-5) and ZNF467 (p=2.9E-4). Deletion of DSCAM in T21 endothelial cells derived from human induced pluripotent stem cells resulted in decreased sclerostin secretion. As Wnt signaling is critical for atrioventricular canal formation, bone health, and pulmonary vascular homeostasis, we conclude that T21-mediated increased sclerostin levels inappropriately inhibits Wnt activities and promotes Down syndrome phenotypes. These findings imply therapeutic potential for anti-sclerostin antibodies in T21.
Project description:The purpose of this study was to understand the effect of sclerostin genetic ablation (gene: Sost) on aortic valve fibrocalcification in an aged, high-cholesterol diet mouse model. Sclerostin is a potent agent in bone remodeling. It both blocks Wnt-mediated osteoblast bone deposition and spurs RANKL-mediated osteoclast maturation and subsequent bone resorption. A monoclonal antibody was recently approved as a treatment for post-menopausal osteoporosis but clinical trials indicated potential cardiovascular side effects. This study aimed to begin to understand the potential role of sclerostin in the aortic valve.
Project description:We collected whole genome testis expression data from hybrid zone mice. We integrated GWAS mapping of testis expression traits and low testis weight to gain insight into the genetic basis of hybrid male sterility.
Project description:Osteolytic destruction is a hallmark of multiple myeloma, resulting from activation of osteoclast mediated bone resorption and reduction of osteoblast-mediated bone formation. However, the molecular mechanism underlying the differentiation and activity of osteoclasts and osteoblasts within a myelomatous microenvironment remains unclear. Here, we demonstrate that the osteocyte-expressed major histocompatibility complex class II transactivator (CIITA) contributes to myeloma-induced bone lesions. CIITA upregulates the secretion of osteolytic cytokines from osteocytes through acetylation at histone 3 lysine 14 in the promoter of TNFSF11 (encoding RANKL) and SOST (encoding sclerostin), leading to enhanced osteoclastogenesis and decreased osteoblastogenesis. In turn, myeloma cell–secreted 2-deoxy-D-ribose, the product of thymidine catalyzed by the function of thymidine phosphorylase, upregulates CIITA expression in osteocytes through the STAT1/IRF1 signaling pathway. Our work thus broadens the understanding of myeloma-induced osteolysis and indicates a potential strategy for disrupting tumor-osteocyte interaction to prevent, or treat patients with, myeloma bone disease.
Project description:A transcriptome study in mouse hematopoietic stem cells was performed using a sensitive SAGE method, in an attempt to detect medium and low abundant transcripts expressed in these cells. Among a total of 31,380 unique transcript, 17,326 (55%) known genes were detected, 14,054 (45%) low-copy transcripts that have no matches to currently known genes. 3,899 (23%) were alternatively spliced transcripts of the known genes and 3,754 (22%) represent anti-sense transcripts from known genes.
Project description:Jason M. Graham, Bruce P. Ayati, Sarah A. Holstein & James A. Martin. The role of osteocytes in targeted bone remodeling: a mathematical model. PLoS ONE 8, 5 (2013).
Until recently many studies of bone remodeling at the cellular level have focused on the behavior of mature osteoblasts and osteoclasts, and their respective precursor cells, with the role of osteocytes and bone lining cells left largely unexplored. This is particularly true with respect to the mathematical modeling of bone remodeling. However, there is increasing evidence that osteocytes play important roles in the cycle of targeted bone remodeling, in serving as a significant source of RANKL to support osteoclastogenesis, and in secreting the bone formation inhibitor sclerostin. Moreover, there is also increasing interest in sclerostin, an osteocyte-secreted bone formation inhibitor, and its role in regulating local response to changes in the bone microenvironment. Here we develop a cell population model of bone remodeling that includes the role of osteocytes, sclerostin, and allows for the possibility of RANKL expression by osteocyte cell populations. We have aimed to give a simple, yet still tractable, model that remains faithful to the underlying system based on the known literature. This model extends and complements many of the existing mathematical models for bone remodeling, but can be used to explore aspects of the process of bone remodeling that were previously beyond the scope of prior modeling work. Through numerical simulations we demonstrate that our model can be used to explore theoretically many of the qualitative features of the role of osteocytes in bone biology as presented in recent literature.