Project description:Craniosynostosis is a disease defined by premature fusion of one or more cranial sutures. The mechanistic pathology of isolated single-suture craniosynostosis is complex and while a number of genetic biomarkers and environmental predispositions have been identified, in many cases the causes remain controversial and inconclusive at best. After controlling for variables contributing to potential bias, FGF7, SFRP4, and VCAM1 emerged as potential genetic biomarkers for single-suture craniosynostosis due to their significantly large changes in gene expression compared to the control population. Furthermore, pathway analysis implicated focal adhesion and extracellular matrix (ECM)-receptor interaction as differentially regulated gene networks when comparing all cases of single-suture synostosis and controls. Lastly, overall gene expression was found to be highly conserved between coronal and metopic cases, as evidenced by the fact that WNT2 and IGFBP2 were the only differentially regulated genes identified in a direct comparison. These results not only confirm the roles of previously reported craniosynostosis-related targets but also introduce novel genetic biomarkers and pathways that may play critical roles in its pathogenesis. In this study, gene expression data from 199 patients with isolated sagittal (n= 100), unilateral coronal (n = 50), and metopic (n = 49) synostosis are compared against both a control population (n = 50), as well as each other.
Project description:Craniosynostosis is a disease defined by premature fusion of one or more cranial sutures. The mechanistic pathology of isolated single-suture craniosynostosis is complex and while a number of genetic biomarkers and environmental predispositions have been identified, in many cases the causes remain controversial and inconclusive at best. After controlling for variables contributing to potential bias, FGF7, SFRP4, and VCAM1 emerged as potential genetic biomarkers for single-suture craniosynostosis due to their significantly large changes in gene expression compared to the control population. Furthermore, pathway analysis implicated focal adhesion and extracellular matrix (ECM)-receptor interaction as differentially regulated gene networks when comparing all cases of single-suture synostosis and controls. Lastly, overall gene expression was found to be highly conserved between coronal and metopic cases, as evidenced by the fact that WNT2 and IGFBP2 were the only differentially regulated genes identified in a direct comparison. These results not only confirm the roles of previously reported craniosynostosis-related targets but also introduce novel genetic biomarkers and pathways that may play critical roles in its pathogenesis.
Project description:Suture mesenchymal stem cell (MSC) drives calvarial suture development, homeostasis, and regeneration. Its loss leads to craniosynostosis, a prevailing craniofacial disorder characterized by premature suture closure. Ribosome biogenesis, historically thought to be a static house-keeping process, is now known to have tissue-specific roles. However, the functional specificity of ribosome biogenesis in suture MSCs remains largely unexplored, hampering development of therapeutic strategies for craniofacial tissue regeneration. We genetically perturb ribosome biogenesis using Snord118, a small nucleolar RNA (snoRNA) required for ribosomal RNA (rRNA) maturation. MSC specific conditional knockout (cKO) of Snord118 in mice leads to p53 activation, cell death, mesenchymal and MSC loss, impaired osteogenic and osteoclastic activity, resulting in suture growth and craniosynostosis defects. Using our newly established human induced pluripotent stem cell (iPSC)-derived MSCs combined with ribosome profiling, we found that SNORD118deficiency in MSCs causes global translation dysregulations and downregulation of complement pathway, a part of innate immune system with selective but poorly characterized physiological functions in craniofacial tissue homeostasis. Overall, ribosome biogenesis controls suture MSC fate via selective regulation of complement pathway.
Project description:Suture mesenchymal stem cell (MSC) drives calvarial suture development, homeostasis, and regeneration. Its loss leads to craniosynostosis, a prevailing craniofacial disorder characterized by premature suture closure. Ribosome biogenesis, historically thought to be a static house-keeping process, is now known to have tissue-specific roles. However, the functional specificity of ribosome biogenesis in suture MSCs remains largely unexplored, hampering development of therapeutic strategies for craniofacial tissue regeneration. We genetically perturb ribosome biogenesis using Snord118, a small nucleolar RNA (snoRNA) required for ribosomal RNA (rRNA) maturation. MSC specific conditional knockout (cKO) of Snord118 in mice leads to p53 activation, cell death, mesenchymal and MSC loss, impaired osteogenic and osteoclastic activity, resulting in suture growth and craniosynostosis defects. Using our newly established human induced pluripotent stem cell (iPSC)-derived MSCs combined with ribosome profiling, we found that SNORD118deficiency in MSCs causes global translation dysregulations and downregulation of complement pathway, a part of innate immune system with selective but poorly characterized physiological functions in craniofacial tissue homeostasis. Overall, ribosome biogenesis controls suture MSC fate via selective regulation of complement pathway.
Project description:Purpose: The cranial suture is a fibrous joint, and similar to the growth plates of the skeletal long bone, they serve as the major centers of calvarial vault morphogenesis. Our group’s identification of a skeletal stem cell isolated from the mouse tibial growth plate prompted us to investigate whether these skeletal stem cells are also resident in the mouse cranial sutures and if they govern postnatal suture patency or fusion. Results: We preformed a spatio-temporal profiling of the mouse cranial sutures by flow cytometry, demonstrating a significant decrease in the temporal representation of skeletal stem cells in fusing versus patent sutures. Moreover, canonical Wnt signaling has a significant impact on skeletal stem cells proliferation and thus representation within the suture, dictating fate: fusion or patency. Breeding an Axin2+/-LacZ mouse, with enhanced activation of canonical Wnt signaling to a Twist1+/− mouse, harboring a coronal craniosynostosis enriched the skeletal stem cell pool in coronal sutures, thereby preventing Twist1+/− craniosynostosis. Conclusions: Our findings suggest an imbalance and/or decrease in resident skeletal stem cells within the cranial sutures gives rise to craniosynostosis, however, restoring this representation by enriching skeletal stem cells within the suture can maintain patency.
Project description:Purpose: The cranial suture is a fibrous joint, and similar to the growth plates of the skeletal long bone, they serve as the major centers of calvarial vault morphogenesis. Our group’s identification of a skeletal stem cell isolated from the mouse tibial growth plate prompted us to investigate whether these skeletal stem cells are also resident in the mouse cranial sutures and if they govern postnatal suture patency or fusion. Results: We preformed a spatio-temporal profiling of the mouse cranial sutures by flow cytometry, demonstrating a significant decrease in the temporal representation of skeletal stem cells in fusing versus patent sutures. Moreover, canonical Wnt signaling has a significant impact on skeletal stem cells proliferation and thus representation within the suture, dictating fate: fusion or patency. Breeding an Axin2+/-LacZ mouse, with enhanced activation of canonical Wnt signaling to a Twist1+/− mouse, harboring a coronal craniosynostosis enriched the skeletal stem cell pool in coronal sutures, thereby preventing Twist1+/− craniosynostosis. Conclusions: Our findings suggest an imbalance and/or decrease in resident skeletal stem cells within the cranial sutures gives rise to craniosynostosis, however, restoring this representation by enriching skeletal stem cells within the suture can maintain patency.
Project description:Sutures separate the flat bones of the skull and enable coordinated growth of the brain and overlying cranium. In order to uncover the cellular diversity within sutures, we conducted single-cell transcriptomic and histological analyses of the embryonic murine coronal suture. We identify Erg and Pthlh as early markers of osteogenic progenitors in sutures, and distinct pre-osteoblast signatures between the bone fronts and periosteum. diverse mesenchymal layers at the coronal suture, including multiple distinct meningeal layers below the suture, and ligamentous, ectocranial, and hypodermal layers above the sutureIn the ectocranial layers above the suture, we observe a ligament-like population spanning the frontal and parietal bones and expressing genes implicated in mechanosensation. Mesenchyme in and around the coronal suture is asymmetrically distributed between the frontal and parietal bones, and we identify different states of osteogenic cells extending from the bone fronts into the more mature bone, and a potential signature for sutural stem cellsIn the meningeal layers, we detect a potential chondrogenic periosteal dura population that may be involved in endochondral ossification that closes sutures. Expression of genes mutated in craniosynostosis is spread across diverse cell types, suggesting multiple points at which homeostasis can fail. This single-cell atlas provides a resource to understand the development of the coronal suture, the suture most commonly fused in craniosynostosis.
Project description:Severity of craniosynostosis in humans varies widely even in patients with identical genetic mutations, and severity corresponds with morbidity. In this study we compared RNA sequencing data from cranial tissues of a severe form of Crouzon craniosynostosis syndrome (C57BL/6 FGFR2C342Y/+ mice) with those of a less severe form of Crouzon craniosynostosis (BALB/c FGFR2C342Y/+ mice) to identify genetic modifiers that influence craniosynostosis phenotype severity. Comparison of the mice revealed neonatal onset of coronal suture fusion in the form of suture obliteration in C57BL/6 mice (88% incidence, p<.001 between genotypes) in C57BL/6 mice. Coronal suture fusion in the form of point fusions across the suture occurred at approximately 4 weeks after birth, with less severe skull shape abnormalities, in BALB/c mice. Substantially fewer genes were differentially expressed in BALB/c FGFR2+/+ vs. FGFR2C342Y/+ mice (87 out of 15,893 expressed genes) than in C57BL/6 FGFR2C+/+ vs. FGFR2C342Y/+ mice (2,043 out of 19,097 expressed genes). Further investigation of the gene expression data revealed differential expression of coronal suture associated genes, eph/ephrin boundary genes, cell proliferation genes and osteoblast differentiation genes, among others. The most striking pattern in the data was the minimal change in gene expression seen in BALB/c FGFR2+/+ vs. FGFR2C342Y/+ mice. Analysis of protein processing and lysosomal components support the hypothesis that the craniosynostosis phenotype is less severe in BALB/c mice because the mutant FGFR2C342Y protein is not expressed to the same extent as that seen in C57BL/6 mice. Together, these results suggest that a strategy aimed at increasing degradation of the mutant receptor could lead to diminished phenotype severity.