Project description:We show that reduced dosage of ERF, which encodes an inhibitory ETS transcription factor directly bound by ERK1/2 , causes complex craniosynostosis (premature fusion of the cranial sutures) in humans and mice. Features of this newly recognized clinical disorder include multiple suture synostosis, craniofacial dysmorphism, Chiari malformation and language delay. Mice with functional Erf reduced to ~30% of normal exhibit postnatal multisuture synostosis; by contrast, embryonic calvarial development appears mildly delayed. Using chromatin immunoprecipitation in mouse embryonic fibroblasts and high-throughput sequencing, we find that ERF binds preferentially to distal regulatory elements containing RUNX or AP1 motifs. This work identifies ERF as a novel regulator of osteogenic stimulation by RAS-ERK signaling, potentially by competing with activating ETS factors in multifactor transcriptional complexes. Examination of Erf binding site in E13.5 mouse embryo fibroblasts, growing in the presence or absence of serum for 4 hours
Project description:We show that reduced dosage of ERF, which encodes an inhibitory ETS transcription factor directly bound by ERK1/2 , causes complex craniosynostosis (premature fusion of the cranial sutures) in humans and mice. Features of this newly recognized clinical disorder include multiple suture synostosis, craniofacial dysmorphism, Chiari malformation and language delay. Mice with functional Erf reduced to ~30% of normal exhibit postnatal multisuture synostosis; by contrast, embryonic calvarial development appears mildly delayed. Using chromatin immunoprecipitation in mouse embryonic fibroblasts and high-throughput sequencing, we find that ERF binds preferentially to distal regulatory elements containing RUNX or AP1 motifs. This work identifies ERF as a novel regulator of osteogenic stimulation by RAS-ERK signaling, potentially by competing with activating ETS factors in multifactor transcriptional complexes.
Project description:Assaying gene expression in sutural bone fragments from patients diagnosed with non-syndromic craniosynostosis. Sutural fragments were collected from both the fused and patent cranial suture of infants during cranial vault reconstruction. Gene expression was compared between the patent and fused sutures using the paired t-test. The aim was to identify thoses genes significantly differentially expressed in fused suture relative to patent. Total RNA isolated from patent and fused human cranial sutures was assayed. Expression in synostosed suture was compared to patent suture.
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:Assaying gene expression in sutural bone fragments from patients diagnosed with non-syndromic craniosynostosis. Sutural fragments were collected from both the fused and patent cranial suture of infants during cranial vault reconstruction. Gene expression was compared between the patent and fused sutures using the paired t-test. The aim was to identify thoses genes significantly differentially expressed in fused suture relative to patent.
Project description:The patterning and ossification of the mammalian skeleton requires the coordinated actions of both intrinsic bone morphogens and extrinsic neurovascular signals, which function in a temporal and spatial fashion to control mesenchymal progenitor cell (MPC) fate. Here we show genetic inhibition of Tropomyosin receptor kinase A (TrkA) sensory nerve innervation of the developing cranium results in premature calvarial suture closure, associated with a decrease in suture MPC proliferation. In vitro, axons from peripheral afferent neurons derived from DRGs of wild type mice induce MPC proliferation in a spatially-restricted manner via a soluble factor when co-cultured in microfluidic chambers. Comparative spatial transcriptomic analysis of the cranial sutures in vivo confirmed a positive association between sensory axons and proliferative MPCs. SpatialTime analysis across the developing suture revealed regional-specific alterations in BMP and TGFβ signaling pathway transcripts in response to TrkA inhibition. RNA sequencing of DRG cell bodies following direct axonal co-culture with MPCs confirmed alterations in BMP/TGFβ signaling pathway transcripts. Among these, the BMP inhibitor FSTL1 (Follistatin-like 1) replicated key features of the neural-to-bone influence, including mitogenic and anti-osteogenic effects via inhibition of BMP/TGFβ signaling. Taken together, our results demonstrate that sensory nerve-derived signals, including FSTL1, function to coordinate cranial bone patterning by regulating MPC proliferation and differentiation in the suture mesenchyme.
Project description:The presence of the extracellular matrix within human bone limits the applicability of conventional protocols for protein extraction. As a result, complete and accurate characterization of human bone proteome is yet to be performed, and as a result, several bone-related diseases such as craniosynostosis and osteosarcoma are still poorly understood. We sought to develop a reproducible method for extracting whole proteins of varying molecular weights from human cranial bone. Whole protein was extracted from human cranial suture by mechanically processing samples using a method that minimized heat introduction to proteins to limit degradation. Western blotting suggests the presence of whole protein while mass spectrometry was used to sequence peptides and identify isolated proteins. Molecular weights of extracted protein ranged from 9.4-629 kDa and contained proteins of both intra- and extra-cellular origin. High correlation scores among suture protein spectral counts suggest the reproducibility of the method. Ontology analytics revealed proteins of myriad functions including mediators of metabolic processes and cell organelles. These results suggest a reproducible method for isolation of whole protein representing a large range of molecular weights, origins and functions.
Project description:Craniosynostosis (CS) is a common birth defect due to the premature fusion of one or more cranial sutures. It manifests with abnormal skull shape and is associated with significant morbidities such as increased intracranial pressure, vision problems, and learning disabilities. Nonsyndromic craniosynostosis (NCS) occurs without any other associated birth defects and/or developmental delays and accounts for approximately 75% of all cases. Synostosis of the sagittal suture is the most common NCS subtype, accounting for 45-58% of all cases. Currently, surgical treatment is the only option to reshape the skull and allow for proper cranial growth. This surgical treatment is extensive and performed during the first year of life. Only one other study has examined the proteomic profile of cranial suture tissue derived from NCS patients. In order to understand how different proteins play a role in premature suture fusion and to potentially identify proteins that can serve as diagnostic and prognostic biomarkers for NCS, we identified biologically relevant differentially expressed proteins in NCS-derived tissues representing different stages in suture development.
Project description:The bone tissue undergoes constant turnover, which relies on skeletal stem cells (SSCs) and/or mesenchymal stem cells (MSCs) and their niches. SSCs/MSCs and their perivascular niche within the bone marrow are well characterized in long bones. As for cranial bones, besides bone marrow, the suture mesenchyme has been identified as a unique niche for SSCs/MSCs of craniofacial bones. However, a comprehensive study of the two different cranial stem cell niches at single-cell resolution is still lacking. In addition, during the progression of aging, age-associated changes in cranial stem cell niches and resident cells remain uncovered. In this study, we investigated age-related changes in cranial stem cell niches via single-cell RNA sequencing (scRNA-seq).