Project description:S309W mutation of SP7 is found in a patient with craniosynostosis, cranial hyperostosis, and long bone fragility. In this experiment we aimed to compare the effect of the mutation on SP7 genomic binding in the presence of DLX5
Project description:SP7/Osterix is a transcription factor critical for osteoblast maturation and bone formation. We identidied a missense variant (c.926C>G:p.S309W) in SP7 in a patient with a unique high turnover bone disease. Mice with the corresponding variant similarly showed a complex skeletal phenotype distinct from that of Sp7-null mice. We therefore performed ChIP-Seq in primary chondrocytes to study how the mutation alters the genomic binding of SP7.
Project description:Some cuboidal osteoblasts differentiate into bone-embedded, dendrite-bearing osteocytes through the poorly-understood process of osteocytogenesis. Here, we report that the transcription factor Sp7 plays an essential role in osteocytogenesis. Severe defects in bone integrity and osteocyte dendrite morphology are noted in mice lacking Sp7 at the stage of the osteoblast-to-osteocyte transition. In osteocytes, Sp7 controls expression of a neuronally-enriched gene network. Analysis of the osteocyte-specific Sp7 cistrome reveals distinct genomic binding motifs and target sites distinct from those in osteoblasts. Amongst osteocyte-specific Sp7 targets, the secreted peptide osteocrin rescues Sp7-deficient defects. Single-cell transcriptional profiling of cells undergoing osteocytogenesis identifies novel Sp7-dependent transitional cell types enriched in genes linked to human fracture risk. Finally, humans with an SP7 R316C mutation display osteocyte morphology defects similar to those observed in mouse models. These findings demonstrate that cuboidal osteoblasts use a neuronally-enriched Sp7/osteocrin gene expression program to differentiate into dendrite-bearing osteocytes.
Project description:Some cuboidal osteoblasts differentiate into bone-embedded, dendrite-bearing osteocytes through the poorly-understood process of osteocytogenesis. Here, we report that the transcription factor Sp7 plays an essential role in osteocytogenesis. Severe defects in bone integrity and osteocyte dendrite morphology are noted in mice lacking Sp7 at the stage of the osteoblast-to-osteocyte transition. In osteocytes, Sp7 controls expression of a neuronally-enriched gene network. Analysis of the osteocyte-specific Sp7 cistrome reveals distinct genomic binding motifs and target sites distinct from those in osteoblasts. Amongst osteocyte-specific Sp7 targets, the secreted peptide osteocrin rescues Sp7-deficient defects. Single-cell transcriptional profiling of cells undergoing osteocytogenesis identifies novel Sp7-dependent transitional cell types enriched in genes linked to human fracture risk. Finally, humans with an SP7 R316C mutation display osteocyte morphology defects similar to those observed in mouse models. These findings demonstrate that cuboidal osteoblasts use a neuronally-enriched Sp7/osteocrin gene expression program to differentiate into dendrite-bearing osteocytes.
Project description:Some cuboidal osteoblasts differentiate into bone-embedded, dendrite-bearing osteocytes through the poorly-understood process of osteocytogenesis. Here, we report that the transcription factor Sp7 plays an essential role in osteocytogenesis. Severe defects in bone integrity and osteocyte dendrite morphology are noted in mice lacking Sp7 at the stage of the osteoblast-to-osteocyte transition. In osteocytes, Sp7 controls expression of a neuronally-enriched gene network. Analysis of the osteocyte-specific Sp7 cistrome reveals distinct genomic binding motifs and target sites distinct from those in osteoblasts. Amongst osteocyte-specific Sp7 targets, the secreted peptide osteocrin rescues Sp7-deficient defects. Single-cell transcriptional profiling of cells undergoing osteocytogenesis identifies novel Sp7-dependent transitional cell types enriched in genes linked to human fracture risk. Finally, humans with an SP7 R316C mutation display osteocyte morphology defects similar to those observed in mouse models. These findings demonstrate that cuboidal osteoblasts use a neuronally-enriched Sp7/osteocrin gene expression program to differentiate into dendrite-bearing osteocytes.
Project description:Sp7/Osterix is a master regulator of osteoblast specification. To identify the Sp7-mediated gene regulatory network in osteoblasts, we performed Sp7 ChIP-seq on primary mouse calvarial osteoblasts comparing the DNA binding profile with the transcriptional profile of Sp7-positive osteoblasts. Analysis of these identified a network of Sp7 regulated osteoblast targets and provides a new insight into the mode of Sp7 action in osteoblast. To further study for the Sp7 mode, we performed ChIP-seq for Sp1, Sp7, Dlx5, as a potential Sp7 partner identified in this study and mutated Sp7 which has mutations in the zinc finger domain, by using in vitro system with a pre-osteoblast mouse cell line, MC3T3E1.
Project description:The transgenic zebrafish line Tg(sp7:sp7-GFP) (ulg071 Tg) was used to obtain fluorescent cells through FACS sorting. Two populations were identifed: P1 displaying low fluorescence, P2 displaying high fluorescence. Cells were collected and sumitted to RNA-Seq
Project description:To identify Sp7’s molecular interactions in vivo, we used gene-targeting strategies to generate an Sp7-Biotin-3xFLAG knock-in mouse (Sp7-BioFL mouse). This approach appends a biotin (Bio) recognition motif and three copies of the FLAG (FL) epitope at the C-terminus of the Sp7 protein. To validate this knockin system, we compared ChIP-seq results in the MC3T3E1 osteoblast cell line, introducing Sp7 forms that were epitope-tagged at either the N- (N-terminal FLAG tag; MC3_FLAG-Sp7) or C-terminus (C-terminal Biotin-FLAG tag, as in the in vivo targeted allele; MC3_Sp7-BioFLAG). These data show an extensive overlap, suggesting that FLAG tagging at different positions gives comparable outcomes. Second, we examined ChIP on wild-type calvarial primary osteoblasts (POB) using an anti-Sp7 antibody (POB_Sp7Ab-ChIP). The majority of Sp7-Ab ChIP-seq peaks (95%) overlapped with the larger set identified by Sp7-BioFL ChIP-seq.