Project description:Chondrocyte differentiation is regulated at a transcriptional level and by various hormonal stimuli. Since chondrocyte differentiation is important for normal skeletal growth, inadequate amounts of differentiation can lead to pathological conditions such as osteoarthritis. Transcriptional regulation can be tightly orchestrated by epigenetic regulators. Among these, ubiquitin-like with PHD and RING finger domains 1 (Uhrf1) is reported to have diverse epigenetic functions, including regulation of DNA methylation. However, the physiological functions of Uhrf1 in skeletal tissues remain unclear. Here we show that limb mesenchymal cell-specific Uhrf1 conditional knockout mice (Uhrf1ΔLimb/ΔLimb) exhibit shortened long bones that have morphological deformities due to impaired chondrocyte differentiation and proliferation. RNA-seq performed on primary cultured chondrocytes obtained from control and Uhrf1ΔLimb/ΔLimb mice revealed that expression levels of proliferative chondrocyte marker genes were downregulated, whereas hypertrophic chondrocyte marker genes were upregulated. In addition, gene ontology analyses and Gene Set Enrichment Analysis (GSEA) suggested that limb growth retardation due to compromised chondrocyte differentiation might be caused by increased activity of the focal adhesion signaling pathway. These results indicated that Uhrf1 has a crucial role in normal skeletal maturation by coordinating transcriptional regulatory networks during chondrocyte differentiation.
Project description:Transcriptional regulation can be tightly orchestrated by epigenetic regulators. Among these, ubiquitin-like with PHD and RING finger domains 1 (Uhrf1) is reported to have diverse epigenetic functions, including regulation of DNA methylation. However, the physiological functions of Uhrf1 in skeletal tissues remain unclear. Here we show that limb mesenchymal cell-specific Uhrf1 conditional knockout mice (Uhrf1ΔLimb/ΔLimb) exhibit remarkably shortened long bones that have morphological deformities due to dysregulated chondrocyte differentiation as well as proliferation. RNA-seq performed on primary cultured chondrocytes obtained from Uhrf1ΔLimb/ΔLimb mice demonstrates abnormal acceleration of chondrocyte differentiation. In addition, integrative analyses using RNA-seq and MBD-seq reveal that Uhrf1 deficiency cause decreased genome-wide DNA methylation status and reduction in the promoters of specific genes such as Hspb1, which affects chondrocyte differentiation. These results indicate that Uhrf1 governs cell-type specific transcriptional regulation through genome-wide DNA methylation alteration and regulates consequent cell differentiation and skeletal maturation.
Project description:Histone lysine-to-methionine (K-to-M) mutations have been identified as driver mutations in human cancers. Interestingly, these ‘oncohistone’ mutations inhibit the activity of histone methyltransferases. Therefore, they can potentially be used as versatile tools to investigate the roles of histone modifications. In this study, we generated a genetically engineered mouse line in which an H3.3K36M mutation could be induced in the endogenous H3f3b gene. Since H3.3K36M has been identified as a causative mutation of human chondroblastoma, we induced this mutation in the chondrocyte lineage in mouse embryonic limbs. We found that H3.3K36M causes a global reduction in H3K36me2 and defects in chondrocyte differentiation. Importantly, the reduction of H3K36me2 was accompanied by a collapse of normal H3K27me3 distribution. Furthermore, the changes in H3K27me3, especially the loss of H3K27me3 at gene regulatory elements, were associated with the mis-regulated expression of a set of genes important for limb development, including HoxA cluster genes. Thus, through the in vivo induction of the H3.3K36M mutation, we reveal the importance of maintaining the balance between H3K36me2 and H3K27me3 during chondrocyte differentiation and limb development.
Project description:Endochondral ossification forms and grows the majority of the mammalian skeleton and is tightly controlled through gene regulatory networks. The forkhead box transcription factors Foxc1 and Foxc2 have been demonstrated to regulate aspects of osteoblast function in the formation of the skeleton but their roles in chondrocytes to control endochondral ossification are less clear. We demonstrate that Foxc1 expression is directly regulated by SOX9 activity, one of the earliest transcription factors to specify the chondrocyte lineages. Moreover we demonstrate that elevelated expression of Foxc1 promotes chondrocyte differentiation in mouse embryonic stem cells and loss of Foxc1 function inhibits chondrogenesis in vitro. Using chondrocyte-targeted deletion of Foxc1 and Foxc2 in mice, we reveal a role for these factors in chondrocyte differentiation in vivo. Loss of both Foxc1 and Foxc2 caused a general skeletal dysplasia predominantly affecting the vertebral column. The long bones of the limb were smaller and mineralization was reduced and organization of the growth plate was disrupted. In particular, the stacked columnar organization of the proliferative chondrocyte layer was reduced in size and cell proliferation in growth plate chondrocytes was reduced. Differential gene expression analysis indicated disrupted expression patterns in chondrogenesis and ossification genes throughout the entire process of endochondral ossification in Col2-cre;Foxc1Δ/Δ;Foxc2Δ/Δ embryos. Our results suggest that Foxc1 and Foxc2 are required for correct chondrocyte differentiation and function. Loss of both genes results in disorganization of the growth plate, reduced chondrocyte proliferation and delays in chondrocyte hypertrophy that prevents correct ossification of the endochondral skeleton.
Project description:Smad4 is a central mediator of canonical TGF/BMP signaling and plays important roles in mesenchymal cell aggregation, chondrocyte differentiation, osteoblast differentiation and maturation. However, the regulatory mechanism of Smad4 underlying chondrocyte hypertrophy during skeletal development is unknown. To elucidate the molecular mechanism by which Smad4 deficiency impairs chondrocyte hypertrophy, we performed high-throughput Chip-seq to identify target genes involved in Smad4-regulated chondrocyte hypertrophy. Our results suggest that Smad4 controls chondrocyte hypertrophy through regulating Runx2 expression during skeletal development.
Project description:Smad4 is a central mediator of canonical TGF/BMP signaling and plays important roles in mesenchymal cell aggregation, chondrocyte differentiation, osteoblast differentiation and maturation. However, the regulatory mechanism of Smad4 underlying chondrocyte hypertrophy during skeletal development is unknown. To elucidate the molecular mechanism by which Smad4 deficiency impairs chondrocyte hypertrophy, we performed high-throughput RNA-seq to identify target genes involved in Smad4-regulated chondrocyte hypertrophy. Our results suggest that Smad4 controls chondrocyte hypertrophy through regulating Runx2 expression during skeletal development.
Project description:Cholangiocarcinoma (CCA) is a highly malignant tumor characterized by a lack of effective targeted therapeutic strategies. The protein UHRF1 plays a pivotal role in the preservation of DNA methylation and works synergistically with DNMT1. Posttranscriptional modifications (PTMs), such as ubiquitination, play indispensable roles in facilitating this process. Nevertheless, the specific PTMs that regulate UHRF1 in CCA remain unidentified. We confirmed the interaction between STUB1 and UHRF1 through mass spectrometry analysis. Furthermore, we investigated the underlying mechanisms of the STUB1-UHRF1/DNMT1 axis via co-IP experiments, denaturing IP ubiquitination experiments, nuclear‒cytoplasmic separation and immunofluorescence experiments. STUB1-UHRF1/DNMT1-mediated DNA methylation plays a crucial role in promoting the epigenetic silencing of tumor suppressor genes (TSGs) and facilitating tumor progression. To investigate the specific TSGs regulated by the STUB1-UHRF1/DNMT1 axis in CCA cells, RNA-seq analysis of overexpressed STUB1 and negative control TFK1 cells was performed.
Project description:Bone morphogenetic proteins (BMPs) regulate many aspects of skeletal development, including osteoblast and chondrocyte differentiation, cartilage and bone formation, and cranial and limb development. Among them, BMP2, one of the most potent osteogenic signaling molecules, stimulates osteoblast differentiation. We used cDNA microarrays to elucidate regulators of BMP-2-induced osteoblast differentiation.
Project description:Bone morphogenetic proteins (BMPs) regulate many aspects of skeletal development, including osteoblast and chondrocyte differentiation, cartilage and bone formation, and cranial and limb development. Among them, BMP2, one of the most potent osteogenic signaling molecules, stimulates osteoblast differentiation, while it inhibits myogenic differentiation in C2C12 cells. We used cDNA microarrays to elucidate regulators of BMP-2-induced osteoblast differentiation.