Transcriptomic Analysis of Wild Type and Mkx-/- Tendon by Next Generation Sequencing
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ABSTRACT: We compared differential gene expression profiles between wild type(WT) and Mkx-/- tendon to reveal how Mkx regulats tendon differentiation and homeostasis maintenance .
Project description:Tendons are crucial connective tissues that link muscle to bone. We have demonstrated that the transcription factor Mkx plays a pivotal role in tendon development and homeostasis by regulating collagen fibril organization through tendon cell fate determination from progenitor cells and promoting the expression of type I collagen and proteoglycans. However, the precise role of Mkx in tendon homeostasis after birth is not well understood. Therefore, we generated conditional Mkx knockout mice by crossing Mkx-CreER mice with Mkx floxed mice. Following tamoxifen administration, we performed transcriptome analysis of tendons from control mice (Mkx-CreER/+ and Mkx flox/+) and Mkx conditional knockout mice (Mkx-CreER/flox)
Project description:Analysis of C3H10T1/2 cells overexpressing Mkx. This microarray results show that Mkx has the potential ability to promote differentiation to tendon, ligament and annulus fibrosus cells.
Project description:The periodontal ligament (PDL), which connects the teeth to the alveolar bone, is essential for periodontal tissue homeostasis. Although the significance of the PDL is recognized, molecular mechanisms underlying PDL function are not well-known. We report that Mohawk homeobox (Mkx), a tendon-specific transcription factor, regulates PDL homeostasis by preventing its degeneration. Mkx is expressed in the mouse PDL at the age of 10 weeks and 12 months. In Mkx-/- mice, age-dependent expansion of the PDL at the maxillary 1st molar (M1) furcation area was observed. Transmission electron microscopy (TEM) revealed that Mkx-/- mice presented collagen fibril degeneration in PDL with age, while the collagen fibril diameter gradually increased in Mkx+/+ mice. PDL cells lost their shape in Mkx-/- mice, suggesting changes in PDL properties. Microarray and quantitative polymerase chain reaction (qPCR) analyses of Mkx-/- PDL revealed an increase in osteogenic gene expression and no change in PDL- and inflammatory-related gene expression. Additionally, COL1A1 and COL1A2 were upregulated in Mkx-overexpressing human PDL fibroblasts, whereas osteogenic genes were downregulated. Our results indicate that Mkx prevents PDL degeneration by regulating osteogenesis. Mohawk transcription factor is essential for homeostasis of the periodontal ligament by regulating osteogenic changes with age.
Project description:The regeneration of craniofacial bones of the mammalian skeleton necessitates the action of both intrinsic and extrinsic inductive factors from multiple cell types, which function in a hierarchical and temporal fashion to control the differentiation of osteogenic progenitors. Single-cell transcriptomics of developing mouse cranial suture recently identified a suture mesenchymal progenitor population with tendon- or ligament-associated gene expression profile previously uncharacterized. Here, we developed a Mohawk homeobox (MkxCG;R26RtdT) reporter mouse, finding that this teno-ligamentous gene identifies a cranial suture resident cell population within the adult mouse that gives rise to calvarial osteoblasts and osteocytes overtime during homeostatic conditions. Single cell RNA-Sequencing (scRNA-Seq) demonstrated that Mkx+ suture cells demonstrate a stem-like phenotype with expression of teno-ligamentous genes. Bone injury with Mkx+ cell ablation showed delayed bone healing. Remarkably, Mkx gene played a critical role as an osteo-inhibitory factor in cranial suture cells, as knockdown or knockout resulted in increased osteogenic differentiation. Furthermore, in vivo local deletion of Mkx in Mkx floxed mice resulted in robustly increased calvarial defect repair. Finally, we observed that mechanical stretch dynamically regulates Mkx expression in turn regulating calvarial cell osteogenesis. Overall, we identify Mkx+ cells within the suture mesenchyme as a progenitor cell population for adult craniofacial bones required for bone repair and Mkx itself as mechanical stretch responsive gene which functions to prevent osteogenic differentiation within the stem cell niche.
Project description:Tendons are composed of a heterogeneous cell environment, with Scleraxis-lineage (ScxLin) cells being the predominant population. Although ScxLin cells are required for maintenance of tendon homeostasis, their functions during tendon healing are unknown. To this end, we first characterized the spatiotemporal dynamics of ScxLin cells during tendon healing, and identified that the overall ScxLin pool continuously expands up to early remodeling healing phase. To better define the function of ScxLin cells during the late proliferative phase of healing, we inducibly depleted ScxLin cells from day 14-18 post-surgery using the Scx-Cre; Rosa-DTR mouse model, with local administration of diphtheria toxin inducing apoptosis of ScxLin cells in the healing tendon. At D28 post-surgery, ScxLin cell depleted tendons (DTRScxLin) had substantial impairments in structure and function, relative to WT, demonstrating the importance of ScxLin cells during tendon healing. Next, bulk RNAseq was utilized to identify the underlying mechanisms that were impaired with depletion and revealed that ScxLin depletion induced molecular and morphological stagnation of the healing process at D28. However, this stagnation was transient, such that by D56 tendon mechanics in DTRScxLin were not significantly different than wildtype repairs. Collectively, these data offer fundamental knowledge on the dynamics and roles of ScxLin cells during tendon healing.
Project description:The progenitors of Drosophila leg tendon are specified among leg disc epithelium during third larval instar. At the end of larval stages and beiginning of pupae formation, tendon cells invaginate and then collectively migrate to form a tube-shaped structure.
Project description:Six rats (treatment group) underwent a 13-week downhill treadmill running exercise programme and six rats (control group) were studied in this experiments. The RNAs were extracted from rat Achille's tendon tissue and sequenced using Illumina Hiseq platform.