ABSTRACT: Tendons are prominent members of the family of fibrous connective tissues (FCTs), which collectively are the most abundant tissues in vertebrates and have crucial roles in transmitting mechanical force and linking organs. Tendon diseases are among the most common arthropathy disorders; thus knowledge of tendon gene regulation is essential for a complete understanding of FCT biology. Here we show autonomous circadian rhythms in mouse tendon and primary human tenocytes, controlled by an intrinsic molecular circadian clock. Time-series microarrays identified the first circadian transcriptome of murine tendon, revealing that 4.6% of the transcripts (745 genes) are expressed in a circadian manner.
Project description:This microarray study compared the gene expression profile of rat tail tendon tissue in three different developmental stages: embryonic day 21, postnatal 3 weeks and postnatal 6 weeks.<br><br><br><br>Key words: rat tail tendon, tissue development, embryonic and postnatal
Project description:Collagen- and fibrin-based gels are extensively used to study cell behaviour. However, 2D-3D, collagen-fibrin, and in vivo-in vitro comparisons of gene expression, cell shape and mechanotransduction have not been reported. Here we compared chick tendon fibroblasts (CTFs) at three stages of embryonic development with CTFs cultured in collagen- or fibrin-based tissue engineered constructs (TECs).
Project description:Proteins destined for secretion move from the endoplasmic reticulum (ER, the site of synthesis) to Golgi cisternae then onto the cell surface in transport vesicles. Although the mechanism of anterograde and retrograde transport via vesicles is well understood the temporal coordination of transport between organelles has not been studied. Here we show that the extracellular levels of collagen-I (the most abundant protein in vertebrates) are 24-h rhythmic in tendon, which is the richest source of collagen-I. Rhythmicity is the result of circadian clock control of the secretory pathway via ER-ribosome docking, Tango1-dependent ER export, phosphodiesterase-dependent Golgi-ER retrograde transport of Hsp47 (a collagen molecular chaperone), and Vps33b-dependent post Golgi export, which pause collagen-I transport at each node in the pathway during a 24-hour cycle. The structure and mechanical properties of tendon are also 24-hourly rhythmic. Thus, the circadian clock is a master logistic operator of the secretory pathway in mammalian cells.
Project description:Circadian clocks drive ~24 hr rhythms in tissue physiology. They rely on transcriptional/translational feedback loops driven by interacting networks of clock complexes.To gain insights into the role of the mammary clock, circadian time-series microarrays were performed to identify rhythmic genes in vivo. Breast tissues were isolated at 4 hr intervals for two circadian (24 hourly) cycles, from mice kept under constant darkness to avoid any light- or dark-driven genes.
Project description:The cornea continues to mature after birth to develop a fully functional, refractive and protective barrier tissue. Here we investigated the complex biological events underlying this process by profiling global genome-wide gene expression patterns of the immature postnatal day 10 and seven week-old adult mouse cornea. The lens and tendon were included in the study to increase the specificity of genes identified as up regulated in the corneal samples. Notable similarities in gene expression between the cornea and the tendon were in the mesenchymal extracellular matrix collagen (types I, III, V, VI) and proteoglycan (lumican, decorin and biglycan) genes. Expression similarities in the cornea and lens were limited to certain epithelial genes and the crystallins. Approximately 76 genes were over expressed in the cornea samples that showed basal expression levels in the lens and tendon. Thirty-two of these were novel with no known functions in the cornea. These include genes with a potential role in protection against oxidative stress (Dhcr24, Cdo1, Akr1b7, Prdx6), inflammation (Ltb4dh, Wdr1), ion-transport (Pdzk1ip1, Slc12a2, Slc25a17) and transcription (Zfp36l3, Pdzk1ip1). Direct comparison of the cornea of two ages showed selective up regulation of 50 and 12 genes in the P10 and adult cornea, respectively. Of the up regulated P10 genes several encode extracellular matrix collagens and proteoglycans that are stable components of the adult cornea and their high transcriptional activity at P10 indicate a period of active corneal growth and matrix deposition in the young cornea. Much less is known about the genes selectively over expressed in the adult cornea; some relate to immune response and innervations (Npy), and possibly to electron transport (Cyp24a1, Cyp2f2) and others of yet unknown functions in the cornea (Rgs10, Psmb8, Xlr4)). This study detected expression of genes with known functions in the cornea, providing additional validation of the microarray experiments. Importantly, it identified several novel genes whose functions have not been investigated in the cornea. Experiment Overall Design: Briefly, the corneas were dissected free of the limbus from postnatal day 10 (P10) and seven-week old (adult) mice. To enrich for stromal contribution, the epithelium was scraped off and the cornea placed in TRIzol (Invitrogen Life Technologies, Carlsbad, CA). The scraping off of the epithelium reduced, but did not abrogate epithelial contribution, as judged by the expression of known epithelial markers. The lens and the flexor digitorum longus (FDL) tendon were removed from seven-week old adult mice for isolation of total RNA. For the adult cornea three independent preparations of total RNA was generated. For all the other tissues two independent preparations of total RNA were used. The adult and the P10 microarrays were used as baselines in our previous study of corneal cells in culture to identify genes differentially expressed by cultured cells of the stroma (Chakravarti et al. 2004). Experiment Overall Design: The output fluorescence of the scanned images was analyzed first using the Affymetrix Microarray Suite 5.0 software to compute absolute expression, background calculation and detection call (present, absent or marginal). Background signal was between 42 to 55 arbitrary units, while the noise to signal ratio was between 1.42 to 1.78 arbitrary units. The expression data from all nine arrays were further analyzed as follows. The model-based DNA-Chip Analyzer (dChip) software (http://www.dchip.org/) was used to normalize the data from the image files for array-to-array comparison (Li and Wong 2001). This software uses an invariant-set algorithm as a basis for normalization and a model-based expression index to calculate the expression value for each transcript. To identify gene expression patterns that were statistically significantly different between any two given tissue types, we used the following criteria: (1) fold change ⥠2; (2) difference of mean expression index ⥠100 arbitrary units; (3) t-statistic, p < 0.05.
Project description:Membrane type I-matrix metalloproteinase (MT1-MMP/Mmp14) is an unusual MMP because it is essential for survival in mice with multiple organ systems being affected for reasons that are unclear. Here, we show that the protein (MT1-MMP) and gene (Mmp14) are under strict circadian clock control and conditional knockout in fibroblasts leads to ~16% of the proteome losing or inverting circadian rhythmicity. The result is loss of the actin cytoskeleton and cell-matrix adhesions and major imbalance of the matrisome. Lack of collagen-I monomer turnover results in excess fibril formation in the absence of Mmp14. In the absence of Mmp14, paired-like homeodomain transcription factor 2 (Pitx2) is upregulated and remains in the nucleus where it drives Plod2 expression. The overall result is accumulation of collagen fibrils and elevated pyridinoline crosslinking that renders collagen fibrils insoluble. In conclusion, Mmp14 is a master regulator of circadian rhythms affecting the actin cytoskeleton and cell microenvironment.
Project description:Oesophageal adenocarcinoma (OAC) is one of the ten most prevalent forms of cancer which is showing a rapid increase in incidence and yet exhibits poor survival rates. Compared to many other common cancers, the molecular changes that occur in this disease are relatively poorly understood although genomic sequencing studies have identified several genes encoding chromatin remodeling enzymes that are frequently mutated in OAC. This finding is consistent with the knowledge that one important change that occurs in cancer cells is a reprogramming of the chromatin environment which leads to subsequent changes in their transcriptional profile.
Project description:To determine whether immortalized cells derived from the rat SCN (SCN2.2) retain intrinsic rhythm-generating properties characteristic of the SCN, oscillatory properties of the SCN2.2 transcriptome were analyzed and compared to those found in the rat SCN in vivo using rat U34A Affymetrix GeneChips. This SuperSeries is composed of the following subset Series:; GSE1654: Circadian Profiling of the Transcriptome in Immortalized Rat SCN Cells (3 biological replicates); GSE1673: Circadian Profiling of the Transcriptome in Immortalized Rat SCN Cells: Comparison to Long-Evans Rat SCN Experiment Overall Design: Refer to individual Series
Project description:Tendon is a highly aligned connective tissue, in which the macro-structure consists of collagen-rich fascicles surrounded by interfascicular matrix (IFM). In a series of recent studies in equine tissue, we have demonstrated specialisation of tendon composition, structure and mechanics to achieve the tendon’s functional requirements, specifically reporting extensive specialisation of the IFM region in the energy storing superficial digital flexor tendon. We have also demonstrated loss of functional specialisms with ageing, leading to a hypothesised new paradigm for tendinopathy, focused on the importance of the IFM. However, to date, there have been no studies focused on structure-function specialisation or the IFM in functionally distinct human tendons. Here, we compare the positional anterior tibialis tendon and energy storing Achilles tendon, performing a detailed analysis of the composition and mechanical properties of both fascicle and IFM regions, to test the hypothesis that the IFM in the energy storing Achilles tendon has specialised composition and mechanical properties, and that these specialisations are lost with ageing. We demonstrate that the IFM is specialised in the energy storing Achilles tendon, with greater elasticity and fatigue resistance than in the positional anterior tibialis tendon. While there were few age-related alterations in mechanics, we did identify age-related alterations in the IFM proteome of the Achilles tendon specifically, which is predicted to be regulated by TGF-beta signalling and may be responsible for the trend towards decreased fatigue resistance observed in the Achilles IFM with ageing.
Project description:Transcription profiling by microarray was performed to pinpoint the roles of transforming growth factor B1 (TGFB1) in embryonic differentiation of the small intestine. An organ culture system in which mouse jejunal rudiments were placed on semipermeable platforms and fed with chemically defined serum-free media, supplemented with two concentrations of TGFB1.