Unknown,Transcriptomics,Genomics,Proteomics

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Regulation of chondrogenesis in early murine limb mesenchyme by BMP signals

ABSTRACT: Numerous studies have established a critical role for BMP signaling in skeletal development. In the developing axial skeleton, sequential SHH and BMP signals are required for specification of a chondrogenic fate in somitic tissue. A similar paradigm is thought to operate in the limb, but the signals involved are unclear. To investigate the nature of these signals we examined BMP action in mesenchymal populations derived from the early murine limb bud (~ E10.5). These populations exhibited a graded response to BMPs, in which early limb mesenchymal (EL) cells (from the distal hind limb) displayed an anti-chondrogenic response, whereas BMPs promoted chondrogenesis in older cell populations. To better understand the molecular basis of disparate BMP action in these various populations, gene expression profiling with Affymetrix microarrays was employed to identify BMP-regulated genes. These analyses showed that BMPs induced a distinct gene expression pattern in the EL cultures versus later mesenchymal limb populations (IM and LT). Mouse embryos at gestational age E10.5 were collected and various portions of the limb were micro-dissected. These led to the generation of three populations of cells, early (EL) limb mesenchymal cells from the distal half of the hind limb, an intermediate (IM) population derived from the distal 1/3 of the fore limb, and a later (LT) population from the proximal 2/3 of the fore limb. Mesenchymal cells were isolated and cultured with and without BMP4 treatment. RNA was extracted from cultures at either Day 0,1 or 2, labelled and hybridized to Affymetrix 430 2.0 microarrays. For each time point, RNA was collected from two biological replicates for each treatment condition.

ORGANISM(S): Mus musculus

SUBMITTER: T Underhill

PROVIDER: E-GEOD-20398 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:WNT signaling is critical in most aspects of skeletal development and homeostasis, and antagonists of WNT signaling are emergning as key regulatory proteins with great promise as therapeutic agents for bone disorders. Until recently Sost and its paralog Sostdc1 have been described as growth factors with highly restricted expression in the adult where Sost was assumed 'osteocyte-' and Sostdc1 'kidney-' specific. Here we show that these two proteins emerged throgh ancestral genome duplication and their expression patterns have diverged to span complimentary domains in most organ systems including musculoskeletal, cardiovascular, nervous, digestive, reproductive and respiratory. In the developing limb, Sost and Sostdc1 display dynamic expression patterns with Sost being restricted to the distal ectoderm and Sostdc1 to the proximal ectoderm and the mesenchyme. While Sostdc1-/- mice lack any obvious limb and skeletal defects, Sost-/- mice recapitulate the hand defects described for sclerosteosis patients. However, elevated WNT signaling in Sost-/-; Sostdc1-/- mice causes misregulation of SHH signaling, ectopic activation of Sox9 in the digit 1 field and ultimately preaxial polydactyly. In addition, we show that the syndactyly documented in Sclerosteosis is present in both Sost-/- and Sost-/-; Sostdc1-/- mice, and is driven by misregulation of Fgf8 in the AER, a region lacking Sost and Sostdc1 expression. This study highlights the complexity of WNT signaling in skeletal biology and disease and emphasizes how redundant mechanisms and non-cell autonomous effects can synergize to unveil new intricate phenotypes caused by elevated WNT signaling. Five arrays were analyzed, consisting of two total embryonic fore-limb RNA (experimental) and three total embryonic forelimb RNA (reference) samples at E11.5 DPC mouse (C57Bl6 strain). Embryos were not pooled to generate samples. Each time point has 3 to 5 biological replicates for limb bud samples, duplicates for whole embryos. Comparisons were made between limb bud samples and whole embryo at the same stage, fore-limb samples of different stages, hind-limb samples of different stages, and fore-limb samples compared to hind-limb samples at the same or the next stage.

Project description:Detailed information about stage-specific changes in gene expression is crucial for understanding the gene regulatory networks underlying development and the various signal transduction pathways contributing to morphogenesis. Here, we describe the global gene expression dynamics during early murine limb development, when cartilage, tendons, muscle, joints, vasculature, and nerves are specified and the musculoskeletal system of the limbs is established. We used whole-genome microarrays to identify genes with differential expression at 5 stages of limb development (E9.5 to 13.5), during fore-limb and hind-limb patterning. We found that the onset of limb formation is characterized by an up-regulation of transcription factors, which is followed by a massive activation of genes during E10.5 and E11.5 which tampers off at later time points. Among 3520 genes identified as significantly up-regulated in the limb, we find ~30% to be novel, dramatically expanding the repertoire of candidate genes likely to function in the limb. Hierarchical and stage-specific clustering identified expression profiles that correlate with functional programs during limb development and are likely to provide new insights into specific tissue patterning processes. Here we provide for the first time, a comprehensve analysis of developmentally regulated genes during murine limb development, and provide some novel insights into the expression dynamics governing limb morphogenesis. Fifty- one arrays were analyzed, consisting of whole fore-limb and hind-limb bud RNA (experimental) and whole embryo RNA (reference) samples from E9.5 to E13.5 DPC mouse (FVB strain). Embryos were not pooled to generate samples. Each time point has 3 to 5 biological replicates for limb bud samples, duplicates for whole embryos. Comparisons were made between limb bud samples and whole embryo at the same stage, fore-limb samples of different stages, hind-limb samples of different stages, and fore-limb samples compared to hind-limb samples at the same or the next stage.

Project description:H1299 cells were stably transfected with the Oct4 promoter/GFP or Nestin promoter/GFP reporter vectors. By FACS, 106 cells expressing high levels of GFP were isolated and placed into cell culture for twenty-four hours. Total RNA was used. Bone morphogenetic proteins (BMP) are aberrantly expressed in most lung carcinomas. BMPs mediate cell fate decisions and self-renewal of stem cells. Inhibition of BMP signaling decreases the growth and induces cell death of lung cancer cells lines. It is not known whether the BMP signaling cascade is growth promoting in lung cancer cells expressing the stem cell markers Oct4 and/or nestin. Lung cancer cells expressing Oct4 or nestin were isolated from lung cancer cell lines by stably transfecting the Oct4 promoter or Nestin promoter expression vectors that activate the green fluorescent protein reporter. Our studies support that lung cancer cells activating the Oct4 or nestin promoter are different cell populations. Microarray and quantitative RT-PCR demonstrated that the expression levels of specific stem cell markers were different between the isolated Oct4 and nestin cells. Both the Oct4 and nestin populations were more tumorigenic that controls but histologically they were quite different. The isolated Oct4 and nestin cells also responded differently to inhibition of BMP signaling. Blockade of BMP signaling with the BMP receptor antagonist DMH2 caused significant growth inhibition in both the Oct4 and nestin cell populations but only increased cell death in the nestin population. DMH2 also induced the expression of nestin in the Oct4 population but not in the nestin cells. We also show that BMP signaling is an important regulator of the inhibitor differentiation proteins Id1 and Id3 in Oct4 and nestin cell populations Lung cancer cells expressing Oct4 or nestin were isolated and transfected with Oct4 or Nestin promoter expression vectors that activate the green fluorescent protein reporter. Microarray and quantitative RT-PCR were performed to study the differentially expressed genes. BMPs mediate cell fate decisions and self-renewal of stem cells were investigated.

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Regulation of chondrogenesis in early murine limb mesenchyme by BMP signals

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