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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).

ORGANISM(S): Mus musculus

PROVIDER: GSE20398 | GEO | 2010/04/01

SECONDARY ACCESSION(S): PRJNA125529

REPOSITORIES: GEO

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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.

Project description:A fundamental question in biology is how an undifferentiated field of cells acquires spatial pattern and undergoes coordinated differentiation. The development of the vertebrate limb is an important paradigm for understanding these processes. The skeletal and connective tissues of the developing limb all derive from a population of multipotent progenitor cells located in its distal tip. During limb outgrowth, these progenitors segregate into a chondrogenic lineage, located in the center of the limb bud, and soft connective tissue lineages located in its periphery. We report that the interplay of two families of signaling proteins, fibroblast growth factors (FGFs) and Wnts, coordinate the growth of the multipotent progenitor cells with their simultaneous segregation into these lineages. FGF and Wnt signals act together to synergistically promote proliferation while maintaining the cells in an undifferentiated, multipotent state, but act separately to determine cell lineage specification. Withdrawal of both signals results in cell cycle withdrawal and chondrogenic differentiation. Continued exposure to Wnt however, maintains proliferation and re-specifies the cells towards the soft connective tissue lineages. We have identified target genes that are synergistically regulated by Wnts and Fgfs, and show how these factors actively suppress differentiation and promote growth. Finally, we show how the spatial restriction of Wnt and FGF signals to the limb ectoderm and to a specialized region of it, the apical ectodermal ridge, controls the distribution of cell behaviors within the growing limb, and guides the proper spatial organization of the differentiating tissues. Keywords: transcriptional response to growth factor treatment Cells derived from mouse embryonic stage 11.5 limb buds were cultured and treated with purified Wnt3a protein or vehicle controls. The transcriptional response was detected using spotted cDNA microarrays after 2 hrs or 4 hrs of treatment. 4 biological replicates were used per condition.

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Regulation of chondrogenesis in early murine limb mesenchyme by BMP signals

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