Characterization of GDF-10 expression patterns and null mice.
(1/12)
Growth/differentiation factor-10 (GDF-10) is a TGF-beta family member highly related to bone morphogenetic protein-3. In order to determine the biological function of GDF-10, we carried out a detailed analysis of the expression pattern of GDF-10 and characterized GDF-10-null mice that we generated by gene targeting. During embryogenesis GDF-10 is expressed prominently in developing skeletal structures both in the craniofacial region and in the vertebral column. In adult animals, GDF-10 is expressed at high levels in the brain, where GDF-10 is localized primarily to cells in the Purkinje cell layer of the cerebellum, and in the uterus, where the expression levels of GDF-10 are regulated both during the menstrual cycle and during pregnancy. Despite the high levels of GDF-10 expression in these tissues, we found no obvious abnormalities in GDF-10-knockout mice with respect to the development of these tissues. These findings suggest either that GDF-10 plays no regulatory role in these tissues or that its function is redundant with that of other growth factor-like molecules. (+info)
Caveolin-1 and caveolin-2,together with three bone morphogenetic protein-related genes, may encode novel tumor suppressors down-regulated in sporadic follicular thyroid carcinogenesis.
(2/12)
Thyroid cancer is common, occurring in 1% of the general population. The relative frequencies of two of the most common subtypes of thyroid carcinoma, follicular (FTC) and papillary (PTC), vary depending on the regional prevalence of iodine deficiency. Although PTC has been more extensively studied, the etiology of sporadic FTC is poorly understood. To further elucidate this, we conducted microarray expression comparison of FTC tumors and normal thyroid tissue. Three commonly down-regulated genes, caveolin-1, caveolin-2, and GDF10/BMP3b, were chosen for further study on the basis of their localization to two chromosomal regions, 7q31.1 and 10q11.1, that commonly show loss of heterozygosity in FTC. Two additional genes, glypican-3 and a novel chordin-like gene, were also analyzed in view of their involvement in bone morphogenetic protein signaling and possible interaction with GDF10. Each of these five genes was down-regulated in >or=15 of 19 FTC tumors (79%) by semiquantitative reverse transcription-PCR. Caveolin-1 showed preferential down-regulation of its beta-isoform at both the mRNA and protein level, suggesting a distinct function for this isoform. Caveolin-1 is of particular functional interest because it has been shown to interact with PTEN, the tumor suppressor gene mutated in Cowden syndrome, an inherited multiple hamartoma syndrome that includes predisposition to FTC. Immunohistochemical analysis of 141 thyroid tumors of various histological types showed significantly fewer caveolin-1-positive tumors in FTCs, including insular type tumors, and Hurthle cell carcinomas in comparison with normal thyroid. PTC and anaplastic thyroid carcinomas did not show significant down-regulation, and thus, caveolin-1 may become a useful molecular marker to differentiate the various histologies of thyroid malignancies. (+info)
Interaction between the bone morphogenetic proteins and Ras/MAP-kinase signalling pathways in lung cancer.
(3/12)
Bone morphogenetic proteins (BMPs) are an integral component of the TGFbeta superfamily, responsible for regulation of cell proliferation, differentiation, migration and programmed cell death in a variety of cell types. The BMPs transduce their signals directly through the SMAD family of proteins but they also have been reported to interact with the MAPK and Erk pathways. Inactivation of the BMP pathway genes has been implicated as important in several cancers. Recent work has shown that BMP3b is epigenetically inactivated in cancer and suggests that BMP6 can be epigenetically inactivated. We investigated whether BMP6 is epigenetically inactivated in cell lines and whether BMP3b and BMP6 are epigenetically inactivated in non-small-cell lung cancer (NSCLC). We also studied the relationship between BMP methylation and k-ras mutation. Here, we demonstrate that the BMP3b and BMP6 genes are common targets of epigenetic inactivation in NSCLC, and that they are significantly more likely to be concurrently inactivated (P=0.009). Furthermore, this coinactivation of BMP3b and BMP6 is significantly associated with mutation of k-ras codon 12 in lung cancer (P=0.003); those with a k-ras mutation were six times more likely to have concurrent methylation of these BMP loci. Hence, these data suggest that concurrent inactivation of the BMP and activation of the Ras signalling pathways are important in lung carcinogenesis. (+info)
Hoxa-10 deficiency alters region-specific gene expression and perturbs differentiation of natural killer cells during decidualization.
(4/12)
Uterine decidualization, a key event for successful implantation, is critically controlled by stromal cell proliferation and differentiation. One hallmark event of decidualization is the acquisition of stromal cell polyploidy through terminal differentiation at the anti-mesometrial pole of the implantation site. Hoxa-10, a developmentally regulated homeobox transcription factor, is highly expressed in decidualizing stromal cells, and targeted deletion of Hoxa-10 in mice shows severe decidualization defects, primarily due to reduced stromal cell responsiveness to progesterone. However, the underlying molecular mechanism by which Hoxa-10 regulates this process remains largely unknown. Here, we show that Hoxa-10 deficiency confers diminished core cell cycle activity during stromal cell proliferation without disturbing polyploidy, suggesting that these events depend on local regulators that impact cell cycle machinery. To further address this question, we compared global gene expression profiles in uteri of wild-type and Hoxa-10(-/-) mice after inducing decidualization. Our studies show two major aspects of decidualization downstream of Hoxa-10. First, Hoxa-10 deficiency results in the aberrant region-specific expression of cyclin-dependent kinase-4 (cdk4) and -6 (cdk6), growth differentiation factor 10 (Gdf10), hepatocyte growth factor (Hgf) and Snail2. Second, Hoxa-10 deficiency compromises natural killer (NK) cell differentiation without altering trafficking of NK precursor cells during decidualization. Collectively, the results provide evidence that Hoxa-10 influences a host of genes and cell functions necessary for propagating normal decidual development during the post-implantation period. (+info)
Gradients in bone morphogenetic protein-related gene expression across the growth plate.
(5/12)
In the growth plate, stem-like cells in the resting zone differentiate into rapidly dividing chondrocytes of the proliferative zone and then terminally differentiate into the non-dividing chondrocytes of the hypertrophic zone. To explore the molecular switches responsible for this two-step differentiation program, we developed a microdissection method to isolate RNA from the resting (RZ), proliferative (PZ), and hypertrophic zones (HZ) of 7-day-old male rats. Expression of approximately 29,000 genes was analyzed by microarray and selected genes verified by real-time PCR. The analysis identified genes whose expression changed dramatically during the differentiation program, including multiple genes functionally related to bone morphogenetic proteins (BMPs). BMP-2 and BMP-6 were upregulated in HZ compared with RZ and PZ (30-fold each, P < 0.01 and 0.001 respectively). In contrast, BMP signaling inhibitors were expressed early in the differentiation pathway; BMP-3 and gremlin were differentially expressed in RZ (100- and 80-fold, compared with PZ, P < 0.001 and 0.005 respectively) and growth differentiation factor (GDF)-10 in PZ (160-fold compared with HZ, P < 0.001). Our findings suggest a BMP signaling gradient across the growth plate, which is established by differential expression of multiple BMPs and BMP inhibitors in specific zones. Since BMPs can stimulate both proliferation and hypertrophic differentiation of growth plate chondrocytes, these findings suggest that low levels of BMP signaling in the resting zone may help maintain these cells in a quiescent state. In the lower RZ, greater BMP signaling may help induce differentiation to proliferative chondrocytes. Farther down the growth plate, even greater BMP signaling may help induce hypertrophic differentiation. Thus, BMP signaling gradients may be a key mechanism responsible for spatial regulation of chondrocyte proliferation and differentiation in growth plate cartilage. (+info)
Hypoxia promotes the differentiated human articular chondrocyte phenotype through SOX9-dependent and -independent pathways.
(6/12)
The chondrocyte is solely responsible for synthesis and maintenance of the resilient articular cartilage matrix that gives this load-bearing tissue its mechanical integrity. When the differentiated cell phenotype is lost, the matrix becomes compromised and cartilage function begins to fail. We have recently shown that hypoxia promotes the differentiated phenotype through hypoxia-inducible factor 2alpha (HIF-2alpha)-mediated SOX9 induction of the main matrix genes. However, to date, only a few genes have been shown to be SOX9 targets, while little is known about SOX9-independent regulators. We therefore performed a detailed microarray study to address these issues. Analysis involved 35 arrays on chondrocytes obtained from seven healthy, non-elderly human cartilage samples. Genes were selected that were down-regulated with serial passage in culture (as this causes loss of the differentiated phenotype) and subsequently up-regulated in hypoxia. The importance of key findings was further probed using the technique of RNA interference on these human articular chondrocytes. Our results show that hypoxia has a broader beneficial effect on the chondrocyte phenotype than has been previously described. Of special note, we report new hypoxia-inducible and SOX9-regulated genes, Gdf10 and Chm-I. In addition, Mig6 and InhbA were induced by hypoxia, predominantly via HIF-2alpha, but were not regulated by SOX9. Therefore, hypoxia, and more specifically HIF-2alpha, promotes both SOX9-dependent and -independent factors important for cartilage homeostasis. HIF-2alpha may therefore represent a new and promising therapeutic target for cartilage repair. (+info)
Retinoic acid receptor gamma-induced misregulation of chondrogenesis in the murine limb bud in vitro.
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