Cloning of a novel TGF-beta related cytokine, the vgr, from rat brain: cloning of and comparison to homologous human cytokines

Hypermethylation leads to bone morphogenetic protein 6 downregulation in hepatocellular carcinoma

BACKGROUND

In the liver, bone morphogenetic protein 6 (BMP-6) maintains balanced iron metabolism. However, the mechanism that underlies greater BMP-6 expression in hepatocellular carcinoma (HCC) tissue than adjacent non-cancerous tissue is unclear. This study sought to investigate the epigenetic mechanisms of BMP-6 expression by analysing the relationship between the DNA methylation status of BMP-6 and the expression of BMP-6.

METHODS

Methylation-specific polymerase chain reaction (PCR), bisulphite sequencing PCR, the MethyLight assay, and quantitative real-time PCR were performed to examine BMP-6 methylation and mRNA expression levels. Immunohistochemistry (IHC) was performed on tissue arrays to evaluate the BMP-6 protein level.

RESULTS

BMP-6 mRNA expression was approximately 84.09% lower in HCC tissues than in adjacent non-cancerous tissues, and this low level of expression was associated with a poor prognosis. Moreover, the hypermethylation observed in HCC cell lines and HCC tissues was correlated with the BMP-6 mRNA expression level, and this correlation was validated following treatment with 5-aza-CdR, a demethylation agent. In addition, BMP-6 DNA methylation was upregulated by 68.42% in 114 clinical HCC tissue samples compared to adjacent normal tissues, whereas the BMP-6 staining intensity was downregulated by 77.03% in 75 clinical HCC tissue samples in comparison to adjacent normal tissues. Furthermore, elevated expression of BMP-6 in HCC cell lines inhibited cell colony formation.

CONCLUSIONS

Our results suggest that BMP-6 CpG island hypermethylation leads to decreased BMP-6 expression in HCC tissues.

N-glycoproteome analysis of the secretome of human metastatic hepatocellular carcinoma cell lines combining hydrazide chemistry, HILIC enrichment and mass spectrometry

Cancer cell metastasis is a major cause of cancer death. Unfortunately, the underlying molecular mechanisms remain unknown, which results in the lack of efficient diagnosis, therapy and prevention approaches. Nevertheless, the dysregulation of the cancer cell secretome is known to play key roles in tumor transformation and progression. The majority of proteins in the secretome are secretory proteins and membrane-released proteins, and, mostly, the glycosylated proteins. Until recently, few studies have explored protein N-glycosylation changes in the secretome, although protein glycosylation has received increasing attention in the study of tumor development processes. Here, the N-glycoproteins in the secretome of two human hepatocellular carcinoma (HCC) cell lines with low (MHCC97L) or high (HCCLM3) metastatic potential were investigated with a in-depth characterization of the N-glycosites by combining two general glycopeptide enrichment approaches, hydrazide chemistry and zwitterionic hydrophilic interaction chromatography (zic-HILIC), with mass spectrometry analysis. A total of 1,213 unique N-glycosites from 611 N-glycoproteins were confidently identified. These N-glycoproteins were primarily localized to the extracellular space and plasma membrane, supporting the important role of N-glycosylation in the secretory pathway. Coupling label-free quantification with a hierarchical clustering strategy, we determined the differential regulation of several N-glycoproteins that are related to metastasis, among which AFP, DKK1, FN1, CD151 and TGFβ2 were up-regulated in HCCLM3 cells. The inclusion of the well-known metastasis-related proteins AFP and DKK1 in this list provides solid supports for our study. Further western blotting experiments detecting FN1 and FAT1 confirmed our discovery. The glycoproteome strategy in this study provides an effective means to explore potential cancer biomarkers.

Comparison of osteogenic potentials of human rat BMP4 and BMP6 gene therapy using [E1-] and [E1-,E2b-] adenoviral vectors

Osteogenic potentials of some recombinant human bone morphogenetic protein (BMP) first-generation adenoviral vectors (ADhBMPs) are significantly limited in immunocompetent animals. It is unclear what role expression of viral proteins and foreign proteins transduced by adenoviral vectors play in the host immune response and in ectopic bone formation. In this study two sets of experiments were designed and performed. First, rat BMP6 cDNA were amplified, sequenced, and recombined in first-generation adenoviral vector (ADrBMP6). A comparison of human and rat BMP6 adenoviral vectors demonstrated identical osteogenic activities in both immunodeficient and immunocompetent rats. Second, the activities of recombinant human BMP6 in E1- (ADhBMP6) and [E1-,E2b-] ( [E1-,E2b-]ADGFP&hBMP6, and [E1-,E2b-]ADhBMP6) adenoviral vectors were compared in both in vitro and in vivo models. Similar activities of these two generations of BMP adenoviral vectors were found in all models. These results indicate that the amount of viral gene expression and the source of the BMP cDNA are not major factors in the interruption of osteogenic potentials of recombinant BMP6 adenoviral vectors in immunocompetent animals.

Localized expression of BMP and GDF mRNA in the rodent brain

Expression of BMP- and GDF-related factors within the transforming growth factor-beta (TGF-beta) superfamily was examined in the rat and mouse brain by in situ hybridization. Strong signals were obtained in neurons for GDF-1 and GDF-10. GDF-1 is expressed at postnatal day 6 in the cerebral cortex, hippocampal CA1 through CA3 neurons, while only weakly expressed by cells in the dentate gyrus. Granule cells and neurons in the polymorph layer of the dentate gyrus are GDF-1-positive, as are the majority of neurons in the cortex. GDF-10 shows a distinct pattern of expression: At P6, strong labelling was seen in the superficial layers of cortex, notably in the posterior cingulate cortex, and in CA3 and dentate gyrus. From postnatal day 21, GDF-1 expression is strong in the hippocampus, cortex, and thalamic nuclei, while GDF-10 expression becomes restricted to the granule cell layer in the dentate gyrus. In contrast, OP-1 expression is restricted throughout development to cells of the medial habenular nucleus, choroid plexus, and leptomeninges. The markedly different expression patterns of these BMPs suggest they serve separate functions in the brain.

Regulation of sexual dimorphism in mammals

Sexual dimorphism in humans has been the subject of wonder for centuries. In 355 BC, Aristotle postulated that sexual dimorphism arose from differences in the heat of semen at the time of copulation. In his scheme, hot semen generated males, whereas cold semen made females (Jacquart, D., and C. Thomasset. Sexuality and Medicine in the Middle Ages, 1988). In medieval times, there was great controversy about the existence of a female pope, who may have in fact had an intersex phenotype (New, M. I., and E. S. Kitzinger. J. Clin. Endocrinol. Metab. 76: 3-13, 1993.). Recent years have seen a resurgence of interest in mechanisms controlling sexual differentiation in mammals. Sex differentiation relies on establishment of chromosomal sex at fertilization, followed by the differentiation of gonads, and ultimately the establishment of phenotypic sex in its final form at puberty. Each event in sex determination depends on the preceding event, and normally, chromosomal, gonadal, and somatic sex all agree. There are, however, instances where chromosomal, gonadal, or somatic sex do not agree, and sexual differentiation is ambiguous, with male and female characteristics combined in a single individual. In humans, well-characterized patients are 46, XY women who have the syndrome of pure gonadal dysgenesis, and a subset of true hermaphrodites are phenotypic men with a 46, XX karyotype. Analysis of such individuals has permitted identification of some of the molecules involved in sex determination, including SRY (sex-determining region Y gene), which is a Y chromosomal gene fulfilling the genetic and conceptual requirements of a testis-determining factor. The purpose of this review is to summarize the molecular basis for syndromes of sexual ambiguity seen in human patients and to identify areas where further research is needed. Understanding how sex-specific gene activity is orchestrated may provide insight into the molecular basis of other cell fate decisions during development which, in turn, may lead to an understanding of aberrant cell fate decisions made in patients with birth defects and during neoplastic change.

Bone morphogenetic proteins: neurotrophic roles for midbrain dopaminergic neurons and implications of astroglial cells

Bone morphogenetic proteins (BMPs) are members of the transforming growth factor beta (TGF-beta) superfamily that have been implicated in tissue growth and remodelling. Recent evidence suggests that several BMPs are expressed in the developing and adult brain. Specifically, we show that BMP 2 and BMP 6 are expressed in the developing midbrain floor of the rat. We studied potential neurotrophic effects of BMPs on the in vitro survival, transmitter uptake and protection against MPP+ toxicity of mesencephalic dopaminergic neurons cultured from the embryonic midbrain floor at embryonic day (E) 14. At 10 ng/ml and under serum-free conditions, most BMPs promoted the survival of dopaminergic neurons visualized by tyrosine hydroxylase immunocytochemistry during an 8-day culture period, but to varying extents (relative potencies: BMP 6 = 12 > 2, 4, 7). BMPs 6 and 12 were as effective as fibroblast growth factor-2 (FGF-2) and glial cell line-derived neurotrophic factor, promoting survival 1.7-fold compared with controls. BMPs 9 and 11 were not effective. Dose-response curves revealed an EC50 for BMPs 2, 6 and 12 of 2 ng/ml. BMPs 2, 4, 6, 7, 9 and 12 also promoted DNA synthesis and astroglial cell differentiation, visualized by 5-bromodeoxyuridine (BrdU) incorporation and glial fibrillary acidic protein (GFAP) immunocytochemistry respectively. Suppression of cell proliferation and subsequent maturation of GFAP-positive cells by 5-fluorodeoxyuridine or aminoadipic acid abolished the neuron survival-promoting effect of BMP 2. This suggests that BMPs, like other non-TGF-beta factors affecting dopaminergic neuron survival, act indirectly, probably by stimulating the synthesis and/or release of glial-derived trophic factors. BMP 6 and BMP 7 also increased the uptake of [3H]dopamine without affecting the uptake of [3H]5-hydroxytryptamine and [3H]GABA, underscoring the specificity of the trophic effect. We conclude that several BMPs share a neurotrophic capacity for dopaminergic midbrain neurons with other members of the TGF-beta superfamily, but act indirectly, possibly through glial cells.

Bone morphogenetic protein-6 is expressed in nonparenchymal liver cells and upregulated by transforming growth factor-beta 1

Bone morphogenetic protein-6 (BMP-6) is a member of the TGF-beta superfamily, which controls growth and differentiation during embryogenesis and acts as an osteoinductive factor in the adult organism. In order to gain further insights into the role of BMP-6, the present study analyzed the expression pattern of BMP-6 in adult rat tissues with special emphasis to the liver, since TGF-beta 1, another member of the TGF-beta superfamily, has been shown to play a fundamental role in liver physiology. Rat BMP-6-coding cDNAs were generated by homology cloning using RT-PCR and displayed 89.6 and 83.4% homology to mouse and human BMP-6, respectively. By Northern blotting BMP-6-specific transcripts 3.7 kb in size were detected in major amounts in lung and in minor quantities in spleen, kidney, heart, brain, and liver. Among the different hepatic cell populations tested BMP-6 expression was confined to nonparenchymal liver cells, namely rat hepatic stellate cells (HSC) and Kupffer cells (KC). During primary culture BMP-6 expression was increased in HSC but declined in KC. Interestingly, TGF-beta 1 stimulated BMP-6 expression of HSC especially at an early time point of culture, while interferon-gamma downregulated BMP-6 expression. The detection of BMP-6 transcripts in the liver, the cell-type-restricted expression pattern, and its regulation propose that, in addition to its osteoinductive properties, BMP-6 might play a role in liver growth and differentiation, in particular after tissue damage.

Immunolocalization of BMP-6, a novel TGF-beta-related cytokine, in normal and atherosclerotic smooth muscle cells

We have analyzed expression of a novel transforming growth factor type beta (TGF-beta)-related cytokine, bone morphogenetic protein-6 (BMP-6) in normal and atherosclerotic brain arteries. BMP-6 immunoreactivity was detected in smooth muscle cells of normal cerebral blood vessels. It is also expressed by smooth muscle cells of intimal plaques in atherosclerotically changed blood vessels. The BMPs regulate tissue modeling and remodeling and aberrant expression of BMPs might contribute to smooth muscle cell migration, proliferation, tissue reorganization and macrophage attraction, which are known mechanisms of atherosclerotic plaque formation.

Immunolocalization of vgr (BMP-6, DVR-6), a TGF-beta related cytokine, to Schwann cells of the rat peripheral nervous system: expression patterns are not modulated by autoimmune disease

The transforming growth factors type beta (TGF-beta) have been implicated in regulation of peripheral nervous system inflammation and regeneration. Here we demonstrate expression of a TGF-beta-related bone morphogenetic protein, the vgr (BMP-6, DVR-6) in Schwann cells of the rat peripheral nervous system. The expression of vgr in the peripheral nervous system suggests that this factor and probably other TGF-beta-related bone morphogenetic proteins might participate in Schwann cell function during aspects of peripheral nervous system physiology and pathology. However, we did not observe changes in expression patterns in response to autoimmune inflammation (experimental autoimmune neuritis) of the peripheral nervous system.

Expression of BMP-6, a TGF-beta related morphogenetic cytokine, in rat radial glial cells

Bone morphogenetic protein-6 (BMP-6) is a member of the TGF-beta superfamily of cytokines. The bone morphogenetic proteins and homologous cytokines participate in realization of the genetic body plan by regulating homeotic gene expression, embryonic development, and neurogenesis. Here we demonstrate expression of BMP-6 in rat radial glial cells which are involved in embryonic organisation of the central nervous system. Thus, morphogenetic cytokines like BMP-6 might contribute to radial glial cell function in organizing the migration of immature neurons during the development of the CNS cortex.

Evolution of the transforming growth factor-beta superfamily

Transforming growth factor beta 1 (TGF-beta 1) is the prototype of an increasingly complex superfamily of growth and differentiation factors. To date, a total of 74 TGF-beta-like sequences have been published, probably representing 23 distinct genes. These sequences were obtained from mammalian, avian, amphibian and insect species, thus emphasising the ancient nature of the TGF-beta superfamily peptides. This article summarises current hypotheses concerning the evolutionary history of this protein superfamily, based on the molecular phylogeny of the published sequences. Comparison of the deduced amino acid sequences leads to the definition of five main groups within the superfamily (TGF-beta, Bone Morphogenetic Proteins [BMP], Anti-Müllerian Hormone [AMH], Inhibin alpha [INH alpha] and GDF-9) and six subgroups within the BMPs (60A, Decapentaplegic [dpp], Vg1, BMP-3, Inhibin beta [INH beta A/B] and nodal). This classification predicts possible phylogenetic and functional relationships among these proteins.