Structural insights on Smad function in TGFbeta signaling

Expression Patterns of TGF-β1, TβR-I, TβR-II, and Smad2 Reveal Insights into Heterosis for Growth of Hybrid Offspring between Acanthopagrus schlegelii and Pagrus major

TGF-β1/Smads is a classic signaling pathway, which plays important roles in the development process of organisms. Black porgy Acanthopagrus schlegelii and red porgy Pagrus major are valuable economic fishes, and their hybrid offspring show excellent heterosis traits. Yet the molecular regulation mechanism of the heterosis traits is less clear. Here, we explored the TGF-β1/Smads pathway's molecular genetic information for heterosis in A. schlegelii ♂ × P. major ♀ (AP) and A. schlegelii ♀ × P. major ♂ (PA) in terms of growth and development. The mRNA expression levels of TGF-β1, TβR-I, TβR-II, and Smad2 genes in different developmental stages of A. schlegelii were detected. Furthermore, the expression levels of TGF-β1, TβR-I, TβR-II, and Smad2 genes in different tissues of adult (mRNA level) and larva (mRNA and protein level) of A. schlegelii, P. major, and their hybrids were determined by both real-time quantitative PCR and Western blot techniques. The results indicated the ubiquitous expression of these genes in all developmental stages of A. schlegelii and in all tested tissues of A. schlegelii, P. major, and its hybrids. Among them, the mRNA of TGF-β1, TβR-I, and TβR-II genes is highly expressed in the liver, gill, kidney, and muscle of black porgy, red porgy, and their hybrid offspring. There are significant changes in gene and protein expression levels in hybrid offspring, which indirectly reflect hybrid advantage. In addition, there was no correlation between protein and mRNA expression levels of Smad2 protein. The results provide novel data for the differential expression of growth and development genes between the reciprocal hybridization generation of black porgy and red porgy and its parents, which is conducive to further explaining the molecular regulation mechanism of heterosis in the growth and development of hybrid porgy.

GLIS3, a novel prognostic indicator of gastric adenocarcinoma, contributes to the malignant biological behaviors of tumor cells via modulating TGF-β1/TGFβR1/Smad1/5 signaling pathway

GLIS3 is highly expressed in multiple cancers, but it has not been studied in gastric adenocarcinoma (GAC). Based on bioinformatics analysis, the prognostic significance of GLIS3 in GAC was analyzed. GAC cells were transfected with small interfering (si)-GLIS3 and GLIS3 overexpression plasmid as well as treated with SB505124 [an inhibitor for transforming growth factor beta receptor 1 (TGFβR1)] and dorsomorphin [an inhibitor for bone morphogenetic protein receptor 1 (BMPR1)]. The GLIS3 expression was detected using qRT-PCR. The impacts of GLIS3 on the proliferation, invasion and migration of GAC cells were measured using cell function assays. The activation of phosphor (p)-Smad1/5 was tested by immunofluorescence. Western blot was utilized to measure the level of transforming growth factor (TGF)-β1/Smad1/5 signaling pathway-related proteins (TGF-β1, p-Smad1, Smad1, p-Smad5, Smad5). GLIS3 was expressed at high levels in GAC tissues and cell lines and its high expression could indicate the poor prognosis of GAC patients. GLIS3 inhibition declined the proliferative, invasive and migratory capabilities as well as TGF-β1 expression and phosphorylation of Smad1/5 in GAC cells. Overexpressed GLIS3 promoted proliferation, migration, invasion, TGF-β1 expression and Smad1/5 phosphorylation in GAC cells, with SB505124 reversing the effects of overexpressed GLIS3 on proliferation, migration, invasion and Smad1/5 phosphorylation whereas dorsomorphin exhibiting no influence on GLIS3-induced effects. GLIS3 facilitated the malignant phenotype of GAC cells via regulating TGF-β1/TGFβR1/Smad1/5 pathway, which may be a novel prognostic indicator of GAC and provided a target for GAC treatment.

Overexpression of MUC1 Induces Non-Canonical TGF-β Signaling in Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDA) is one of the most lethal human cancers. Transforming Growth Factor Beta (TGF-β) is a cytokine that switches from a tumor-suppressor at early stages to a tumor promoter in the late stages of tumor development, by yet unknown mechanisms. Tumor associated MUC1 is aberrantly glycosylated and overexpressed in >80% of PDAs and is associated with poor prognosis. MUC1 expression is found in the early stages of PDA development with subsequent increase in later stages. Analysis of human PDA samples from TCGA database showed significant differences in gene expression and survival profiles between low and high MUC1 samples. Further, high MUC1 expression was found to positively correlate to TGF-βRII expression and negatively correlate to TGF-βRI expression in PDA cell lines. We hypothesized that MUC1 overexpression induces TGF-β mediated non-canonical signaling pathways which is known to be associated with poor prognosis. In this study, we report that MUC1 overexpression in PDA cells directly activates the JNK pathway in response to TGF-β, and leads to increased cell viability via up-regulation and stabilization of c-Myc. Conversely, in low MUC1 expressing PDA cells, TGF-β preserves its tumor-suppressive function and inhibits phosphorylation of JNK and stabilization of c-Myc. Knockdown of MUC1 in PDA cells also results in decreased phosphorylation of JNK and c-Myc in response to TGF-β treatment. Taken together, the results indicate that overexpression of MUC1 plays a significant role in switching the TGF-β function from a tumor-suppressor to a tumor promoter by directly activating JNK. Lastly, we report that high-MUC1 PDA tumors respond to TGF-β neutralizing antibody in vivo showing significantly reduced tumor growth while low-MUC1 tumors do not respond to TGF-β neutralizing antibody further confirming our hypothesis.

Osteoarthritis-Related Inflammation Blocks TGF-β's Protective Effect on Chondrocyte Hypertrophy via (de)Phosphorylation of the SMAD2/3 Linker Region

Osteoarthritis (OA) is a degenerative joint disease characterized by irreversible cartilage damage, inflammation and altered chondrocyte phenotype. Transforming growth factor-β (TGF-β) signaling via SMAD2/3 is crucial for blocking hypertrophy. The post-translational modifications of these SMAD proteins in the linker domain regulate their function and these can be triggered by inflammation through the activation of kinases or phosphatases. Therefore, we investigated if OA-related inflammation affects TGF-β signaling via SMAD2/3 linker-modifications in chondrocytes. We found that both Interleukin (IL)-1β and OA-synovium conditioned medium negated SMAD2/3 transcriptional activity in chondrocytes. This inhibition of TGF-β signaling was enhanced if SMAD3 could not be phosphorylated on Ser213 in the linker region and the inhibition by IL-1β was less if the SMAD3 linker could not be phosphorylated at Ser204. Our study shows evidence that inflammation inhibits SMAD2/3 signaling in chondrocytes via SMAD linker (de)-phosphorylation. The involvement of linker region modifications may represent a new therapeutic target for OA.

Regulation of metabolic homeostasis by the TGF-β superfamily receptor ALK7

ALK7 (Activin receptor-like kinase 7) is a member of the TGF-β receptor superfamily predominantly expressed by cells and tissues involved in endocrine functions, such as neurons of the hypothalamus and pituitary, pancreatic β-cells and adipocytes. Recent studies have begun to delineate the processes regulated by ALK7 in these tissues and how these become integrated with the homeostatic regulation of mammalian metabolism. The picture emerging indicates that ALK7's primary function in metabolic regulation is to limit catabolic activities and preserve energy. Aside of the hypothalamic arcuate nucleus, the function of ALK7 elsewhere in the brain, particularly in the cerebellum, where it is abundantly expressed, remains to be elucidated. Although our understanding of the basic molecular events underlying ALK7 signaling has benefited from the vast knowledge available on TGF-β receptor mechanisms, how these connect to the physiological functions regulated by ALK7 in different cell types is still incompletely understood. Findings of missense and nonsense variants in the Acvr1c gene, encoding ALK7, of some mouse strains and human subjects indicate a tolerance to ALK7 loss of function. Recent discoveries suggest that specific inhibitors of ALK7 may have therapeutic applications in obesity and metabolic syndrome without overt adverse effects.

Functional evidence that Activin/Nodal signaling is required for establishing the dorsal-ventral axis in the annelid Capitella teleta

The TGF-β superfamily comprises two distinct branches: the Activin/Nodal and BMP pathways. During development, signaling by this superfamily regulates a variety of embryological processes, and it has a conserved role in patterning the dorsal-ventral body axis. Recent studies show that BMP signaling establishes the dorsal-ventral axis in some mollusks. However, previous pharmacological inhibition studies in the annelid Capitella teleta, a sister clade to the mollusks, suggests that the dorsal-ventral axis is patterned via Activin/Nodal signaling. Here, we determine the role of both the Activin/Nodal and BMP pathways as they function in Capitella axis patterning. Antisense morpholino oligonucleotides were targeted to Ct-Smad2/3 and Ct-Smad1/5/8, transcription factors specific to the Activin/Nodal and BMP pathways, respectively. Following microinjection of zygotes, resulting morphant larvae were scored for axial anomalies. We demonstrate that the Activin/Nodal pathway of the TGF-β superfamily, but not the BMP pathway, is the primary dorsal-ventral patterning signal in Capitella. These results demonstrate variation in the molecular control of axis patterning across spiralians, despite sharing a conserved cleavage program. We suggest that these findings represent an example of developmental system drift.

Summary: Morpholino knockdown experiments in the annelid Capitella teleta demonstrate that the dorsal-ventral axis is primarily patterned by the Activin/Nodal pathway of the TGF-β superfamily, rather than by the BMP pathway.

TGFβ/BMP Signaling Pathway in Cartilage Homeostasis

Cartilage homeostasis is governed by articular chondrocytes via their ability to modulate extracellular matrix production and degradation. In turn, chondrocyte activity is regulated by growth factors such as those of the transforming growth factor β (TGFβ) family. Members of this family include the TGFβs, bone morphogenetic proteins (BMPs), and growth and differentiation factors (GDFs). Signaling by this protein family uniquely activates SMAD-dependent signaling and transcription but also activates SMAD-independent signaling via MAPKs such as ERK and TAK1. This review will address the pivotal role of the TGFβ family in cartilage biology by listing several TGFβ family members and describing their signaling and importance for cartilage maintenance. In addition, it is discussed how (pathological) processes such as aging, mechanical stress, and inflammation contribute to altered TGFβ family signaling, leading to disturbed cartilage metabolism and disease.

MiR-1 suppresses tumor cell proliferation in colorectal cancer by inhibition of Smad3-mediated tumor glycolysis

Aberrant expression of microRNA (miR)-1 has been observed in many human malignancies. However, the function and underlying mechanism of miR-1 remains elusive. To address the specific role of miR-1 in tumor glycolysis using the gain- or loss-of-function studies. Metabolic studies combined with gene expression analysis were performed in vitro and in vivo. We demonstrated aberrant expression of miR-1 in aerobic glycolysis, the Warburg effect, in cancer cells. MiR-1 suppressed aerobic glycolysis and tumor cell proliferation via inactivation of Smad3 and targeting HIF-1α, leading to reduce HK2 and MCT4 expression, which illustrated a novel pathway to mediate aerobic glycolysis in cancer cells. Overexpression of miR-1 mimics significantly decreased tumor glycolysis, including lactate production and glucose uptake, and cell proliferation, and these effects were reversed by ectopic expression of Smad3. Importantly, endogenous Smad3 regulated and interacted with HIF-1α, resulting in increasing activity of Smad3, and this interaction was dramatically abolished by addition of miR-1. We further demonstrated that Smad3 was central to the effects of miR-1 in colorectal cancer cells, establishing a previously unappreciated mechanism by which the miR-1/Smad3/HIF-1α axis facilitates the Warburg effect to promote cancer progression in vitro and in vivo. The results indicate that miR-1 may have an essential role as a tumor suppressor, suggesting its potential role in molecular therapy of patients with advanced colorectal cancer.

Deciphering the genetic programme triggering timely and spatially-regulated chitin deposition

Organ and tissue formation requires a finely tuned temporal and spatial regulation of differentiation programmes. This is necessary to balance sufficient plasticity to undergo morphogenesis with the acquisition of the mature traits needed for physiological activity. Here we addressed this issue by analysing the deposition of the chitinous extracellular matrix of Drosophila, an essential element of the cuticle (skin) and respiratory system (tracheae) in this insect. Chitin deposition requires the activity of the chitin synthase Krotzkopf verkehrt (Kkv). Our data demonstrate that this process equally requires the activity of two other genes, namely expansion (exp) and rebuf (reb). We found that Exp and Reb have interchangeable functions, and in their absence no chitin is produced, in spite of the presence of Kkv. Conversely, when Kkv and Exp/Reb are co-expressed in the ectoderm, they promote chitin deposition, even in tissues normally devoid of this polysaccharide. Therefore, our results indicate that both functions are not only required but also sufficient to trigger chitin accumulation. We show that this mechanism is highly regulated in time and space, ensuring chitin accumulation in the correct tissues and developmental stages. Accordingly, we observed that unregulated chitin deposition disturbs morphogenesis, thus highlighting the need for tight regulation of this process. In summary, here we identify the genetic programme that triggers the timely and spatially regulated deposition of chitin and thus provide new insights into the extracellular matrix maturation required for physiological activity.

In this work we studied the maturation of the extracellular matrix during Drosophila embryogenesis. Drosophila deposit a chitin-rich extracellular matrix with key physiological functions, such as the control of organ size and shape, and cuticle formation. Chitin synthesis depends on chitin synthases, and in Drosophila the gene krotzkopf verkehrt (kkv) encodes the main enzyme of this family. Our observations indicate that Kkv alone is not sufficient to induce chitin formation. We have identified another function (which is exerted by the activity of two genes encoding MH2-domain proteins) that are equally required for chitin deposition. The most striking result of our analysis is that the presence of Kkv and the newly identified function is sufficient to trigger chitin deposition in ectodermally-derived tissues, even if they are normally devoid of this polysaccharide. Importantly, we also demonstrate that unregulated chitin deposition (absent, advanced, or ectopic) leads to severe defects in morphogenesis. We show that the temporal and spatial pattern of kkv and the other two genes perfectly recapitulates the deposition of chitin, thereby unveiling a highly co-ordinated mechanism for the acquisition of mature traits.

Mowat-Wilson syndrome: neurological and molecular study in seven patients

OBJECTIVE

To present a seven-cases serie of Mowat-Wilson syndrome (MWS).

METHOD

All patients with positive mutation for the ZEB2 were evaluated by a geneticist and a neurologist, with clinical and laboratorial characterization.

RESULTS

A peculiar facies and mental retardation were present in all patients. The Denver II scale showed intense delay in all aspects, especially fine motor and adaptive. Acquired microcephaly was observed in five patients. Only one patient did not present epilepsy. Epilepsy was focal and predominating in sleep, with status epilepticus in three patients. The initial seizure was associated with fever in most patients (4/6). The EEG showed epileptic focal activity (5/7). The imaging studies revealed total agenesis (4/7) and partial agenesis of the corpus callosum (1/7).

CONCLUSION

Physicians who care for patients with mental retardation and epilepsy should be aware of SMW.

Expression of histone deacetylase-1 and p300 in aristolochic acid nephropathy models

Aristolochic acid nephropathy (AAN) is mainly caused by aristolochic acid I (AAI), but the actual mechanism is still uncertain. The current study explored the correlation among the expression of Smad7, p300, histone deacetylase-1 (HDAC1) and the development of AAN using transmission electron microscopy (TEM), RT-PCR, and western blotting in the AAN mouse model and in the AAN cell model. TEM revealed that the renal tubular epithelial cells from the AAI-treated mice presented organelle damages and nuclear deformation. We found that a certain dose of AAI caused renal fibrosis and induced renal tubular epithelial cells to differentiate into myofibroblasts. There was a gradual increase in the expression of HDAC1 mRNA and protein observed using RT-PCR and western blotting in the AAN cell model compared with the control group. Gradual decrease in the expression of Smad7 and p300 mRNA and protein was revealed in the AAN mouse and cell models compared with the control group. These results suggest that AAI dose dependently contributed to the development of AAN, and HDAC1 and p300 participate in the modulation of TGF-β/Smad pathway-mediated renal interstitial fibrosis.

The novel Smad protein Expansion regulates the receptor tyrosine kinase pathway to control Drosophila tracheal tube size

Tubes with distinct shapes and sizes are critical for the proper function of many tubular organs. Here we describe a unique phenotype caused by the loss of a novel, evolutionarily-conserved, Drosophila Smad-like protein, Expansion. In expansion mutants, unicellular and intracellular tracheal branches develop bubble-like cysts with enlarged apical membranes. Cysts in unicellular tubes are enlargements of the apical lumen, whereas cysts in intracellular tubes are cytoplasmic vacuole-like compartments. The cyst phenotype in expansion mutants is similar to, but weaker than, that observed in double mutants of Drosophila type III receptor tyrosine phosphatases (RPTPs), Ptp4E and Ptp10D. Ptp4E and Ptp10D negatively regulate the receptor tyrosine kinase (RTK) pathways, especially epithelial growth factor receptor (EGFR) and fibroblast growth factor receptor/breathless (FGFR, Btl) signaling to maintain the proper size of unicellular and intracellular tubes. We show Exp genetically interacts with RTK signaling, the downstream targets of RPTPs. Cyst size and number in expansion mutants is enhanced by increased RTK signaling and suppressed by reduced RTK signaling. Genetic interaction studies strongly suggest that Exp negatively regulates RTK (EGFR, Btl) signaling to ensure proper tube sizes. Smad proteins generally function as intermediate components of the transforming growth factor-β (TGF-β, DPP) signaling pathway. However, no obvious genetic interaction between expansion and TGF-β (DPP) signaling was observed. Therefore, Expansion does not function as a typical Smad protein. The expansion phenotype demonstrates a novel role for Smad-like proteins in epithelial tube formation.

Serine-204 in the linker region of Smad3 mediates the collagen-I response to TGF-β in a cell phenotype-specific manner

Regulation of TGF-β1/Smad3 signaling in fibrogenesis is complex. Previous work by our lab suggests that ERK MAP kinase phosphorylates the linker region (LR) of Smad3 to enhance TGF-β-induced collagen-I accumulation. However the roles of the individual Smad3LR phosphorylation sites (T179, S204, S208 and S213) in the collagen-I response to TGF-β are not clear. To address this issue, we tested the ability of Smad3 constructs expressing wild-type Smad3 or Smad3 with mutated LR phosphorylation sites to reconstitute TGF-β-stimulated COL1A2 promoter activity in Smad3-null or -knockdown cells. Blocking ERK in fibroblasts and renal mesangial cells inhibited both S204 phosphorylation and Smad3-mediated COL1A2 promoter activity. Mutations replacing serine at S204 or S208 in the linker region decreased Smad3-mediated COL1A2 promoter activity, whereas mutating T179 enhanced basal COL1A2 promoter activity and did not prevent TGF-β stimulation. Interestingly, mutation of all four Smad3LR sites (T179, S204, S208 and S213) was not inhibitory, suggesting primacy of the two inhibitory sites. These results suggest that in these mesenchymal cells, phosphorylation of the T179 and possibly S213 sites may act as a brake on the signal, whereas S204 phosphorylation by ERK in some manner releases that brake. Renal epithelial cells (HKC) respond differently from MEF or mesangial cells; blocking ERK neither changed TGF-β-stimulated S204 phosphorylation nor prevented Smad3-mediated COL1A2 promoter activity in HKC. Furthermore, re-expression of wild type-Smad3 or the S204A-Smad3 mutant in Smad3-knockdown HKC reconstituted Smad3-mediated COL1A2 promoter activity. Collectively, these data suggest that Serine-204 phosphorylation in the Smad3LR is a critical event by which ERK enhances Smad3-mediated COL1A2 promoter activity in mesenchymal cells.

Transforming growth factor-β signalling: role and consequences of Smad linker region phosphorylation

Transforming growth factor-β (TGF-β) is a secreted homodimeric protein that plays an important role in regulating various cellular responses including cell proliferation and differentiation, extracellular matrix production, embryonic development and apoptosis. Disruption of the TGF-β signalling pathway is associated with diverse disease states including cancer, renal and cardiac fibrosis and atherosclerosis. At the cell surface TGF-β complex consists of two type I and two type II transmembrane receptors (TβRI and TβRII respectively) which have serine/threonine kinase activity. Upon TGF-β engagement TβRII phosphorylates TβRI which in turn phosphorylates Smad2/3 on two serine residues at their C-terminus which enables binding to Smad4 to form heteromeric Smad complexes that enter the nucleus to initiate gene transcription including for extracellular matrix proteins. TGF-β signalling is also known to activate other serine/threonine kinase signalling that results in the phosphorylation of the linker region of Smad2. The Smad linker region is defined as the domain which lies between the MH1 and MH2 domains of a Smad protein. Serine/threonine kinases that are known to phosphorylate the Smad linker region include mitogen-activated protein kinases, extracellular-signal regulated kinase, Jun N-terminal kinase and p38 kinase, the tyrosine kinase Src, phosphatidylinositol 3'-kinase, cyclin-dependent kinases, rho-associated protein kinase, calcium calmodulin-dependent kinase and glycogen synthase kinase-3. This review will cover the role of Smad linker region phosphorylation downstream of TGF-β signalling in vascular cells. Key factors including the identification of the kinases that phosphorylate individual Smad residues, the upstream agents that activate these kinases, the cellular location of the phosphorylation event and the importance of the linker region in regulation and expression of genes induced by TGF-β are covered.

Colorectal cancer: molecular mutations and polymorphisms

Colorectal cancer (CRC) is one of the major causes of mortality and morbidity, and is the third most common cancer in men and the second most common cancer in women worldwide. The incidence of CRC shows considerable variation among racially or ethnically defined populations in multiracial/ethnic countries. The tumorigenesis of CRC is either because of the chromosomal instability (CIN) or microsatellite instability (MIN) or involving various proto-oncogenes, tumor-suppressor genes, and also epigenetic changes in the DNA. In this review I have focused on the mutations and polymorphisms of various important genes of the CIN and MIN pathways which have been implicated in the development of CRC.

A novel human Smad4 mutation is involved in papillary thyroid carcinoma progression

Smad proteins are the key effectors of the transforming growth factor β (TGFβ) signaling pathway in mammalian cells. Smad4 plays an important role in human physiology, and its mutations were found with high frequency in wide range of human cancer. In this study, we have functionally characterized Smad4 C324Y mutation, isolated from a nodal metastasis of papillary thyroid carcinoma. We demonstrated that the stable expression of Smad4 C324Y in FRTL-5 cells caused a significant activation of TGFβ signaling, responsible for the acquisition of transformed phenotype and invasive behavior. The coexpression of Smad4 C324Y with Smad4 wild-type determined an increase of homo-oligomerization of Smad4 with receptor-regulated Smads and a lengthening of nuclear localization. FRTL-5 clones overexpressing Smad4 C324Y showed a strong reduction of response to antiproliferative action of TGFβ1, acquired the ability to grow in anchorage-independent conditions, showed a fibroblast-like appearance and a strong reduction of the level of E-cadherin, one crucial event of the epithelial-mesenchymal transition process. The acquisition of a mesenchymal phenotype gave the characteristics of increased cellular motility and a significant reduction in adhesion to substrates such as fibronectin and laminin. Overall, our results demonstrate that the Smad4 C324Y mutation plays an important role in thyroid carcinogenesis and can be considered as a new prognostic and therapeutic target for thyroid cancer.

Frequency of subtypes of biliary intraductal papillary mucinous neoplasm and their MUC1, MUC2, and DPC4 expression patterns differ from pancreatic intraductal papillary mucinous neoplasm

BACKGROUND

Biliary intraductal papillary mucinous neoplasm (B-IPMN) has been proposed as a unique clinicopathologic disease with distinct histopathologic features, although wide acceptance remains controversial. A recent consensus conference classified pancreatic IPMN (P-IPMN) into 4 subtypes (ie, gastric, intestinal, pancreatobiliary, oncocytic) based on morphologic appearance and mucin (MUC) staining properties. The aim of this study was to determine whether B-IPMN has similar histopathologic and immunologic subtypes to P-IPMN.

STUDY DESIGN

Specific immunostaining for MUC1, MUC2, and deleted for pancreas cancer, locus 4 were performed on specimens from 19 patients with a histopathologic diagnosis of B-IPMN. Immunostaining patterns of B-IPMN were correlated with histopathology.

RESULTS

Based on histopathology, the following subtypes of B-IPMN were identified: pancreatobiliary n = 9 (47%), intestinal n = 8 (42%), oncocytic n = 2 (11%), and gastric n = 0 (0%). Pancreatobiliary and oncocytic subtypes of B-IPMN were positive for MUC1 and negative for MUC2, and intestinal subtypes were positive for MUC2 and negative for MUC1. Thirteen of the 19 B-IPMN were associated with invasive carcinoma; loss of deleted for pancreas cancer, locus 4 was found in 6 of 13 invasive components and in 3 of 19 noninvasive components of B-IPMN. Five-year survival for patients with resected B-IPMN and invasive carcinoma was 38%, which is similar to that for resected P-IPMN with invasive carcinoma.

CONCLUSIONS

Histopathologic subtypes and type-specific MUC expression patterns of B-IPMN resemble those of P-IPMN. MUC1 expression and/or absence of MUC2 expression, which correlate with aggressive features of P-IPMN, were found in B-IPMN and correlate with invasive B-IPMN. Loss of deleted for pancreas cancer, locus 4 parallels the findings observed in P-IPMN. These findings provide additional support that B-IPMN is a unique entity with similarities to main duct P-IPMN.

USP15 is a deubiquitylating enzyme for receptor-activated SMADs

The TGFβ pathway is critical for embryonic development and adult tissue homeostasis. On ligand stimulation, TGFβ and BMP receptors phosphorylate receptor-activated SMADs (R-SMADs), which then associate with SMAD4 to form a transcriptional complex that regulates gene expression through specific DNA recognition. Several ubiquitin ligases serve as inhibitors of R-SMADs, yet no deubiquitylating enzyme (DUB) for these molecules has so far been identified. This has left unexplored the possibility that ubiquitylation of R-SMADs is reversible and engaged in regulating SMAD function, in addition to degradation. Here we identify USP15 as a DUB for R-SMADs. USP15 is required for TGFβ and BMP responses in mammalian cells and Xenopus embryos. At the biochemical level, USP15 primarily opposes R-SMAD monoubiquitylation, which targets the DNA-binding domains of R-SMADs and prevents promoter recognition. As such, USP15 is critical for the occupancy of endogenous target promoters by the SMAD complex. These data identify an additional layer of control by which the ubiquitin system regulates TGFβ biology.

SMAD4--molecular gladiator of the TGF-beta signaling is trampled upon by mutational insufficiency in colorectal carcinoma of Kashmiri population: an analysis with relation to KRAS proto-oncogene

BACKGROUND

The development and progression of colorectal cancer has been extensively studied and the genes responsible have been well characterized. However the correlation between the SMAD4 gene mutations with KRAS mutant status has not been explored by many studies so far. Here, in this study we aimed to investigate the role of SMAD4 gene aberrations in the pathogenesis of CRC in Kashmir valley and to correlate it with various clinicopathological variables and KRAS mutant genotype.

METHODS

We examined the paired tumor and normal tissue specimens of 86 CRC patients for the occurrence of aberrations in MCR region of SMAD4 and exon 1 of KRAS by PCR-SSCP and/or PCR-Direct sequencing.

RESULTS

The overall mutation rate of mutation cluster region (MCR) region of SMAD4 gene among 86 patients was 18.6% (16 of 86). 68.75% (11/16) of the SMAD4 gene mutants were found to have mutations in KRAS gene as well. The association between the KRAS mutant genotype with SMAD4 mutants was found to be significant (P = or < 0.05). Further more, we found a significant association of tumor location, tumor grade, node status, occupational exposure to pesticides and bleeding PR/Constipation with the mutation status of the SMAD4 gene (P = or < 0.05).

CONCLUSION

Our study suggests that SMAD4 gene aberrations are the common event in CRC development but play a differential role in the progression of CRC in higher tumor grade (C+D) and its association with the KRAS mutant status suggest that these two molecules together are responsible for the progression of the tumor to higher/advanced stage.

Novel regulation of Smad3 oligomerization and DNA binding by its linker domain

Smad proteins are key effectors of the transforming growth factor beta (TGFbeta) signaling pathway in mammalian cells. Smads are composed of two highly structured and conserved domains called Mad homology 1 (MH1) and 2 (MH2), which are linked together by a nonconserved linker region. The recent identification of phosphorylation sites and binding sites for ubiquitin ligases in the linker regions of TGFbeta and bone morphogenetic protein (BMP) receptor-regulated Smads suggested that the linker may contribute to the regulation of Smad function by facilitating cross-talks with other signaling pathways. In the present study, we have generated and characterized novel Smad3 mutants bearing individual substitutions of conserved and nonconserved amino acid residues within a previously described transcriptionally active linker fragment. Our analysis showed that the conserved linker amino acids glutamine 222 and proline 229 play important roles in Smad functions such as homo- and hetero-oligomerization, nuclear accumulation in response to TGFbeta stimulation, and DNA binding. Furthermore, a Smad3 mutant bearing a substitution of the nonconserved amino acid asparagine 218 to alanine displayed enhanced transactivation potential relative to wild type Smad3. Finally, Smad3 P229A inhibited TGFbeta signaling when overexpressed in mammalian cells. In conclusion, our data are in line with previous studies supporting an important regulatory role of the linker region of Smads in their function as key transducers of TGFbeta signaling.

Finding partners: how BMPs select their targets

The bone morphogenetic protein (BMP) signaling pathway is a conserved and evolutionarily ancient regulatory module affecting a large variety of cellular behaviors. The evolutionary flexibility in using BMP responses presumably arose by co-option of a canonical BMP signaling cascade to regulate the transcription of diverse batteries of target genes. This begs the question of how seemingly interchangeable BMP signaling components elicit widely different outputs in different cell types, an important issue in the context of understanding how BMP signaling integrates with gene regulatory networks to control development. Because a molecular understanding of how BMP signaling activates different batteries of target genes is an essential prerequisite to comprehending the roles of BMPs in regulating cellular responses, here we review the current knowledge of how BMP-regulated target genes are selected by the signal transduction machinery. We highlight recent studies suggesting the evolutionary conservation of BMP target gene regulation signaling by Schnurri family zinc finger proteins. Developmental Dynamics 238:1321-1331, 2009. (c) 2009 Wiley-Liss, Inc.

Crystal structure of the MH2 domain of Drosophila Mad

The decapentaplegic(Dpp), a member of the TGF-beta superfamily, plays a pivotal role in the control of proliferation, global patterning and induction of specific cell fates during Drosophila development. Mother against Dpp(Mad) is the founding member of the conserved Smad protein family which specifically transduces the intracellular TGF-beta signaling cascade. Here we report the 2.80 A structure of the MH2 domain of Mad(Mad-MH2) that was readily superposed to the mammal Smad-MH2 structures. This unphosphorylated Mad-MH2 forms a symmetric homotrimer in crystals, consistent with the result of the size-exclusion chromatography that Mad-MH2 exhibited a propensity for concentration-dependent oligomerization prior to phosphorylation. Structural analysis revealed that the formation of homotrimeric Mad-MH2 is mainly mediated by contacts involving the extreme C-terminal SSVS motif, and is strengthened by phosphorylation of the last two Ser residues which was confirmed by the gel filtration analysis of the pseudophosphorylated Mad-MH2(DVD). Intriguingly, the homotrimer within an asymmetric unit only possesses two ordered C-terminal tails, reminiscent of the arrangement of the R-Smad/Smad4 complexes, indicating that the subunit with a flexible SSXS motif would be readily replaced by Co-Smad to form a functional heterotrimer.

Study of interaction between Smad7 and DNA by single-molecule force spectroscopy

Smad7 is an antagonist of TGF-beta signaling pathway and the mechanism of its inhibitory effect is of great interest. We recently found that Smad7 could function in the nucleus by binding to the DNA elements containing the minimal Smad binding element CAGA box. In this work, we further applied single-molecule force spectroscopy to study the DNA-binding property of Smad7. Smad7 showed similar binding strength to the oligonucleotides corresponding to the CAGA-containing activin responsive element (ARE) and the PAI-1 promoter, as that of Smad4. However, Smad7 also exhibited a binding activity to the mutant ARE with the CAGA sequence substituted, indicating its DNA-binding specificity is different from other Smads. Moreover, we demonstrated that the MH2 domain of Smad7 had a higher binding affinity to the DNA elements than the full-length Smad7, while the N-terminal domain exhibited an inhibitory effect.

Structure of Drosophila Mad MH2 domain

In Drosophila, decapentaplegic (Dpp), a member of the TGF-beta superfamily, plays a pivotal role in control of proliferation, global patterning and induction of specific cell fates. Together with Medea, mother against Dpp (Mad), the founding member of the Smad family, specifically transduces the Dpp signal from the plasma membrane to the nucleus. Here, the crystal structure of the MH2 domain of Mad, which closely matches those of other Smad MH2 domains, is reported at 3.2 A resolution. The conservation of Smad protein structures is consistent with their evolutionary conserved and significant function. Furthermore, sequence alignment revealed that most of the variant amino acids in Smad proteins specific to the BMP pathway (Smad1, Smad5 and Mad) were clustered at the surface. In particular, Ser296 and Asp297 of Mad introduced a negative patch into the positive surface observed in the surface electrostatic potential of Smad1 MH2.

Structure-function relationship of inhibitory Smads: Structural flexibility contributes to functional divergence

Smads are a small family of eukaryotic transcription regulators that play key roles in the transforming growth factor-beta signaling cascade. Smad6 and Smad7, the inhibitory or I-Smads, inhibit signaling downstream of TGF-beta type I receptors, thereby acting as negative regulators of signaling mediated by TGF-beta superfamily of ligands. Smad6 is known to specifically inhibit BMP type I receptor mediated signaling, while Smad7 is a more general inhibitor, able to block signaling mediated by a set of related TGF-beta type I receptors, including type I receptors for BMP and TGF-beta/Activin. In this study we have sought to understand the structural basis for this functional divergence of I-Smads. We have created homology-based models for the MH1 and MH2 domains of the two I-Smads and have carried out detailed molecular dynamics (MD) simulations of these proteins in explicit solvent to investigate the flexibility of the domains. The molecular models show that the I-Smads have lost many of the secondary structural elements found in the R-Smads, giving rise to longer loops in the tertiary structure of Smad6 and Smad7. Detailed analysis of the structural models and the MD trajectories clearly reveal that compared to Smad6, Smad7 has a more flexible overall folding, marked by the presence of highly flexible amino acid residues in functionally important regions of the protein. Interestingly, three of these residues-Phe411, Lys401, and Cys406, map to L3 loop of Smad7 MH2 domain, which is a critical structural determinant in Smad-type I receptor interactions. The increased structural flexibility of Smad7, arising out of longer, more flexible loops in its MH2 domain, might enable Smad7 to interact with a set of related yet structurally diverse type I receptors. Taken together with experimental evidence published in recent literature that hint at structural factors underlying the generic nature of inhibition by Smad7, our results strongly suggest that structural flexibility could be a prime contributor to the functional differences between Smad6 and Smad7. Additionally, we have been able to use the Smad7 structural model to successfully rationalize the results of in vitro site-specific mutagenesis experiments in published literature. This also provides biological validation for our model. Apart from this, analysis of the MH1 molcular model of Smad6 delineates a basic patch on the surface of the domain that might take part in nonspecific DNA binding by Smad6. This finding is consistent with earlier experimental data and is relevant since the characteristic beta-hairpin DNA binding element of R-Smads is completely absent in the I-Smads. Finally, the molecular models described here can serve to guide future biochemical and genetic studies on I-Smads.

Smad3 is overexpressed in advanced human prostate cancer and necessary for progressive growth of prostate cancer cells in nude mice

PURPOSE

The purpose of this study was to investigate the potential role of Smad3, a key mediator of transforming growth factor-beta signaling, in progression of prostate cancer.

EXPERIMENTAL DESIGN

Expression of Smad proteins was determined in human prostate cancer tissue array and cell lines. Growth and metastasis of cells overexpressing dominant-negative Smad3 (Smad3D) were studied to determine its role in tumor progression in mice. Cell growth, apoptosis, and expression of angiogenic molecules in tumor lesions were studied to determine potential pathways that Smad3 promotes tumor progression.

RESULTS

Smad3 was overexpressed in human prostate cancer, which correlated with Gleason score and expression of proliferating cell nuclear antigen. Androgen-independent PC-3MM2 and DU145 cells expressed much higher levels of Smad3 than did androgen-dependent LNCaP, 22Rv1, and LAPC-4 cells. Overexpression of Smad3D in PC-3MM2 cells (PC-3MM2-Smad3D) had minimal direct effects on cell growth but attenuated effects of transforming growth factor-beta1 on gene expression and cell growth. Overexpression of Smad3D did not significantly alter tumor incidence but reduced tumor growth rate and metastasis incidence. Most cells in the control tumors, but not PC-3MM2-Smad3D tumors, were positively stained by an antibody to proliferating cell nuclear antigen. Microvessels and expression of angiogenic molecule interleukin-8 were significantly reduced in tumors from PC-3MM2-Smad3D cells. PC-3MM2-Smad3D tumors also expressed lower levels of vascular endothelial growth factor and platelet-derived growth factor.

CONCLUSIONS

These data suggest that Smad3, through regulating angiogenic molecule expression in tumor cells, is critical for progression of human prostate cancer.

Mowat-Wilson syndrome

Mowat-Wilson syndrome (MWS) is a multiple congenital anomaly syndrome characterized by a distinct facial phenotype (high forehead, frontal bossing, large eyebrows, medially flaring and sparse in the middle part, hypertelorism, deep set but large eyes, large and uplifted ear lobes, with a central depression, saddle nose with prominent rounded nasal tip, prominent columella, open mouth, with M-shaped upper lip, frequent smiling, and a prominent but narrow and triangular pointed chin), moderate-to-severe intellectual deficiency, epilepsy and variable congenital malformations including Hirschsprung disease (HSCR), genitourinary anomalies (in particular hypospadias in males), congenital heart defects, agenesis of the corpus callosum and eye anomalies. The prevalence of MWS is currently unknown, but 171 patients have been reported so far. It seems probable that MWS is under-diagnosed, particularly in patients without HSCR. MWS is caused by heterozygous mutations or deletions in the Zinc finger E-box-binding homeobox 2 gene, ZEB2, previously called ZFHX1B (SIP1). To date, over 100 deletions/mutations have been reported in patients with a typical phenotype; they are frequently whole gene deletions or truncating mutations, suggesting that haploinsufficiency is the main pathological mechanism. Studies of genotype-phenotype analysis show that facial gestalt and delayed psychomotor development are constant clinical features, while the frequent and severe congenital malformations are variable. In a small number of patients, unusual mutations can lead to an atypical phenotype. The facial phenotype is particularly important for the initial clinical diagnosis and provides the hallmark warranting ZEB2 mutational analysis, even in the absence of HSCR. The majority of MWS cases reported so far were sporadic, therefore the recurrence risk is low. Nevertheless, rare cases of sibling recurrence have been observed. Congenital malformations and seizures require precocious clinical investigation with intervention of several specialists (including neonatologists and pediatricians). Psychomotor development is delayed in all patients, therefore rehabilitation (physical therapy, psychomotor and speech therapy) should be started as soon as possible.

The DNA Binding Activities of Smad2 and Smad3 Are Regulated by Coactivator-mediated Acetylation

Phosphorylation-dependent activation of the transcription factors Smad2 and Smad3 plays an important role in TGFbeta-dependent signal transduction. Following phosphorylation of Smad2 and Smad3, these molecules are translocated to the nucleus where they interact with coactivators and/or corepressors, including p300, CBP, and P/CAF, and regulate the expression of TGFbeta target genes. In the current study, we demonstrate that both Smad2 and Smad3 are acetylated by the coactivators p300 and CBP in a TGFbeta-dependent manner. Smad2 is also acetylated by P/CAF. The acetylation of Smad2 was significantly higher than that of Smad3. Lys(19) in the MH1 domain was identified as the major acetylated residue in both the long and short isoform of Smad2. Mutation of Lys(19) also reduced the p300-mediated acetylation of Smad3. By generating acetyl-Lys(19)-specific antibodies, we demonstrate that endogenous Smad2 is acetylated on this residue in response to TGFbeta signaling. Acetylation of the short isoform of Smad2 improves its DNA binding activity in vitro and enhances its association with target promoters in vivo, thereby augmenting its transcriptional activity. Acetylation of Lys(19) also enhanced the DNA binding activity of Smad3. Our data indicate that acetylation of Lys(19) induces a conformational change in the MH1 domain of the short isoform of Smad2, thereby making its DNA binding domain accessible for interactions with DNA. Thus, coactivator-mediated acetylation of receptor-activated Smad molecules could represent a novel way to regulate TGFbeta signaling.

Potentiation of Smad-mediated transcriptional activation by the RNA-binding protein RBPMS

Smad2, Smad3 and Smad4 proteins are considered to be key mediators of transforming growth factor-beta (TGF-beta) signaling. However, the identities of the Smad partners mediating TGF-beta signaling are not fully understood. Here, we show that RNA-binding protein with multiple splicing (RBPMS), a member of the RNA-binding protein family, physically interacts with Smad2, Smad3 and Smad4 both in vitro and in vivo. The presence of TGF-beta increases the binding of RBPMS with these Smad proteins. Consistent with the binding results, overexpression of RBPMS enhances Smad-dependent transcriptional activity in a TGF-beta-dependent manner, whereas knockdown of RBPMS decreases this activity. RBPMS interacts with TGF-beta receptor type I (TbetaR-I), increases phosphorylation of C-terminal SSXS regions in Smad2 and Smad3, and promotes the nuclear accumulation of the Smad proteins. Moreover, RBPMS fails to enhance the transcriptional activity of Smad2 and Smad3 that lack the C-terminal phosphorylation sites. Our data provide the first evidence for an RNA-binding protein playing a role in regulation of Smad-mediated transcriptional activity and suggest that RBPMS stimulates Smad-mediated transactivation possibly through enhanced phosphorylation of Smad2 and Smad3 at the C-terminus and promotion of the nuclear accumulation of the Smad proteins.

Cellular, molecular, and tissue-level reactions to orthodontic force

Remodeling changes in paradental tissues are considered essential in effecting orthodontic tooth movement. The force-induced tissue strain produces local alterations in vascularity, as well as cellular and extracellular matrix reorganization, leading to the synthesis and release of various neurotransmitters, cytokines, growth factors, colony-stimulating factors, and metabolites of arachidonic acid. Recent research in the biological basis of tooth movement has provided detailed insight into molecular, cellular, and tissue-level reactions to orthodontic forces. Although many studies have been reported in the orthodontic and related scientific literature, a concise convergence of all data is still lacking. Such an amalgamation of the rapidly accumulating scientific information should help orthodontic clinicians and educators understand the biological processes that underlie the phenomenon of tooth movement with mechanics (removable, fixed, or functional appliances). This review aims to achieve this goal and is organized to include all major findings from the beginning of research in the biology of tooth movement. It highlights recent developments in cellular, molecular, tissue, and genetic reactions in response to orthodontic force application. It reviews briefly the processes of bone, periodontal ligament, and gingival remodeling in response to orthodontic force. This review also provides insight into the biological background of various deleterious effects of orthodontic forces.

Divergent effects of BMP-2 on gene expression in pulmonary artery smooth muscle cells from normal subjects and patients with idiopathic pulmonary arterial hypertension

Bone morphogenetic proteins (BMPs) inhibit proliferation and induce apoptosis in pulmonary artery smooth muscle cells (PASMCs) from normal subjects. Dysfunction of BMP signaling due to mutations in and/or down-regulation of BMP receptors has been implicated in idiopathic pulmonary arterial hypertension (IPAH). The authors examined whether BMP differentially regulates gene expression in PASMCs from normal subjects and IPAH patients using the Affymetrix microarray analysis. BMP-2 treatment (200 nM for 24 hours) altered expression levels of 6206 genes in normal and IPAH PASMCs. Of these genes, 1063 were regulated oppositely by BMP-2: 523 genes were down-regulated by BMP-2 in normal PASMCs but up-regulated in IPAH PASMCs, whereas 540 genes were up-regulated by BMP-2 in normal PASMCs but down-regulated in IPAH PASMCs. The divergent effects of BMP-2 on gene expression profiles indicate that PASMCs may undergo significant phenotypic changes in IPAH patients during development of the disease. The transition of the antiproliferative effect of BMP-2 in normal PASMCs to its proliferative effect in IPAH patients is attributed potentially to its differential effect on expression patterns of various genes that are involved in cell proliferation and apoptosis. Among the 6206 BMP-2-sensitive genes, there are more than 1800 genes whose expression levels were negatively (correlation coefficient, r, <-0.9) or positively (with r >+ 0.9) correlated with the pulmonary arterial pressure. These results suggest that BMP-mediated gene regulation is significantly altered in PASMCs from IPAH patients and mRNA expression changes in BMP-regulated genes may be involved in the development of IPAH.

Homology modeling of the DNA-binding domain of human Smad5: A molecular model for inhibitor design

Members of the Smad protein family function as signal transducers of the transforming growth factor (TGF-beta) superfamily proteins. The human Smad5 protein, a signal transducer downstream of TGF-beta/BMP receptors, is composed of N-terminal DNA binding domain (MH1) and C-terminal protein-protein interaction domain (MH2) connected together by a linker motif. We used homology-modeling techniques to generate a reliable molecular model of the Smad5 MH1 domain based on the crystal structure of Smad3 MH1 domain. Our study presents the structural features of a BMP-regulated, R-Smad subfamily member (consisting of Smad1, Smad5 and Smad8) for the first time. This model provides a structural basis for explaining both functional similarities and differences between Smad3 and Smad5. Also, the structural model of this molecular target would be useful for structure-based inhibitor design because of its high accuracy. The results of our study provide important insights into understanding the structure-function relationship of the members of the Smad protein family and can serve to guide future genetic and biochemical experiments in this area.

Dpp-responsive Silencers Are Bound by a Trimeric Mad-Medea Complex

Transcriptional regulation by transforming growth factor-beta signaling is mediated by the Smad family of transcription factors. It is generally accepted that Smads must interact with other transcription factors to bind to their targets. However, recently it has been shown that a complex of the Drosophila Smad proteins, Mad and Medea, binds with high affinity to silencer elements that repress brinker and bag of marbles in response to Dpp signaling. Here we report that these silencers are bound by a heterotrimer containing two Mad subunits and one Medea subunit. We found that the MH1 domains of all three subunits contributed directly to sequence-specific DNA contact, thus accounting for the exceptionally high stability of the Smad-silencer complex. The Medea MH1 domain binds to a canonical Smad box (GTCT), whereas the Mad MH1 domains bind to a GC-rich sequence resembling Mad binding sites previously identified in Dpp-responsive enhancer elements. The consensus for this sequence, GRCGNC, differs from that of the canonical Smad box, but we found that Mad binding nonetheless required the same beta-hairpin amino acids that mediate base-specific contact with GTCT. Binding was also affected by alanine substitutions in Mad and Med at a subset of basic residues within and flanking helix 2, indicating a contribution to binding of the GRCGNC and GTCT sites. The slight alteration of the Dpp silencers caused them to activate transcription in response to Dpp signaling, indicating that the potential for Smad complexes to recognize specific targets need not be limited to repression.

A complex pattern of mutations and abnormal splicing of Smad4 is present in thyroid tumours

Sensitivity to transforming growth factor-beta is impaired in thyroid tumours. Similar to Mad -- Mother Against Decapentaplegic-(Smad)4 is frequently altered in cancers, but its involvement in this system is unknown. We analysed 56 thyroid tumours of various histotypes for Smad4 mutations by PCR-SSCP and sequencing, linking them to Smad4 reactivity as examined by immunohistochemistry (IHC), and 29 of them also for abnormalities in RNA expression due to alternative splicing. In all, 15/56 cases (27%), both benign and malignant lesions, harbour alterations of Smad4 coding sequence. We found several novel intragenic mutations (13 missense, two silent, one frameshift and one large insertion-deletion), with high incidence in the linker region. A subset of mutated tumours failed to express Smad4 protein by IHC. We have also detected four alternatively spliced tumour-associated Smad4 isoforms, lacking portions of the linker region, and three more due to unreported internal exon-exon rearrangements. Smad4 is both frequently mutated and deregulated by aberrant splicing in thyroid tumours and these alterations may contribute as an early event to thyroid tumorigenesis.

Recent advances in understanding transforming growth factor beta regulation of orofacial development

Members of the transforming growth factor (TGF) family have emerged as critical contributors to the choreography of cellular and tissue interactions underlying morphogenesis of the orofacial region. The TGFs beta, and their downstream effector molecules, the Smads, play a pivotal role in normal as well as abnormal development of first branchial arch structures. Components of the TGFbeta signal transduction machinery are discussed in relation to regulation of transcription, cell division and tissue differentiation in developing orofacial tissue, as evidence for a functional linkage between the TGFbeta and retinoic acid signal transduction pathways during orofacial development.

Genitourinary anomalies in Mowat-Wilson syndrome with deletion/mutation in the zinc finger homeo box 1B gene (ZFHX1B). Report of three Italian cases with hypospadias and review

Hypospadias, when the urethra opens on the ventral side of the penis, is a common malformation seen in about 3 per 1,000 male births. It is a complex disorder associated with genetic and environmental factors and can be part of genetic syndromes. Mowat-Wilson syndrome (MWS) is a multiple congenital anomaly syndrome characterized by a distinct facial phenotype, Hirschsprung disease, microcephaly and mental retardation. It is caused by mutations in the zinc finger homeo box 1B gene, ZFHX1B (SIP1). To date, 68 deletion/mutation-positive cases have been reported. Genitourinary anomalies are common in MWS. Here we report that hypospadias is common in males with this syndrome. In 39 patients where this information was available, hypospadias was present in 46% of patients (18/39). In the 3 Italian male cases reported here, hypospadias was always present. MWS should be considered by endocrinologists in patients with hypospadias associated with developmental delays/mental retardation, in particular in the presence of a distinct facial phenotype.

Nuclear integration of positive Dpp signals, antagonistic Wg inputs and mesodermal competence factors during Drosophila visceral mesoderm induction

Tissue induction during embryonic development relies to a significant degree on the integration of combinatorial regulatory inputs at the enhancer level of target genes. During mesodermal tissue induction in Drosophila, various combinations of inductive signals and mesoderm-intrinsic transcription factors cooperate to induce the progenitors of different types of muscle and heart precursors at precisely defined positions within the mesoderm layer. Dpp signals are required in cooperation with the mesoderm-specific NK homeodomain transcription factor Tinman (Tin) to induce all dorsal mesodermal tissue derivatives, which include dorsal somatic muscles, the dorsal vessel and visceral muscles of the midgut. Wingless (Wg) signals modulate the responses to Dpp/Tin along anteroposterior positions by cooperating with Dpp/Tin during dorsal vessel and somatic muscle induction while antagonizing Dpp/Tin during visceral mesoderm induction. As a result, dorsal muscle and cardiac progenitors form in a pattern that is reciprocal to that of visceral muscle precursors along the anteroposterior axis. Our present study addresses how positive Dpp signals and antagonistic Wg inputs are integrated at the enhancer level of bagpipe (bap), a NK homeobox gene that serves as an early regulator of visceral mesoderm development. We show that an evolutionarily conserved bap enhancer element requires combinatorial binding sites for Tin and Dpp-activated Smad proteins for its activity. Adjacent binding sites for the FoxG transcription factors encoded by the Sloppy paired genes (slp1 and slp2), which are direct targets of the Wg signaling cascade, serve to block the synergistic activity of Tin and activated Smads during bap induction. In addition, we show that binding sites for yet unknown repressors are essential to prevent the induction of the bap enhancer by Dpp in the dorsal ectoderm. Our data illustrate how the same signal combinations can have opposite effects on different targets in the same cells during tissue induction.

Novel Function of Androgen Receptor-associated Protein 55/Hic-5 as a Negative Regulator of Smad3 Signaling

Androgen receptor-associated protein 55 (ARA55/Hic-5) belongs to the LIM protein superfamily and is featured by three or four N-terminal LD motifs and four C-terminal zinc finger-like LIM domains. Both LD motifs and LIM domains can serve as protein-protein interaction interfaces. Recently, we found that enforced expression of ARA55 inhibits transforming growth factor-beta-mediated up-regulation of Smad binding element-luciferase reporter activity in NRP-154 and NRP-152 rat prostate and LNCaP human prostate cell lines. Moreover, ARA55 also inhibits the induction of Smad-binding element 4-luciferase and 3TP-luciferase (a plasminogen activator inhibitor-1 (PAI-1) promoter construct) reporters by constitutively active (CA)-Smad3 in these cell lines. Co-immunoprecipitation studies suggest an interaction between ARA55 and either CA-Smad3 or wild-type Smad3 in HEK293 cells that occurs through the MH2 domain of Smad3 and the C terminus of ARA55 with wild-type Smad3 having stronger affinity than CA-Smad3 to ARA55. Glutathione S-transferase pull-down assays demonstrate that this interaction can occur in a cell-free system. These results are consistent with the luciferase data showing that the C terminus of ARA55 is critical for suppression of Smad3 activity. Furthermore, using a mammalian two-hybrid system, we confirmed that ARA55 interacts with the MH2 domain of Smad3 and suppresses CA-Smad3-induced transcriptional responses. In conclusion, these results support that ARA55 selectively intercepts transforming growth factor-beta signaling through an interaction of the LIM domain of ARA55 with the MH2 domain of Smad3.

Four types of smad4 found in the common carp,Cyprinus carpio

Smad4 is defined as the common-mediator Smad (Co-Smad) required for transducing signals for all transforming growth factor-beta (TGF-beta) superfamily members. In this study, we have isolated eight distinct Smad4 full-length cDNAs from the common carp (Cyprinus carpio). These cDNAs were classified into four types and each type consisted of two subtypes. The eight cDNAs encoded four distinct proteins ranging from 505aa to 568aa in size, with close similarities in the Mad homology 1 and 2 (MH1 and MH2, respectively), but with differences in the linker regions and the C-terminus as well as in the 5'- and 3'-untranslated regions. Genomic Southern blotting demonstrated the existence of at least six Smad4 gene loci in the carp genome, meaning that the multiple forms of the carp Smad4 cDNAs were not due to allelic variations. Reverse transcriptase polymerase chain reaction (RT-PCR)/Southern hybridizations showed different expression patterns among the four types of Smad4s. These results suggest that some of carp Smad4s have deviated from the original function of Smad4 through vertebrate evolution, and regulated the TGF-beta signaling pathway by changing the expression level in tissues.

Proteomics-based identification of proteins interacting with Smad3: SREBP-2 forms a complex with Smad3 and inhibits its transcriptional activity

Smad3 is an important component of transforming growth factor-beta (TGFbeta) intracellular signalling. To identify novel interacting proteins of Smad3, we performed pull-down assays with Smad3 constructs fused to glutathione-S-transferase. Proteins which formed complexes with these constructs were analyzed by two-dimensional gel electrophoresis, and were identified by matrix-assisted laser desorption-ionization time-of-flight mass spectrometry. We identified 14 proteins interacting with the Smad3 construct lacking the N-terminal Mad homology domain 1 (MH1), and 12 proteins interacting with the construct lacking the C-terminal MH2 domain. Proteins involved in signalling processes, in metabolism regulation, novel proteins, and components of cytoskeleton form four groups of interacting proteins. Interactions of AGP7, sex-determining region Y protein, actin beta and sterol regulatory element binding protein-2 (SREBP-2) proteins with Smad3 constructs were confirmed by immunoblotting with specific antibodies. Interaction of Smad3 with SREBP-2 was also confirmed by co-immunoprecipitation of myc-Smad3 and Flag-SREBP-2 upon expression in mammalian cells. We found that SREBP-2 inhibited the transcriptional activity of Smad3 in luciferase reporter assays.

TGF-β signaling is disrupted in endometrioid-type endometrial carcinomas

OBJECTIVE

Previous studies have demonstrated deregulation of the expression and changes in the intracellular distribution of TGF-beta pathway components in human endometrial cancer (EC). The aim of this study was to assess the relationship between the expression of TGF-beta cascade components, including TGF-beta receptor type I (TGF beta RI) and type II (TGF beta RII), SMAD2, SMAD3, SMAD4, and clinicopathological features--tumor grade, FIGO classification, and depth of myometrial invasion--of type I (endometrioid-type) ECs to give some insight into the role of TGF-beta cascade components in endometrial tumorigenesis.

METHODS

The expression of TGF beta RI, TGF beta RII, SMAD2, SMAD3, and SMAD4 was evaluated both at the mRNA and protein level using reverse transcription polymerase chain reaction (RT-PCR) and ELISA, respectively.

RESULTS

Infiltrating endometrial carcinomas (less and more than half of the myometrial wall thickness) express significantly higher TGF beta RII protein level compared with non-infiltrating tumors (P = 0.04 and P = 0.01, respectively). Decreased level of SMAD2 and SMAD4 mRNAs was observed in the uterine tumors infiltrating less and more than half of the myometrial wall (P = 0.03 and P = 0.02, respectively) compared with noninfiltrating ECs. Significantly higher SMAD4 protein level in the cytoplasmic fraction of ECs was found when tumor grade and depth of myometrial invasion were considered (P < 0.05). Generally, tumor progression was associated with a decreased number of cases characterized by the presence of SMADs in the nuclear fraction only.

CONCLUSION

Our data suggest that disturbances of the TGF beta RII and SMAD4 expression as well as localization of SMADs may be important to the infiltration of the myometrial wall by the type I endometrial carcinomas.

Molecular biology of primary pulmonary hypertension

Primary pulmonary hypertension (PPH) is a rare but often fatal condition characterized by pulmonary artery remodeling leading to chronic elevation of pulmonary artery pressure in the absence of causes. The pathophysiology of PPH is not completely understood, but a number of recent studies have elucidated many possible gentic, hormonal, and environmental factors. Current treatment options slow the progression of the disease but do not halt it. The study of molecular mechanisms that result from mutations in onmental and hormonal modifiers holds great promise for the development of novel therapies that may halt the progression of the disease.

Retinoic acid receptors interfere with the TGF-beta/Smad signaling pathway in a ligand-specific manner

Transforming growth factor-beta (TGF-beta) and retinoic acid (RA) are important regulators of cell growth and differentiation. The TGF-beta receptors utilize Smad proteins to transduce signals intracellularly and regulate transcription of target genes, either directly or in combination with other sequence-specific transcription factors. Two classes of nuclear receptors, the retinoic acid receptors (RARs) and the retinoic X receptors, are involved in mediating transcriptional responses to RA. Given the known interactions between the TGF-beta and RAR pathways, we have investigated the role played by RAR ligands in modulating functional interactions between Smad3 and RARs. Using transient cell transfection experiments with an artificial Smad3/Smad4-dependent reporter construct, we demonstrate that RAR overexpression enhances Smad-driven transactivation, an effect that requires both Smad3 and Smad4. We provide evidence that RAR effect on Smad3/Smad4-driven transcription is prevented by natural and synthetic RAR agonists, and potentiated by synthetic RAR antagonists. The activity of two TGF-beta-responsive human gene promoter constructs was regulated in a parallel fashion. Using both mammalian two-hybrid and immunoprecipitation/Western methods, we demonstrate a direct interaction between the region DEF of RARgamma and the MH2 domain of Smad3, inhibited by RAR agonists and enhanced by their antagonists. We propose that RARs may function as coactivators of the Smad pathway in the absence of RAR agonists or in the presence of their antagonists, a phenomenon that contrasts with their known role as agonist-activated transcriptional regulators of RA-dependent genes.

Controlling mesenchymal stem cell differentiation by TGFBeta family members

Mesenchymal stem cells can differentiate into various tissue types including bone, cartilage, fat, and muscle. Transforming growth factor-Beta (TGFBeta) family members, including TGFBetas and bone morphogenetic proteins (BMPs), play important roles in directing fate decisions for mesenchymal stem cells. TGFBeta can provide competence for early stages of chondroblastic and osteoblastic differentiation, but it inhibits myogenesis, adipogenesis, and late-stage osteoblast differentiation. BMPs also inhibit adipogenesis and myogenesis, but they strongly promote osteoblast differentiation. TGFBeta family members signal via specific serine/threonine kinase receptors and their nuclear effectors, termed Smad proteins. In this review we discuss recent advances in our understanding of the molecular mechanisms by which TGFBeta family members control mesenchymal stem cell differentiation.

Intracellular dynamics of Smad-mediated TGFbeta signaling

The transforming growth factor-beta (TGFbeta) family represents a class of signaling molecules that plays a central role in morphogenesis, growth, and cell differentiation during normal embryonic development. Members of this growth factor family are particularly vital to development of the mammalian secondary palate where they regulate palate mesenchymal cell proliferation and extracellular matrix synthesis. Such regulation is particularly critical since perturbation of either cellular process results in a cleft of the palate. While the cellular and phenotypic effects of TGFbeta on embryonic craniofacial tissue have been extensively catalogued, the specific genes that function as downstream mediators of TGFbeta action in the embryo during palatal ontogenesis are poorly defined. Embryonic palatal tissue in vivo and murine embryonic palate mesenchymal (MEPM) cells in vitro secrete and respond to TGFbeta. In the current study, elements of the Smad component of the TGFbeta intracellular signaling system were identified and characterized in cells of the embryonic palate and functional activation of the Smad pathway by TGFbeta1, TGFbeta2, and TGFbeta3 was demonstrated. TGFbeta-initiated Smad signaling in cells of the embryonic palate was found to result in: (1) phosphorylation of Smad 2; (2) nuclear translocation of the Smads 2, 3, and 4 protein complex; (3) binding of Smads 3 and 4 to a consensus Smad binding element (SBE) oligonucleotide; (4) transactivation of transfected reporter constructs, containing TGFbeta-inducible Smad response elements; and (4) increased expression of gelatinases A and B (endogenous genes containing Smad response elements) whose expression is critical to matrix remodeling during palatal ontogenesis. Collectively, these data point to the presence of a functional Smad-mediated TGFbeta signaling system in cells of the developing murine palate.

Molecular fingerprinting of TGFß-treated embryonic maxillary mesenchymal cells

The transforming growth factor-beta (TGF(beta)) family represents a class of signaling molecules that plays a central role in normal embryonic development, specifically in development of the craniofacial region. Members of this family are vital to development of the secondary palate where they regulate maxillary and palate mesenchymal cell proliferation and extracellular matrix synthesis. The function of this growth factor family is particularly critical in that perturbation of either process results in a cleft of the palate. While the cellular and phenotypic effects of TGF(beta) on embryonic craniofacial tissue have been extensively cataloged, the specific genes that function as downstream mediators of TGF(beta) in maxillary/palatal development are poorly defined. Gene expression arrays offer the ability to conduct a rapid, simultaneous assessment of hundreds to thousands of differentially expressed genes in a single study. Inasmuch as the downstream sequelae of TGF(beta) action are only partially defined, a complementary DNA (cDNA) expression array technology (Clontech's Atlas Mouse cDNA Expression Arrays), was utilized to delineate a profile of differentially expressed genes from TGF(beta)-treated primary cultures of murine embryonic maxillary mesenchymal cells. Hybridization of a membrane-based cDNA array (1178 genes) was performed with 32P-labeled cDNA probes synthesized from RNA isolated from either TGF(beta)-treated or vehicle-treated embryonic maxillary mesenchymal cells. Resultant phosphorimages were subject to AtlasImage analysis in order to determine differences in gene expression between control and TGF(beta)-treated maxillary mesenchymal cells. Of the 1178 arrayed genes, 552 (47%) demonstrated detectable levels of expression. Steady state levels of 22 genes were up-regulated, while those of 8 other genes were down-regulated, by a factor of twofold or greater in response to TGF(beta). Affected genes could be grouped into three general functional categories: transcription factors and general DNA-binding proteins; growth factors/signaling molecules; and extracellular matrix and related proteins. The extent of hybridization of each gene was evaluated by comparison with the abundant, constitutively expressed mRNAs: ubiquitin, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), ornithine decarboxylase (ODC), cytoplasmic beta-actin and 40S ribosomal protein. No detectable changes were observed in the expression levels of these genes in-response to TGF(beta) treatment. Gene expression profiling results were verified by Real-Time quantitative polymerase chain reaction. Utilization of cDNA microarray technology has enabled us to delineate a preliminary transcriptional map of TGF(beta) responsiveness in embryonic maxillary mesenchymal cells. The profile of differentially expressed genes offers revealing insights into potential molecular regulatory mechanisms employed by TGF(beta) in orchestrating craniofacial ontogeny.