<p>IPF is a respiratory condition of unknown etiology that has poor survival prognosis. The stiffening of the lung associated with this condition is attributed to the irreversible turnover of healthy lung tissue into scar tissue, which affects gas exchange and can eventually lead to organ failure. Numerous studies have implicated the pro-fibrogenic growth factor TGF-β, through activation of the SMAD2/3 pathway, as a central mediator in the pathology of this condition. However, other cytokines, including members of the IL-6/gp130 family such as OSM, and other signaling pathways may be implicated in ECM accumulation in certain conditions. In particular, STAT3 activation and an impairment of the BMP-SMAD1 signaling axis is thought to contribute to lung ECM accumulation. Based on the finding that transient pulmonary overexpression of OSM induces lung ECM accumulation in C57Bl/6 mice, it was hypothesized that OSM-induced ECM remodeling would be associated with STAT3 activation and suppression of the BMP-SMAD1-signaling axis.</p> <p>Findings in this thesis revealed that transient pulmonary overexpression of OSM induces ECM remodeling in both BALB/c and C57Bl/6 mice after seven days, despite a dichotomous response in other experimental models of ECM remodeling. However, parenchyma, but not airway, pathology resolved after 28 days in AdOSM-treated BALB/c mice. Furthermore, OSM-induced ECM remodeling occurred independently of IL-6-associated inflammation as well as TGF-β/SMAD3 signaling. MLF cultures treated with OSM did not directly regulate gene expression of ECM-related genes, suggesting that other cells may be responsible for OSM-induced ECM accumulation <em>in vivo</em>. OSM overexpression <em>in vivo </em>was associated with STAT3 activation and SMAD1 suppression, and an assessment of STAT3 and SMAD signaling <em>in vitro</em> showed that OSM activated the STAT3 pathway in MLF cultures, mouse type two pneumocytes, and human airway cells, while OSM suppressed the SMAD1 pathway in mouse type two pneumocytes, and human airway cells. Collectively, this thesis shows that OSM induces novel pathways in models of lung ECM remodeling, and this may have implications for IPF pathogenesis.</p> / Master of Science (MSc)

Transforming growth factor beta 1 (TGF-beta1) ist ein multifunktionales Zytokin, welches eine Rolle in der Sepsis und in der Sepsis-induzierten Myopathie spielen könnte. Weiterhin könnten erhöhte TGF-beta1-Level zur Muskelschwäche, die mit der Intensivpflege assoziiert ist (engl. intensiv care unit-acquired weakness, ICUAW), beitragen. Der TGF-beta1- Signalweg wurde in Skelettmuskelbiopsien von ICUAW-Patienten heraufreguliert. Secreted frizzled related protein 2 (SFRP2) wurde in einer Gen-Set-Anreicherungsanalyse als das am höchsten regulierte Gen identifiziert. Im Mausmodell führten Sepsis und Hunger zu einer verringerten Sfrp2-Expression, während dies in der Denervation-induzierten Skelettmuskelatrophie nicht festzustellen war. In differenzierten C2C12-Myotuben führte TGF-beta1 zu einer verringerten Sfrp2-mRNA- und Proteinexpression. Luciferase-Assays deuteten auf eine TGF-beta1-abhängige Herunterregulation von Sfrp2 hin, welche auf Promoterebene durch mögliche negative regulatorische Elemente im Sfrp2-Promoter vermittelt wurde. Weiterhin wurde eine TGF-beta1 induzierte Muskelatrophie durch transkriptionelle Repression der myosin heavy chain Gene beobachtet. Im Gegensatz dazu veränderte TGF-beta1 nicht den proteasomalen Abbau muskulärer Proteine. Die Genexpression von Tripartite motif containing 63 und F-box only protein 32 war hingegen leicht herunterreguliert. TGF-beta1-induzierte Atrophie in differenzierten C2C12-Myotuben wurde teilweise durch rekombinantes Sfrp2 aufgehoben. Weiterhin wurde eine direkte physikalische Interaktion zwischen Sfrp2 und TGF-beta1 gefunden, welche diesen Effekt verursacht haben könnte. Zusammengefasst lässt sich feststellen, dass der TGF-beta1- Signalweg eine wichtige Rolle in der ICUAW durch Inhibition der myosin heavy chain Expression spielt. TGF-beta1-abhängige Herunterregulation von Sfrp2 könnte zu einer Feedback-Antwort, die das Ausmaß der Atrophie durch TGF-beta1 verstärkt, führen. / Transforming growth factor beta 1 (TGF-beta1) is a multifunctional cytokine that may play a role in sepsis and in sepsis-induced myopathy. Our group speculated that increased TGF-beta1 could contribute to intensive care (ICU)-acquired weakness (ICUAW), a catastrophic muscle disease in critically ill patients. We found that TGF-beta1 signaling in skeletal muscle biopsies of ICUAW patients was upregulated. Secreted frizzled related protein 2 (SFRP2) was the most regulated gene identified by gene set enrichment analysis (GSEA). I then studied the regulation and function of SFRP2 in different skeletal muscle atrophy models. In three mouse models, downregulated Sfrp2 expression was observed in sepsis and starvation, but not in denervation-induced skeletal muscle atrophy. In differentiated C2C12 myotubes, TGF-beta1 downregulated Sfrp2 expression on both mRNA and protein levels. Luciferase assays suggested that TGF-beta1-dependent downregulation of Sfrp2 was mediated at the promoter level through possible negative regulatory elements in the Sfrp2 promoter. I also observed that TGF-beta1-induced muscle atrophy was accompanied by transcriptional repression of myosin heavy chain genes. In contrast, TGF-beta1 did not increase proteasomal degradation of muscular proteins since gene expression of Tripartite motif containing 63 (Trim63) and F-box only protein (Fbxo32) was not upregulated; instead, they were slightly downregulated. TGF- beta1-induced differentiated C2C12 myotube atrophy was partially reversed by recombinant Sfrp2. This inhibitory effect could have resulted from direct interaction between Sfrp2 and TGF-beta1, since I found a physical interaction between these two proteins. Taken together, TGF-beta1 signaling pathway could play an important role in ICUAW via inhibition of myosin heavy chain expression. TGF-beta1-dependent downregulation of Sfrp2 may establish a feedback loop augmenting the atrophic effect of TGF-beta1.

La protéine du TGF-[bêta]1 est une protéine multifonctionnelle qui agit dans plusieurs types cellulaires. Son action varie selon le type de cellulaire. Bien qu'elle ait un rôle inhibiteur chez les astrocytes normaux, elle posséderait un rôle principalement activateur de nombreuses voies carcinogéniques chez les tumeurs astrocytaires primaires malignes. L'isoforme du TGF-[bêta]1 est celle qui est la plus impliquée dans ces processus. Elle joue un rôle dans l'activation des voies d'invasion tissulaire et d'angiogenèse, mais inhibe des mécanismes d'apoptose et d'immunosuppression.La présente étude vise à évaluer l'effet de l'inhibition de la protéine du TGF-[bêta]1 sur le modèle cellules de glioblastome F98/Fischer sur la prolifération et la migration cellulaire. Pour ce faire, un inhibiteur sélectif au récepteur a d'abord été utilisé. Par la suite, des techniques d'inhibitions nucléotidiques (oligoantisens, siRNA, shRNA) ont été testées. Nous avons d'abord validé l'utilisation du modèle F98/Fischer dans l'étude des fonctions du TGF-[bêta]1 et de l'inhibition de la production de cette protéine. Nous avons observé la production importante de TGF-[bêta]1 par les cellules F98 avec des essais immunologiques (Western, ELISA). Avec l'essai ELISA, nous avons observé la production considérable de TGF-[bêta]1 actif d'emblée.La présence de notre protéine d'intérêt a été détectée dans le cerveau de rat Fischer implanté avec les cellules F98 contrairement aux animaux sains qui ne montrent aucune trace de TGF-[bêta]1. Ensuite, nous avons tenté de mettre au point une approche nucléotidique pour inhiber la production du TGF-[bêta]1. Pour les oligoantisens et les siRNA qui ont été couplés avec le vecteur liposomale Metafecten, nous n'avons pas réussi à obtenir de diminution significative du TGF-[bêta]1 dans les surnageants des cultures de F98 . Pour l'approche au shRNA/lentivirus, nous n'avons pas réussi à former de bactéries contenant la construction recherchée. Par la suite, nous avons testé sur notre modèle cellulaire un inhibiteur pharmacologique sélectif, le SB-431642, du récepteur permettant la phosphoryllation de la voie instracellulaire Smad, le T[bêta]R-I. Les essais de prolifération (WST-1) ont permis de constater un ralentissement dans la croissance des F98 traitées au SB-431542. Un essai immunologique western a permis de constater que la production de VEGF était d'ailleurs influencée par cette inhibition du TGF-[bêta]1. L'utilisation d'un vecteur luciférase couplé à un élément de réponse Smad a permis de constater que la voie du TGF-[bêta]1 était bel et bien affectée à la baisse par cet inhibiteur. En effet, le dosage luminescent de la luciférase a permis de noter une diminution significative de sa quantité. L'activité d'un tel vecteur est proportionnelle à l'activité Smad intracellulaire. Nous avons aussi testé cet inhibiteur sur le modèle de croissance tumorale tridimensionnelle de sphéroïdes F98.La croissance des sphéroïdes a été ralentie par la présence de l'inhibiteur et l'invasion de la matrice de collagène observée chez les sphéroïdes contrôles a été freinée par l'ajout de SB-431542. Bien que certains de nos essais n'aient pas donné les résultats escomptés, l'utilisation de l'inhibiteur SB-431542 nous a permis de voir l'implication à du TGF-[bêta]1 dans les mécanismes de progression tumorale chez la lignée cellulaire F98, tel que la prolifération et la migration cellulaire. Ces résultats sont le préalable à d'éventuels essais avec le modèle d'étude animal, le rat Fischer avec l'utilisation de cellules de glioblastomes F98.

Le TGFβ (Transforming Growth Factor-β) est une cytokine ayant de nombreusesfonctions au cours de la vie embryonnaire et de la vie adulte. Au cours de la cancérogenèse,le TGFβ a un effet anti-tumoral sur les épithelia sains ou immortalisés, et acquière despropriétés facilitant la progression tumorale des épithélia transformés. Afin d’étudier cettedualité fonctionnelle du TGFβ, nous avons choisi comme modèle d’étude l’adénocarcinomedu pancréas, une tumeur de très mauvais pronostic, qui représente la cinquième cause demortalité par cancer dans les pays développés. Les cancers du pancréas, dans leur grandemajorité, présentent des mutations activatrices de l’oncogène Kras, sécrètent de grandequantités de TGFβ et présentent des mutations inactivatrices au niveau de gènes régulateursde la voie du TGFβ. L’objectif général de mes travaux de thèse était de comprendre le rôle duTGFβ au cours des différentes phases de la cancérogenèse pancréatique grâce à l'utilisationde souris génétiquement modifiées. Tout d’abord, nous avons montré que l’activation cibléede la voie du TGFβ dans le pancréas coopérait avec l’oncogène Kras afin d’induire unepancréatite, une inflammation du pancréas favorisant le développement tumoral. Nous avonségalement démontré le rôle suppresseur de tumeur de TIF1γ, une protéine dont la fonction estméconnue mais qui a été proposée pour réguler la voie du TGFβ. En conclusion, mes travauxont tout d’abord contribué à une meilleure compréhension des mécanismes à l’origine del’inflammation du pancréas. Ceci ouvre de nouvelles perspectives de traitement visant àinactiver le programme pro-inflammatoire du TGFβ et ainsi d’inhiber l’effet pro-tumoral dela pancréatite. D’autre part, mes travaux ont permis de mettre en évidence une nouvelle voiesuppresseur de tumeur dans le pancréas. La caractérisation des programmes anti-tumorauxmis en jeu par TIF1γ devrait permettre de définir de nouvelles stratégies thérapeutiques. / The TGFβ (Transforming Growth Factor-β) belongs to a wide family of cytokinesinvolved in numerous functions during embryogenesis and adult life. During tumorigenesis,TGFβ is considered as a double-edge-sword preventing tumor initiation in normal orimmortalized epithelia but, in contrast, facilitating tumor progression in transformedepithelia. We have studied this dual functionality of TGFβ in Pancreatic DuctalAdenocarcinoma (PDAC), a devastating disease representing the fifth leading-cause ofrelated-cancer death in industrialized countries. Most of pancreatic cancers present activatingKras oncogene mutations, high expression level of secreted TGFβ and inactivating mutationsof affecting major mediators of the TGFβ signaling. The main objective of my thesis was tounderstand the role of TGFβ during pancreatic tumorigenesis using genetically modifiedmouse models, then mimicking the human disease. First, we showed that targeted activationof TGFβ signaling in the pancreas could cooperate with Kras oncogene to induce pancreatitis,an inflammation of the pancreas described as a tumor-promoting environment. Second, wedemonstrated the tumor suppressor role of TIF1γ, a protein recently involved in the TGFβsignaling. In conclusion, this work has contributed to a better understanding of the molecularmechanisms responsible for pancreatitis initiation. Our results open new therapeuticsperspectives leading to the inhibition of the TGFβ-mediated program of thus inhibiting prooncogeniceffect of pancreatitis. Moreover, we defined a new tumor suppressor pathwayactivated in the pancreas. The molecular characterization of programs engaged by TIF1γcould allow defining new therapeutic strategies.

INTRODUÇÃO: A cirurgia associada à radioterapia proporciona altas taxas de preservação de membros e de controle local em sarcomas de partes moles de extremidade de adultos, mas ainda apresenta elevadas taxas de complicações locais e de metástases à distância. O valor da quimioterapia adjuvante ou neoadjuvante ainda é controverso e objeto de investigações clínicas. A identificação de fatores moleculares preditivos de resposta à quimioterapia pode selecionar pacientes que se beneficiem ou não da sua aplicação. OBJETIVOS: identificar perfis de expressão gênica capazes de diferenciar tumores respondedores e não respondedores a quimioterapia neoadjuvante em sarcomas de partes moles. Analisar os resultados preliminares relativos à efetividade de um esquema de quimioterapia neoadjuvante em sarcomas de partes moles. MÉTODOS: amostras foram coletadas a partir de um ensaio clínico fase II não controlado que testa um esquema de quimioterapia neoadjuvante com doxorrubicina e ifosfamida em sarcomas de alto grau histológico, localizados em extremidades de pacientes adultos. O perfil de expressão gênica foi determinado pela análise de cDNA microarrays. RESULTADOS: 14 pacientes foram incluídos no estudo clínico e 6 amostras foram utilizadas para análise molecular. 222 seqüências diferentemente expressas entre respondedores e não respondedores foram identificadas. Entre os genes com maior diferença de expressão, foram observados genes envolvidos com via de sinalização de TGF, genes envolvidos com angiogênese, com degradação de matriz extracelular e com desenvolvimento. A taxa de resposta objetiva à quimioterapia neoadjuvante foi de 28,6%, a taxa de amputação foi de 7,1% e taxa de complicações relacionadas à ferida operatória foi de 23%. Complicações graus 3 e 4 ocorreram em 50% dos pacientes e nenhum deles faleceu ou teve a proposta cirúrgica suspensa em decorrência de complicações da quimioterapia. CONCLUSÕES: tumores respondedores a quimioterapia neoadjuvante com doxorrubicina e ifosfamida apresentaram um perfil de expressão gênica diferente dos não respondedores, particularmente em genes envolvidos na via de sinalização de TGF. O esquema terapêutico testado mostrou-se efetivo e seguro para ser investigado em um estudo fase III / INTRODUCTION: Surgery combined with adjuvant radiotherapy provides high rates of limb sparing and local control for adult extremity soft tissue sarcomas, but is still associated with high rates of local morbidity and distant recurrences. The role of adjuvant or neoadjuvant chemotherapy is still controversy and target of clinical investigations. The identification of molecular predictive factors of response to chemotherapy could select patients who have benefits or not with its use. OBJECTIVES: to identify gene expression profiles that discriminate tumors with respect to response to neoadjuvant chemotherapy. Analyze the preliminary results of a protocol of neoadjuvant chemotherapy in soft tissue sarcomas. METHODS: samples were collected from subjects of a single-arm prospective clinical trial that investigates the effectiveness of a neoadjuvant doxorubicin and ifosphamide-based chemotherapy regimen in high grade extremity soft tissue sarcomas in adults. Gene expression profiles were determined by the analysis of cDNA microarrays. RESULTS: 14 patients were included in the clinical trial and six samples were used in the molecular study. 222 sequences differentially expressed between responders and non responders were identified. Among the genes with higher differences in expression, we have identified genes involved with TGF signaling pathway, angiogenesis, extracelular matrix degradation and development. The objective response rate to neoadjuvant chemotherapy was 28,6%, the amputation rate was 7,1%, and the wound complication rate was 23%. Grades 3 and 4 complications have occurred in 50 % of the cases, but no deaths or modifications on surgical intent related to chemotherapy complications have occurred. CONCLUSIONS: tumors considered responders to neoadjuvant chemotherapy showed a gene expression profile significantly different from non responders, especially with respect to the TGF signaling pathway. The neoadjuvant regimen tested has showed to be effective and safe to be considering for a phase III clinical trial

Introdução: A exposição à poluição atmosférica durante a gestação provoca alterações nas características da placenta e pode resultar em restrição de crescimento intrauterino. Sabe-se que o transforming growth factor beta 1 (TGFbeta1), o sistema renina-angiotensina uteroplacentário (SRA) e os fatores angiogênicos, tais como vascular endothelial growth factor A (VEGF-A) participam do processo de placentação e regulação do fluxo sanguíneo uteroplacentário. Assim, o objetivo do presente estudo foi investigar o efeito da exposição à poluição do ar sobre a morfologia, função e SRA placentários. Métodos: Ratas Wistar fêmeas foram expostas ao ar filtrado (F) ou ao material particulado 2.5um (P) durante 15 dias. Depois o cruzamento, as ratas foram divididas em 4 grupos e novamente expostas a F ou P (FF, FP, PF, PP). No 19º dia de gestação, as porções maternas e fetais das placentas foram coletadas. Estrutura da placenta, TGFbeta1, VEGF-A e seus receptores e os componentes do SRA foram avaliados. Resultados: A exposição ao material particulado diminuiu massa, tamanho e área de superfície placentária, um indicativo da interação materno-fetal. As concentrações placentárias de TGF beta1, VEGF-A e Flk-1 e os componentes do SRA foram alterados e isso pode indicar um prejuízo na invasão do trofoblasto, angiogênese placentária e troca de nutrientes e gases entre mãe e fetos. Discussão: Os resultados indicam que a exposição a partículas compromete a interação materno-fetal e pode refletir sobre a nutrição e crescimento fetal / Introduction: Exposure to air pollution during pregnancy causes alterations in placental characteristics and may result in intrauterine growth restriction. It was suggested that transforming growth factor beta 1 (TGFbeta1), the uteroplacental renin-angiotensin system (RAS) and angiogenic factors, such as vascular endothelial growth factor A (VEGF-A) participates of the placentation process and regulation of the uteroplacental blood flow. Thus, the aim of the present study was to investigate the effect of exposure to air pollution on the placental morphology, function and placental RAS. Methods: Female Wistar rats were exposed to filtrated air (F) or to concentrated particulate matter 2.5um (P) for 15 days. After mating, rats were divided in 4 groups and again exposed to F or P (FF, FP, PF, PP). At 19th day of pregnancy, maternal and fetal portions of placenta were collected. Placental structure, TGFbeta1, VEGF-A and its receptors and RAS components were evaluated. Results: Exposure to particulate matter decreased placental mass, size and surface area, an indicative of maternal-fetal interaction. Placental TGFbeta1, RAS components and VEGF-A and receptors Flk-1 concentrations were altered and this may indicate a prejudice in the trophoblast invasion, placental angiogenesis and maternal-fetal nutrients and gases exchange. Discussion: These findings indicate that exposure to particulate matter compromises the maternal-fetal interaction and may reflect on fetal nutrition and growth

Para identificar, quantificar e correlacionar os eosinófilos, mastócitos, miofibroblastos e células TGF-beta positivas nos pólipos nasais de pacientes com e sem asma foi realizado a imunoistoquímica. A quantidade de eosinófilos, miofibroblastos e células TGF-beta positivas esteve aumentada no pólipo nasal de indivíduos asmáticos. O número de mastócitos não mostrou diferença entre os grupos. O miofibroblasto foi o denominador comum na correlação entre eosinófilos, mastócitos, células TGF-beta positivas e presença de asma / Introduction: Nasal polyposis is a chronic inflammatory disease of the nasal mucosa or paranasal sinuses characterized by the formation of benign polyps. The pathogenesis is not known, although nasal polyps are associated with several systemic diseases, with asthma being the most frequent. The aim of the present study was to identify, quantify, compare and correlate eosinophils, mast cells, myofibroblasts and TGF-ß-positive cells in nasal polyps of patients with and without asthma. Material and Methods: Seventy-eight subjects with nasal polyps undergoing endoscopic sinus surgery were selected. Control specimens were obtained from eight subjects with a normal sinus mucosa. One group consisted of polyps from 56 patients with asthma and the other of polyps from 22 patients without asthma. Immunohistochemistry was performed using monoclonal antibodies against eosinophil cationic protein to stain eosinophils, against tryptase to stain mast cells, against alpha-smooth muscle actin to stain myofibroblasts, and against TGF-ß to stain TGF-ß-positive cells. Results: The number of eosinophils, myofibroblasts and TGF-ß-positive cells was significantly higher in the asthma group than in the nonasthma group, whereas no significant difference in the number of mast cells was observed between the two groups. The number of eosinophils, mast cells, myofibroblasts and TGF-ß-positive cells was significantly higher in nasal polyps than in the control group. Myofibroblasts showed a significant correlation with eosinophils, mast cells, TGF-ß-positive cells, and asthma. Conclusion: Eosinophils, mast cells, myofibroblasts and TGF-ß-positive cells were identified in all nasal polyps, although the number of eosinophils, myofibroblasts and TGF-ß-positive cells was higher in the asthma group. The number of mast cells was similar regardless of the presence or absence of asthma. Myofibroblasts were a common denominator in the correlation between eosinophils, mast cells, TGF-ß-positive cells, and asthma

Para identificar, quantificar e correlacionar os eosinófilos, mastócitos, miofibroblastos e células TGF-beta positivas nos pólipos nasais de pacientes com e sem asma foi realizado a imunoistoquímica. A quantidade de eosinófilos, miofibroblastos e células TGF-beta positivas esteve aumentada no pólipo nasal de indivíduos asmáticos. O número de mastócitos não mostrou diferença entre os grupos. O miofibroblasto foi o denominador comum na correlação entre eosinófilos, mastócitos, células TGF-beta positivas e presença de asma / Introduction: Nasal polyposis is a chronic inflammatory disease of the nasal mucosa or paranasal sinuses characterized by the formation of benign polyps. The pathogenesis is not known, although nasal polyps are associated with several systemic diseases, with asthma being the most frequent. The aim of the present study was to identify, quantify, compare and correlate eosinophils, mast cells, myofibroblasts and TGF-ß-positive cells in nasal polyps of patients with and without asthma. Material and Methods: Seventy-eight subjects with nasal polyps undergoing endoscopic sinus surgery were selected. Control specimens were obtained from eight subjects with a normal sinus mucosa. One group consisted of polyps from 56 patients with asthma and the other of polyps from 22 patients without asthma. Immunohistochemistry was performed using monoclonal antibodies against eosinophil cationic protein to stain eosinophils, against tryptase to stain mast cells, against alpha-smooth muscle actin to stain myofibroblasts, and against TGF-ß to stain TGF-ß-positive cells. Results: The number of eosinophils, myofibroblasts and TGF-ß-positive cells was significantly higher in the asthma group than in the nonasthma group, whereas no significant difference in the number of mast cells was observed between the two groups. The number of eosinophils, mast cells, myofibroblasts and TGF-ß-positive cells was significantly higher in nasal polyps than in the control group. Myofibroblasts showed a significant correlation with eosinophils, mast cells, TGF-ß-positive cells, and asthma. Conclusion: Eosinophils, mast cells, myofibroblasts and TGF-ß-positive cells were identified in all nasal polyps, although the number of eosinophils, myofibroblasts and TGF-ß-positive cells was higher in the asthma group. The number of mast cells was similar regardless of the presence or absence of asthma. Myofibroblasts were a common denominator in the correlation between eosinophils, mast cells, TGF-ß-positive cells, and asthma

The amphibian species Xenopus laevis, along with mouse and chicken is a very important model system, used widely to dissect the molecular intricacies of various aspects of vertebrate development. Study with Xenopus has clear advantages in terms of various technical considerations including the ease of handling early stage of embryos and due to the remarkable documentation of several early molecular events during development. The concept of inductive interactions between various cell types during early development was first revealed by the studies performed in Xenopus, and among the various factors proposed for mesoderm induction, the members of transforming growth factor-β (TGF- β) superfamily have been considered to be the most probable candidates. About forty different members of the TGF-β superfamily have been cloned and characterized from various organisms. The superfamily members like activins and BMPs have been studied extensively with respect to their functional role during development. While BMPs were assigned as candidates for inducing ventral mesoderm, activins oppose the role of BMPs by inducing dorsal mesoderm. Studies that helped in delineating their roles were performed using three approaches that utilized the ligands, receptors or down stream signaling components (Smads). All the three components were studied with respect to their endogenous expression pattern and effects of ectopic expressions of the wild type or dominant negative mutants. These approaches led to the accumulation of evidences supporting the importance of these signaling molecules. All the above mentioned studies were only possible due to the cloning and characterization of cDNAs of the various proteins involved in the signaling pathway including the ligands. TGF-β2 and 5 are the two isoforms of TGF-β cloned from the amphibian system. We have earlier cloned and characterized the promoter for TGF-β5 gene, which suggested possible regulation of this factor by tissue specific transcription factors. Messenger RNA in situ hybridization analysis to study the TGF-β5-expression pattern during Xenopus development, showed spatial and temporal expression pattern. The expression was confined to specific regions that include notochord, somites, and tail bud among others, in the various stages analyzed. This suggested a possible role for TGF-β5 in organogenesis during the amphibian development. To better understand the role of TGF-β in Xenopus development, studies to examine the specific receptor expression pattern for this growth factor is very essential. With the lack of any reports on cloning of TGF-β receptors from this system, the aim of the present study was to isolate and characterize the receptors for TGF-β from Xenopus laevis. PCR cloning using degenerate primers based on the conserved kinase domains of this class of receptors, coupled to library screenings enabled the identification of two novel receptor cDNAs of the TGF-β receptor superfamily. Characterization of the isolated cDNAs suggested that one of them codes for a type II receptor for TGF-β. Further the cDNAs were found to be ubiquitously expressed during development, as judged by RT-PCR analysis. The cloned cDNAs can now be employed as tools, to study the expression pattern by means of mRNA in situ hybridization, on the various developmental stage embryos and to perform studies using antisense and dominant negative mRNA injection experiments in vivo. Such studies will greatly assist in delineating the role of TGF-β ligands and receptors during amphibian development.

Einen Aspekt dieser Arbeit stellt die Analyse der Stimulation von Ratten-Calvaria-Osteoblasten (RCA) mit den beiden Wachstumsfaktoren TGF-b1 und BMP-4 während der Proliferations- sowie Differenzierungs- und Mineralisierungsphase dar. Hierfür soll die Phosphorylierung und Aktivierung von Erk1 und Erk2, sowie von Smad1 und Smad2 mit Hilfe eines Kinase-Aktivitätsassays sowie der Westernblot-Analyse untersucht werden. Im Rahmen dieser Arbeit soll weiterhin untersucht werden, welche Bedeutung die Wachstumsfaktoren TGF-b1 und BMP-4 auf die Aktivität der alkalischen Phosphatase (ALP), einem wichtigen Differenzierungsmarker in Osteoblasten, ausüben. Enzymatische Aktivitätsbestimmungen und zytochemische Färbung aktiver ALP sollen darüber Aufschluss geben. Weiterhin soll der Gehalt an ALP-mRNA durch PCR bestimmt werden. Ein weiteres wichtiges Ziel dieser Arbeit ist die Analyse der Bedeutung von Erk1, Erk2, Smad1 und Smad2 auf die Aktivität der ALP. Dafür sollen Inhibitoren eingesetzt werden. Die enzymatische Aktivitätsbestimmung soll darüber aufklären. Außerdem soll mit Hilfe von kurzen, doppelsträngigen RNA-Molekülen (siRNA) ein knock down der Kinasen herbeigeführt werden und dessen Auswirkung auf die Aktivität der ALP enzymatisch bestimmt werden. Dafür muss zunächst die Wirksamkeit der siRNA auf RNA-Ebene mittels PCR und auf Proteinebene mittels Westernblot-Analysen überprüft werden. Zusätzlich soll die Bedeutung der Wachstumsfaktoren und der Kinasen Erk1 und Erk2 auf die Mineralisierung der RCA analysiert werden. Dafür wird die Menge des zellassoziierten Kalziums und Phosphats experimentell bestimmt, wodurch der Mineralisationsgrad der Zellen wiedergegeben werden kann.