Medullary thyroid carcinoma (MTC) is a rare malignant tumor originating from thyroid parafollicular C cells. This tumor accounts for 3-4% of thyroid gland neoplasias. MTC may occur sporadically or inherited. The hereditary MTC is part of syndromes of multiple endocrine neoplasia (MEN) 2A and 2B, familial medullary thyroid carcinoma (FMTC). Germline mutations of the RET (REarranged during Transfection) protooncogene cause hereditary form of cancer, whereas somatic mutations can be present in sporadic form of the disease. The RET gene encodes a receptor tyrosine kinase involved in the activation of intracellular signaling pathways leading to proliferation, growth, differentiation, migration and survival. Nowadays, the only possibility of cure for MTC patients consists of total thyroidectomy associated with lymph node dissection. Based on the knowledge of the pathogenic mechanisms of MTC, new drugs have been developed in attempt to control metastatic disease. Of these, the small-molecule tyrosine kinase inhibitors (TKIs) represent one of the most promising agents for MTC treatment and clinical trials have shown encouraging results. Hopefully, the cumulative knowledge about the targets of action of these drugs as well as TKI-associated side effects will help on choosing the best therapeutic approach in order to enhance its benefits.

abstract: A reform movement in the United States has focused on STEM education and 21st century soft skills such as critical thinking, communication, collaboration, and creativity. This spotlight on STEM instruction provided an opportunity to explore how K-14 STEM teacher participants perceived a Design Thinking Instructional Problems (DTIP) approach to developing instructional lessons. The study used a convergent parallel mixed-methods design with a survey instrument and a multiple case study focused on K-14 in-service STEM teachers. Data were collected from teacher participants during two five-week summer Research Experience for Teachers (RET) programs as part of two separate National Science Foundation (NSF) funded Engineering Research Centers (ERC) located at a large southwestern university in the United States (n=16). The study was conducted over three phases. During Phase I and II, teacher participants experienced a Design Thinking Overview workshop and weekly DTIP professional development sessions to facilitate the development of an RET instructional lesson. Pre- and post-program DTIP surveys and background interviews were conducted with all teacher participants (n=16). From this original group, teacher participants were selected as cases. Implementation observations and post-implementation interviews were conducted with these case-teachers (n=10). The study included frequency analysis and descriptive statistics of survey data. Qualitative data were analyzed using direct interpretation, thematic analysis, and open coding with the constant comparative method. A variety of arrays, summaries, and matrices were used to visualize patterns across and within individual case-teacher results. All 16 teacher participants viewed themselves as designers solving complex instructional problems. All 16 teacher participants found the DTIP professional development sessions to have somewhat to very much provided additional value during their RET summer programs. Six of the 10 case-teachers perceived the DTIP model graphic as mostly to completely corresponding to the way in which they developed their RET instructional lesson. Lastly, eight of the 10 case-teachers chose to embed a Design Thinking student learning strategy into the RET instructional lesson they developed. / Dissertation/Thesis / Doctoral Dissertation Educational Technology 2018

Abstract The embryonic urogenital system (UGS) generates the metanephric kidney, gonad and the adrenal gland. It is well known that the development of the UGS is regulated by sequential and reciprocal epithelial and mesenchymal tissue interactions but the secreted mediators involved are still poorly known. The action of such inductive signals is typically regulated by specific antagonists. The Sprouty (Spry) proteins compose one family of cytoplasmic regulators that typically repress the function of the receptor tyrosine kinase (RTK) signal transduction pathways. The DAN/Cerberus (Cer) family that encodes secreted proteins bind and antagonize the Bmp, Wnt and Nodal signals. In this study the roles of Spry and Cer1 was addressed during mouse UGS development by targeted expression of SPROUTY2 (SPRY2) and Cer1 in the ureteric bud and Wolffian duct under the Pax2 promoter. Changes induced in the UGS assembly process were analyzed in detail to reveal the normal developmental roles of these proteins. SPRY2 expression led to either complete lack of the kidney, reduction in the kidney size or formation of unilateral kidney with reduced size. The SPRY2 mediated reduction in kidney size was accompanied by inhibition of expression of genes that are known to regulate kidney development. The results indicated that the Spry may take part in kidney development by coordinating the reciprocal cell signaling between the ureteric bud, the mesenchymal cells and stromal cells. In addition to the kidney, the gain of SPRY2 function revealed an important role in the control of male gonadogenesis. SPRY2 over expression in the Wolffian duct malformed the Wolffian duct derivatives, diminished the number of seminiferous tubules and the amount of the interstitial tissue associated with reduced mesonephric cell migration to the testis. Exogenous FGF9 rescued mesonephric cell migration inhibited by SPRY2. It was concluded that Spry protein contribute to male sexual organogenesis by antagonizing Fgf9 signaling. When the Cer1 gene was over expressed in the ureteric bud this lead unexpectedly to increased kidney size. The Cer1 mediated promotion of kidney size was demonstrated to involve enhanced ureteric bud morphogenesis. At the molecular level Cer1 protein function lead to inhibition of Bmp4 gene expression and concurrent upregulation of Gdnf and Wnt11 expression. Notably, excess BMP4 reduced the Cer1 stimulated ureteric bud branching and downregulated normally expression of Gdnf and Wnt11 in the embryonic kidney. Based on the presented data it is proposed that the establishment of mammalian organ size is under the control of both systemic and the intrinsic factors. Together the work demonstrates significant roles for the proteins that typically inhibit growth factor signaling or signal transduction. Hence organogenesis is controlled by coordination between positive and negative growth factor regulator signals.

Le stockage optique de l’information et l’imagerie à super-résolution sont des champs d’application dont les besoins en matériaux et en molécules photocommutables sont grandissants. Une des approches consiste à associer au sein d’une même structure moléculaire des photochromes et des fluorophores au sein de laquelle des transferts d’énergie résonants sont possibles. La combinaison des propriétés photophysiques des deux types d’entités conduit à la photocommutation de fluorescence recherchée. Pour concevoir de tels systèmes, nous avons basé notre approche sur le concept de click chemistry qui permet d’avoir une grande flexibilité du point de vue synthétique. Ainsi, en utilisant des plateformes moléculaires comme les dérivés de sucres et la β-cyclodextrine, nous avons synthétisé de nombreuses architectures multichromophoriques. En variant le ratio entre le nombre de photochromes (DAE) et de fluorophores (DCM) au sein d’une même molécule, nous avons pu progresser dans la compréhension des relations entre les structures et les propriétés photophysiques de ces systèmes, impliquant des transferts d’énergie multiples entre les différentes entités. Cette démarche nous a permis, d’une part, d’appréhender les effets d’extinction non-linéaire de fluorescence, et d’autre part, de découvrir l’effet d’hystérèse photocontrôlable résultant de la compétition entre les transferts d’énergie et les réactions photochromes. / The fields of optical data storage and super-resolution imaging are in expansion and attract an increasing demand on photoswitchable materials and molecules. One approach consists in associating photochromic and fluorophores units in the same molecular structure, allowing resonant energy transfer processes. The combination of the photophysical properties of the two units leads to the expected fluorescence photoswitching. To design such systems, we based our approach on the click chemistry concept which offers a great flexibility in terms of synthesis pathways. Thus, using molecular platforms such as sugar derivatives and β-cyclodextrin, we have synthesized many multichromophoric architectures. By varying the ratio between photochromic (DAE) and fluorophore (DCM) units in the same molecule, we improved our comprehension of the structure-properties relationships, involving multiple energy transfers between the different entities. This allowed us, first, to understand the effects of non-linear fluorescence quenching, and secondly, to discover the light-controlled hysteresis effect resulting from the competition between energy transfers and photochromic reactions.

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A limited number of drug targets can be exploited by conventional drug-like compounds as the vast majority of disease-associated targets are involved in protein-protein interactions (PPI). PPI targets possess binding surfaces that lack a well-defined hydrophobic pocket amenable for binding to small drug-like compounds. A new class of therapeutics that has shown great potential at modulating PPI are macrocyclic peptides, particularly for their ability to bind to large and topologically complex protein surfaces as well as their potential to access intracellular targets. However, the efficiency of macrocyclic peptides at mediating PPIs and permeating cell membranes is conformation dependent. Here, I describe the role of peptide conformation on target recognition using three clinically relevant PPI targets: the Kelch like ECH Associated Protein-1 (KEAP1), (Chapter Two and Chapter Three); the RET receptor tyrosine kinase (Chapter Four); and β-catenin (Chapter Five). Guided by published X-ray crystal structures, peptides derived from PPI epitopes were designed and structurally constrained to mimic the conformation of the natural PPI recognition motif. In Chapter Two, I report the development of a cyclic heptapeptide derived from the transcription factor Nuclear Factor (Erythroid-derived 2)-Like 2 (Nrf2) with similar affinity for KEAP1 as native Nrf2 through conformational optimization of a linear Nrf2-derived heptapeptide. Efforts to improve the potency and physicochemical properties of the cyclic heptapeptide are discussed in Chapter Three. In Chapter Four, I describe the design of dimeric peptides as tool compounds to investigate the mechanism by which the interaction between glial cell-line derived neurotrophic factor family ligands (GFLs) and GPI-linked co-receptors, GFRα, induce RET signaling. These peptides were derived from the β-sheet regions of GFLs, GDNF and ART, that interact with GFRα1 and GFRα3, respectively. Peptide cyclization and the introduction of a β-turn promoting motif yielded GFL mimetic peptides with stronger affinity for GFRα. Lastly, Chapter Five focuses on exploring the scope of i, i+4 carbamate and amino-staples as a novel peptide stapling system to stabilize α-helical peptides. An axin-derived α-helical peptide that disrupts the β-catenin/TCF4 interaction was used as a model to determine the effect of peptide α-helical stabilization on binding affinity for β-catenin. / 2023-07-07T00:00:00Z

Receptor tyrosine kinases (RTKs) are key regulators of critical cellular processes, such as cell cycle, differentiation, proliferation, apoptosis and survival. Mutations, hyperactivity and loss of function of RTKs are responsible for numerous diseases. Because of the therapeutic importance of RTK signaling, intensive studies have been devoted to understanding the signaling mechanisms of RTKs, and the key components in their signaling networks. However, studying the cellular responses to RTK stimulation in a native cellular context is technically challenging. Consequently, many details of RTK signaling kinetics, and the underlying molecular mechanisms of action, remain unclear. The RET receptor tyrosine kinase is important for neuronal cell survival and function, and for the development of the kidneys and nervous system. Gain of function of RET leads to tumor formation, while loss of function in RET’s kinase activity is associated with the developmental kidney defect Hirschsprung’s disease. RET is activated by ligands of glial cell line-derived neurotrophic factor (GDNF) family, which consist of four homologs—GDNF, Neuturin, Artemin (ART) and Persephin. GDNF family ligands activate RET only in the presence of GPI-linked co-receptors (GFRα1–4). Formation of the pentameric ligand/co-receptor2/RET2 complex leads to dimerization of RET and autophosphrylation of its cytoplasmic kinase domain. RET phosphorylation results in the activation of multiple downstream signaling pathways, including the Ras-Raf-MEK-ERK and PI3K-Akt pathways. The ERK and Akt signaling pathways participate in a variety of cellular activities, including cell survival, proliferation, and differentiation. My project addresses the following questions: (1) What are the kinetics of RET activation and deactivation processes after ART stimulation? (2) How is RET activation coupled to the phosphorylation of ERK1/2 and Akt? (3) How does ligand-induced internalization of RET affect RET signaling? (4) How does each step in the RET-Ras-Raf-MEK-ERK cascade quantitatively regulate ERK phosphorylation levels? The results will elucidate the spatial and temporal dynamics of RET signaling upon stimulation by ART, and to determine how downstream signaling is regulated by the amplitude and timing of RET activation. Overall, the thesis aims to advance our understanding of RTK signaling, by establishing methods and principles that can potentially be applied to other RTK systems.

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