Cell fate decision mechanism in yeast S. cerevisiae: mating pheromone response pathway and its interaction with the cell cycle machinery

Las vías de señalización celulares son las encargadas de transmitir la información sobreel estado del ambiente intra e extracelular. Con esta información, las células "tomandecisiones" que afectan su destino, tales como dividirse, arrestarse, diferenciarse, o morir. A su vez, es común que células genéticamente idénticas, expuestas al mismo ambientetomen decisiones diferentes. Así, el objetivo general de mi tesis doctoral es, mediante unenfoque de Biología de Sistemas, estudiar los mecanismos moleculares que median estastomas de decisión de destino celular y el origen de la variabilidad observada en esa tomade decisión. Para esto, utilizamos a la respuestas a la feromona sexual de la levadura S.cerevisiae como sistema modelo. Los destinos celulares pueden ser clasificados en distintos fenotipos morfológicos, quedependen de la dosis del estímulo. Sin embargo, encontramos que dichos fenotipos coexistenen concentraciones de feromona intermedia, mostrando así una gran variabilidaden la población. Las causas de esta variabilidad son múltiples y actúan simultáneamente:influye la posición del ciclo celular, el tipo celular (madre o hija), la capacidad de lascélulas de sintetizar más o menos proteínas en general, y su "historia". Seguidamente, nosenfocamos en un fenotipo complejo observado a concentraciones intermedias de feromona:primero se arresta el ciclo celular y se desarrolla una proyección de apareamiento, paraluego reentrar en el ciclo celular. Descubrimos que esta desensibilización está mediadapor una rama estimulatoria del ciclo celular (paralela a la clásica inhibitoria) que se activatardíamente y depende del factor de transcripción Kar4. Asimismo estudiamos lasconsecuencias que el desarrollo de este fenotipo tiene sobre la progenie. Utilizamos paraesto experimentos genéticos combinando con microscopía de epifluorescencia y confocal,modelado matemático.Signal transduction pathways register and transmit information about the intra- andextracellular environment. Using this information, cells "make decisions" that affect theirfate, leading to division, cell cycle arrest, differentiation or death. At the same time, it iscommonly found that genetically identical cells, exposed to the same conditions, behavedifferently. Therefore, the general goal of my thesis is to study the molecular mechanismsthat govern a cell-fate decision system, and the origin of the observed cell-to-cell variability. For this studies, we used the pheromone response pathway in yeast S. cerevisiae as a modelsystem. Cell fates may be classified in different morphological phenotypes, which depend on theconcentration of the stimulus. However, we found that at intermediate doses of pheromone,some of the phenotypes coexist, generating a large population variability. We found severalcauses of this variability, which act simultaneously: cell cycle position, cell type (mother ordaughter cell), the ability of cells to express genes into proteins, and the cell history. Subsequently,we focused our efforts in exploring a particular phenotype/behavior that occursat intermediate doses of pheromone: first, cells arrest the cell cycle and grow a matingprojection, and then, cells reenter into the cell cycle. We found that this desensitization ismediated by a pathway branch that stimulates the cell cycle (opperating in parallel withthe classic inhibitory branch) and that it requires the transcription factor Kar4. We thenstudied the consequences of this behavior on the progeny. We used genetic experimentscombining fluorescence and confocal microscopy with mathematical modeling.Fil: Grande, Alicia Viviana. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

The use of a chronic disease and risk factor surveillance system to determine the age, period and cohort effects on the prevalence of obesity and diabetes in South Australian adults--2003-2013

Age, period and cohort (APC) analyses, using representative, population-based descriptive data, provide additional understanding behind increased prevalence rates

Identifying Behavioral Phenotypes and Heterogeneity in Heart Valve Surface Endothelium

Heart valvular endothelial cells (VECs) are distinct from vascular endothelial cells (ECs), but have an uncertain context within the spectrum of known endothelial phenotypes, including lymphatic ECs (LECs). Profiling the phenotypes of the heart valve surface VECs would facilitate identification of a proper seeding population for tissue-engineered valves, as well as elucidate mechanisms of valvular disease. Porcine VECs and porcine aortic ECs (AECs) were isolated from pig hearts and characterized to assess known EC and LEC markers. A transwell migration assay determined their propensity to migrate toward vascular endothelial growth factor, an angiogenic stimulus, over 24 h. Compared to AECs, Flt-1 was expressed on almost double the percentage of VECs, measured as 74 versus 38%. The expression of angiogenic EC markers CXCR4 and DLL4 was >90% on AECs, whereas VECs showed only 35% CXCR4+ and 47% DLL4+. AECs demonstrated greater migration (71.5 ± 11.0 cells per image field) than the VECs with 30.0 ± 15.3 cells per image field (p = 0.032). In total, 30% of VECs were positive for LYVE1+/Prox1+, while these markers were absent in AECs. In conclusion, the population of cells on the surface of heart valves is heterogeneous, consisting largely of nonangiogenic VECs and a subset of LECs. Previous studies have indicated the presence of LECs within the interior of the valves; however, this is the first study to demonstrate their presence on the surface. Identification of this unique endothelial mixture is a step forward in the development of engineered valve replacements as a uniform EC seeding population may not be the best option to maximize transplant success

Compartmentalization of a Bistable Switch Enables Memory to Cross a Feedback-Driven Transition

SummaryCells make accurate decisions in the face of molecular noise and environmental fluctuations by relying not only on present pathway activity, but also on their memory of past signaling dynamics. Once a decision is made, cellular transitions are often rapid and switch-like due to positive feedback loops in the regulatory network. While positive feedback loops are good at promoting switch-like transitions, they are not expected to retain information to inform subsequent decisions. However, this expectation is based on our current understanding of network motifs that accounts for temporal, but not spatial, dynamics. Here, we show how spatial organization of the feedback-driven yeast G1/S switch enables the transmission of memory of past pheromone exposure across this transition. We expect this to be one of many examples where the exquisite spatial organization of the eukaryotic cell enables previously well-characterized network motifs to perform new and unexpected signal processing functions

Cytochrome P17 inhibition with ketoconazole as treatment for advanced granulosa cell ovarian tumor

Originally published by the American Society of Clinical Oncology. García-Donas et al.: Journal of Clinical Oncology Vol. 31.10, April 1 - 2013: e165-e16

Synthetic Crossfeeding Cocultures in Yeast: Computational Model of Autoregulation and Design of a Tryptophan Export Device

In order to contribute to the design of crossfeeding systems, we modeled population control in a coculture of two crossfeeding strains of an organism, each of which secretes a metabolite the other strain requires to grow. Differential equations show that the steady-state population ratio can be tuned by varying the ratio of the metabolite secretion rates, as long as they fall within a range determined by the nature of the organism. Numerical simulations of Trp/His crossfeeding in budding yeast suggest that the time required to reach steady state populations critically depends on the capacity of the cells to uptake the crossfeeding amino acids. We also engineered and evaluated a novel genetic device that secretes tryptophan-rich peptides with a cell penetrating sequence. Experimental validation showed that the device increases tryptophan secretion and enables growth of a trp− strain in a coculture in synthetic medium lacking tryptophan.Fil: Bush, Alan. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Fisiología, Biología Molecular y Celular; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; ArgentinaFil: Gimenez, Manuel. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Computación; ArgentinaFil: Grande, Alicia Viviana. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Fisiología, Biología Molecular y Celular; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; ArgentinaFil: Morosi, Luciano Gastón. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Parasco, Veronica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Parreño, Maria Alejandra. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Rugiero, Mario. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Sabio, Germán. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Colman Lerner, Alejandro Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; ArgentinaFil: Nadra, Alejandro Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Biológica; ArgentinaFil: Sánchez Miguel, Ignacio Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; Argentin

Herramienta automatizada para evaluación rápida de la vulnerabilidad estructural y no estructural de hospitales

A tool for rapid and automatic assessment of the seismic structural and non-structural vulnerability of hospitals is presented; this vulnerability refers to the operability after strong earthquakes. The non-structural elements are classified into architectural components (exterior and interior), facilities (mechanical, electrical and communications, and distribution), medical equipment, and content; the damages caused by drifts and by accelerations are considered. The vulnerability is determined from the answers to a series of questions. The tool is calibrated with observed damages; the seismic actions that generated these damages are known (obtained from accelerograms recorded in the nearest seismological stations). The calibration is based in comparing the observed damages with the predicted ones; such damages are obtained by combining the vulnerability indexes provided by the tool with the actual seismic demand.Se presenta una herramienta para evaluar de forma rápida y automatizada la vulnerabilidad sísmica estructural y no-estructural de hospitales en relación a su operatividad después de un sismo fuerte. Los elementos no-estructurales se clasifican en componentes arquitectónicos (exteriores e interiores), instalaciones (mecánicas, eléctricas y comunicaciones, y distribución), equipamiento médico, y contenido; se consideran los daños causados por desplazamientos entre plantas y por aceleraciones absolutas. La vulnerabilidad se determina a partir de las respuestas a una serie de preguntas. La herramienta se calibra con dan~os observados; se conocen las acciones sísmicas que generaron estos dan~os (obtenidas de los acelerogramas registrados en estaciones sismológicas cercanas). La calibración consiste en comparar los daños observados con los predichos; éstos se obtienen combinando los índices de vulnerabilidad proporcionados por la herramienta con la amenaza sufrida.Peer ReviewedPostprint (published version

The use of a chronic disease and risk factor surveillance system to determine the age, period and cohort effects on the prevalence of obesity and diabetes in South Australian adults--2003-2013

Age, period and cohort (APC) analyses, using representative, population-based descriptive data, provide additional understanding behind increased prevalence rates