Candida albicans is an opportunistic pathogen, which is responsible for causing systemic infection in immunocompromised patients in hospital settings (nosocomial infections). 90% of these nosocomial fungal infections are caused by C. albicans, and the estimated annual cost of treating them exceeds $1 billion per year. Despite this expenditure, there is a high mortality rate of 50%. There are two main routes of infections, first a mucosal infection that can spread and invades deeper into the tissues and gets disseminated into the bloodstream. Second, more frequently seen in hospital settings, is when Candida cells dislodge from a biofilm that has formed on intravenous devices or catheters. Treatment of these diseases is difficult due to a dearth of antifungal drugs and new strategies are required to explore mechanisms used by Candida in causing infection. One way of approaching these significant scientific challenges is to identify virulence determinants and mechanisms, which apart from providing insightful knowledge of fungal pathogenesis, can also be used as targets for antifungal drug development. The innate immune responses in humans, which are important for defense against fungal infections, are conserved in Caenorhabditis elegans. In order to identify Candida virulence factors, I have developed a C. elegans based pathogenesis assay, where nematodes were infected with fungi (both S. cerevisiae and C. albicans) and observed for disease phenotypes including death. This assay can be used to study several aspects of disease progression in worms from swelling (inflammation a bio-marker of infection) to colonization in the intestine, leading to intestinal distension and ultimately death of the host worm. The assay offers a fast and simple way of identifying unknown genes, which when established as a virulence determinant in the worm model, can be further studied in mammalian models. I demonstrate the utility of this assay in multiple ways. First as proof of principle using this assay I have identified a fungal mutant cap1, which is susceptible to reactive oxygen species (ROS), and fails to cause disease, except in bli-3 mutant worms that carry a mutation in an oxidase gene and is responsible for the oxidative stress. Second, we screened a library of ~1200 C. albicans mutants, and identified 7 genes, 3 known (CMP1, IFF11 and SAP 8), validating the assay and 4 novel genes (orf19.1219, orf19.6713, DOT4 and ZCF15) that play a role in fungal infection. Third use of this assay is to test potential drugs in a high throughput fashion. Families of related compounds were identified through a screen of 30,000 compounds, for their ability as potential inhibitors of C. albicans adhesion to biological and inert surfaces. These compounds were further tested in this assay for their ability to reduce infection of C. albicans in worms. The assay provides us with a method to test efficacy of antifungals in vivo. Finally, using the survival assay, a test for mortality caused by infection, we can observe disparity in the different C. albicans fluconazole resistant strains isolated from AIDS patients. In addition this assay after small modification can be potentially employed to screen the C. elegans RNAi library to identify the modulators of innate immune responses during fungal infection.

Nearly one billion people worldwide have a neurological disease, and one out of every six adults in the United States has a mental illness. For rare and severe neurodevelopmental disorders, like Timothy syndrome (TS), exact genetic causes have been identified and studied extensively. TS is caused by a single point mutation in CACNA1C, a voltage-gated calcium channel (VGCC), which results in severe developmental defects, cardiac arrhythmia, and autism. Studies using patient derived cells are useful in identifying impaired cellular function, especially for TS and other neural activity-dependent disorders. Also, functional high-throughput screening assays that use disease-relevant cell types can lead to more targeted therapeutics that regulate cellular activity. Although these approaches are promising, cell-based assays do not consider the diversity of disease pathology or efficacy of broad-acting therapeutics in multi-cellular organisms. Therefore, we developed several whole-organism disease models using CRISPR-Cas9 and transgenes in the nematode C. elegans that harbor human VGCC mutations. We evaluated and identified behavioral, morphological, and functional phenotypes, and invented new high-throughput functional screening technologies to identify transient and potent suppressors of neural activity in these animals. We expect that these new disease models and methods will provide a pipeline for investigating activity- dependent neurological disorders in whole organisms to identify more effective therapeutics. Altogether, we aim to deepen our understanding about the brain and discover treatments for the millions of individuals that suffer from neurological disease.

Cellular migration is an essential process for establishing neural connections during development. The MIG-10/RIAM/Lamellipodin signaling proteins are thought to send positional information from guidance cues to actin polymerization machinery, promoting the polarized outgrowth of axons. In C. elegans, mutations in the gene mig-10 result in the truncation of the migration of the mechanosensory neurons. Biochemical analysis demonstrates that MIG-10 interacts with abelson-interactor protein 1 (ABI-1), and therefore investigation into whether these proteins work together in the neuron to promote migration was completed. To demonstrate MIG-10 cell autonomy in the neuron, transgenic strains with specific expression of mig-10 were created. mig-10 mutants were rescued in the mechanosensory, anterior lateral microtubule neuron (ALM) by neuron specific expression of mig-10 but not by epithelial expression, suggesting that MIG-10 is acting cell autonomously. To determine ABI-1 cell autonomy, transgenic strains with specific neuronal expression of abi-1 were compared to the wild type strain. abi-1 mutants were rescued by neuron specific expression of abi-1 in the ALM, suggesting that ABI-1 also functions cell autonomously in the ALM during this migration. Further investigation into the MIG-10/ABI-1 relationship was done by feeding RNAi of abi-1 in a mig-10(ct41) mutant strain. The ALM migration was not more severely truncated in the double mutant, suggesting that MIG-10 and ABI-1 work in the same pathway. Taken together, this evidence supports a model where MIG-10 and ABI-1 work together autonomously within the ALM to promote migration.

Submitted by Marcos Anselmo (marcos.anselmo@unipampa.edu.br) on 2016-04-04T16:58:41Z No. of bitstreams: 1 Cristiane de Freitas Rodrigues.pdf: 1197178 bytes, checksum: 5dd8d78c2302bcebac49fdf2b31c3c10 (MD5) / Made available in DSpace on 2016-04-04T16:58:41Z (GMT). No. of bitstreams: 1 Cristiane de Freitas Rodrigues.pdf: 1197178 bytes, checksum: 5dd8d78c2302bcebac49fdf2b31c3c10 (MD5) Previous issue date: 2015-09-26 / A Ceratonia siliqua L. popularmente conhecida como alfarroba, faz parte da classe dos diversos alimentos que apresentam uma grande quantidade de antioxidantes, principalmente pela composição dos compostos fenólicos. Além disso, este alimento tem sido utilizado como substituinte do cacau em diversos produtos alimentícios em função do sabor e cor similares, porém com reduzido conteúdo de lipídeos. Alguns estudos sugerem que o extrato aquoso de alfarroba apresenta uma ação protetora contra os radicais livres. Entretanto, são necessários testes in vitro e in vivo a fim de comprovar a eficácia deste alimento funcional. Para tanto, utilizamos o Caenorhabditis elegans como modelo experimental em prol de substituir o uso de mamíferos e oferecer novas possibilidades de ensaios para avaliar a eficácia de produtos naturais. Neste presente estudo observou que o extrato aquoso da alfarroba apresentou um excelente potencial sequestrador de espécies reativas in vitro pelos ensaios de redução do radical DPPH e de redução do Ferro. Tal efeito pode ser devido à presença dos compostos fenólicos, conforme verificado na análise bromatológica. A partir disso, no estudo percorreu as atividades in vivo. O extrato não apresentou toxicidade significativa até a concentração testada (62.0μg/mL), conforme observado nos ensaios de sobrevivência e longevidade. Também foi observado que o extrato de alfarroba protege contra a mortalidade induzida por paraquat em curto prazo, porém o mesmo não ocorreu ao longo prazo. Encontrou-se também redução da peroxidação lipídica e um aumento da atividade enzimática da catalase, sugerindo estar relacionada ao fator de transcrição DAF-16, importante para a defesa antioxidante nestes animais. Além disso, nosso estudo demonstrou que o extrato aquoso da alfarroba é mais eficiente do que o extrato de cacao na redução dos níveis de triglicerídeos em nematoides selvagens e em mutantes tub-1 (mais obesos), não alterando a ingestão alimentar. Este efeito pode estar relacionado com elevado de teor de fibras presentes no extrato, conforme observado pelo ensaio bromatológico. Em 8 conclusão, nosso estudo sugere que a utilização de alfarroba é segura e pode ser de fato bastante benéfica ao consumidor, fornecendo compostos fenólicos e fibras que podem auxiliar no envelhecimento e na redução de peso. / The Ceratonia siliqua L. popularly known as Carob, part of the class of many foods contain a large number of antioxidants, especially phenolic compounds of the composition. Moreover, this food has been used as cocoa substituent in many food products depending on the flavor and color similar, but with reduced lipid content. Some studies suggest that the aqueous extract of carob has a protective effect against free radicals. However, they are necessary in vitro and in vivo in order to prove the effectiveness of this functional food. Therefore, Caenorhabditis.elegans used as an experimental model towards replace the use of mammalian and offer new opportunities assays to assess the efficacy of natural products. Our study has shown that the aqueous extract of carob showed excellent potential kidnapper of reactive species by in vitro assays to reduce the DPPH radical and reduction of iron. This effect may be due to the presence of phenolic compounds as found in chemical analysis. From this, our study ran activities in vivo. The extract showed no significant toxicity to the tested concentration (62.0μg / ml), as noted in survival and longevity tests. It was also noted that the carob extract protects against mortality induced by paraquat in the short term, but the same was not true in the long run. It was found also reducing lipid peroxidation and an increase in the enzymatic activity of catalase, suggesting be related to the transcription factor DAF-16 important for the antioxidant defense in these animals. Furthermore, our study has demonstrated that the aqueous extract of carob is more efficient than cacao extract in reducing triglyceride levels in wild nematodes and tub-1 mutants (most obese) without altering food intake. This effect may be related to high content of fiber present in the extract, as observed by bromatological assay. In conclusion, our study suggests that the use of carob is safe and can be very beneficial to the consumer fact, phenolic compounds and providing fibers which can assist in aging and weight reduction.

One central question of neuroscience asks how a neural system can generate the diversity of complex behaviors needed to meet the range of possible demands placed on an organism by an ever changing environment. In many cases, it appears that animals assemble complex behaviors by recombining sets of simpler behaviors known as behavioral primitives. The crawling behavior of the nematode worm Caenorhabditis elegans represents a classic example of such an approach since worms use the simple behaviors of forward and reverse locomotion to assemble more complex behaviors such as search and escape. The relative simplicity and well-described anatomy of the worm nervous system combined with a high degree of genetic tractability make C. elegans an attractive organism with which to study the neural circuits responsible for assembling behavioral primitives into complex behaviors. Unfortunately, difficulty probing the physiological properties of central synapses in C. elegans has left this opportunity largely unfulfilled. In this dissertation we address this challenge by developing techniques that combine whole-cell patch clamp recordings with optical stimulation of neurons. We do this using transgenic worms that express the light-sensitive ion channel Channelrhodopsin-2 (ChR2) in putative pre-synaptic neurons and fluorescent protein reporters in the post-synaptic neurons to be targeted by electrodes. We first apply this new approach to probe C. elegans circuitry in chapter II where we test for connectivity between nociceptive neurons known as ASH required for sensing aversive stimuli, and premotor neurons required for generating backward locomotion, known as AVA. In chapter III we extend our analysis of the C. elegans locomotory circuit to the premotor neurons required for generating forward locomotion, known as AVB. We identify inhibitory synaptic connectivity between ASH and AVB and between the two types of premotor neurons, AVA and AVB. Finally, we use our observations to develop a biophysical model of the locomotory circuit in which switching emerges from the attractor dynamics of the network. Primitive selection in C. elegans may thus represent an accessible system to test kinetic theories of decision making. This dissertation includes previously published co-authored material.

Defects in meiotic prophase I events, resulting in aneuploidy, are a leading cause of birth defects in humans; however, these are difficult to study in mammalian systems due to their occurrence very early in development. The nematode, Caenorhabditis elegans, is an excellent model for prophase I studies as its gonad is temporally and spatially organized around these meiotic events. Homolog pairing, synapsis, meiotic recombination and crossover formation are essential to the proper segregation of chromosomes into the respective gametes, either the egg or sperm. Disturbances in these events leads to missegregation of chromosomes in the gametes in the meiotic divisions. Synapsis is especially critical in meiosis as it precedes and is required for meiotic recombination in C. elegans. The formation of the synaptonemal complex (SC) is fundamental to chromosomal synapsis, yet the molecular mechanisms of synaptonemal complex morphogenesis are largely unknown. The investigations described in this thesis were undertaken to better understand the molecular contributions to synaptonemal complex morphogenesis. Chapter One reviews knowledge of morphogenesis and its relationship to the events of meiotic prophase I. Recent studies in our laboratory have implicated AKIRIN, a nuclear protein with multiple biological functions, as having a role in synaptonemal complex disassembly, specifically preventing the aggregation of synaptonemal proteins (Clemons et al., 2013). As a result of our efforts to discern the mechanism by which AKIRIN regulates disassembly, we found that the highly conserved CSN/COP9 signalosome has a role in SC assembly, leading to defects in prophase I events and in MAPK signaling , leading to the arrest of nuclei in the later stages of meiosis. While the CSN/COP9 signalosome has been implicated in general fertility in C. elegans (Pintard et al., 2003), no role had been defined in earlier meiotic stages until this study. Chapter Two describes an RNAi enhancer/suppressor screen undertaken in the akir-1 mutant background. Several RNAi clones were selected for future study based on a reduction in brood size; one of which, csn-5/, is the focus of the analysis presented in Chapter 3. Chapter Three describes the phenotypic characterization of two CSN/COP9 signalosome subunits, csn-2 and csn-5. Alleles of both genes display synaptonemal complex protein aggregation and defects in mitotic cell proliferation, homologous chromosome pairing, meiotic recombination and crossover formation, leading to an increase in apoptosis. Oocyte maturation is also disrupted by a lack of MAPK signaling, resulting in a lack of viable oocytes, which renders the csnmutant homozygotes sterile. These findings support a model suggesting the CSN/COP9 signalosome has an essential role in regulating meiotic prophase I events and oocyte maturation. Chapter 4 describes the methodology used in this study. Chapter 5 provides a summary of the thesis findings and examines the future directions to extend this work.

Meiosis is a specialized cellular division occurring in organisms capable of sexual reproduction that leads to the formation of gametes containing half of the original chromosome number. Meiosis involves two cell divisions, the first of which segregates homologous chromosomes to opposite poles, reducing ploidy by half. In most organisms, this segregation requires crossovers, the exchange of DNA sequences between homologous chromosomes, which in turn, is dependent upon stable associations of homologs. In early meiotic prophase I, chromosomes form pairing interactions that bring chromosomes into close physical associations. The process of synapsis then stabilizes these pairing interactions throughout the homolog pair, and is mediated by the synaptonemal complex (SC), a meiosis specific protein complex. Absent or misregulated assembly of the SC prevents the stabilization of pairing interactions that are essential for meiosis, leading to chromosome missegregation. Divided into two main projects, my work aimed to further our understanding of the regulation of synaptonemal complex assembly. One project examined meiotic chromosomal movement by characterizing a relatively unstudied protein in C. elegans, FKB-6. We showed that FKB-6 is important for creating pauses between chromosome movements. These pauses are needed for allowing chromosomes to properly pair and thus allowing for proper SC assembly. In the absence of FKB-6, a decrease in pausing occurs which perturbs chromosome pairing and causes SC assembly defects. A second project examined the role of CUL-4, an E3 ubiquitin ligase, in meiotic prophase I. We show that CUL-4 plays a role in both SC assembly and meiotic recombination. This work exemplifies the multiple levels of control of SC assembly which still require further study.

Background: Insulin is a hormone released by the pancreatic beta cells in response to elevated levels of nutrients in the blood. Insulin triggers the uptake of glucose, fatty acids and amino acids into the liver, adipose tissue and muscles. Genes regulating insulin signalling are thus of vital importance for metabolic homeostasis and for preventing the development of diabetes. This thesis aims to identify new modifiers of insulin signalling, while carrying out functional studies of a homolog to human arsenite translocating ATPase, ASNA1. ASNA1 activates the insulin signalling pathway and promotes insulin secretion in mammalian cell lines and in Caenorhabditis elegans. A second aim is to better understand how ASNA1 and its interactors regulate sensitivity to the chemotherapeutic drug, cisplatin. Results: Regulators of insulin/IGF signalling (IIS) in C. elegans were identified based on the Larval arrest arrest aspect of the asna-1 depletion phenotype. Sixty-five genes were selected by virtue of their predicted interaction with ASNA-1 and screened for asna-1-like larval arrest upon inactivation of the genes . mrps-2, mrps-10, mrpl-43 encoding mitochondrial ribosomal protein subunits, and enpl-1 encoding an ER chaperone, GRP94 homolog were identified as the genes which when inactivated caused larval arrest without any associated feeding defects. IIS was weaker and insulin secretion was defective in these knockdown animals. ENPL-1 and ASNA-1 proteins interacted with one another both ex vivo and in vitro. ASNA-1 protein and mRNA level swere greatly reduced in enpl-1 mutants and enpl-1(-);asna-1(-) double-mutant worms displayed synthetic lethality. Overexpression of the insulins INS-4 and DAF-28 caused partial rescue of the germline phenotype of enpl-1 mutants, indicating that the phenotype of enpl-1 mutants was due at least in part to insufficient insulin levels. Studies of enpl-1 mutants also helped to understand the role of asna-1 in cisplatin sensitivity. The unfolded protein response (UPR) was induced in asna-1 and enpl-1 knockdown animals. enpl-1 mutants displayed higher sensitivity to cisplatin, when compared to asna-1 mutants and this correlated to higher UPR in enpl-1 knockdown animals. Pharmacological induction of the UPR in intrinsically cisplatin resistant wildtype worms also resulted in increased cisplatin sensitivity. This suggests that manipulation of ENPL-1 levels or of the UPR could enhance the anti-tumoral effects of cisplatin based cancer therapy. With a yeast two hybridscreen 27 putative physical interactors of ASNA-1 were identified. Amongst these candidate swas smn-1, which encodes survival of motor neuron protein homolog. RNAi knockdown of smn-1 caused a larval arrest phenotype similar to asna-1 depleted animals and smn-1 positively regulated IIS, like asna-1. Defects in IIS may be at the level of insulin release because neuropeptide secretion was impaired upon smn-1 knockdown. Further in vitro binding studies showed that SMN-1 and ASNA-1 interacted and inactivation of smn-1 in asna-1 mutants resulted in decreased viability. This implies that SMN-1 is another modifier of ASNA-1 and also a new component in IIS. Conclusion: With a directed RNAi screen and a yeast two hybrid screen several interactors of ASNA-1 that are also IIS modifiers were identified. ENPL-1 and SMN-1 are both involved in insulin release. We also found that induction of the UPR in enpl-1 and asna-1 mutants is a possible mechanism for increased sensitivity to cisplatin.

The correct polarity of a neuron underlies its ability to integrate precise circuitries in the nervous system. The goal of my thesis was to investigate the pathways that establish and maintain neuron polarity/orientation in vivo. To accomplish this, I used bipolar VC4/5 motor neurons, which innervate the C. elegans egg-laying musculature, as a model system. Vulval proximal VC4/5 neurons extend axons in the left-right (LR) orientation, around the vulva; whereas vulval distal VC1-3,6 neurons extend axons along the anterior-posterior (AP) axis. A previous study showed that vang-1, a core planar cell polarity (PCP) gene, suppresses AP axon growth in VC4/5 neurons. In order to identify new components of this pathway we performed genetic screens for mutants with abnormal VC4/5 polarity/morphology. We isolated and mapped alleles of farnesyl transferase b (fntb-1) and of core PCP genes, prickle- 1 (prkl-1) and dishevelled-1 (dsh-1); all of which display tripolar VC4/5 neurons, similar to vang-1 lof. In prkl-1 and dsh-1 mutants, primary LR and ectopic AP VC4/5 axons are born simultaneously, suggesting an early role in establishing polarity. In addition, prkl-1 and dsh-1 act persistently to maintain neuron morphology/orientation. Genetic analysis of double mutants suggests that prkl-1 interacts with vang-1 in a common PCP pathway to prevent AP axon growth, while dsh-1 also acts in a parallel pathway. Furthermore, prkl-1 functions cell autonomously in neurons, whereas dsh-1 acts both cell autonomously and cell nonautonomously in epithelial cells. Notably, prkl-1 overexpression results in unipolar VC4/5 neurons, in a dose-dependent manner. In contrast, dsh-1 overexpression in VC4/5 neurons results in a lof phenotype, similar to vang-1 lof and overexpression phenotype. Remarkably, prkl-1 overexpression restores normal VC4/5 polarity in dsh-1 and vang-1 mutants, which is suggestive of a downstream role for prkl-1. Both PRKL-1 and DSH-1 are expressed in iii uniformly distributed puncta at the plasma membrane of VC4/5, similar to VANG-1; suggesting that their asymmetric distribution is not critical for neuron polarity. Furthermore, we found that the vulva epithelium induces prkl-1 expression in VC4/5; indicating a functional relationship between the egg-laying organ and neuron morphology. Moreover, a structure-function analysis of PRKL-1 revealed that the conserved PET domain and the Cterminal region are crucial to prevent AP axon growth, whereas the three LIM domains are dispensable for this role. In addition, we showed that dsh-1 also regulates the morphology of AP-oriented PDE neurons. dsh-1 promotes the formation of PDE posterior axons, contrary to its function in VC5 neurons; which indicates a context-dependent role for dsh-1 in neuronal polarity. Altogether, this thesis implicates the PCP signalling pathway in a previously unknown role, in establishing and maintaining neuronal polarity, by controlling AP axon growth in response to organ-derived polarizing cues.

Learning can be either non-associative or associative, though the molecular mechanisms underlying both remain enigmatic. The nematode Caenorhabditis elegans can adapt to both the AWC sensed odorants benzaldehyde (Bnz) and isoamyl alcohol (IsoA) and reciprocally cross-adapt. Surprisingly, however, these four adaptation permutations actually represent two distinct forms of learning: non-associative habituation and associative learning by pairing with starvation. Conditioning to the single odorant IsoA leads to both associative and non-associative memory traces, which can be preferentially accessed by choice of a Bnz or IsoA retrieval stimulus, respectively. Furthermore, we show that the molecular mechanisms underlying each form of memory can be genetically double dissociated, with insulin signalling and egl-4 being required for associative learning and osm-9 and arr-1 being essential for IsoA olfactory habituation. This represents the first demonstration where the form of learning displayed after conditioning to a single stimulus is a function of the retrieval stimulus employed.