Bio- ja ympäristötieteellinen tiedekunta

 

Recent Submissions

  • Woestmann, Luisa (Helsingin yliopisto, 2017)
    With increasing global warming and habitat fragmentation, environmental conditions are becoming more variable, and the risk and prevalence of diseases may increase in nature. As a consequence, many species have to adapt or respond to rapid changes in their environment. Ectotherms, such as insects, are thought to be especially prone to such changes and thus are interesting and relevant species for assessing life-history responses towards variable conditions. In my thesis, I investigated how the Glanville fritillary butterfly responds to different environmental conditions, and how this translates to fitness-related traits and offspring performance. I was further interested in the potential positive and negative correlations between immunity and other life-history traits. I used experimental approaches conducted in the laboratory to generate changes in individual condition, resulting from variable environmental conditions that were induced via altered nutrition, bacterial and viral infection or via forced flight. Flight was included, as it represents a key life-history trait for this species and is a stressful and energy demanding physiological process. I compared female reproductive strategies, but also assessed how male contribution to female reproduction was affected by variable conditions. Moreover, I assessed potential trans-generational effects on the offspring, and whether the strength or direction of the effect depended on the type of poor condition the individual experienced. Overall the results of this thesis suggest that the Glanville fritillary butterfly is highly sensitive to its surrounding environment, and is able to rapidly change its reproductive strategy according to the conditions it experiences. While more optimal conditions lead to higher offspring quantity, poor or stressful conditions often result in the production of fewer but of higher quality offspring, indicated by e.g. increased hatching success. An increase in offspring quality further translates to increased offspring performance in response to nutritional deficit, thus implying adaptive trans-generational effects. Flight, a key trait in many organisms, has been previously shown to interact with immune response in the Glanville fritillary butterfly. Results from this thesis confirmed this relationship but suggest that the relationship is a general stress response rather than an adaptive response to cope with infections. Bacterial and viral infections drastically reduce lifespan, and hence have the potential to influence population dynamics. Responses to variable environmental conditions including risk of infection are complex in the wild, as several conditions are often acting simultaneously, making it difficult to generalize the observed results. However, the data of this thesis provides important insights in condition-dependent responses of the Glanville fritillary butterfly to stress, and how this translates to fitness-related traits and even offspring performance. Further studies on the adaptive nature and underlying mechanisms behind the observed responses will further contribute to our understanding of the drivers of maintenance of life-history variation and evolution in this species.
  • Pereira, Pedro (Helsingin yliopisto, 2017)
    Parkinson’s disease (PD) and Primary Sclerosing Cholangitis (PSC) are idiopathic diseases for which an external agent, e.g. a microorganism, has been hypothesised as being causally related to the condition or as having a potential role in disease progression. In the present work, we present evidence that gut and oral microbiota, but not nasal, differ between controls and PD patients, and that, regardless of hypothetical causal relationships, some of these changes show potential for use as biomarkers for diagnostic purposes. Although none of our studies are designed to investigate causality, we nevertheless find no suggestion that the bile microbiota is aetiologically related to PSC. On the other hand, our results suggest that Streptococcus may contribute to disease progression. All the studies are unified by the same methodology, consisting on case-control studies using high-throughput amplicon sequencing of the bacterial 16S rRNA gene, followed by bioinformatic processing of the raw data, and finally by statistical analysis.
  • Stucki, Dimitri (Helsingin yliopisto, 2017)
    Compared to solitary insects, the social organization and interactions in eusocial insects are expected to render them more vulnerable to parasitic exploitation. As a consequence, eusocial insects in turn evolved social immune defenses – sophisticated behaviors that complement the individual immune defenses and increase their resistance against parasitic exploitation. Thus, within the network of the eusocial community, host-parasite interactions occur not only between a single host and its parasites,but among all individuals in the network. Yet, although in eusocial insects host-parasite interactions and other ecological stresses affect the entire community, the individuals provide the basic physiological responses in the defense against external influences. Thus, individual stress responses are an important factor in mediating the variation within the colony to ecological stresses. In this thesis I investigated the physiological stress responses of the ant F. exsecta in the light of host-parasite interactions. I found that oral exposure to bacteria can have a beneficial effect on the survival of food deprivation. Yet, the response to the infection in combination with starvation showed temporal variation. Furthermore, I found striking similarities in the immune responses of young males and foraging workers,as compared to young queens and nursing workers. This suggests that the residual life expectancy may have a role in mediating immune defenses among the castes of F. exsecta. Stress responses not only varied among the castes, but also between two natural populations. I found different reaction norms to temperature and humidity, possibly due to the different environmental conditions that the ants experience in their natural habitat. Given that these reaction norms also affected the expression of immune genes, it is likely that variation in the environmental conditions can affect the immune defenses, and thus, may influence host-parasite interactions. In conclusion, this thesis provides insight into the impact of ecological factors on the resistance and responses to stress in a social insect. I show that individual stress responses are tightly linked to immune defenses, which in turn may affect the stress response of the entire community. As a consequence, variation in the environmental conditions, and thus, exposure to different ecological stresses, may result in different evolutionary trajectories among populations, and even among colonies.
  • Tiainen, Joni (Helsingin yliopisto, 2017)
    Pike (Esox lucius) is a keystone species and top predator, which has an important role in lake ecosystems and in recreational fishing. Recreational fishing is strongly size-selective on large fish, which can have detrimental effects on fish populations. The aim of this thesis was to study the ecologically sustainable recreational fishing of pike, and the importance of large pike to population resilience and ecosystem balance. The field studies of this thesis were conducted in four small and almost pristine forest lakes in southern Finland in years 2006-2013. Two different size-selective fishing procedure for pike were applied; minimum length limit -regulation (MLL) of 40 cm and harvestable slot length limit -regulation (HSL) of 40-64.9 cm. During the study, fishing-induced responses in pike population abundance, demographics, production and consumption, as well as reflection of these changes in prey fish populations were monitored. Changes of pike diet and trophic position were studied by stomach content and stable isotope analysis. Also the relation of size-dependent maternal and juvenile characteristics was examined. The main finding of this thesis is that HSL is capable to maintain viable pike populations. HSL preserved population density, biomass and diverse size-structure, as well as high pike production and consumption by diverse sized pike. By MLL those features were greatly degenerated. By protecting large fish, HSL is able to preserve the productivity of the fish population, because fishing mortality is compensated by increased recruitment and growth. In addition, HSL maintained stability of pike consumption, which enables a strong piscivore effect on the ecosystem. Based on the high quality and amount of reproductive products of large females, they are important for the reproduction of pike populations, which should be considered in fisheries management.
  • Kuuluvainen, Emilia (Helsingin yliopisto, 2017)
    Precise control of transcription, the copying of the genetic DNA code to an expressed RNA molecule, is fundamental for all processes of an organism. Transcriptional regulation is dependent on the activity of proteins and protein complexes including general and cell specific transcription factors and co-activators. Studying how these transcriptional regulators function is crucial for understanding processes such as development and disease. This PhD thesis focuses on the function of one evolutionarily conserved transcriptional co-activator, called the Mediator complex, and in particular on the role of its kinase module. This kinase module consists of four proteins: Cdk8, cyclin C, Med12 and Med13 in lower metazoans and CDK8 or CDK19, cyclin C, MED12 or MED12L and MED13 or MED13L in vertebrates. The Mediator kinase module regulates transcription through various mechanisms, including association with transcription factors and regulation of enhancer-dependent transcription. Kinase module deregulation is implicated in developmental disorders and cancer, but the molecular mechanisms underlying these diseases remain poorly understood. CDK8 was found to be dispensable for cell-autonomous survival but required for mouse embryonic development at the pre-implantation stage. Cdk8-CycC-mediated regulation of transcription was dependent on Med12-Med13 while Cdk8 and CycC depletion caused distinct and even opposite effects on gene expression as compared to Med12 and Med13 depletion in fruit fly cells. This work identified highly similar effects on transcription after depletion of fruit fly Med12 or Med13, suggesting limited Med12-independent functions for Med13. Kinase module subunit hierarchy was conserved in human colon cancer cells where depletion of MED12 or double depletion of the redundant MED13 and MED13L also resulted in highly similar transcriptional responses. Med12 and Med13 were found to be activators of innate immunity genes that are dependent on the serpent/GATA transcription factor in fruit fly cells and larvae. In human colon cancer cells, MED12, MED13 and MED13L were disproportionally required for the expression of genes associated with cancer-acquired super-enhancers. MED12 or MED13 and MED13L depletion caused a dramatic decrease in the expression of the super-enhancer associated MYC oncogene and impaired proliferation of colon cancer cells, suggesting that targeting of these kinase module subunits is a possible future therapeutic opportunity. This thesis extends the present understanding of the relationships between Mediator kinase module subunits in metazoan species and identifies kinase module-dependent functions in development, immunity and cancer-acquired transcription. Further research should be directed at studying the molecular mechanisms of kinase module functions in vivo and at the potential to target this complex with the goal of treating human diseases such as cancer.
  • Mikula, Kornelia (Helsingin yliopisto, 2017)
    During host invasion, pathogenic bacteria express a variety of virulence factors that facilitate their escape from the immune system and thus enable propagation of the infection. The trimeric autotransporter adhesins (TAAs) are one example of a specialised virulence factors expressed by many Gram- negative bacteria, such as Yersinia spp, Escherichia coli, Moraxella catarrhalis, and others. TAAs are highly modular proteins consisting of passenger and translocation domain. Passenger domains are variable domains, constructed of repetitive, structurally homologous subdomains: heads, connectors and stalks. In contrast, the translocation domain is a highly conserved β-barrel anchoring the passenger into the outer membrane of bacteria. TAAs are a key part of Gram-negative bacterial virulence, and as such could be potential drug targets. However, to develop novel drugs, we need to understand the nature of TAAs as well as the molecular details of their interactions with host molecules. In my thesis, I showed that the intact TAA translocation domain is essential and capable of translocating heterologous passengers to the bacterial cell surface. Additionally, heterotrimeric passenger domains have the functionality of the individual monomers, which can generate an extra diversity on the bacterial cell surface to combat immune attack, especially as multiple TAA genes are present in one bacterium. In addition, I have solved the structure of a fragment of the ubiquitous surface protein A (UspA1) from M. catarrhalis, revealing the C3d-binding surface. C3d binding by UspAs is essential in serum resistance preventing formation of the membrane attack complex. Finally, I studied interactions between E. coli immunoglobulin binding protein D (EibD) and IgG Fc. Eibs bind to the Fc region of IgG and IgA in a non-immune manner, which appears to mask the bacterium from the immune system. Attempts to solve crystallographic structure of the EibD-Fc complex were not successful, but they resulted in the another binding. I showed that a single mutation within the linker region between CH2 and CH3 domains of IgG Fc could drastically change the relative structural arrangement of constant heavy chains 2 and 3.
  • Laos, Maarja (Helsingin yliopisto, 2017)
    Supporting cells (SCs) of the mammalian inner ear are differentiated, postmitotic cells that hold promise as a platform in therapeutic interventions to replace lost sensory cells, the hair cells (HCs). However, SCs exhibit an age-dependent decline in their responsiveness to regenerative manipulations that aim to trigger cell cycle re-activation or to stimulate transdifferentiation into HCs. The aim of this PhD thesis project was to identify barriers restricting the therapeutic potential of auditory and vestibular SCs. Using viral-mediated ectopic expression of cyclin D1 (cD1) in organotypic cultures to force postmitotic SCs to re-enter the cell cycle, the efficiency of the cells to complete cell cycles was shown to decrease with maturation. Unscheduled cell cycle re-activation was found to be associated with accumulation of DNA double-strand breaks (DSBs), indicated by the upregulation of the serine 139 phosphorylated form of histone H2AX (γH2AX). By studying the dynamics of the DNA repair protein Rad51, the underlying reason for age-related restrictions in proliferative plasticity was shown to be delayed or inefficient DNA repair. Furthermore, delayed repair of DNA damage was found to lead to SC death. To study the possible involvement of DNA damage in stimulated SC-to-HC transdifferentiation, the pharmacological inhibitor of Notch signaling that triggers SC transdifferentiation into HCs was applied to inner ear explant cultures. It was shown that unlike forced cell cycle re-activation, stimulated transdifferentiation does not trigger DNA damage, suggesting that it might be a “safe” way generate HCs. p53 has been shown to antagonize cell proliferation and regenerative events in other contexts. Thus, it was investigated here whether this is the case also in the inner ear. Using a loss-of-function mutant mouse model, p53 was shown to be dispensable for inner ear development. By applying various growth-promoting manipulations on cochlear explants from these mutant mice in vitro, inactivation of p53 was shown to not confer regenerative potential to SCs. Excess levels of p53 that are generally associated with cellular stress response have been shown to direct cells to cell death. Thus, p53 levels are under a tight control. The significance of controlled levels of p53 in different developmental situations and in a tissue context is poorly understood. Thus, inner ear was used here as a model to study the consequences of p53 overexpression in various developmental contexts: proliferation; differentiation; and homeostasis. Mutant mouse models in which the interaction between p53 and its negative regulator Mouse double minute 2 (Mdm2) was abolished demonstrated that p53 accumulation is lethal to both proliferating HC, SC and neuronal progenitors, and quiescent, differentiating SCs and HCs. More thorough analysis that focused on SCs showed that their sensitivity to p53 decreases with postnatal maturation. The data presented here thus suggests that epigenetic signaling and maturation-related mechanisms that regulate chromatin conformation might limit p53´s pro-apoptotic functions in maturing SCs. This PhD work has revealed DNA damage signaling and inefficient DNA repair as important barriers restricting the proliferative potential of mammalian SCs. This work also demonstrates the importance of controlled levels of p53 for the survival of cells of the auditory organ. Furthermore, the data obtained from this work can be extrapolated to other postmitotic, differentiated cell types when evaluating their potential for regenerative therapies.
  • Kerminen, Kaisa (Helsingin yliopisto, 2017)
    The wide use of pesticides has led to the contamination of soils, subsoils, surface and ground waters. This motivated research on pesticide dissipation and remediation of pesticide contaminated soils and groundwater. The herbicide dissipation was studied in boreal surface soils, subsurface sediment slurries and pilot-scale sediment columns. The sediments were from a groundwater area that was contaminated with atrazine, desethylatrazine (DEA), simazine and 2,6-dichlorobenzamide (BAM). The aim was to enhance dissipation by microbes (indigenous / Pseudomonas ADP), sonication (0, 5, 10, 20 or 30 min, 43 kHz, 320 W) or the following additives: surfactant methyl-β-cyclodextrin, a mixture of zero-valent iron and organic matter (EHC®), peat or a compost-peat-sand (CPS) mixture. Microbes enhanced atrazine (half-lives 57–181 d) and terbutryn (70–291 d) degradation in surface soils. Atrazine was also degraded chemically in four soils (half-lives 120–183 d). Oxygen did not affect atrazine half-lives significantly, while terbutryn was only degraded in aerobic soils. Herbicide dissipation was poorest in the soil that had the lowest amounts of organic matter and nitrogen. Sonication did not decrease the atrazine concentrations, compared with the non-sonicated controls, despite of indications of microbial and chemical degradation. Surfactant did not stimulate atrazine degradation by indigenous sediment microbes, and Pseudomonas ADP degraded atrazine even without surfactant. EHC® enhanced chemical atrazine dissipation under aerobic conditions and, in columns, cleaned atrazine-, DEA- and BAM-contaminated groundwater for about a month. Peat and CPS enhanced the chemical dissipation of atrazine and simazine. Peat also enhanced hexazinone dissipation. Only trace amounts of atrazine, simazine and hexazinone could be extracted from peat and sediment, which indicates that the dissipation was caused by chemical degradation and/or unextractable bound residue formation. In conclusion, the addition of peat, CPS and Pseudomonas ADP were the best approaches for reducing pesticide concentrations. EHC® could also be useful in remediation of small quantities of pesticides, preferably in the presence of oxygen. However, the usability of peat, CPS and EHC® in remediation should be further studied to avoid the possible adverse effects of organic matter additions to drinking water quality.
  • Keto, Antton (Helsingin yliopisto, 2017)
    Water-levels of lakes in Finland are artificially regulated for energy production, flood protection, navigation and recreational use. There is a need for changing water-level regulation practices, due to changing climate, increasing recreational use of lakes, and implementation of legally binding national targets for electrification of renewable sources. To obtain more knowledge-based assessments of new water management regulations, we need to develop water-level regulation assessment tools and to increase the sensitivity of ecological classification systems for hydromorphological pressures, as the European Union Water Framework Directive (WFD)requires. The main objectives of this study were to 1) develop criteria and threshold values for assessing the ecological status in regulated lakes, 2) identify both high-hydrological status and heavily modified lakes and 3) estimate the role of helophytes in the uppermost littoral zone. Impacts of water-level fluctuation on macrophytes, macrozoobenthos, and littoral fish fauna were clearly evident, and the threshold value between moderate and good ecological status was a 3.5 m winter water-level drawdown with the mean ecological quality ratio assessment method (1.8 m with the one-out-all-out principle). The vertical extension of Phragmites was most strongly associated with the water-level fluctuation of open water period (OWP), followed by Carex spp. and Equisetum. Overall, the RF models explained 4--41% of the variation observed in the helophytes zones. The models indicated that OWP fluctuation, slope, openness and cover of other macrophyte groups were key factors explaining the extent of the helophyte zones. The hydrological regime could be classified as having high hydrological status in 20% of the regulated lakes. Quite often, the ecological status was poorer, implying that high-hydrological status lakes often face other anthropogenic pressures, such as eutrophication that degrades high ecological status. Provisional designation with hydrological criteria seemed to work quite well, because 13 of the 15 lakes were estimated similarly with simple hydrological criteria, compared with the national HMWB designation only later produced by the environmental authorities.
  • Davidsson, Pär (Helsingin yliopisto, 2017)
    Necrotrophic phytopathogens, such as soft rot bacteria, cause large losses in agriculture. Unlike biotrophic pathogens, these typically rely on toxins and plant cell wall-degrading enzymes (PCWDEs) to kill and degrade the host tissue. As such, the methods utilised by the plants to defend themselves against biotrophs, such as the hypersensitivity response (HR), could instead be beneficial for necrotrophic pathogens. One key component in plant defence against necrotrophic pathogens is the recognition of oligogalacturonides (OGs), a breakdown product of the pectin in the plant cell wall, formed by the action of PCWDEs. Similar to direct recognition of the pathogen itself, recognition of OGs trigger a wide array of defence responses, resulting in improved protection against pathogens. Long OGs with a degree of polymerisation (DP) between 10 and 20 have been well studied. In this study, we explored the role of the relatively less understood short OGs (DP < 9). We utilised trimeric OGs to study the changes induced by short OGs on the transcriptome of Arabidopsis thaliana. We established that, similarly to long OGs, short OGs up-regulate genes related to defence and down-regulate genes related to plant growth and development. Phenotypic assays confirmed that pre-treatment with short OGs could improve resistance in A. thaliana against the soft rot bacteria Pectobacterium carotovorum, to the same degree as long OGs. Furthermore, we showed that treatment with both types of OGs results in seedling growth retardation. As part of investigating the signalling triggered by short OGs, we confirmed that trimeric OGs do not trigger the characteristic initial ROS (reactive oxygen species) burst, but do trigger expression of a large set of peroxidases. Similar to long OGs, part of the signalling in response to short OGs goes via phosphorylation of Mitogen-activated protein kinases (MAPKs). Our results show that short OGs are indeed biologically active elicitors of plant defence, with a signalling pathway that appears to be in part distinct from long OG signalling. We used the established trade-off between plant defence and plant growth and development to develop screens for mutants with altered OG sensitivity. One mutant line exhibiting hypersensitivity to OGs, resistance to the necrotrophic pathogens Botrytis cinerea and P. carotovorum, as well as sensitivity to the hemibiotrophic pathogen Pseudomonas syringae, was chosen for further studies. We established that the observed phenotypes were due to overexpression a cell wall-localised apoplastic peroxidase (class III peroxidase, CIII Prx) – PEROXIDASE 57 (PER57). We detected increased levels of ROS and increased cuticle permeability, associated with downregulation of genes involved in cutin formation and biosynthesis. We also observed a priming of OG related response genes. The phenotypes could be recaptured by overexpression of several CIII Prxs, indicating a general phenomenon. ABA treatment of these lines restored the phenotypes to wild-type. This appears to be mediated via removal of ROS. Noticeably, the peroxidase activity remained high in the peroxidase overexpression lines, indicating that while exogenous application of ABA was able to remove the ROS produced by the peroxidases it only had a minor direct effect on the activity of the peroxidases. Our results, combined with previous research on cuticular and ABA mutants, led us to propose that cuticle integrity is influenced by a positive feed-back loop. A disturbed cuticle leads to elevated ROS levels via increased peroxidase activity, which in turn impairs cuticle formation and biosynthesis. Under normal circumstances this loop is regulated by ABA. In the situation where a necrotrophic pathogen is invading the plant recognition of cell-wall derived DAMPs, such as OGs, it leads to activation of peroxidases that further promote resistance signalling via the creation of ROS.
  • Keskitalo, Salla (Helsingin yliopisto, 2017)
    A decade after identification of the human kinome, only a fraction of the kinome has been systematically studied. This clearly illustrates the lack of knowledge regarding the functions and cellular effects that these proteins have in the establishment of cellular phenotypes. Surprisingly, recent evidence suggests that approximately 23% of all kinase genes were estimated to function as cancer genes. The overall aim of this thesis project was to shed light on the mechanisms controlling protein kinase activity and function, particularly in human cancers. A global and comprehensive interactomics analysis of the signaling networks of the evolutionarily conserved CMGC-protein kinase family, consisting of cyclin-dependent kinases [CDK], mitogen-activated protein kinases [MAPK], glycogen synthase kinases [GSK3] and CDC-like kinases [CLK]) was performed. From this physical and functional interaction analysis, hundreds of novel interactions, kinase-substrate relationships and previously unknown links to human diseases, such as cancer were identified. The unprecedented sensitivity and specificity of this approach was also illustrated, and highlighted, for example, by the purification and identification of the complete translational co-activator complex (the Mediator complex) with two of the CMGC kinases (CDK8 and CDK19). At the same time, the Mediator complex was identified mutated in benign uterine human tumors (uterine leiomyomas). To further deepen the understanding of the role of CDK8 and CDK19 kinases in controlling human disease pathways, we studied the functional role of two MED12 mutations in uterine leiomyoma and prostate cancer. Based on these studies, MED12 was found essential for the kinase activity of CDK8 in the context of the Mediator kinase module. Furthermore, disruption of the Mediator kinase module subunit interactions was shown as a common mechanism contributing to the formation of uterine leiomyoma. The MED12 mutants in leiomyoma and prostate cancer were shown functionally different. Finally, a novel MED12 nuclear localization signal was identified, and its importance in the correct nuclear localization of MED12 and subsequent proper assembly and function of the Mediator kinase module was experimentally proven. The described results from the multidisciplinary studies clarify the cellular roles of CMGC kinases and Mediator subunits, facilitating the design of targeted future therapies/therapeutics against human diseases.
  • Kilpinen, Lotta (Helsingin yliopisto, 2017)
    Human mesenchymal stromal cells (hMSCs) are currently used in many advanced cellular therapies. The clinical use of hMSCs requires extensive cell expansion, but the consequences of expansion, especially at the molecular level, are not fully understood. The therapeutic effect of hMSCs is mediated paracrine interactions with immune cells modulating both innate and adaptive immune response. Membrane glycerophospholipids (GPLs) provide precursors for signaling lipids, which modulate cellular functions, including immunological effects. In this thesis, I investigated the effect of the donor’s age and cell doublings on the GPLs, gene expression and microRNA (miRNA) profiles of human bone marrow MSCs (hBM-MSCs). In order to gain more insight into the functional mechanisms of hMSCs, I investigated the extracellular vesicle secretion from human umbilical cord blood derived MSCs, and evaluated their immunosuppressive capacity in vitro as well as their possible immunomodulative and protective effect in kidney ischemia-reperfusion injury in vivo. In this study, I was able to demonstrate that the hBM-MSCs, harvested from 5 young adults and 5 old donors, showed clear compositional changes in their GPL profiles during expansion. Most strikingly, the molar ratio of arachidonic acid (20:4n-6) containing species of phosphatidylcholine and phosphatidylethanolamine accumulated, while the species containing monounsaturated fatty acids decreased during passaging. The lipid changes correlated with the decreased immunosuppressive capacity of hBM-MSCs suggesting a connection between lipid signaling and immunomodulatory functions. Although there were clear alterations in gene expression levels and lipid profiles, the miRNA expression levels were more stable. The expression levels of 37 miRNAs were changed in the old donors group and 36 miRNAs were changed in the young donors group. Of these, only 12 were differentially expressed in both young and old donor BM-MSCs and their predicted target mRNAs, the expression of which was changed, were mainly linked to cell proliferation and senescence. This thesis provides a detailed analysis of molecular changes during MSC expansion. The combination of in vitro and in vivo models accompanied with a detailed analysis of molecular characteristics is essential to understand the complexity of the MSC paracrine mechanisms and functionality.
  • Laakso, Senja (Helsingin yliopisto, 2017)
    This dissertation examines local experimentation from a practice theoretical perspective. By doing this, the dissertation bridges the gap between two fields of research: one relating to the governance of experiments and the other to the dynamics of practices. In this way the dissertation contributes to the timely issue of steering consumption in a more sustainable direction by utilising experiments and interventions at multiple societal levels – an issue attracting wide interest within both research and policy communities. The dissertation focuses on the role of participants in accommodating novel technologies and services into their everyday lives, and the role of social interplay between individuals and their collectives in supporting or opposing the change and diffusion of practices. These factors – how everyday practices are linked together, how change in one practice affects other surrounding practices, and how individuals adjust and evaluate their performances with respect to social norms, expectations, standards and rules – are fundamental to both stability and change in practices. The dissertation comprises of five articles that illustrate, firstly, what can be expected from a local experiment and what the role of each experiment is and, secondly, what can be learnt from an everyday practice perspective on experiments and how the experiments are accommodated into the system of everyday practices. The study draws on a meta-study on 25 papers on climate governance experiments and on three empirical case studies on local experiments in Jyväskylä, Finland. This dissertation asserts that a practice approach and a participant perspective can provide new opportunities for experimental governance by illustrating the complexities of everyday practices and how to acknowledge them in experimentation. Although sustainability transitions require changes in practices as entities, a focus on the performances of practices is crucial for any intervention, as it sheds light on individual learning and experiences. The findings highlight the interdependencies and path dependencies of practices, as well as the collective perceptions of normality steering understandings of acceptable or unacceptable actions. The results also demonstrate that the participants are active contributors in experimentation, adjusting the new configurations of elements and practices in the prevailing system and reflecting on their performances in relation to others. Addressing the dynamics between individual performers of practice and their communities in (re)producing practices, and then targeting the interventions at the collective underpinnings preventing (or accelerating) change might be the key to stabilising emerging, sustainable practices.
  • Teesalu, Mari (Helsingin yliopisto, 2017)
    Simple carbohydrates constitute a big part of our everyday diet, as significant consumption increases have occurred in recent decades. This has coincided with a dramatic rise in people suffering from metabolic disorders, such as diabetes and obesity. However, the genetic factors ensuring a healthy response to sugar intake remain poorly understood. To keep blood glucose in a healthy range even upon overnight fasting or following a rich meal, animals need to be able to adapt quickly. In a healthy organism, high sugar intake leads to rapid conversion of excess sugars into stored glycogen and triacylglycerols, while starvation triggers glucose production through gluconeogenesis and glycogen breakdown. To cope with these fluctuating nutritional conditions organisms possess glucose-sensing mechanisms. Such pathways have a key role in monitoring changes in cellular and organismal nutrient status and readjusting animal physiology accordingly to maintain homeostasis. Intracellular sugar metabolites are sensed by the conserved Mondo family transcription factors (TFs)(MondoA and MondoB/ChREBP in mammals, Mondo in Drosophila), which act together with TF Mlx. Together, they control the expression of metabolic target genes by binding to the carbohydrate response elements present in their promoters. The known Mondo-Mlx targets include genes involved in carbohydrate metabolism and biosynthesis of fatty acids. Yet, the physiological output of these transcription factors has remained largely elusive. As these TFs are very well conserved in Drosophila, this model organism has been used in this thesis to understand the physiological role of Mondo-Mlx and their target genes in vivo. We show that Mondo-Mlx interact in the fly and are crucial for dietary sugar tolerance. Loss of either transcription factor leads to impaired growth and lethality upon high sugar diet. We further characterize the mlx mutant phenotype to reveal high circulating glucose, and increased glycogen levels. We uncover transcriptional repressor Cabut as a direct target of Mondo-Mlx. The Cabut promoter is directly bound by Mondo-Mlx in a sugar-dependent manner. Loss of Cabut similarly results in dietary sugar intolerance, pointing to a crucial function in carbohydrate metabolism. Mondo-Mlx through Cabut are essential for repressing the expression of pepck – the rate limiting gene in gluconeogenesis and glyceroneogenesis. A failure to regulate this step results in pepck over-expression, leading to several fold higher levels of circulating glycerol, and pupal lethality of mlx mutants. Moreover, we reveal that Cabut interconnects nutrient sensing with the circadian clock, and contributes to circadian gene expression oscillation. We also identify Salt inducible kinase 3 (SIK3) as a direct transcriptional target of Mondo-Mlx required for dietary sugar tolerance. Moreover, we show that the activity of the rate-limiting enzyme in the pentose phosphate pathway, glucose-6-phosphate dehydrogenase (G6PD), is increased following sugar feeding. The sugar-augmented increase in G6PD activity is achieved through SIK3-dependent activating G6PD phosphorylation. Collectively, Mondo-Mlx-mediated transcriptional upregulation, as well as SIK3-dependent phosphorylation promote G6PD enzyme activity in response to high high sugar diet. The increased G6PD activity is required for elevating NADPH/NADP+ ratio in order to reduce glutathione in high sugar conditions. We determine that upregulating G6PD activity through Mondo-Mlx and SIK3 is essential for redox balance maintenance, and dietary sugar tolerance. In sum, thesis demonstrates that maintaining redox balance, directing the flow of carbon backbones, and regulating the expression of metabolic circadian genes is essential for dietary sugar tolerance. We highlight the central role of Mondo-Mlx in orchestrating the necessary transcriptional response required for safe glucose utilization, and ultimately, for maintaining metabolic homeostasis.
  • Li, Ling (Helsingin yliopisto, 2017)
    The increasing use of titanium dioxide nanoparticles (TiO2 NPs) and their consequent release into the environment, make it important to understand the behaviour, fate and potential adverse effects that TiO2 NPs may have upon organisms. After being introduced into the aquatic environment, TiO2 NPs will undergo transformation processes, which will affect their properties, including, chemical composition, size, surface charge and coating, and these may also have substantial implications on the fate and toxicity of the NPs. This highlights the importance of physiochemical characterization of the NPs in conjunction with a toxicological assessment. The transformation processes are dependent both on the physicochemical properties of the NPs and on the physicochemical properties of the ambient environment. However, these properties have been seldom studied in complex natural waters. Therefore, the research done for this PhD dissertation aimed to investigate the behaviour of TiO2 NPs in natural waters, and to associate the NPs colloidal stability with various water properties. The toxicity tests of TiO2 NPs were performed on two aquatic organisms each of which represent different trophic levels: Lemna minor (L. minor) and Daphnia magna (D. magna) according to ISO 20079 and OECD test 202, respectively. The specific aim was to assess the possible toxic effects of TiO2 NPs with maintained colloidal stability in an optimized ecotoxicological test medium. Given the potential of TiO2 NPs to carry other pollutants, the mixture toxicity of TiO2 NPs with cadmium (Cd) and lead (Pb) on D. magna were also investigated. TiO2 NPs exhibited different colloidal stability, which depend on the physicochemical properties of the natural waters. Total phosphorus, total nitrogen, alkalinity, pH, electrical conductivity and turbidity were shown by experimental and linear regression analysis to be the main water properties that negatively influence NPs stability among 14 water properties that were compared. All six of these physicochemical properties of water had positive correlations on the deposition of TiO2 NPs in lake waters. TiO2 NPs showed low colloidal stability in standard ecotoxicological test media, but modification of the current standard medium enabled the steady exposure of L. minor and D. magna. TiO2 NPs showed no adverse effect on the growth rate or chlorophyll a content of L. minor, or immobility of D. magna. However, TiO2 NPs were found to become attached to the cell wall of L. minor and to the body surface of D. magna, both of which may cause the potential transfer of TiO2 NPs into the aquatic food chains. Such a transfer would lead to an exposure of other organisms and contribute to the environmental fate of NPs. The presence of TiO2 NPs also influenced the bioaccumulation and toxicity of Cd and Pb in D. magna. TiO2 NPs increased the bioaccumulation and toxicity of Cd in daphnia, whereas it reduced the toxicity of Pb regardless of the 3- to 4-fold increase of bioaccumulation found. Surface attached TiO2 NPs combined with adsorbed heavy metals, caused adverse effects on D. magna swimming and moulting behaviour, which was assumed to lead to chronic toxicity. The research findings presented in this thesis elucidate the water physicochemical properties that control the aggregation and deposition of TiO2 NPs in complex natural waters, and offer an insight into their biological effects and accumulation potential upon aquatic organisms.