Väitöskirjat

Recent Submissions

  • Kontro, Inkeri (Helsingin yliopisto, 2016)
    Elastic X-ray scattering is a probe which provides information on the structure of matter in nanometer lengthscales. Structure in this size scale determines the mechanical and functional properties of materials, and in this thesis, small- and wide-angle X-ray scattering (SAXS and WAXS) have been used to study the structure of biological and biomimetic materials. WAXS gives information on the structures in atomistic scales, while SAXS provides information in the important range above atomistic but below microscale. SAXS was used together with dynamic light scattering and zeta potential measurements to study protein and liposome structures. The S-layer protein of Lactobacillus brevis ATCC 8287 was shown to reassemble on cationic liposomes. The structure of the reassembled crystallite differed from that of the S-layer on native bacterial cell wall fragments, and the crystallite was more stable in the direction of the larger lattice constant than in the direction of the shorter. Liposomes were also used as a biomembrane model to study the interactions of phosphonium-based ionic liquids with cell membrane mimics. All studied ionic liquids penetrated multilamellar vesicles and caused a thinning of the lamellar distance that was dependent on ionic liquid concentration. The ability of the ionic liquids to disrupt membranes was, however, dependent on the length of hydrocarbon chains in the cation. In most cases, ionic liquids with long hydrocarbon chains in the cation induced disorder in the system, but in one case also selective extraction of lipids and reassembly into lamellae was observed. The effects depended both on ionic liquid type, concentration, and lipid composition of the vesicle. WAXS was used as a complementary technique to provide information on the structure-function relationship of a novel biomimicking material composed of a genetically engineered protein, chitin and calcium carbonate, and films composed of hydroxypropylated xylan. The presence of calcium carbonate and its polymorph (calcite) was determined from the biomimetic material. For the xylan films, crystallinity was assessed. In both cases, also the crystallite size was determined. These parameters influence the mechanical properties of the developed materials. In all cases, X-ray scattering provided information on the nanostructure of biological or biomimetic materials. Over a hundred years after the principle behind X-ray scattering was first explained, it still provides information about the properties of matter which is not available by other means.
  • Ilmonen, Klaus (Helsingin yliopisto, 2016)
    The significance of EU level corporate governance regulation has been increasing in the years following the financial crisis. At the same time EU regulatory initiatives in this field have been subject to much criticism. The corporate governance systems in the EU vary significantly and it has been argued that EU initiatives have not been adapted to corporate environments prevalent in member states. This has been argued to have decreased the competitiveness of listed companies and the financial markets in the EU. Several EU corporate governance initiatives have also failed or been subject to considerable political compromise emphasizing the challenging political nature of the EU regulatory system. EU integration represents a model for coordinating interaction between different economies and political systems. Understanding how supranational systems work and developing regulation at this level remains an important venture. More attention is needed to adapt the design of EU regulation to the varied institutional environment across the EU. To be able to develop EU legal strategies and regulatory design in the field of corporate governance, a better understanding of the dynamics of EU policymaking remains important. The goal of the study is to provide a basis for developing legal strategies used in EU corporate governance regulation in light of the challenges of the (i) varied regulatory requirements of different corporate environments in the EU and (ii) the supranational political dynamics of corporate governance regulation. This requires a better awareness of the factors that affect (i) the impact and effectiveness of different legal strategies and regulatory mechanisms in different corporate environments and (ii) the political dynamics of EU policy-making with respect to corporate governance regulation. The study analyses corporate governance regulation in the context of specific environments of corporate governance and corporate ownership. With an emphasis on institutional and political aspects of corporate governance, the study analyses and compares the effects of different legal strategies in these environments; i.e. what the effects of different regulatory mechanisms have been on the relationships between corporate constituencies. The study focuses on corporate governance regulation in the context of concentrated ownership in a Nordic institutional environment. The study also analyses the political dynamics of EU policymaking based on economic theories of regulation and an institutional analysis of EU policy-making. The results of study include a framework for a corporate governance index that incorporates the prevalent institutional dynamic, as well as a qualitative model for developing regulatory policy at the EU level. The study relates to comparative corporate governance research and to political economy analysis of EU regulation.
  • Nieminen, Eeva-Liisa (Helsingin yliopisto, 2016)
    In this study, students' discourse of science learning is explored with a special focus on interest in learning. The research group is an optional science class. The data consist of 20 interviews. The entire collection of interviews served as data for searching discourses, which further led to closer case studies. A portrait of the class is created, first searching dominant discourses and then taking a closer look at students who exemplify influential discourses contributing to interest generation in the whole class. The research starts from individual narratives and follows the idea of Roth and Lucas (1997) that individuals belonging to a community represent the discourses of that community. Qualitative content analysis is used inductively to trace categories, which represent the interpretive repertoires of the students. By further abstraction, the latent contents of these discourses are abstracted to more general concepts in order to find recurrent patterns. Eventually, based on the created concepts and then deductively drawing on the theoretical models of Vygotsky, interest development, self-regulation and affective neuroscience, a model of the students interest generation is formed. The science class context offers the students possibilities to make choices. Students experience a feeling of succeeding when they understand the subject contents. This, in turn, creates a zeal for school and learning. Interest in learning seems to derive from a desire to succeed in life; a constant search for that which is new, exciting and fun; picking one's own handbag of choices; taking one's own action and feeling success; interest in the subject; and togetherness and identification with the science class. From the students' experiences, a twofold image appears: students like projects, practical work and other student-centred methods, but they are not considered superior to the traditional teacher explanation, which in itself promotes understanding, leading to a feeling of succeeding. A clear division between students appears: those who expect firm teacher guidance and those who prefer independent working. Belonging to a special class reinforces self-regulation. I construct a pattern, a pyramid of learning, where emotions, play and fun along with togetherness form the foundation for motivation. Learning and gaining experience contribute to increasing independence and the mastery of situations. One's own effort, attention and concentration make it possible to advance in learning and independence. The degree of teacher involvement needed depends on the individual student's position on this pyramid: on the bottom, more control and teacher guidance are needed, whereas students situated on the top of the pyramid are able to work on their own. Through a process of development aided by cultural and social influence, the students move in steps from bottom to top on the pyramid. These students are searching for their identities, picking up what is useful for them and building a set of knowledge and skills within the limits the school. I identify the science class as a community of the practice of science, where the how-aspect of science is conveyed from the science community through its practices and artefacts and is embraced and developed further by students through their social relations and communication. Keywords: science education, interest, discourse, interpretive repertoire, zest, enthusiasm, community of practice, identity, seeking
  • Hyvärinen, Satu (Helsingin yliopisto, 2016)
    The complement system is a network of over 30 plasma proteins that act in, for example, protecting the body against invading microbes and removing damaged self cells. Complement activation proceeds in a cascade-like fashion, resulting in deposition of certain protein fragments on cell surfaces and liberation of others to the fluid nearby. Due to the destructive nature of complement attacks, it is imperative that this system be stringently controlled. When regulation fails, deleterious complement activation on self cells follows. This is the case for example in atypical hemolytic uremic syndrome (aHUS), a rare thrombotic microangiopathy characterized by hemolysis, thrombocytopenia and renal impairment. In roughly two thirds of aHUS patients, abnormalities in complement genes can be detected. A frequent observation is a mutation in the regulator factor H (FH). The majority of FH mutations in aHUS cluster in the two C-terminal domains of the protein, i.e. FH19-20. These are critical for directing FH onto cell surfaces under complement attack. Several important aspects of the syndrome have been uncovered, but the mechanisms underlying aHUS pathogenesis remain incompletely understood. The general aim of this work was to better explain the molecular events leading to aHUS. First it was asked, whether disturbances in the recently described interactions between FH19-20 and malondialdehyde (MDA) adducts could be involved in aHUS. To study this, binding assays employing MDA-modified proteins and wt and mutant FH19-20 fragments were performed. FH19-20 binding was observed only if a high density of MDA adducts on the surface was present. Since such extensive MDA modification of cell surface proteins is improbable in vivo, it was concluded that disturbed recognition of MDA adducts on cells by FH is unlikely to be relevant in aHUS. Next, the hypothesis of plasminogen to regulate propagation of the complement cascade on cell surfaces was tested. Serum complement was activated on erythrocytes, endothelial cells, and platelets with or without added plasminogen, and complement activation determined as cell lysis or deposition of C5b-9 or C3b. Plasminogen was observed to cause only a very minor inhibition of complement activation on platelets. It was concluded that reduced complement control by plasminogen does not properly explain the recent association of plasminogen deficiency with aHUS. The final aim of this work was to determine the role of sialic acid in FH-mediated regulation on not only erythrocytes, but also on endothelial cells and platelets. To this end, the abilities of several FH19-20 fragments carrying aHUS-associated mutations to antagonize FH function on different types of cells was compared. Flow cytometry detection of FH binding and C3b deposition revealed identical patterns of FH19-20 function on all types of cells. Removal of sialic acid from cells impaired FH function on them. With the help of recent structural data, it was concluded that mutations impair simultaneous binding of the C-terminus of FH to surface sialic acid and C3b, providing a unifying explanation for association between the C-terminus mutations of FH and the clinical disease aHUS. In conclusion, the work presented in this thesis improves our understanding of the pathogenic mechanisms involved in aHUS. Most importantly, the results show that in aHUS, the underlying common defect of various FH C-terminus mutations is the inability to simultaneously bind sialic acid and C3b on cells under complement attack.
  • Paolini, Gianluca (Helsingin yliopisto, 2016)
    The subject of this doctoral thesis is the mathematical theory of independence, and its various manifestations in logic and mathematics. The topics covered in this doctoral thesis range from model theory and combinatorial geometry, to database theory, quantum logic and probability logic. This study has two intertwined centres: - classification theory, independence calculi and combinatorial geometry (papers I-IV); - new perspectives in team semantics (papers V-VII). The first topic is a classical topic in model theory, which we approach from different directions (implication problems, abstract elementary classes, unstable first-order theories). The second topic is a relatively new logical framework where to study non-classical logical phenomena (dependence and independence, uncertainty, probabilistic reasoning, quantum foundations). Although these two centres seem to be far apart, we will see that they are linked to each others in various ways, under the guiding thread of independence.
  • Kallonen, Aki (Helsingin yliopisto, 2016)
    X-ray tomography is a widely used and powerful tool; its significance to diagnostics was recognized with the Nobel award, and tomographic imaging has also become a large contributor to several fields of science, from material physics to biological and palaeontological sciences. Current technology enables tomography on the micrometre scale, microtomography, in the laboratory. This provides a non-destructive three-dimensional microscope to probe the internal structure of radiotranslucent objects, which has obvious implications towards its applicability. Further, x-rays may be utilized for x-ray scattering experiments, which probes material properties on the ångström-scale. Crystallographic studies on various forms of matter, not least of which famously being the DNA molecule, have also been awarded the Nobel. In this thesis, the construction of a combined experimental set-up for both x-ray microtomography and x-ray scattering is documented. The device may be used to characterize materials on several levels of their hierarchical structure, and the microtomography data may be used as a reference for targeting the crystallographic experiment. X-ray diffraction tomography is demonstrated. An algorithm for x-ray tomography from sparse data is presented. In many scenarios, the amount of data collected for a tomogram is not sufficient for traditional algorithms, and would benefit from more robust computational schemes. Real x-ray data was used for computing a tomographic reconstruction from a data set two orders of magnitude smaller than what is conventionally used with set-ups such as the one presented in the thesis. Additionally, x-ray microtomography was utilized for morphological studies in developmental and evolutionary biology, evo-devo for short. The fossil record shows vast changes in morphology as more complex forms of life evolved, while the morphology of any given individual organism is the product of its developmental process. Understanding both evolution and development is essential for a comprehensive view on the history of life. In this thesis, two studies on teeth and their development are discussed. In both, dental morphology was investigated with high-resolution x-ray tomography.
  • Shubin, Mikhail (Helsingin yliopisto, 2016)
    The dissertation presents five problem-driven research articles, representing three research domains related to micro-organisms causing infectious disease. Articles I and II are devoted to the A(H1N1)pdm09 influenza (`swine flu') epidemic in Finland 2009-2011. Articles III and IV present software tools for analysing experimental data produced by Biolog phenotype microarrays. Article V studies a mismatch distribution as a summary statistic for the inference about evolutionary dynamics and demographic processes in bacterial populations. All addressed problems share the following two features: (1) they concern a dynamical process developing in time and space; (2) the observations of the process are partial and imprecise. The problems are generally approached using Bayesian Statistics as a formal methodology for learning by confronting hypothesis to evidence. Bayesian Statistics relies on modelling: constructing a generative algorithm mimicking the object, process or phenomenon of interest.
  • Liu, Jiao (Helsingin yliopisto, 2016)
    The aim of the thesis was to investigate the interaction between sarcoplasmic proteins and myofibrillar proteins, considering the effects on the loss of water-holding in mild heat induced denaturation such as occurring in pale, soft and exudative (PSE) condition. Porcine longissimus thoracis et lumborum muscles were incubated at temperature 0, 10, 20, 30 or 40 ˚C to 6 h post mortem. Incubation at 40 ˚C reduced the water-holding of meat compared to the lower temperatures (P < 0.001). SDS-PAGE and Western blot analyses indicated that glycogen phosphorylase and creatine kinase precipitated with the myofilaments, which was already accomplished at 6 h post mortem. Substantial meat tenderization was measured after incubation at 40 ˚C, but with less activity of extracted μ- and m- calpains compared to lower temperatures (P < 0.001), which suggests that an early activation of calpains at the highest incubation temperature could have been the reason for the tenderization. Surface hydrophobicity of myofilanments was higher after the pre-rigor incubation at 40 ˚C compared to lower temperatures (P < 0.001). Less myosin subfragment-1 (S1) units were released by chymotryptic cleavage simultaneously with the loss of Ca2+ ATPase activity after incubation at 40 ˚C than at lower incubation temperatures (P < 0.001). The results suggest that the high temperature incubation induce microstructural alterations on the myosin head (S1) region, which may in turn have been related to the loss of water-holding. The roles of the denaturation of sarcoplasmic proteins and myofibrillar proteins were compared. Sarcoplasm not-incubated or incubated at 44 ˚C were mixed with protein-depleted sarcoplasm in different rations and the mixtures were combined with myofibrils and subjected to PSE-like condition pH 5.6/44 ˚C for 1 h . Water-holding was the poorest without the incubated sarcoplasmic proteins. Precipitated sarcoplasmic proteins shrank the myofilamental lattice spacing by 6.3%, compared to protein-free sarcoplasm, during post-rigor incubation at 44 ˚C, shown by X-ray diffraction. These results challenge the current understanding of the role of the denaturation of different proteins in water-holding, and therefore, a new hypothesis is proposed in this thesis: 1) in the intramyofibrillar space, the presence of precipitating sarcoplasmic proteins is associated with the filamental lattice compression that expels water; 2) in the space outside the myofibrils (intermyofibrillar space) within fiber and up to the extracellular space, the coagulated sarcoplasmic proteins form a network that traps water expelled from the intramyofibrillar space.
  • Barreto, Goncalo (Hansaprint Oy, 2016)
    Osteoarthritis (OA), the most common form of arthritis, is estimated to be in the top 5 leading causes of disability worldwide. Yet OA incidence is estimated to keep growing partly due to the overall worldwide trend of increased obesity and ageing population. Cartilage erosion, a hallmark of OA, has its onset in the traumatic events caused by incorrect biomechanical loading of the joint and the consequent biological response. Currently we still poorly comprehend the molecular pathophysiology of preclinical and clinical symptomatic OA, which consequently results in no current available therapy to prevent OA progression. We hypothesize that innate immunity and its receptor, in particularly toll-like receptors (TLRs), could be major drivers of OA disease progression and onset. The process could be initiated as a proinflammatory reaction against extracellular matrix (ECM)-derived damage-associated molecular patterns (DAMPs). DAMPs accumulate in avascular articular cartilage as a result of traumatization and degeneration, leading directly at their source to a reactive chondrocyte-mediated and TLR-dependent production of proinflammatory and algogenic secondary mediators, which then cause a secondary synovitis with consequent joint pain. For this propose, we collected cartilage and isolated primary chondrocytes from a total of 27 OA patients. Synovial fluid was obtained from knee meniscectomy, total knee arthroplasty (TKA) due to OA, and rheumatoid arthritis (RA) patients generating a total of 30 patient samples. HEK (human embryonic kidney)-blue TLR4 reporter cell line, primary OA chondrocytes, and cartilage explants were used for functional studies. Our results confirmed that TLR1, TLR2 and TLR9 expression is present in healthy primary chondrocytes isolated from articular cartilage, and derived from chondroprogenitors. During our chondrogenesis differentiation studies initial high expression of TLR1, TLR2 and TLR9 was significantly reduced to baseline levels. We demonstrated that proinflammatory cytokine tumour necrosis factor alpha (TNF-α) is able to increase the expression of TLR2 in both healthy primary chondrocytes and mesenchymal stem cells (MSC) derived chondrocytes cultured for 21 days. TNF-α stimulation was demonstrated to induce cartilage degradation in de novo ECM matrix from pellet cultures of MSC-derived chondrocytes cultured for 21 days. This implicates TNF-α as an inducer of matrix degradation, with wide implications in the use of MSCs strategies in cartilage repair strategies for OA. Our study also added further evidence of a role for TNF-α in TLR-innate immunity in the OA synovial joint. TLRs protein expression in cartilage between knee and first carpometacarpal (CMC-I) joints from OA patients was shown to be strikingly different. Our study demonstrated for the first time all TLRs being expressed at protein levels in articular cartilage from knee OA patients. Moreover, we demonstrated that their expression is up-regulated in a cartilage zone-dependent fashion accordingto the histological progression of knee OA. TLRs expression in cartilage from CMC-I OA patients was highly heterogeneous although it followed an expression pattern according to TLRs cellular organization. This indicates that TLR-mediated innate immune response between the two joints may be significantly different. Decorin (DCN), a known small structural proteoglycan with leucine-rich repeats (SLRP) ligand able to activate TLR2 and TLR4, was discovered in knee synovial fluid from OA and RA patients. We confirmed the ability of soluble DCN (sDCN) to activate to TLR4 signaling. However, the observed low and stable concentration levels across the studied groups mean that this may not be of clinical relevance in OA pathogenesis and the associated TLR-mediated inflammatory events. Biglycan (BGN), another known SLRP ligand able to activate TLR2 and TLR4, was discovered in knee synovial fluid from OA and RA patients. Interestingly, we discovered that soluble BGN (sBGN) is upregulated in synovial fluid from OA and RA patients. sBGN ability to activate TLR-innate immunity as confirmed to be essentially activated through TLR4 signaling by studies in articular chondrocytes and human HEK-blue TLR4 reporter cell line. The sBGN stimulation lead to the upregulation and release of proinflammatory cytokines, matrix-degrading enzymes and the release of ECM degradation products. Overall, the results of this thesis demonstrate that TLRs are markedly present in articular cartilage from OA patients at different progression stages of the disease. The detection of BGN and DCN in synovial fluid, and their ability to activate TLR4-mediated proinflammatory cellular responses gives new knowledge of proinflammatory molecules present in the OA synovial joint. An enhanced molecular understanding of the triggering mechanisms by which TLRs are activated and regulated during OA progression stages may help find therapeutic options in the treatment of OA.
  • Ylösmäki, Leena (Helsingin yliopisto, 2016)
    Src homology 3 (SH3) domains are small modular protein structures that recognize and bind to short proline-rich sequence motifs in their ligand proteins. Viral proteins may also harbor such binding motifs and thereby serve as SH3 ligands in order to regulate the host cell signaling to support virus growth and replication, and to modulate virulence. The aim of this study was to examine if influenza A virus (IAV) might also use this strategy to take control of its host cells, and to characterize possible SH3 domain-containing host cell binding partners of IAV to establish their role in the cell biology of IAV infection. IAVs cause seasonal epidemics and occasional pandemics that pose a major threat to human health. The nonstructural protein 1 (NS1) is an important virulence factor of IAV. It is a multifunctional protein that suppresses the host interferon response via multiple mechanisms. Another function of NS1 is to activate phosphatidylinositol-3 kinase (PI3K) signaling in the host cell through direct binding to the p85β regulatory subunit of PI3K. The NS1-induced activation of PI3K is required for efficient replication of many IAV strains. We found that NS1 proteins from some IAV strains contain an SH3 binding site that mediates strong and selective binding to the N-terminal SH3 (nSH3) domain of Crk-family proteins, an important class of adaptor proteins involved in the coordination of cellular signal transduction. This Crk SH3 binding motif was present in the NS1 of infamous 1918 Spanish Flu pandemic virus as well as in many contemporary avian IAV strains. In contrast, it is not found in most NS1 proteins of seasonal human IAV strains. We found that the capacity of avian and Spanish Flu NS1 proteins to interact with Crk SH3 domains provided them with a greatly enhanced capacity to activate PI3K signaling. The molecular mechanism underlying this potentiation was found to be due to a reorganization of the natural PI3K-Crk complex by the SH3-binding competent NS1 protein. Of note, Crk proteins were found to indirectly (via p85β binding) contribute also to PI3K regulation by NS1 proteins of common human IAV strains that lack an SH3 binding motif and a capacity for direct Crk recruitment. Moreover, we found that the role of the NS1/Crk interaction is not limited to PI3K regulation. We observed that binding of NS1 to the Crk SH3 domain induced a robust nuclear accumulation of the predominantly cytoplasmic Crk proteins. This nuclear translocation of Crk proteins was shown to lead to a change in tyrosine phosphorylation pattern of nuclear proteins. In summary, our studies establish Crk adaptor proteins as important cellular co-factors exploited by the IAV virulence factor NS1 to manipulate host cell signaling. These results increase our understanding of the role of NS1 in IAV cell biology, and reveal possible new targets for future antiviral drug development aimed against critical host cell interactions rather than highly mutable viral proteins.
  • Kauranen, Tatu (Helsingin yliopisto, 2016)
    The global burden of stroke is huge and increasing despite significant improvements in acute stroke care in recent decades. The indirect costs, such as productivity losses due to patients inability to return to work after stroke, are a major factor in the accumulation of this burden and are estimated to outweigh the direct costs of stroke. Post-stroke cognitive impairments seem to relate intimately to functional outcomes and quality of life after stroke, but their role in the creation of strokerelated productivity losses remains uncertain. The aim of this study was threefold: to compare the prevalence and severity of post-stroke cognitive impairments in relation to the severity of clinical neurological impairments; to specify the role of cognitive impairments in patients ability to return to work after stroke; and to assess the use of stroke-related income supplements and the role of cognitive impairments in supplement use. A consecutive cohort of 230 working-aged patients with a first-ever ischaemic stroke was enrolled in two Finnish hospitals. The patients underwent repeated neuropsychological assessments in order to describe their cognitive sequelae. Cognitive data from baseline, six-month and two-year follow-up examinations were analysed in relation to demographic, clinical and occupational information on the patients. Cognitive impairments were defined based on the performance of a healthy demographic control group (N =50). Cognitive impairments frequently appeared among otherwise intact patients. After taking into account other relevant factors, baseline cognitive impairments most effectively predicted the return to work of the patients six months after the stroke. Regarding the use of stroke-related income supplements, atrial fibrillation was the most effective health-related predictor, and cognitive impairments the most effective stroke-related predictor. The results of the study emphasize the usefulness of early neuropsychological assessments in treatment planning and the importance of cognitive impairments in the accumulation of post-stroke productivity losses.
  • Magalhães, Ana Cathia Dias (Helsingin yliopisto, 2016)
    The time of arrival of interneurons and oligodendrocytes to the neocortex is critical for proper functional brain development. Aberrances in this sequence can be detrimental, and involved in different developmental diseases. Thus, understanding the mechanisms for temporal control of the genesis and migration of neural cells is crucial. The aim of this study was to focus on the ventral telencephalon, a major source of interneurons and oligodendrocytes, in more detail. A more sensitive method was developed for detecting and quantifying oligodendrocyte precursor cells, e.g. Olig2. The device decloaking chamber was compared to the microwave oven-based heat-induced epitope retrieval (HIER) method by studying the labeling of Olig2 marker in paraffin-embedded sections from embryonic mouse brain. The results demonstrated that the decloaking chamber-based HIER method is the most suitable technique for the detection of single Olig2-labeled cells in the ventral telencephalon. This qualitative result was reflected in the quantitative analyses: more Olig2-labeled cells were quantifiable with the decloaking chamber- than with the microwave oven-approach. Thus, the decloaking chamber-based HIER method constitutes a sensitive technique for the detection of oligodendrocyte precursor cells, and therefore for its quantification in the developing ventral telencephalon. The development of telencephalon depends on fundamental processes, which include proliferation and migration of neural cells. The Na-K-Cl cotransporter isoform 1 (NKCC1) is an important protein for the process of volume regulation, and has been implicated in cell division. Within the developing brain, the ventral telencephalon showed the highest expression of NKCC1. This expression corresponded to neural progenitor cells in the lateral ganglionic eminence (LGE). Using NKCC1 knockout mice, it was demonstrated that NKCC1 influenced cell cycle reentry. Consequently, mice lacking NKCC1 have impaired Sp8-expressing interneurons and Olig2-labeled cells. Thus, NKCC1 is crucial in vivo for cell cycle decision, thereby altering the production of oligodendrocyte and interneuron progenitor cells in the LGE. Once interneurons are born, they migrate to the neocortex. The implication of syndecan-3 was assessed in their tangential migration. The results showed that the Glial cell line-derived neurotrophic factor GDNF interacts with syndecan-3 to promote the tangential migration of calbindin-expressing interneurons within the telencephalon. Consistently, mice lacking syndecan-3 have an accumulation of migrating interneurons in the LGE. In summary, two important mechanisms were found for temporal and spatial control of cortical oligodendrocytes and interneurons.
  • Muona, Mikko (Helsingin yliopisto, 2016)
    Epilepsies are a heterogeneous group of central nervous system diseases characterised by recurrent epileptic seizures. They are one of the most common neurological diseases with a lifetime prevalence of ~4%. Epileptic seizures are also a common comorbidity of various neurobiological disorders where epilepsy is not the primary diagnosis. Most epilepsies have a genetic origin, either monogenic or polygenic, however, the causal genetic variants have remained unknown in a substantial proportion of individuals with epilepsies. Over the past decade, technological advances in DNA sequencing have allowed the characterisation of the genetic basis of human disorders rapidly and efficiently. One of the most widely used methods is whole-exome sequencing (WES) where genetic variants in the protein coding regions of the genome, the exome, are captured. Even though the exome constitutes only ~1.5% of the genome, the majority of disease-causing variants underlying severe, monogenic diseases are located in the protein coding regions. Here, we aimed to decipher the molecular genetic basis of severe epilepsy syndromes by utilising WES to identify disease-causing genetic variants in patients without a genetic diagnosis. We studied patients with progressive myoclonus epilepsy (PME, n=84) or severe infantile-onset epileptic syndromes (n=30), which are one of the most devastating forms of genetic syndromes with epilepsy and characterised by frequent, pharmacoresistant seizures and poor prognosis. Given that the patients had undergone genetic testing to varying extent prior to this study, we specifically aimed to establish novel genes and molecular biological mechanisms underlying these syndromes. We made substantial progress in understanding the genetic architecture and molecular basis of the studied syndromes. For PMEs, we established a new major genetic cause and also expanded the genotypic and phenotypic spectrum of previously established disease genes. For severe infantile-onset epileptic syndromes, we identified one new, definite causal gene and one that requires identification of additional patients to confirm the causal role. The three newly identified disease genes represent three different molecular functions that together give new insight on epileptogenic mechanisms. The new PME subtype is caused by a heterozygous missense variant c.959G>A (p.Arg320His) in KCNC1 that was identified in 11 unrelated patients (13%) in the PME exome sequencing cohort. We have subsequently identified six additional patients. The gene encodes a potassium ion channel KV3.1 that has an important role in generating action potentials in the central nervous system, with the mutation disrupting the ability to transport potassium ions across the cell membrane. This mutation occurs in most families de novo, that is, it is a newly arising mutation. Based on the estimated mutation rate, the recurrent KCNC1 mutation is a worldwide cause of PME with likely hundreds of affected individuals globally. In five families with altogether nine affected siblings, we identified compound heterozygous variants in UBA5 as the cause of an infantile-onset syndrome characterised initially by irritability, followed by epilepsy, dystonic movements, moderate to severe intellectual disability, microcephaly and stagnation of development. The gene encodes an activating enzyme for UFM1, which is a small ubiquitin-like protein that is conjugated to its target proteins. The function of the highly conserved UFM1 conjugation system is still largely unknown. Functional analysis of the UBA5 mutants suggest that the identified variants cause reduced enzymatic activity of UBA5. Symptoms of the UBA5 patients and our findings in the central nervous system specific knockout mice for Ufm1 together indicate that UFM1-cascade is essential for normal development and function of the central nervous system. Finally, we identified compound heterozygous variants in ADAM22 as the likely cause of the disease in a patient with an infantile-onset rapidly progressing encephalopathy with epilepsy and cortical atrophy. The gene encodes a postsynaptic protein that functions as a receptor for LGI1, and we show that the identified variants abolish the ability of ADAM22 to bind to LGI1. The LGI1-ADAM22 complex is an antiepileptogenic factor regulating synaptic transmission throughout life. Highlighting the important role of this complex, knockout of Adam22 and Lgi1 in mice causes lethal epilepsy. Autosomal dominant LGI1 variants also cause epilepsy in humans. Identification of a patient with loss-of-function variants in ADAM22 suggest that also this gene is linked to epilepsy in humans. This connection should be confirmed through identification of additional affected individuals with ADAM22 variants. Altogether, this thesis demonstrates the power of WES in identification of causal genetic variants even in phenotypically heterogeneous patient cohorts subjected to prior genetic screenings. The findings improve diagnostics of these syndromes, increase knowledge of the underlying molecular mechanisms and potentially aid in developing new therapeutic interventions. Finally, for these families, establishment of the genetic diagnosis ends years of uncertainty and frustration of not knowing the cause of the disease and prevents need for unnecessary diagnostic testing.
  • Kaipio, Marja-Liisa (Helsingin yliopisto, 2016)
    Abstract In the present thesis, auditory event-related brain potentials (ERPs), mismatch negativity (MMN) and P3a, were used to investigate involuntary attention shifting, that is, distractibility in people with moderate-to-severe traumatic brain injury (TBI) and healthy controls. In passive oddball paradigms, the participants either watched a silent movie (Studies II, III and IV) or concentrated on a visuomotor task (Study I) to ensure that their attention was directed away from the stimuli. Abnormal distractibility in TBI patients was suggested in Study I by an enhanced late portion of the P3a amplitude to unattended unexpected novel environmental sounds with the participants concentrating on a continuous visuomotor task. In Study II, the healthy controls successfully ignored background speech stimuli when watching a silent movie, whereas the patients enhanced P3a amplitudes revealed their inability to exclude the meaningless deviances of these semisynthetic speech stimuli. In Study IV, hyperexcitability of the MMN, suggesting excessively reactive involuntary attention mechanisms and abnormal distractibility, was found in patients with no abnormalities detected by conventional magnetic resonance imaging (MRI) of the brain. These MMN and P3a findings elucidate on the neurophysiological level ~150–300 milliseconds from the onset of the deviant auditory stimuli, a phenomenon described by TBI patients as the excessive intrusion of meaningless background noises and sounds from everyday surroundings. Moreover, Study III gave neurophysiological evidence for a fast vigilance decrement in TBI patients, reflected by a significant MMN amplitude decline during an hour-long experiment. This amplitude decline not present in controls was found both in patients with and without neuroradiological abnormalities. The patients did not exhibit significant latency delays for MMN or P3a in Studies I to IV. The present MMN and P3a findings indicate overly sensitive involuntary attention shifting, that is, abnormal distractibility in TBI. Distractibility was found in both patients with cerebral MRI/computerized tomography (CT) abnormalities and patients without neuroradiological abnormalities on conventional MRI. The fast vigilance decrement suggested by the MMN amplitude decline was found similarly in patients with and without neuroradiological abnormalities.
  • Danielsbacka, Mirkka (Helsingin yliopisto, 2016)
    Intergenerational relations have in recent decades become an integral part of both sociology and evolutionary research. These disciplines are, however, rarely in dialogue with each other. The present study is a social and public policy thesis, the main purpose of which is to combine theories from family sociology and evolutionary theory. Empirically, the study asks the following question: What factors are associated with the strengths and weaknesses of intergenerational relations, grandparental care and differences between types of grandparents? The thesis consists of five empirical articles and a summary chapter. The sub-studies were conducted with three large and representative surveys, which include respondents from 16 European countries. These datasets are the Survey of Health, Ageing and Retirement in Europe, the Involved Grandparenting and Child Well-Being Survey, and the Generational Transmissions in Finland data. The Methods used in the empirical articles are quantitative. Article I tested and gained support for the existence of a biased grandparental investment pattern where the maternal grandmother invests the most, followed by the maternal grandfather, the paternal grandmother and finally by the paternal grandfather, who invests the least. In addition, the study showed that grandmothers as well as grandfathers invest preferentially in their daughters children compared to their sons if both options are available. Thus gender and lineage of a grandparent are important factors determining grandparental investment. Articles II and III examined family dynamics, especially between young couples and their parents-in-law, and detected a significant difference in emotional closeness as well as conflict proneness according to whether or not the couple had children. In general, women and men perceived their relationship with their own parents to be emotionally closer but also more conflict-prone than their relationship with their parents-in-law. Particularly for men, having children seemed to render the relationship with parents-in-law more similar to their relationship with their own parents. Article IV studied more closely the socio-ecological factors associated with grandparental investments, and showed that the effect of these factors tend to differ according to grandparents sex and lineage. Finally, in article V the marital status of grandparents was found to be strongly associated with their investments in their grandchildren. Living without a spouse appeared to be more detrimental to grandfathers than grandmothers relationships with their grandchildren. To conclude, intergenerational relations and grandparental investments are biased according to both gender and kin lineage and tend to favour maternal kin. This can ultimately be accounted for by evolutionary explanations, especially sex-specific reproductive strategies and paternity uncertainty. In certain situations, and especially when taking into account in-law relations between parental and grandparental generations, contextual factors may restrict the typical associations between gender, lineage and grandparental investment behaviour. At the end of the summary chapter policy and practical implications of the results are discussed.