| 1. |
- Löfgren, Sara E, 1977-
(författare)
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Functional Role of Genetic Polymorphisms Associated with Systemic Lupus Erythematosus
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Systemic lupus erythematosus (SLE) is a chronic and complex autoimmune disorder characterized by a failure in the mechanism of self-tolerance and production of autoantibodies, potentially affecting any organ in the body. The genetic factors behind the disease have been extensively studied in the past years and to date a list of more than 30 loci have been associated with SLE. However, very little is known about the functional significance of the risk variants. In this thesis, we focused on the analysis of SLE-associated variants in three genes: interferon regulatory factor 5 (IRF5), CD226 and the microRNA 146a. In paper I, we analyzed four polymorphisms in the IRF5 gene in a large set of individuals from different populations. We replicated a strong association of a promoter indel in our meta-analysis, but expression analysis indicated that it is rather another variant, SNP rs10954213 in the poly(A) signal of the gene that is in fact the major contributor to the altered gene expression in leukocytes. In manuscript II, we further characterized the regulation of IRF5 expression, showing that this gene can be up-regulated by estrogen in PBMCs and monocytes, regardless of the genotype, which could to some extent, explain the sex-bias of SLE. In paper III, we investigated the association of CD226 with SLE and the potential functional effect of the associated variants. The genetic analysis showed an association of a three-SNP-haplotype located at the 3’UTR region of the gene. The risk haplotype correlated with lower CD226 protein expression on the surface of cytotoxic and helper T cells, as well as in NK T cells. Reporter assays pointed to rs727088 in the 3’UTR as the main responsible variant for altered gene expression. In paper IV, we described the association of a variant in microRNA miR-146a, involved in the interferon pathway, with SLE in Europeans, which could in addition be correlated with decreased expression of both mature and primary miR-146a in leukocytes. In summary, we have investigated the genetic association of three genes with SLE in a large cohort of individuals and identified variants responsible for functional alterations of these genes, providing further insight into the pathogenesis of SLE.
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| 2. |
- Nilsson Ardnor, Sofie, 1967-
(författare)
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Genetic studies of stroke in Northern Sweden
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Stroke is a common disorder of later life with a complex etiology, including both environmental and genetic risk factors. The inherited predisposition is challenging to study due to the complexity of the stroke phenotype. Genetic studies in an isolated population have successfully identified a positional candidate gene for stroke, phosphodiesterase 4D (PDE4D). The aim of this thesis was to identify stroke susceptibility loci and positional candidate genes, taking advantage of low genetic variation in the northern Sweden population. All stroke cases were identified in a population-based stroke registry at the northern Sweden MONICA Centre. 56 families containing multiple cases of stroke and a follow up set of an additional 53 families were used for linkage studies. For association studies, 275 cases of first ever stroke together with 550 matched community controls were included. In paper I, we used a candidate region approach to investigate the PDE4D region on chromosome 5q. Linkage was obtained with a maximum allele-sharing LOD score of 2.06; P = 0.001. However, no significant association of ischemic stroke to the previously defined at-risk allele in PDE4D was observed. We next performed a genome wide linkage scan to explore new susceptibility loci for common forms of stroke (paper II). Non-parametric multipoint linkage analysis yielded allele-sharing LOD scores > 1.2 at nine locations; 1p34, 5q13, 7q35, 9q22, 9q34, 13q32, 14q32, 18p11, 20q13. The highest allele-sharing LOD score was obtained on chromosome 18p (LOD = 2.14). Fine mapping resulted in increased allele-sharing LOD scores for chromosome 5q13 and 9q22. In the follow up analysis of the nine regions, including all 109 families, the highest allele-sharing LOD scores were obtained on chromosomes 5q, 13q and 18p although none reached the initial genome wide values. In paper III, we focused on the chromosome 5q region, and further mapping and haplotype analysis in the families was performed. A common 1 cM haplotype was found to be shared among affected members of five families. In this region only the regulatory subunit 1 of phosphatidylinositol 3-kinase (PIK3R1) gene was located. Association of three single nucleotide polymorphisms in the PIK3R1 gene to common stroke was obtained in the case-control material. Finally, in paper IV, an extended pedigree containing seven families connected to common founders eight generations back was identified by genealogical analysis, and submitted to a separate genome wide scan analysis. A significant allele-sharing LOD score of 4.66 (genome wide P < 0.001) at chromosome 9q31-33 was obtained. Haplotype analysis identified a minimal common region of 3.2 cM, which was shared by four of the seven families. These four families contained all of the primary intracerebral hemorrhagic cases present in the extended pedigree. In conclusion we have replicated linkage of stroke susceptibility to the PDE4D region on chromosome 5q, but no significant association of ischemic stroke to PDE4D was observed. Linkage analysis of stroke did not identify any new major stroke loci, indicating that multiple minor susceptibility loci in addition to the previously known locus on chromosome 5q could contribute to the disease. In the chromosome 5q region a novel positional candidate gene for stroke was identified, the PIK3R1 gene. The PIK3R1 protein has several biological actions with potential roles in stroke susceptibility. Also a novel susceptibility locus for common forms of stroke at chromosome 9q was identified in a large pedigree, which may be of special importance for susceptibility to hemorrhagic stroke.
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| 3. |
- Rüdhmer-Dahle, Charlotte, 1956-
(författare)
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Studies on T cells and cytokines in Guillain-Barré syndrome and experimental allergic neuritis
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Guillain-Barrésyndrome (GBS) is an inflammatory disease of peripheral nerves, characterised by muscle weakness. The nerves are attacked and destroyed by the immune system. The symptoms usually progress over a few weeks and many patients become severely disabled. However, in contrast to many other organspecific autoimmune diseases, GBS is self-limiting and most patients recover. Individuals of all ages can be affected. The incidence is about 1/100 000 per year. An infection often precedes the onset of neurological symptoms and probably triggers the immune-mediated attack.Activation of T cells and the resulting release of cytokines are decisive for the regulation of antigen-specific inflammation. Different cytokine patterns promote different types of responses. Interferon-y (lFN-γ) has a key role in Th type 1 responses, and is thought to be a driving force in many organ-specific autoimmune diseases. Interleukin-4 (IL-4) promotes Th type 2 responses, characterised by the production of certain antibodies and activation of mastcells and eosinophils. Th type 1 and Th type 2 responses down-regulate one another and the balance between them is important for the immune homeostasis. TGF-ß is an important cytokine with strong down-regulatory properties.Flow cytometry studies showed that circulating T cells were activated in patients with GBS as determined by expression of HLA-DR on T cells, increased proportion of activated memory phenotype (CD4+CD29+), and decreased proportion of naive phenotype (CD4+CD45RA+). A sensitive Ell-spot method was used to determine cytokine secretion from circulating mononuclear cells with or without stimulation with immunogenic peptides from myelin proteins P2 and PO. Both spontaneous and myelin-specific cytokine secretion were increased in patients compared with controls. Increased numbers of myelin-specific cells secreting IL-4 and TGF-ß were found in the majority of the patients, indicating a Th2 type and down-regulatory cytokine profile, in line with the self-limiting character of the disease.An animal model of GBS, experimental allergic neuritis (EAN), is known to be inducible by myelin-specific T cells, supporting the pathogenetic role of T cells. A Th1 deviated, IFN-y-producing cell population from EAN, was in vitro stimulated with autoantigen and IL-4, thereby obtaining a Th2 cytokine profile. These myelin-specific cells were subsequently transferred to rats with EAN, and were found to ameliorate the disease course.In conclusion, Circulating T cells are activated in patients with GBS. Most patients have myelin-specific T cells that mainly secrete down-regulatory cytokines such as IL-4 and TGF-ß, which probably have a beneficial role in regulating the disease process. In vitro deviation of myelin-specific T cells into Th2 phenotype and subsequent transfer of these cells ameliorated the disease course in EAN.
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| 4. |
- Strand, Magnus, 1974-
(författare)
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Estrogen signaling in stroke : genetic and experimental studies
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Stroke is a common and multifactorial disease influenced by genetic and environmental risk factors. It is a highly heterogeneous entity consisting of two main types, ischemic (80%) and hemorrhagic (20%) stroke. The most common form of hemorrhagic stroke is intracerebral hemorrhage (ICH). Ischemic stroke mainly results from thrombotic or embolic events, while ICH is caused by the rupture of an artery in the brain.The mean age of first-ever stroke is 75 years (73 vs. 78 years, for men and women, respectively) and the age-specific stroke incidence is higher for men as compared to women, suggesting that hormonal factors confer protection. A large body of experimental and observational studies shows that estrogens exert beneficial effects in the cardiovascular system. However, large, recent, clinical randomized trials have failed to demonstrate a lower risk of stroke with hormone replacement therapy (HRT) in elderly postmenopausal women. It is possible that HRT may only protect a subgroup of women. Here, genetic predisposition might be involved. Stroke incidence is 50% higher in northern compared to southern Sweden, suggesting a genetic predisposition in this population. This relatively homogeneous population displays founder effects, making it well suited for genetic studies. Since 1985, the MONICA and VIP projects have conducted large-scale cardiovascular health surveys in this population. Information about conventional stroke risk determinants and also DNA have been collected, and two prospective, nested case-referent cohorts (113 cases and 226 controls; 275 cases and 549 controls) have been sampled.To investigate whether genes of the estrogen signaling system may be important in stroke development, we performed genetic association studies, including specific functional single nucleotide polymorphisms in the genes for estrogen receptor alpha (ERα, ESR1), and its target genes osteoprotegerin (OPG, TNFRS11B) and interleukin-6 (IL-6, IL6). We found a significant association between the common c.454-397T/T genotype in ESR1 and ICH, remaining after adjustments for conventional stroke risk factors. The c.454-397T/T genotype also associated with increased systolic (SBP) and diastolic blood pressure (DBP). The combination of c.454- 397T/T and either hypertension, increased SBP, or increased DBP boosted this association substantially and significant synergistic effects on ICH risk between this genotype and increased blood pressure were demonstrated. In a second study, we found a similar association between the common OPG-1181C/C genotype and ICH.Cognitive impairments, including spatial memory and learning deficiencies, are common after stroke. Estrogens improve cognitive functions, including memory and learning processes, in postmenopausal women and ovariectomized rodents. Post-ischemic housing of rats in an enriched environment (EE) improves recovery of spatial memory and learning impairments. Both estrogen and EE induce neuroplasticity in the hippocampus. We hypothesized that 17β- estradiol combined with EE would accelerate recovery after experimental focal brain ischemia in ovariectomized rats and that such improvements could be related to expression of nerve growth factor-induced gene A (NGFI-A) in the hippocampus. Five to six weeks after middle cerebral artery occlusion, 17β-estradiol–treated rats housed in an EE showed significant improvements in cognitive function (i.e., shorter latency and path in the Morris water maze task) and significantly higher NGFI-A mRNA expression in bilateral cornu ammonis 1 (CA1) and ipsilateral dentate gyrus (DG) compared to placebo-treated animals in EE.In conclusion, we present evidence for the association between polymorphic variants in the ESR1 and TNFRS11B genes and ICH and show that 17β-estradiol in combination with EE accelerates cognitive functions in a rat stroke model, putatively through upregulation of NGFI-A in hippocampal subregions. These findings may contribute to an increased understanding of the underlying genetic etiology of ICH and may be informative for the primary prevention of this disease. They also provide hope for 17β-estradiol combined with early environmental enrichment as a novel therapeutic option following ischemic stroke.
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| 5. |
- Blom, Elin, 1979-
(författare)
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Genetic Studies of Alzheimer's Disease
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Patients with Alzheimer's disease (AD) often have a family history of the disease, implicating genetics as a major risk factor. Three genes are currently known to cause familial early-onset AD (<65 years): the amyloid precursor protein (APP) and the presenilins (PSEN1 and PSEN2). For the much more common late-onset disease (>65 years), only the APOE gene has repeatedly been associated to AD, where the ε4 allele increases disease risk and decreases age at onset. As APOE ε4 only explains part of the total estimated disease risk, more genes are expected to contribute to AD.This thesis has focused on the study of genetic risk factors involved in AD. In the first study, we conducted a linkage analysis of six chromosomes previously implicated in AD in a collection of affected relative pairs from Sweden, the UK and the USA. An earlier described linkage peak on chromosome 10q21 could not be replicated in the current sample, while significant linkage was demonstrated to chromosome 19q13 where the APOE gene is located. The linkage to 19q13 was further analyzed in the second study, demonstrating no significant evidence of genes other than APOE contributing to this peak. In the third study, the prevalence of APP duplications, a recently reported cause of early-onset AD, was investigated. No APP duplications were identified in 141 Swedish and Finnish early-onset AD patients, implying that this is not a common disease mechanism in the Scandinavian population. In the fourth study, genes with altered mRNA levels in the brain of a transgenic AD mouse model (tgAPP-ArcSwe) were identified using microarray analysis. Differentially expressed genes were further analyzed in AD brain. Two genes from the Wnt signaling pathway, TCF7L2 and MYC, had significantly increased mRNA levels in both transgenic mice and in AD brains, implicating cell differentiation and possibly neurogenesis in AD.
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| 6. |
- Kvarnström, Maria, 1971-
(författare)
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Mechanisms in inflammatory demyelinating diseases of the nervous system : immunological and methodological aspects
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The diseases studied in this thesis, Guillain-Barré Syndrome (GBS), Multiple Sclerosis (MS) and Polyneuropathy associated with monoclonal gammopathy of uncertain significance (PNMGUS), are of autoimmune origin with myelin components as putative auto antigens. T cells are important for the pathogenesis, as well as the cytokine network and autoantibodies. For all of these diseases, the immunopathogenisis is not fully understood and even if there are treatments available, none of them are curative and there are side effects. Thus there is a need for further clues in the immune mechanisms. Contrary to PNMGUS and MS, GBS is generally self-limiting. The mechanisms of the beneficial effect of interferon-beta (IFN-ß) treatment in MS are not fully understood, (although alterations in the cytokine levels are subject to many reports). In PNMGUS, the proliferation of a monoclonal B cell clone and its antibody production are of great significance, however additional immune mechanisms are also of interest like the role of T cells and the role of B cells as antigen presenting cells.In studies of cytokines, frozen cells are often used, sometimes for practical reasons, so also in this thesis. Therefore effects of cryopreservation on cellular expression/secretion of cytokines were studied. The expression before compared to after cryopreservation of IFN-γ, IL-4, IL-5, IL-9, IL-10 and IL-13 was analysed with ELISA, ELISPOT and/or real time RT-PCR We found that the process of cryopreservation and thawing does affect the expression of cytokines, both at the protein and the mRNA level. The most consistent fmding was that expression of IL-4 was generally decreased in spontaneous and auto-antigen/allergen induced expression in cryopreserved cells. Thus, this study points out the importance of investigation of the effects of freezing for each cytokine, stimuli and patient group before using frozen cells in studies of in vitro cytokine secretion.The secretion of IL-4, IFN-γ, TGF-ß, IL-6, and TNF-α during the course of GBS was analysed with ELISPOT and cell-ELISA. Our findings indicate a down-regulatory role for TGF-ß and IL-4 in GBS.The longitudinal effects over one year of IFN-ß treatment on secretion of IL-4, IFN-γ and IL-10 was analysed with the ELISPOT technique and IL-13 and IL-17 was analysed in cell supernatants with ELISA. A general finding was that surprisingly few changes occurred, and that most changes occurred early (6 weeks - 3 months). However, we found a shift in the cytokine balance towards more IL-4 and IL-10 secretion and/or less IFN-γ secretion during the treatment as the ratios of IL-4/IFN-γ as well as of IL-10/IFN-γ were increased. The interesting pro-inflammatory cytokine IL-17, associated with T cell mediated autoimmunity, has not been previously investigated during IFN-ß treatment in MS and our findings of decreased IL-17 levels after one year of treatment could be a beneficial result of the IFN-ß treatment.B cell clones from a patient with PNMGUS were successfully established by isolating B cells with myelin protein zero (P0) coated magnetic beads and subsequently transforming with Epstein-Barr virus (EBV). The clones were characterised and for instance they strongly expressed HLA-DR and CD80, compatible with antigen-presenting properties. The cell lines may provide useful tools in studies of PNMGUS.
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