Browsing by Issue Date

Sort by: Order: Results:

Now showing items 1-20 of 41
  • Maliniemi, Pilvi (Pilvi Maliniemi, 2015)
    This thesis concentrates on exploring novel agents in the pathogenesis of cutaneous T cell lymphomas (CTCL) and reveals potential new biomarkers and therapeutic targets to improve diagnostics. CTCLs are also known as a heterogeneous group of non-Hodgkin lymphomas. The clinical behavior of these lymphomas varies from benign forms of lymphoproliferative diseases such as lymphomatoid papulosis (LyP) to non-progressive mycosis fungoides (MF) and further to rapidly-progressing leukaemic Sézary syndrome (SS). The incidence of the disease is growing, particularly in Western countries. The mechanisms underlying the disease are still largely unknown and thus far no curative therapy exists. Regarding pathogenesis, it has been suggested that persistent antigen stimulation leads to continuous stimulation of T cells and chronic inflammation, eventually causing the development of a malignant T cell clone. Another hypothesis suggests that a specific viral agent could serve as a triggering factor. The first part of this thesis explores the activity of human endogenous retroviruses (HERVs) in CTCLs. HERVs are retroviral sequences comprising about 8% of the human genome and are derived from ancient retrovirus infections of germ line cells. HERVs have their own promoter areas and genes, some of which encode functional proteins. HERVs may also affect the function of neighbouring genes and influence chromosomal instability (e.g. due to random positioning in the genome). However, HERVs are usually epigenetically silenced, but are reactivated in situtations such as cancer. Healthy tissues also show HERV activity. Moreover, tissue-specificity is typical feature of HERVs. We show that a skin-specific HERV pattern is actively transcribed in MF. We also found that the HERV-W-derived viral protein Syncytin-1 is expressed in morphologically malignant lymphocytes. The second part of this thesis is a unique molecular study on a rare subtype of CTCL. Known as subcutaneous panniculitis-like T cell lymphoma (SPTL), this subtype primarily affects young individuals. The diagnosis of SPTL is challenging and SPTL is usually confused with other panniculitis-related inflammatory diseases. The most important finding of the gene expression profiling was the high expression of indoleamine-2,3-dioxygenase (IDO-1), which catabolises the essential amino acid tryptophan (Trp) into kynurenine (Kyn) metabolites. The enzymatic activity of IDO-1 results in the depletion of Trp in the local microenvironment. Because T cells are particularly sensitive to low Trp levels, the process ultimately leads to immunosuppression and subsequent inhibition of T cell responses. Our results suggest that autoimmune inflammation is underlying the development the disease with the support of an immunosuppressive microenvironment. The last part of this thesis is focused on further studying IDO-1 expression in other CTCL subtypes and lymphoproliferative diseases and also how the tumor microenvironment could be involved in malignant transformation. In this study, we showed that distinct subpopulations of CTCL can be recognized based on IDO1-expressing cells. Especially interesting was the finding that IDO-1 is more extensively expressed in LyP rather than in MF, bearing in mind that LyP is a benign disease. Analyzing the Kyn/Trp ratio from patient sera also showed significant differences between MF and LyP. The Kyn/Trp ratio may therefore serve as a potential prognostic biomarker for evaluating disease activity. Taken together, this study revealed completely new information on gene and protein expression in CTCL. The results will likely be most useful in improving future diagnostics as well as patient care. The results may also be further applied in finding new therapeutic targets and developing novel therapies.
  • Lotsari-Salomaa, Johanna (2015)
    Lynch syndrome (LS) is the most common hereditary colon cancer syndrome with germline mutated DNA mismatch repair (MMR) genes predisposing to early onset colon tumors and various extracolonic tumors. Microsatellite instability (MSI) is a hallmark of the Lynch syndrome, but 15% of sporadic tumors show instability of repeated sequences, too. Endometrial carcinoma is the most common LS related extra-colonial tumor. Whether or not breast carcinoma belongs to the Lynch syndrome tumor spectrum has been under debate because of controversial study results. Epigenetic mechanisms regulate gene expression without altering the DNA sequence. DNA methylation is a well-established epigenetic modification. Colon, endometrial and breast carcinomas and endometrial hyperplasia from 256 Finnish Lynch syndrome families were examined for methylation changes as well as several types of genetic alterations. In addition, Finnish sporadic breast tumors with similar hormone receptor statuses to LS breast carcinomas were analyzed. Sporadic colon tumors with microsatellite unstable (MSI) and microsatellite stable (MSS) subgroups from Finnish and Australian populations were also investigated. The first aim was to investigate whether or not breast tumors belong to the Lynch syndrome tumor spectrum by studying the MMR status and the methylation profiles of several tumor suppressor genes. The second aim was to identify epigenetically regulated miRNA genes relevant for colon and endometrial tumorigenesis. The third aim was to examine tumorigenic mechanisms in the minor subset of colon carcinomas with inactive Wnt signaling. The candidate genes identified in the second and third studies were examined for promoter methylation in patient specimens. Breast carcinomas from LS mutation carriers showed significantly higher frequencies of MSI(35%) and loss of MMR protein expression (65%) compared to breast tumors from proven noncarriers (0%) and sporadic cases (0%). This suggested that breast carcinoma is a likely LS spectrum tumor. MMR deficient breast tumors were diagnosed at age 53. RASSF1, APC, CDH13, and GSTP1 genes were often methylated in LS breast tumors, the same as in tumors from several other organs from LS mutation carriers. The CDKN2B gene showed breast cancer specific methylation. A breast tumor may be the first sign of LS, and therefore female MMR mutation carriers should participate in mammographic surveillance. Novel associations between promoter methylation of tumor-suppressive miRNAs or protein coding tumor suppressor genes and clinical subtypes were observed. miR-132 was frequently hypermethylated in sporadic Finnish and Australian MSI tumors compared to paired normal mucosa. miR-132 hypermethylation correlated with traditional (so called CpG island methylator phenotype; CIMP) markers and were associated with the female gender, later onset, and tumors located in the proximal colon. miR-129-2 hypermethylation was seen in advanced endometrial hyperplasia and may be an early marker for endometrial tumorigenesis. The CMTM3, DGKI, and OPCML genes showed frequent hypermethylation in LS and sporadic colon tumors. The EPCAM and KLK10 genes had LS specific methylation. Colon tumors with inactive Wnt signaling were found to constitute a group of tumors with varying features of chromosomal instability and epigenetic dysregulation.
  • Vlachopoulou, Efthymia (2015)
    The Human Leukocyte Antigen (HLA) region is located on chromosome 6 (6p21.3) and its main function is to regulate the immune system. This region has been associated with several autoimmune and other inflammatory conditions. However, many aspects of these associations remain unknown due to high polymorphism, high linkage disequilibrium (LD) and high gene density of this region that increase the complexity and create computational challenges. In this Thesis, the aim is to investigate the HLA haplotype variation in the Finnish population, to evaluate the HLA imputation using two of the existed softwares and to analyze the HLA association with Acute Coronary Syndrome (ACS). The main question in this study is whether the HLA region varies in the Finnish population compared to other populations and how this variation can influence the results of further analyses. The HLA haplotypes showed great variation in the Finnish population compared to other European populations due to different linkage disequilibrium (LD) structures and this highlights the diversity of the HLA haplotypes among different populations. The most common European haplotype HLA-A*01~HLA-B*08~HLA-DRB1*03 shows a lower frequency in Finland, whereas the enrichment of the haplotype HLA-A*03~HLA-B*35~HLA-DRB1*01 was observed (I). Furthermore, the poor imputation results of the HLA-DRB1 gene enhance the power of the previously mentioned arguments (from I) due to the inaccurate imputation from other European populations. The study emphasizes the need for population-specific reference materials for a successful imputation (II). The diversity of HLA alleles, the variability in the frequencies of Single Nucleotide Polymorphisms (SNP) among populations, the difference of the rare HLA alleles appearing in various populations and the extremely high amount of combinations of HLA alleles (due to high polymorphism) contribute to the low success rates of imputation. The association (OR = 4.43, 95% CI = 3.57-5.50) of a novel BTNL2;HLA-DRA;HLA-DRB1*01-haplotype with the risk of Acute Coronary Syndrome (ACS) was identified (III). The analysis showed the implication of the HLA-DRB1*01 allele and the BTNL2 gene to the inflammation process. These two genes affect the antigen presentation and its immune response. Overall, the associated haplotype appeared approximately in 15% of ACS patients and in 5% of healthy individuals. Furthermore, the survival analysis shows that the HLA-DRB1*01 allele does not affect the survival time after an ACS event. Our results provide more insight into the detailed patterns of the haplotypes in the Finnish population, into the success of the imputation approaches and into the HLA association with ACS. Genetic diversity is depicted on these haplotypes which might lead to different immune responses. These findings help future development of appropriate statistical tools for the HLA region.
  • Rautiola, Juhana (2015)
    Renal cell carcinoma (RCC) is the seventh most common cancer in men and the ninth most common in women and it comprises 2-3% of all malignant tumors in adults. In its localized form, the five-year survival is almost 60%. However, in metastatic renal cell carcinoma (mRCC), the five-year survival has historically remained under 10%. Renal cell carcinoma is highly tolerant to traditional chemotherapy and and recent treatment has instead relied on inhibiting the vascular endothelial growth factor (VEGF) and mammalian target of rapamycin (mTOR) signaling pathways. Since 2005, seven new agents have been approved for the treatment of metastatic RCC. Despite the increased knowledge of RCC, the molecular mechanisms behind acquired and intrinsic resistance to treatment remain largely unknown. Our results demonstrate that hypertension is a strong predictor of good prognosis and response to sunitinib treatment. In addition to hypertension we identified neutropenia and thrombocytopenia as predictive markers of good prognosis. A novel, triple biomarker profile consisting of these adverse events strongly predicts improved survival and outcome in mRCC patients. Results from our investigation of sequential treatment suggest that a newer VEGF receptor inhibitor, pazopanib, has clinically meaningful activity in a patient population where mRCC has progressed through sunitinib treatment and in patients who do not tolerate sunitinib. Encouraged by the fuller understanding of tumor biology, we then investigated the role of an endothelial-cell derived growth factor, angiopoietin-2 (Ang2), on patients outcome. High expression of Ang2 was demonstrated to correlate with a high vessel density and to predict a better response to sunitinib-based first-line therapy.
  • Koskela, Elina (2015)
    Intracranial aneurysms (IAs) affect 2-3% of the population. In Finland, their rupture rate has been exceptionally high. This study aims to evaluate the prevalence and risk factors affecting neuro-ophthalmic findings in patients undergoing treatment for IAs. We also investigate the utility of conventional head computed tomography (CT) in the diagnosis of Terson´s syndrome (TS, vitreous hemorrhage in association with aneurysmal subarachnoid hemorrhage (aSAH)). Patients treated endovascularly or microsurgically for their IAs at the Department of Neurosurgery, Helsinki University Central Hospital, in 2011 prospectively underwent a neuro-ophthalmic examination preoperatively and at 3 days, 14 days, 2 to 4 months, and 6 months postoperatively. Findings suggestive of TS, as independently reviewed by two radiologists, on conventional CT head scans were compared with dilated fundoscopic findings. Participants comprised 121 patients with a ruptured aneurysm and 142 patients with an unruptured intracranial aneurysm (UIA). TS was present on fundoscopy in 13 patients (11%); the overall observed agreement between the two radiologists was 96% (116/121), with a substantial κ of 0.69 (95% CI 0.56-0.82). On average, CT demonstrated sensitivity of 42% and specificity of 97%. Factors independently predicting TS were female gender (OR 5.34, 95% CI 1.05-27.17) and World Federation of Neurosurgical Societies (WFNS) grade (OR 15.05 for grades IV-V vs. I-III, 95% CI 3.07-73.89). For patients with aSAH, the frequencies of a third, fourth, or sixth nerve palsy were 11 (9%; preoperatively), 16 (13%; immediately postoperatively), and 3 (3%; at the last follow-up), compared with corresponding frequencies of 6 (4%), 15 (11%), and 7 (5%) for patients with UIAs. Significant risk factors for postoperative eye movement disorders (EMDs) among patients with UIAs were aneurysm location in the posterior circulation (OR 142.02, 95% CI 20.13-1002.22) and aneurysm size (OR 1.28, for each 1-mm increase in diameter, 95% CI 1.12-1.47). After a follow-up time of 6 months, patients with aSAH presenting with visual field defects (VFDs) for aneurysm- or operation-related reasons numbered 20 (19%); homonymous VFDs were the most prevalent finding, and in logistic regression analysis, they were significantly associated with the Hunt and Hess (H and H) grade (OR 4.45 for grades IV-V vs. I-III, 95% CI 1.21-16.39) and presence of intracranial hemorrhage (OR 8.93, 95% CI 2.14-37.28). By contrast, seven patients (5%) treated for a UIA had VFDs. Poor-grade aSAH (H and H or WFNS grade IV-V) appears to be a strong predictive factor for TS and VFDs. With a high specificity value, conventional head CT scan might prove a useful tool in the diagnosis of TS. Although a common finding in the acute postoperative stage of ruptured and unruptured IAs, EMDs show marked improvement during follow-up.
  • Lindh, Erika (Hansaprint, 2015)
    Influenza A virus (IAV) is a significant zoonotic pathogen, with a diverse range of subtypes infecting both humans and birds. NDV is the causative agent of Newcastle Disease, a significant infectious disease of poultry. While wild waterfowl, the natural host, remains apparently healthy during the even frequent infections with these viruses, poultry is susceptible for mild to severe disease. Both viruses have a heavy impact on the poultry industry by causing outbreaks with significant economical losses. Low pathogenic IAV and NDV viruses are efficiently transmitted in host populations and have the ability to mutate and become virulent. The segmented genome of IAV also allows it to reassort during dual infections, giving rise to novel viruses with unpredictable pathogenic properties including the potential to transmit to humans and other mammals. Extensive surveillance studies of IAV and NDV during the past decades have revealed their wide global distribution and host species range. Previous surveillance studies have yielded limited information about avian IAV in Finland and so far, NDV has been the causative agent of varying outbreaks in Finland, for example in poultry, a zoo and domestic pigeons. This project was initiated for surveillance purposes, to gather information about prevalence and subtype/genotype distribution of IAVs and NDVs and to assess the potential presence of highly pathogenic strains in wild waterfowl in Finland. Through annual sampling and screening of wild waterfowl, 875 birds were screened during the years 2006-2010 and 2014. The birds represent mainly young, hunted ducks from local breeding areas. We detected altogether 76 IAVs (in 8.7%) and 39 NDVs (in 5.5%). From most of the samples (75%) the viruses were successfully propagated in embryonated chicken eggs and partially sequenced for phylogenetic and pathogenicity analyses. Importantly, while no highly pathogenic strains were encountered, several of the wild waterfowl derived viruses detected in Finland were phylogenetically closely related to viruses detected during outbreaks in Finland and elsewhere in Europe. These viruses includ IAV subtypes H5N2, H7N3, H9N2 as well as NDVs. An unexpectedly high subtype dominance of H3N8 was recorded each year, counting for over 60% of all the subtyped IAVs. Genetic characterization of these viruses demonstrated high sequence homology, even between temporally separated viruses and suggests local perpetuation of the viruses. The past decades have witnessed an increase in the incidence of IAV outbreaks in poultry in Europe and zoonotic transmission of a growing number of subtypes. Surveillance data of IAV in the natural host is important for designing efficient national policies aiming to control the transmission of IAV to susceptible populations and for risk assessment. Our results also show that the northern breeding sites have implications on a European scale.
  • Niinistö, Sari (Unigrafia, 2014)
    The aim of the present study was to evaluate the associations between the maternal intakes of fatty acids, vitamin D, and their respective dietary sources during pregnancy or lactation, as well as the child s fatty acid status, and the risk of type 1 diabetes. The present study is a prospective cohort belonging to the nutrition part of the Finnish Type 1 Diabetes Prediction and Prevention Study (DIPP). The cohort comprised children at increased genetic risk for type 1 diabetes (n=6069) born at the Oulu and Tampere University Hospitals between the years 1997 and 2004. Maternal diet was assessed with a validated food frequency questionnaire during the 8th month of pregnancy and the 3rd month of lactation. The children were monitored for the appearance of autoantibodies associated with type 1 diabetes and for the development of clinical type 1 diabetes, at intervals between 3 and 12 months. The associations between the maternal intakes of fatty acids, vitamin D, as well as their respective food sources and the endpoints, were analyzed by the piecewise linear log-hazard survival model and Cox proportional hazard analyses. The associations between the children s serum fatty acid composition and the risk of type 1 diabetes were studied in a nested case-control study design that included 108 children with preclinical type 1 diabetes and 216 matched controls. The total serum fatty acid composition was analyzed by gas chromatography from samples that were taken from the children between the ages of 1 and 6 years. Conditional logistic regression was applied in the statistical analysis. After adjustment for putative confounders, neither the maternal intake of fatty acids during pregnancy and lactation nor the intake of vitamin D during pregnancy, showed any association with the development of type 1 diabetes. The maternal use of fresh milk and cheese, and the intake of protein from fresh milk during pregnancy, were associated with a lower risk of clinical type 1 diabetes. The maternal total consumption of red meat and meat products, particularly processed meat, during lactation was associated with an increased risk of type 1 diabetes. The child s serum profile of milk-associated fatty acids at, or closest to, the time of seroconversion, was associated with a higher risk of preclinical type 1 diabetes. Findings give one of the first indications that prenatal exposure to certain dairy foods may affect immune regulation, and our results on the milk-associated fatty acid biomarkers confirm the previous findings that the child s own direct cow s milk exposure is associated with autoimmunity in children with increased genetic risk of type 1 diabetes. These results thus indicate that milk and meat products in particular, are interesting topics for future studies on potential nutritional risk and protective factors for type 1 diabetes.
  • Nevalainen, Maarit (Unigrafia, 2014)
    The aim of this study was to investigate medical students and primary care physicians feelings of uncertainty, experiences of medical errors and ways of coping with them, and attitudes towards the career of a GP. In Study I the learning diaries (n=79) and writings on specific themes (n=94) of 22 students during their first clinical year were analysed by thematic content analysis. The topics uncertainty and medical errors were studied in more detail. Studies II and III are based on the responses of 5th-year students to a cross-sectional survey (Study II, n=307 and Study III, n=309, response rate 86%) during their main course in general practice. Study IV concerned younger (n=85) and experienced physicians (n=80) responses to an electronic survey related to uncertainty and experiences of medical errors (response rate 68%). Factors predisposing physicians to medical errors and means to avoid making them were assessed. In the second, third and fourth studies the responses were cross-tabulated. The variables are presented as means with standard deviations and percentages. Comparisons of categorial variables were carried out by using the X2 test or Fischer s exact test, comparisons of non-normally distributed continuous variables were made by using the Mann-Whitney U-test. (P values less than 0.05 were considered significant.) 95% CIs are presented for the most important results. Logistic regression analysis was used to explore which factors predicted good tolerance of uncertainty among GPs. A developmental path among the 3rd- to 4th-year medical students was discovered regarding their experiences of uncertainty and fears medical errors. All students wrote about several aspects of uncertainty. They also feared mistakes. However, they started gradually to be more confident in coping with responsibility. The 5th-year medical students were divided into two groups based on their tolerance of uncertainty and fear of medical errors. Those who tolerated uncertainty quite well or well (n=240, 78%) were older, more often males, and had been working for a longer time as locum doctors than those tolerating uncertainty poorly (n=67, 22%). In the latter group, 100% were afraid of medical errors, in the former group the figure was 86%. Those tolerating uncertainty poorly felt more often that a GP s work is too challenging and difficult and involves too much responsibility. About 3/4 of the fifth-year medical students considered the work of a GP positively versatile and challenging, but about 2/3 of them considered it to be too hasty and pressing. The females thought that a GP s work is too lonely. The males considered that a GP deals too much with non-medical problems and the work may be too routine and tedious. According to the majority of the students (82%) the most important aim of a GP s work is to identify serious diseases and refer such patients to specialized care. In the fourth study 6% of the younger and 1% of the experienced physicians tolerated uncertainty poorly. The younger physicians feared medical errors more (70% vs. 48%) and more often admitted having made an error (84% vs. 69%) compared to the experienced ones (48%). The experienced physicians apologized more willingly to their patients for an error. The younger physicians were more prone to use electronic databases and consult on site. Tolerance of uncertainty seems to develop gradually during the medical studies and this development also continues after graduation. Students are already aware of the possibility of a medical error. Almost all of them are afraid of them. Also half of the experienced physicians admitted to feeling some fear. The attitudes of fifth-year medical students reflect their experiences of general practice.
  • Malmivaara, Kirsi (Helsingin yliopisto, 2014)
    The overall purpose of this study was to evaluate the health-related quality of life (HRQoL) and cost-effectiveness of the treatment of severely, acutely ill neurosurgical patients. The majority of the study illnesses and conditions are known to have a relatively high mortality or an otherwise poor outcome but, they are also known to be highly resource-demanding. Since the economics of health care is attracting more and more interest, it will become more important to evaluate the cost-effectiveness of treatment so that it can be demonstrated that the resource allocation is justified. The patients (n=620) for these four separate studies were treated in the Department of Neurosurgery of Helsinki University Central Hospital between 1998 and 2006. The first of these four studies was a Step-Down Unit study in which we evaluated a group of patients (n=346) who underwent a major neurosurgical operation and were treated in the neurosurgical intensive care unit (NICU) and, due to a poor prognosis, were then discharged from the NICU to the step-down unit, still depending on life support devices. The following two studies evaluated patients who underwent a decompressive craniectomy (DC) for intractable intracranial pressure. The first of these, the DC after SAH study, concerned patients (n=42) with subarachnoid haemorrhage (SAH) or other neurological emergencies, and the second one, the DC after TBI study, evaluated patients (n=54) with traumatic brain injury (TBI). The fourth study, the SAH study (n=178), evaluated the long-term outcome, HRQoL and cost-effectiveness of the treatment of the SAH patients. The mortality in the Step-Down Unit study and both of the DC studies was high and moderate in the SAH study, 59%, 53%, 41%, and 24% respectively. The median follow-up times were 5, 3, 5.6 and 10.8 years. The health-related quality of life was assessed with the EuroQol EQ5D instrument and the median HRQoL index was compared to the median index of the Finnish reference population (0.85). The indices were 0.71, 0.41, 0.85 and 1.00. The outcome was also evaluated on the Glasgow outcome scale (GOS), and 49%, 25%, 69% and 75% of the patients achieved a good outcome (GOS 1-2). An important measure of well-being is the ability to live at home, and 49%, 50%, 78% and 88% of the study patients were able to live at home. The direct costs of the neurosurgical treatment per quality adjusted life year (QALY) were 2521 , 5000 , 2400 and 1700 . For the total of 620 severely ill neurosurgical patients treated in the Helsinki Department of Neurosurgery between 1998 and 2006, we found the treatment to be cost-effective, and it resulted in health-related quality of life that varied from acceptable to good when compared to the reference population. We found no evidence of unnecessary prolongation of human suffering when death was inevitable. The worst state of health-related quality of life did not occur among the survivors. In summary, these studies indicate that current healthcare resources are utilized cost-effectively to achieve a life that is meaningful. Allocation of healthcare resources to the severely ill neurosurgical patients seems to be justified.
  • Zheng, Wei (2013)
    Blood vessels deliver nutrients and oxygen to tissues, whereas lymphatic vessels collect interstitial fluid and absorb lipids. Both types of vessels are involved in immune surveillance. Malformation or malfunction of either vasculature is closely associated with various diseases. Although the molecular mechanisms regulating the growth, development and function of these vessels have begun to emerge in recent decades, many questions remain. This study aimed to understand if and how the growth of new blood and lymphatic vessels (angiogenesis and lymphangiogenesis, respectively) is regulated by the endothelial signaling molecules BMX, VEGFR-3, notch 1 and angiopoietin-2. BMX, a non-receptor tyrosine kinase, is upregulated in some types of cancer and promotes cell survival, migration and proliferation. Under physiological conditions, it is also highly expressed in blood endothelial cells (BECs). Thus, we hypothesized that BMX might contribute to tumor growth by promoting tumor angiogenesis. Using multiple tumor implantation and spontaneous tumor models in Bmx gene-deleted mice, we found that tumor angiogenesis and growth were significantly reduced in the absence of BMX. Conversely, when BMX was overexpressed in epithelial keratinocytes, chemical carcinogen led to increased tumor angiogenesis and growth. VEGFR-3 is a growth factor receptor on the surface of endothelial cells (ECs). Here, we characterized a blocking antibody that inhibits VEGFR-3 signaling by a novel mechanism. In contrast to conventional blocking antibodies that prevent ligand-receptor binding, this new antibody inhibited dimerization of two identical VEGFR-3 molecules, thereby impairing signaling activation and sprouting of lymphatic endothelial cells (LECs). These inhibitory effects persisted even at ligand concentrations so high that conventional blocking antibodies were no longer effective. Importantly, concurrent treatment with both types of antibodies yielded combined additive benefits. Notch signaling regulates angiogenic sprouting. We found in this study that Notch inhibitors enhance VEGF-induced lymphatic sprouting in 3-dimensional EC sprouting assays in vitro. In vivo, VEGF alone induced only lymphatic dilation but not sprouting. However, concomitant treatment with a Notch inhibitor induced both vascular events. In addition, a mosaic-sprouting assay showed that Notch signaling also determined the fates of tip/stalk cells (the cell leading a vessel sprout and the following cells, respectively) during lymphatic sprouting. Angiopoietin-2 (Ang2) is an endothelial growth factor required for proper lymphatic remodeling during development, but the exact mechanisms of this process have previously remained unclear. In contrast to the zipper-like pattern of cell-cell junctions (zippers) in collecting lymphatic vessels, mature lymphatic capillaries have a distinct pattern of button-like junctions (buttons), which transform from zippers during development. We found in this study that Ang2 is indispensable for such transformation of the junctional patterns during embryogenesis. At the molecular level, Ang2 is required for phosphorylation of the adherens junction marker vascular endothelial cadherin (VE-cadherin) at the tyrosine residue 685. Ang2 blocking antibody treatment of mouse neonates disrupted cell-cell junctions in the mesenteric lymphatic vessels, causing leakage of chyle (milky fluids containing fat droplets and lymph). Ang2 blockade also inhibited lymphatic valve formation and maturation and resulted in abnormal smooth muscle recruitment. Together, these results provide new insights into the molecular mechanisms of angiogenesis and lymphangiogenesis. Elucidation of these mechanisms is important in developing new drugs for the treatment of vessel-related diseases, including cancer and pathological inflammation. Moreover, these findings introduce the reorganization of cell-cell junctions as a novel parameter for evaluating lymphatic development and call for future research into this new field.
  • Matilainen, Olli (2013)
    The ubiquitin-proteasome system (UPS) is the major pathway for controlled protein degradation in the cell. Substrates destined for degradation are polyubiquitinated by ubiquitin ligating enzymes and degraded by the proteasome, which is a complex multisubunit enzyme of over 2.5 MDa. Due to its essential role in maintenance of the cellular protein homeostasis, dysfunctions in proteasome activity have been linked to many severe disorders, such as Alzheimer s, Parkinson s and Huntington s disease and some cancers. Although the proteasome takes part in almost all cellular processes, it is still unclear which factors contribute to regulation of proteasome function. The aim of this thesis was to elucidate mechanisms of how proteasome activity is regulated in a multicellular organism. To enable monitoring and quantification of proteasome activity in vivo, a photoconvertible reporter system was developed to live image proteasome activity in C. elegans. By using this system, it was uncovered that proteasome activity varies between different tissues, as GABAergic and dopaminergic neurons showed faster reporter degradation than muscle cells, and that aging affects proteasome activity in a tissue-dependent manner. Subsequently, it was investigated whether signaling pathways regulating aging also affect proteasome activity. Insulin/IGF-1 signaling (IIS) is an evolutionarily conserved signaling pathway regulating lifespan in worms, flies, rodents and possibly humans. By using C. elegans as a model organism, this thesis shows that IIS regulates proteasome activity through the FOXO/DAF-16 and Nrf/SKN-1 transcription factors. Moreover, it was demonstrated that DAF-16, which is activated by reduced IIS, inhibits the expression of the proteasome-associated deubiquitinating enzyme UBH-4, which was shown to function as a tissue-specific proteasome inhibitor. The role of UBH-4 appears to be well-conserved, as downregulation of its mammalian ortholog, UCHL-5, increases proteasome activity and degradation of proteotoxic proteins in mammalian cells. Taken together, this thesis provides tools to study proteasome activity in vivo, and establishes a molecular mechanism linking IIS to efficiency of proteasomal degradation. These results can be utilized when designing new therapies for proteasome-associated diseases, especially for disorders that may be alleviated with tissue-specific modulation of proteasome activity.
  • Hankaniemi, Minna (2012)
    Bone morphogenetic protein 15 (BMP15) and growth differentiation factor 9 (GDF9) are growth factors expressed by oocytes and are among the key regulators transmitting the signaling between the oocyte and the surrounding granulosa cells. Genetic studies have shown that these factors are essential regulators of normal fertility in mammals. BMP15 gene deficient mice exhibit a mild reduction in fertility, whereas sheep homozygous for a mutant form of BMP15 are sterile. In the case of GDF9, knockout mice and homozygous mutant sheep are also sterile the ovaries being non functional due to an early block in folliculogenesis. In humans, aberrant expression of these factors has been involved in premature ovarian failure (POF), polycystic ovary syndrome (PCOS) or dizygotic twinning. ----- This thesis was aimed to define the signaling and activation of human BMP15 (hBMP15) and GDF9 (hGDF9) proteins. The lack of bioactive hGDF9 had restricted the in vitro studies previously and the first aim of this thesis was to produce and purify bioactive hGDF9 protein. We found that hGDF9 is secreted in a latent form. Although mouse GDF9 (mGDF9) and hBMP15 are produced in active form their bioactivity is lost when a C-terminal affinity purification tag is added. We found also, that an N-terminal epitope tag does not have a deleterious effect on the bioactivity of mGDF9 or hBMP15 and they can be purified using immobilized metal affinity (IMAC) and high performance liquid chromatography approaches. A purified wild type hGDF9 (hGDF9wt) mature region became available to us during this thesis project and we found that it is a highly bioactive and stable protein activating the Smad3/4 signaling pathway. Subsequently we produced and purified a bioactive wild type hBMP15 (hBMP15wt) form, which was highly bioactive and activated the Smad1/5/8 signaling pathway in human granulosa luteal (hGL) cells. Physico-chemical characterization of BMP15 revealed that it consists of P16 and P17 forms, where P16 seems to be phosphorylated and P17 glycosylated. ------ It has been shown previously that a recombinant BMP type II receptor ectodomain Fc fusion protein (BMPR2ecd Fc) is able to inhibit the actions of BMP15 and GDF9 in vitro. For studying the effect of BMPR2ecd Fc on mouse folliculogenesis, we produced and purified this protein. These in vivo studies demonstrated that by administering the BMPR2ecd-Fc protein, we were able to dose-dependently modulate ovarian folliculogenesis in mice. -------- In order to determine the cell surface receptor binding components for human BMP15, we engineered and produced a covalent dimer of hBMP15 and labeled it radioactively. We found that it behaves biologically in a similar manner as the hBMP15wt. Human BMP15 strongly bound to BMPR1B and BMPR2 on the COV434 cell surface, an association which was further verified in COS-7 cells by overexpression of these receptors. In conclusion, we have for the first time produced and characterized recombinant human GDF9 and BMP15 protein in native form and thus developed valuable tools for studies aiming at understanding their role in human reproductive medicine. The production and purification methods developed during this thesis are widely applicable for the isolation and characterization of comparable oocyte growth factors in other species and thus have wide applicability in reproductive biology studies in the future.
  • Sarajuuri, Anne (Unigrafia Oy, 2012)
    Hypoplastic left heart syndrome (HLHS) and other forms of functionally univentricular heart (UVH) are complex congenital heart defects (CHD) that during the past few decades have gained viability with staged palliative surgery. It results in the passive return of systemic venous blood to the lungs without passing through the heart. The aim of this study was to evaluate the neurodevelopmental outcome of children with HLHS and UVH in Finland with neurological, neuropsychological, and motor assessments and brain imaging, and to detect possible risk factors associated with an adverse outcome. Parental perceptions of child behavior and parenting stress were also assessed with parental question-naires. The first study cohort of patients born between 1995 and 1999, which included most of the first HLHS survivors in Finland, showed a significantly lower cognitive outcome compared to normative data among both patients with HLHS (n = 7) and with UVH (n = 19). Cerebral palsy was present in 14% of the patients with HLHS and in 10% of those with UVH, and milder difficulties in gross and fine motor functions were also commonly found. Patients with HLHS or UVH born between 2002 and 2005 were recruited in a prospective neurodevelopmental follow-up study as newborns. The neurodevelopmental evaluations at the ages of 12 months, 30 months, and 5 years revealed a significantly lower cognitive and motor outcome among the patients with HLHS (n = 23) compared to healthy age- and gender-matched controls (n = 40). The patients with UVH (n = 14) only demonstrated a statistically significant difference to controls in motor development during the earlier assessments, and at the age of 5 years also in cognitive development. A smaller sample size may have contributed to the lack of statistically significant difference in cognitive development in the earlier assessments. Major neurodevelopmental impairment was found in 26% of the patients with HLHS, and 23% of the patients with UVH at the age of 5 years. Brain magnetic resonance imaging revealed abnormalities in 82% of the patients with HLHS and 56% of those with UVH most commonly infarcts or ischemic findings of different degrees. Other than minimal ischemic findings were significantly associated with neurodevelopmental outcome. The level of parenting stress was significantly higher among the patients with HLHS compared to controls at the age of 18 months. The parents of the patients with UVH, however, did not report more stress than those of the controls. In conclusion, neurodevelopmental deficits remain a major concern among patients with UVH, and especially among those with HLHS. Neurodevelopmental follow-up is recommended for this seriously ill patient group and psychosocial support for their parents.
  • Päiväniemi, Outi (2011)
    Chronic rejection in the form of obliterative bronchiolitis (OB) is the major cause of death 5 years after lung transplantation. The exact mechanism of OB remains unclear. This study focused on the role of cyclo-oxygenase (COX) -2, tenascin, and C-reactive protein (CRP) expression, and the occurrence of ingraft chimerism (= cells from two genetically distinct individuals in a same individual) in post-transplant OB development. In our porcine model, OB developed invariably in allografts, while autografts stayed patent. The histological changes were similar to those seen in human OB. In order to delay or prevent obliteration, animals were medicated according to certain protocol. In the beginning of the bronchial allograft reaction, COX-2 induction occurred in airway epithelial cells prior to luminal obliteration. COX-2 expression in macrophages and fibroblasts paralleled the onset of inflammation and fibroblast proliferation. This study demonstrated for the first time, that COX-2 expression is associated with the early stage of post- transplant obliterative airway disease. Tenascin expression in the respiratory epithelium appeared to be predictive of histologic features observed in human OB, and influx of immune cells. Expression in the bronchial wall and in the early obliterative lesions coincided with the onset of onset of fibroblast and inflammatory cell proliferation in the early stage of OB and was predictive of further influx of inflammatory and immune cells. CRP expression in the bronchial wall coincided with the remodelling process. High grade of bronchial wall CRP staining intensity predicted inflammation, accelerated fibroproliferation, and luminal obliteration, which are all features of OB. In the early obliterative plaque, majority of cells expressed CRP, but in mature, collagen-rich plaque, expression declined. Local CRP expression might be a response to inflammation and it might promote the development of OB. Early appearance of chimeric (= recipient-derived) cells in the graft airway epithelium predicted epithelial cell injury and obliteration of the bronchial lumen, which both are features of OB. Chimeric cells appeared in the airway epithelium after repair following transplantation-induced ischemic injury. Ingraft chimerism might be a mechanism to repair alloimmune-mediated tissue injury and to protect allografts from rejection after transplantation. The results of this study indicate, that COX-2, tenascin, CRP, and ingraft chimerism have a role in OB development. These findings increase the understanding of the mechanisms of OB, which may be beneficial in further development of diagnostic options.
  • Söderlund, Sanni (2011)
    AIMS An independent, powerful coronary heart disease (CHD) predictor is a low level of high-density lipoprotein cholesterol (HDL-C). Discoidal preβ-HDL particles and large HDL2 particles are the primary cholesterol acceptors in reverse cholesterol transport, a key anti-atherogenic HDL mechanism. The quality of HDL subspecies may provide better markers of HDL functionality than does HDL-C alone. We aimed I) to study whether alterations in the HDL subspecies profile exist in low-HDL-C subjects II) to explore the relationship of any changes in HDL subspecies profile in relation to atherosclerosis and metabolic syndrome; III) to elucidate the impact of genetics and acquired obesity on HDL subspecies distribution. SUBJECTS The study consisted of 3 cohorts: A) Finnish families with low HDL-C and premature CHD (Study I: 67 subjects with familial low HDL-C and 64 controls; Study II: 83 subjects with familial low HDL-C, 65 family members with normal HDL-C, and 133 controls); B) a cohort of 113 low- and 133 high-HDL-C subjects from the Health 2000 Health Examination Survey carried out in Finland (Study III); and C) a Finnish cohort of healthy young adult twins (52 monozygotic and 89 dizygotic pairs) (Study IV). RESULTS AND CONCLUSIONS The subjects with familial low HDL-C had a lower preβ-HDL concentration than did controls, and the low-HDL-C subjects displayed a dramatic reduction (50-70%) in the proportion of large HDL2b particles. The subjects with familial low HDL-C had increased carotid atherosclerosis measured as intima-media-thickness (IMT), and HDL2b particles correlated negatively with IMT. The reduction in both key cholesterol acceptors, preβ-HDL and HDL2 particles, supports the concept of impaired reverse cholesterol transport contributing to the higher CHD risk in low-HDL-C subjects. The family members with normal HDL-C and the young adult twins with acquired obesity showed a reduction in large HDL2 particles and an increase in small HDL3 particles, which may be the first changes leading to the lowering of HDL-C. The low-HDL-C subjects had a higher serum apolipoprotein E (apoE) concentration, which correlated positively with the metabolic syndrome components (waist circumference, TG, and glucose), highlighting the need for a better understanding of apoE metabolism in human atherosclerosis. In the twin study, the increase in small HDL3b particles was associated with obesity independent of genetic effects. The heritability estimate, of 73% for HDL-C and 46 to 63% for HDL subspecies, however, demonstrated a strong genetic influence. These results suggest that the relationship between obesity and lipoproteins depends on different elements in each subject. Finally, instead of merely elevating HDL-C, large HDL2 particles and discoidal preβ-HDL particles may provide beneficial targets for HDL-targeted therapy.
  • Hovi, Petteri (Helsingin yliopisto, 2011)
    Background: The improved prognosis of early preterm birth has created a generation of surviving very low birth weight (PIENEMPI KUIN 1500 g, VLBW) infants whose health risks in adulthood are poorly known. Of every 1000 live-born infants in Finland, about 8 are born at VLBW. Variation in birth weight, even within the normal range, relates to considerable variation in the risk for several common adult disorders, including cardiovascular disease and osteoporosis. Small preterm infants frequently exhibit severe postnatal or prenatal growth retardation, or both. Much reason for concern thus exists, regarding adverse health effects in surviving small preterm infants later lives. We studied young adults, aiming at exploring whether VLBW birth and postnatal events after such a birth are associated with higher levels of risk factors for cardiovascular disease or osteoporosis. Subjects and Methods: A follow-up study for VLBW infants began in 1978; by the end of 1985, 335 VLBW survivors at Helsinki University Central Hospital participated in the follow-up. Their gestational ages ranged from 24 to 35 weeks, mean 29.2 and standard deviation 2.2 weeks. In 2004, we invited for a clinic visit 255 subjects, aged 18 to 27, who still lived in the greater Helsinki area. From the same birth hospitals, we also invited 314 term-born controls of similar age and sex. These two study groups underwent measurements of body size and composition, function of brachial arterial endothelium (flow-mediated dilatation, FMD) and carotid artery intima-media thickness (cIMT) by ultrasound. In addition, we measured plasma lipid concentrations, ambulatory blood pressure, fasting insulin, glucose tolerance and, by dual-energy x-ray densitometry, bone-mineral density. Results: 172 control and 166 VLBW participants underwent lipid measurements and a glucose tolerance test. VLBW adults fasting insulin (adjusted for body mass index) was 12.6% (95% confidence interval, 0.8 to 25.8) higher than that of the controls. The glucose and insulin concentrations 120 minutes after 75 g glucose ingestion showed similar differences (N=332) (I). VLBW adults had 3.9 mmHg (1.3 to 6.4) higher office systolic blood pressure, 3.5 mmHg (1.7 to 5.2) higher office diastolic blood pressure (I), and, when adjusted for body mass index and height, 3.1 mmHg (0.5 to 5.5) higher 24-hour mean systolic blood pressure (N=238) (II). VLBW birth was associated neither with HDL- or total cholesterol nor triglyceride concentrations (N=332) (I), nor was it associated with a low FMD or a high cIMT (N=160) (III). VLBW adults had 0.51-unit (0.28 to 0.75) lower lumbar spine Z scores and 0.56-unit (0.34 to 0.78) lower femoral neck Z scores (N=283). Adjustments for size attenuated the differences, but only partially (IV). Conclusions: These results imply that those born at VLBW, although mostly healthy as young adults, already bear several risk factors for chronic adult disease. The significantly higher fasting insulin level in adults with VLBW suggests increased insulin resistance. The higher blood pressure in young adults born at VLBW may indicate they later are at risk for hypertension, although their unaffected endothelial function may be evidence for some form of protection from cardiovascular disease. Lower bone mineral density around the age of peak bone mass may suggest increased risk for later osteoporotic fractures. Because cardiovascular disease and osteoporosis are frequent, and their prevention is relatively cheap and safe, one should focus on prevention now. When initiated early, preventive measures are likely to have sufficient time to be effective in preventing or postponing the onset of chronic disease.
  • Niittymäki, Iina (2011)
    Both inherited genetic variations and somatically acquired mutations drive cancer development. The aim of this thesis was to gain insight into the molecular mechanisms underlying colorectal cancer (CRC) predisposition and tumor progression. Whereas one-third of CRC may develop in the context of hereditary predisposition, the known highly penetrant syndromes only explain a small fraction of all cases. Genome-wide association studies have shown that ten common single nucleotide polymorphisms (SNPs) modestly predispose to CRC. Our population-based sample series of around thousand CRC cases and healthy controls was genotyped for these SNPs. Tumors of heterozygous patients were analyzed for allelic imbalance, in an attempt to reveal the role of these SNPs in somatic tumor progression. The risk allele of rs6983267 at 8q24 was favored in the tumors significantly more often than the neutral allele, indicating that this germline variant is somatically selected for. No imbalance targeting the risk allele was observed in the remaining loci, suggesting that most of the low-penetrance CRC SNPs mainly play a role in the early stages of the neoplastic process. The ten SNPs were further analyzed in 788 CRC cases, 97 of which had a family history of CRC, to evaluate their combined contribution. A significant association appeared between the overall number of risk alleles and familial CRC and these ten SNPs seem to explain around 9% of the familial clustering of CRC. Finding more CRC susceptibility alleles may facilitate individualized risk prediction and cancer prevention in the future. Microsatellite instability (MSI), resulting from defective mismatch repair function, is a hallmark of Lynch syndrome and observed in a subset of all CRCs. Our aim was to identify microsatellite frameshift mutations that inactivate tumor suppressor genes in MSI CRCs. By sequencing microsatellite repeats of underexpressed genes we found six novel MSI target genes that were frequently mutated in 100 MSI CRCs: 51% in GLYR1, 47% in ABCC5, 43% in WDTC1, 33% in ROCK1, 30% in OR51E2, and 28% in TCEB3. Immunohistochemical staining of GLYR1 revealed defective protein expression in homozygously mutated tumors, providing further support for the loss of function hypothesis. Another mutation screening effort sought to identify MSI target genes with putative oncogenic functions. Microsatellites were similarly sequenced in genes that were overexpressed and, upon mutation, predicted to avoid nonsense-mediated mRNA decay. The mitotic checkpoint kinase TTK harbored protein-elongating mutations in 59% of MSI CRCs and the mutant protein was detected in heterozygous MSI CRC cells. No checkpoint dysregulation or defective protein localization was observable however, and the biological relevance of this mutation may hence be related to other mechanisms. In conclusion, these two large-scale and unbiased efforts identified frequently mutated genes that are likely to contribute to the development of this cancer type and may be utilized in developing diagnostic and therapeutic applications.
  • Lundbom, Jesper (Helsingin yliopisto, 2010)
    Lipid analysis is commonly performed by gas chromatography (GC) in laboratory conditions. Spectroscopic techniques, however, are non-destructive and can be implemented noninvasively in vivo. Excess fat (triglycerides) in visceral adipose tissue and liver is known predispose to metabolic abnormalities, collectively known as the metabolic syndrome. Insulin resistance is the likely cause with diets high in saturated fat known to impair insulin sensitivity. Tissue triglyceride composition has been used as marker of dietary intake but it can also be influenced by tissue specific handling of fatty acids. Recent studies have shown that adipocyte insulin sensitivity correlates positively with their saturated fat content, contradicting the common view of dietary effects. A better understanding of factors affecting tissue triglyceride composition is needed to provide further insights into tissue function in lipid metabolism. In this thesis two spectroscopic techniques were developed for in vitro and in vivo analysis of tissue triglyceride composition. In vitro studies (Study I) used infrared spectroscopy (FTIR), a fast and cost effective analytical technique well suited for multivariate analysis. Infrared spectra are characterized by peak overlap leading to poorly resolved absorbances and limited analytical performance. In vivo studies (Studies II, III and IV) used proton magnetic resonance spectroscopy (1H-MRS), an established non-invasive clinical method for measuring metabolites in vivo. 1H-MRS has been limited in its ability to analyze triglyceride composition due to poorly resolved resonances. Using an attenuated total reflection accessory, we were able to obtain pure triglyceride infrared spectra from adipose tissue biopsies. Using multivariate curve resolution (MCR), we were able to resolve the overlapping double bond absorbances of monounsaturated fat and polyunsaturated fat. MCR also resolved the isolated trans double bond and conjugated linoleic acids from an overlapping background absorbance. Using oil phantoms to study the effects of different fatty acid compositions on the echo time behaviour of triglycerides, it was concluded that the use of long echo times improved peak separation with T2 weighting having a negligible impact. It was also discovered that the echo time behaviour of the methyl resonance of omega-3 fats differed from other fats due to characteristic J-coupling. This novel insight could be used to detect omega-3 fats in human adipose tissue in vivo at very long echo times (TE = 470 and 540 ms). A comparison of 1H-MRS of adipose tissue in vivo and GC of adipose tissue biopsies in humans showed that long TE spectra resulted in improved peak fitting and better correlations with GC data. The study also showed that calculation of fatty acid fractions from 1H-MRS data is unreliable and should not be used. Omega-3 fatty acid content derived from long TE in vivo spectra (TE = 540 ms) correlated with total omega-3 fatty acid concentration measured by GC. The long TE protocol used for adipose tissue studies was subsequently extended to the analysis of liver fat composition. Respiratory triggering and long TE resulted in spectra with the olefinic and tissue water resonances resolved. Conversion of the derived unsaturation to double bond content per fatty acid showed that the results were in accordance with previously published gas chromatography data on liver fat composition. In patients with metabolic syndrome, liver fat was found to be more saturated than subcutaneous or visceral adipose tissue. The higher saturation observed in liver fat may be a result of a higher rate of de-novo-lipogenesis in liver than in adipose tissue. This thesis has introduced the first non-invasive method for determining adipose tissue omega-3 fatty acid content in humans in vivo. The methods introduced here have also shown that liver fat is more saturated than adipose tissue fat.
  • Isohanni, Pirjo (2010)
    Childhood-onset mitochondrial diseases comprise a heterogeneous group of disorders, which may manifest with almost any symptom and affect any tissue or organ. Due to challenging diagnostics, most children still lack a specific aetiological diagnosis. The aim of this thesis was to find molecular causes for childhood-onset mitochondrial disorders in Finland. We identified the underlying cause for 25 children, and found three new diseases, which had not been diagnosed in Finland before. These diseases caused severe progressive infantile-onset encephalomyopathies, and were due to defects in mitochondrial DNA (mtDNA) maintenance. Furthermore, the thesis provides the molecular background of Finnish patients with ‘leukoencephalopathy with brain stem and spinal cord involvement and elevated brain lactate’ (LBSL). A new phenotype was identified to be due to mutations in Twinkle, resembling ‘infantile onset spinocerebellar ataxia’ (IOSCA). These mutations caused mtDNA depletion in the liver, thus confirming the essential role of Twinkle in mtDNA maintenance, and expanding the molecular background of mtDNA depletion syndromes. The major aetiology for infantile mitochondrial myopathy in Finland was discovered to be due to mutations in thymidine kinase 2 (TK2). A novel mutation with Finnish ancestry was identified, and a genotype-phenotype correlation with mutation-specific distribution of tissue involvement was found, thus proving that deficient TK2 may cause multi-tissue depletion and impair neuronal function. This work established the molecular diagnosis and advanced the knowledge of phenotypes among paediatric patients with polymerase gamma (POLG) mutations. The patients showed severe early-onset encephalopathy with intractable epilepsy. POLG mutations are not a prevalent cause of children’s ataxias, although ataxia is a major presenting symptom among adults. Our findings indicate that POLG mutations should be investigated even if typical MRI, histochemical or biochemical abnormalities are lacking. LBSL patients showed considerable variation in phenotype despite identical mutations. A common, most likely European, ancestry, and a relative high carrier frequency of these mutations in Finland were discovered; suggesting that LBSL may be a quite common leukoencephalopathy in other populations as well. The results suggest that MRI findings are so unique that the diagnosis of LBSL is possible to make without genetic studies. This thesis work has resulted in identification of new mitochondrial disorders in Finland, enhancing the understanding of the clinical variability and the importance of tissue-specificity of these disorders. In addition to providing specific diagnosis to the patients, these findings give light to the underlying pathogenetic mechanisms of childhood-onset mitochondrial disorders.
  • Koski, Taru (Helsingin yliopisto, 2010)
    Hereditary Leiomyomatosis and Renal Cell Cancer (HLRCC) is a hereditary tumour predisposition syndrome. Its phenotype includes benign cutaneous and uterine leiomyomas (CLM, ULM) with high penetrance and rarer renal cell cancer (RCC), most commonly of papillary type 2 subtype. Over 130 HLRCC families have been identified world-wide but the RCC phenotype seems to concentrate in families from Finland and North America for unknown reasons. HLRCC is caused by heterozygous germline mutations in the fumarate hydratase (FH) gene. FH encodes the enzyme fumarase from mitochondrial citric acid cycle. Fumarase enzyme activity or type or site of the FH mutation are unassociated with disease phenotype. The strongest evidence for tumourigenesis mechanism in HLRCC supports a hypoxia inducible factor driven process called pseudohypoxia resulting from accumulation of the fumarase substrate fumarate. In this study, to assess the importance of gene- or exon-level deletions or amplifications of FH in patients with HLRCC-associated phenotypes, multiplex ligation-dependent probe amplification (MLPA) method was used. One novel FH mutation, deletion of exon 1, was found in a Swedish male patient with an evident HLRCC phenotype with CLM, RCC, and a family history of ULM and RCC. Six other patients with CLM and 12 patients with only RCC or uterine leiomyosarcoma (ULMS) remained FH mutation-negative. These results suggest that copy number aberrations of FH or its exons are an infrequent cause of HLRCC and that only co-occurrence of benign tumour types justifies FH-mutation screening in RCC or ULMS patients. Determination of the genomic profile of 11 HLRCC-associated RCCs from Finnish patients was performed by array comparative genomic hybridization. The most common copy number aberrations were gains of 2, 7, and 17 and losses of 13q12.3-q21.1, 14, 18, and X. When compared to aberrations of sporadic papillary RCCs, HLRCC-associated RCCs harboured a distinct DNA copy number profile and lacked many of the changes characterizing the sporadic RCCs. The findings suggest a divergent molecular pathway for tumourigenesis of papillary RCCs in HLRCC. In order to find a genetic modifier of RCC risk in HLRCC, genome-wide linkage and identical by descent (IBD) analysis studies were performed in Finnish HLRCC families with microsatellite marker mapping and SNP-array platforms. The linkage analysis identified only one locus of interest, the FH gene locus in 1q43, but no mutations were found in the genes of the region. IBD analysis yielded no convincing haplotypes shared by RCC patients. Although these results do not exclude the existence of a genetic modifier for RCC risk in HLRCC, they emphasize the role of FH mutations in the malignant tumourigenesis of HLRCC. To study the benign tumours in HLRCC, genome-wide DNA copy number and gene expression profiles of sporadic and HLRCC ULMs were defined with modern SNP- and gene-expression array platforms. The gene expression array suggests novel genes involved in FH-deficient ULM tumourigenesis and novel genes with putative roles in propagation of sporadic ULM. Both the gene expression and copy number profiles of HLRCC ULMs differed from those of sporadic ULMs indicating distinct molecular basis of the FH-deficient HLRCC tumours.