| 1. |
- Norgren, Nina, 1985-
(författare)
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Hereditary transthyretin amyloidosis (ATTR V30M) : from genes to genealogy
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: Hereditary transthyretin amyloidosis is an autosomal dominant disease with a reduced penetrance. The most common mutation in Sweden is the V30M mutation in the transthyretin gene. Clustering areas of the disease can be found in Northern Sweden, Portugal, Brazil and Japan, although sporadic cases exist worldwide. Despite being caused by the same mutation, there are large differences in onset, penetrance and symptoms of the disease. Swedish V30M patients typically have a later onset with a lower penetrance compared to those from the clustering Portuguese V30M areas. The reasons for these differences have not been fully understood. The aim of this thesis is to study mechanisms that may influence onset and symptoms and investigate why patients carrying the same mutation have different phenotypes.Methods: Genealogy studies were performed on all known V30M carriers in Sweden using standard genealogy methods. DNA samples from patients, asymptomatic carriers and controls from different countries were collected and the transthyretin gene was sequenced. Liver biopsies from patients were used for allele specific expression analysis and a cell assay was used for miRNA analysis with the mutated allele. Gene expression analysis was performed on biopsies from liver and fat from patients and controls.Results and conclusions: Genealogic analysis of all known Swedish V30M carriers managed to link together 73% of the Swedish ATTR V30M population to six different ancestors from the 17th and 18th century, thus dating the Swedish V30M mutation to be more than 400 years old. A founder effect was also visible in descendants to one of the ancestors, producing a later age at onset. Sequencing of the transthyretin gene revealed a SNP in the 3’ UTR of all Swedish V30M carriers that was not found in any of the Japanese or French V30M carriers. The SNP was present on the Swedish transthyretin haplotype and defined the Swedish V30M population as separate from others. However, the SNP itself had no effect upon phenotype or onset of disease. Gene expression analysis of liver and fat tissue revealed a change in genetic profile of the patients’ livers, in contrast to the unchanged profile of the fat tissue. A changed genetic profile of the liver could explain why domino liver recipients develop the disease much earlier than expected.
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| 2. |
- Olsson, Malin, 1972-
(författare)
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Familial amyloidosis with polyneuropathy : studies of genetic factors modifying the phenotype of the disease
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background. Familial Amyloidosis with Polyneuropathy (FAP) is an autosomal dominantly inherited systemic amyloid disease. The disease is caused by mutations in the transthyretin (TTR) gene, where close to 100 different amyloidogenic mutations have been identified. FAP is found worldwide, but endemic areas with a high frequency of patients are found in Portugal, Japan and northern Sweden. Cases from these endemic areas all share the same TTR c.148G>A, p.V50M ("V30M") mutation, but the phenotype of the disease varies between the areas, and also within the endemic areas. The mean onset of the disease is two decades earlier in Portugal and Japan compared to Sweden, but late as well as early age at onset cases occur within all the populations. Interestingly, the different populations all display a maternal anticipation, where an earlier onset is observed for those individuals who inherit the trait from their mother. Since substantial variation in the phenotype is observed for different populations, epigenetic/genetic and/or environmental factors must exert a significant impact on the penetrance of the disease. Amyloid formation is caused by conformational changes of proteins, which facilitates their assembly into fibrils, amyloid. Oxidative stress can mediate conformational changes of proteins and since the mitochondria regulate oxidative processes within the cell, mitochondrial function may affect amyloid formation. The mitochondrial DNA is a non-nuclear DNA, which is entirely maternally inherited, and therefore could be related to the observed maternal anticipation of the disease. In addition, differences within the surrounding regions of the TTR gene may have an impact on the transcription of the gene and thereby on the expression of the different alleles. Material and methods. DNA from early and late onset V30M cases and from non-carriers (the latter utilised as controls) from Swedish, French, Japanese and Portuguese populations were analysed. In addition, DNA from healthy Swedish V30M carriers was analysed. Conventional analytical methods were employed, such as PCR, sequencing and genotyping. Conventional statistical methods used were t-test, Chi-squared test and maximum likelihood. Results. The study of V30M carrier frequency in two counties (Lycksele and Skellefteå) within the Swedish endemic area revealed a carrier frequency of 2.14% and 2.54%, respectively. The mitochondrial haplogroup analysis showed that in populations with generally late onset (French and Swedish), the haplogroup distribution of late onset cases resembled that of the controls derived from the same area, whereas haplogroup distribution for early onset patients was significantly different. The most pronounced difference was for the rare haplogroup K, of which early onset cases had a higher frequency than the controls. Analysis of the Portuguese population, with predominantly early onset, showed that haplogroup distribution for early onset cases were similar to the Portuguese control group, which had a different distribution than the Swedish control group. By analysis of pedigrees from Swedish and Portuguese patients it could be shown that mitochondrial genetic variation entirely could explain maternal anticipation in the Portuguese patients, whereas for Swedish patients, an additional parent of origin effect is present. Our analysis of the TTR gene disclosed a polymorphism (rs62093482) in the 3'UTR region of the Swedish patients. This polymorphism was found in all V30M carriers, irrespective of symptoms. In addition, homozygous TTR V30M carriers were homozygous also for the polymorphism. Since Swedish patients share a common founder this polymorphism thus is localised on the V30M allele. This polymorphism was found in only 4% of the Swedish controls. French controls showed the same frequency, but none of the French V30M patients displayed the polymorphism. In the Japanese population the polymorphism was not present at all. Interestingly, this polymorphism generates a potential binding site for microRNA and thereby possibly could down-regulate the expression of the mutated TTR allele. Conclusions. The carrier frequency in the endemic area is remarkably high, above 2% in the Lycksele and Skellefteå areas. The prevailing haplogroup distributions in the different endemic areas are consistent between the general population and the patient group with the predominant phenotype of that area. Mitochondrial genetic differences may explain maternal anticipation in Portuguese patients, and have an influence in Swedish patients. A polymorphism in the 3'UTR regulatory region of the mutated TTR allele is found in all Swedish patients. This polymorphism may down-regulate TTR V30M expression and thereby contribute to the late onset of the disease noted in the Swedish population.
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| 3. |
- Heldestad, Victoria, 1970-
(författare)
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Methodological aspects and usefulness of Quantitative Sensory Testing in early small fiber polyneuropathy : a clinical study in Swedish hereditary transthyretin amyloidosis patients
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Generalised polyneuropathy (PNP) is a common cause to neurological impairment, and may be an early symptom of a severe systemic disease. One such illness is hereditary transthyretin (TTR) amyloidosis (ATTR), a progressive fatal disorder caused by a mutation on the TTR gene. More than 100 such mutations have been found worldwide, of which Val30Met is the most common neuropathic variant with initial clinical manifestations indicating small fiber impairment. Differences in onset age, penetrance and phenotypes are present between endemic areas. Liver transplantation generally slows the progress of the symptom development, especially in patients with short disease duration. Ongoing research has also shown promising results with drug interventions. In any event, early diagnosis of PNP onset in ATTR patients is crucial to ensure early therapeutic interventions. Nerve conduction studies (NCS) and electromyography (EMG) provide the basis for evaluation of the functional state of the thick myelinated nerve fibres in patients with symptoms of PNP, but no such quantitative methods are available for the thin myelinated or unmyelinated fibers. Instead, a psychophysical method with thermal quantitative sensory testing (QST) can provide indirect information about the overall function in the afferent small fiber systems. The purpose of thesis was to evaluate the applicability of QST by the Method-of-limits (MLI) for early detection of PNP in Swedish ATTR patients with the Val30Met mutation. In healthy subjects the repeatability of the MLI was assessed, and reference values for thermal perception thresholds (TPT) in several body regions were determined. No significant differences in TPT or pain thresholds were found at repeated testing with MLI, indicating that the MLI is a reliable method. However, the results show that the arrangement of the testing order is of importance, as cold (CT) and warm (WT) perception thresholds were significantly elevated when tested after thermal pain assessments, instead of before. I general, the TPT was more elevated at lower parts of the body compared to the upper part, and with higher WT than CT, fully in accordance with the underlying anatomical and physiological prerequisites for QST. In biopsy verified ATTR patients lacking EMG and NCS abnormalities, significantly elevated TPT were found compared to controls. Furthermore, significantly more increased TPT were observed in patients with an early onset of the disease, compared those with a late onset. Finally, a combined detailed evaluation of QST and heart rate variability (HRV) analyses demonstrated correlations between QST and HRV abnormalities in patients with late onset, but not in those with early onset. The present thesis emphasizes the importance of incorporating QST early in the clinical evaluation of ATTR patients with a Val30Met mutation and with symptoms of thin fiber PNP. This is particularly indicated when patients report symptoms, or show signs, of neuropathic small fiber affection, but simultaneously exhibit normal EMG and NCS findings. The results furthermore underline the importance of performing both QST and HRV for a complete evaluation of both the thin somatic and autonomic nerve fibers, as both types of nerves may be affected early in the ATTR disease.
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| 4. |
- Wixner, Jonas, 1980-
(författare)
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Gastrointestinal disturbances in hereditary transthyretin amyloidosis
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- BackgroundTransthyretin amyloid (ATTR) amyloidosis is a systemic disorder caused by amyloid deposits formed by misfolded transthyretin (TTR) monomers. Two main forms exist – wild-type and hereditary ATTR amyloidosis, the latter associated with TTR gene mutations. Wild-type ATTR amyloidosis has a late onset and primarily cardiac manifestations, whereas hereditary ATTR amyloidosis is a rare autosomal dominant condition with a considerable phenotypic diversity. Both disorders are present all over the world, but endemic areas of the hereditary form are found in Sweden, Portugal, Brazil and Japan. Gastrointestinal (GI) complications are common in hereditary ATTR amyloidosis and play an important role in the patients’ morbidity and mortality. Malfunction of the autonomic and enteric nervous systems has been proposed to contribute to the GI disturbances, but the underlying mechanisms have not been fully elucidated. The aims of this thesis were to assess the prevalence of GI disturbances for different subtypes of ATTR amyloidosis, to further explore the mechanisms behind these disturbances, and to evaluate the outcome of the patients’ GI function after liver transplantation, which currently is the standard treatment for hereditary ATTR amyloidosis.MethodsThe Transthyretin Amyloidosis Outcomes Survey (THAOS) is the first global, multicenter, longitudinal, observational survey that collects data on patients with ATTR amyloidosis. THAOS enrollment data were used to assess the prevalence of GI symptoms and to evaluate their impact on nutritional status (mBMI) and health-related quality of life (EQ-5D Index Score). Data from routine investigations of heart-rate variability and cardio-vascular response to tilt tests were utilized to evaluate the impact of autonomic neuropathy on the scintigraphically measured gastric emptying half-times in Swedish patients with hereditary ATTR amyloidosis. Gastric wall autopsy specimens from Japanese patients with hereditary ATTR amyloidosis and Japanese non-amyloidosis controls were analyzed with immunohistochemistry and computerized image analysis to assess the densities of interstitial cells of Cajal (ICC) and nervous tissue. Data from gastric emptying scintigraphies and validated questionnaires were used to evaluate the outcome of Swedish patients’ GI function after liver transplantation for hereditary ATTR amyloidosis.ResultsSixty-three percent of the patients with TTR mutations and 15 % of those with wild-type ATTR amyloidosis reported GI symptoms at enrollment into THAOS. Subsequent analyses focused on patients with TTR mutations and, among them, unintentional weight loss was the most frequent symptom (32 %) followed by early satiety (26 %). Early-onset patients (<50 years of age) reported GI symptoms more frequently than late-onset cases (70 % vs. 50 %, p <0.01), and GI symptoms were more common in patients with the V30M mutation than in those with non-V30M mutations (69 % vs. 56 %, p <0.01). Both upper and lower GI symptoms were significant negative predictors of nutritional status and health-related quality of life (p <0.01 for both). Weak but significant correlations were found between gastric emptying half-times and the function of both the sympathetic (rs = -0.4, p <0.01) and parasympathetic (rs = -0.3, p <0.01) nervous systems. The densities of c-Kit-immunoreactive ICC were significantly lower in the circular (median density 0.0 vs. 2.6, p <0.01) and longitudinal (median density 0.0 vs. 1.8, p <0.01) muscle layers of the gastric wall in patients compared to controls. Yet, no significant differences in protein gene product 9.5-immunoreactive nervous cells were found between patients and controls either in the circular (median density 3.0 vs. 6.8, p = 0.17) or longitudinal (median density 1.4 vs. 2.5, p = 0.10) muscle layers. Lastly, the patients’ GI symptoms scores had increased slightly from before liver transplantation to the follow-ups performed in median two and nine years after transplantation (median score 7 vs. 10 vs. 13, p <0.01). However, their gastric emptying half-times (median half-time 137 vs. 132 vs. 125 min, p = 0.52) and nutritional statuses (median mBMI 975 vs. 991 vs. 973, p = 0.75) were maintained at follow-ups in median two and five years after transplantation.ConclusionGI disturbances are common in hereditary ATTR amyloidosis and have a negative impact on the patients’ nutritional status and health-related quality of life. Fortunately, a liver transplantation appears to halt the progressive GI involvement of the disease, although the patients’ GI symptoms tend to increase after transplantation. An autonomic neuropathy and a depletion of gastrointestinal ICC seem to contribute to the GI disturbances, but additional factors must be involved.
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