Karin Axelman

A mutation in Alzheimer's disease destroying a splice acceptor site in the presenilin-1 gene

A series of mutations has been reported in the presenilin-1 (PS-1) gene which cause early onset Alzheimers disease (AD). The mutations reported to date have encoded missense mutations which alter residues conserved between PS-1 and the presenilin-2 (PS-2) gene. We have recently determined the intron/exon structure of the PS-1 gene and this information has been used to identify a mutation in the splice acceptor site for exon 9 in a family with early onset AD. Amplification of cDNA from lymphoblasts of affected individuals revealed that the effect of the mutation was to cause splicing out of exon 9, however it does not change the open reading frame of the mRNA. The importance of this observation is discussed.

Amyloid precursor protein mutation causes Alzheimer's disease in a Swedish family

Since the report of a double mutation at codons 670 and 671 of the amyloid precursor protein (APP) gene identified in two Swedish families with clinically diagnosed Alzheimers disease (AD), a carrier with dementia has died. Neuropathology confirmed the clinical diagnosis of AD. Genealogical investigations have confirmed that the two families are related to common founders. Two-point linkage analysis of the mutation versus the disease in the revised pedigree now gives a lod score of 7.62.

Mapping of a disease locus for familial rapidly progressive frontotemporal dementia to chromosome 17q12-21

Familial frontotemporal dementia (FTD) is a complex disorder with lack of distinctive histopathological markers found in other types of dementia. Most of the linkage reports from FTD families map the disease loci to chromosome 17q21-22. However, FTD is genetically heterogeneous, as linkage also has been reported to chromosome 3. In the present study, we investigated the genetics of a Swedish family with an early-onset type of rapidly progressive FTD, associated with muscular rigidity and akinetic movements. Neuropathological features such as severe frontal lobe degeneration, spongy changes, and gliosis were present in affected family members. We here report probable linkage to chromosome 17q12-21 with a maximum two-point lod score of 2.76 at theta = 0 for marker D17S806, and a peak multipoint lod score of 2.86 for the same marker. Linkage to chromosome 3 was excluded, as two-point lod scores of -2.79, and -2.27 at theta = 0.01 for markers D3S1603 and D3S1552, respectively, were obtained. Sequencing of the translated exons of a strong candidate gene in the linked region of chromosome 17, the tau gene, failed to identify any mutations segregating with the disease.

Interaction between estrogen receptor 1 and the ε4 allele of apolipoprotein E increases the risk of familial Alzheimer's disease in women

Estrogens may be implicated in the development of Alzheimers disease (AD). Most of their effects are mediated via receptors whose function and expression may be modified by DNA polymorphisms. Here the estrogen receptor 1 gene (ESR1) polymorphisms XbaI and PvuII were analyzed in 214 AD patients and 290 controls. In logistic regression analysis, a significantly increased risk of familial AD due to interaction between the ESR1 xx genotype and the apolipoprotein E epsilon4 allele was observed in women in a Swedish clinic-based sample, taking subjects who had neither the xx genotype nor epsilon4 as reference (OR 11.3, 95% CI 2.9-43.8). The risk of AD was more pronounced in early-onset (OR 22.0, 95% CI 3. 7-132.7) than in late-onset (OR 6.0, 95% CI 1.2-29.7) female patients. For women carrying the pp genotype together with epsilon4 the risk of AD was similarly elevated. Likewise in a Swedish community-based set of women, an increased risk of familial AD was observed in subjects who had either the ESR1 xx or pp genotype together with epsilon4. Furthermore, the Pp genotype frequency was found to be significantly increased in Finnish women with sporadic AD. We, thus, conclude that the ESR1 gene may have a role in the development of AD in females.

Clinical and Neuropathological Features of the Arctic APP Gene Mutation Causing Early-Onset Alzheimer Disease

BACKGROUND A majority of mutations within the beta-amyloid region of the amyloid precursor protein (APP) gene cause inherited forms of intracerebral hemorrhage. Most of these mutations may also cause cognitive impairment, but the Arctic APP mutation is the only known intra-beta-amyloid mutation to date causing the more typical clinical picture of Alzheimer disease. OBJECTIVE To describe features of 1 Swedish and 1 American family with the previously reported Arctic APP mutation. DESIGN, SETTING, AND PARTICIPANTS Affected and nonaffected carriers of the Arctic APP mutation from the Swedish and American families were investigated clinically. In addition, 1 brain from each family was investigated neuropathologically. RESULTS The clinical picture, with age at disease onset in the sixth to seventh decade of life and dysfunction in multiple cognitive areas, is indicative of Alzheimer disease and similar to the phenotype for other Alzheimer disease APP mutations. Several affected mutation carriers displayed general brain atrophy and reduced blood flow of the parietal lobe as demonstrated by magnetic resonance imaging and single-photon emission computed tomography. One Swedish case and 1 American case with the Arctic APP mutation came to autopsy, and both showed no signs of hemorrhage but revealed severe congophilic angiopathy, region-specific neurofibrillary tangle pathological findings, and abundant amyloid plaques. Intriguingly, most plaques from both of these cases had a characteristic ringlike character. CONCLUSIONS Overall, our findings corroborate that the Arctic APP mutation causes a clinical and neuropathological picture compatible with Alzheimer disease.

Tau gene polymorphisms and apolipoprotein E ε4 may interact to increase risk for Alzheimer’s disease

Abstract In an effort to analyze the genetic role of tau in Alzheimers disease (AD), 17 polymorphisms were identified. Eleven of these polymorphisms were in complete linkage disequilibrium and segregated as two haplotypes, A and B. The A and B haplotypes were investigated in 269 AD cases and 238 controls from two different sources, a clinic-based group (mean age of onset 65±9 years), and a population-based group (mean age of onset 80±5 years). A synergistic effect between the common tau genotype AA and apolipoprotein E (APOE e4) was found in the clinic-based AD group. Our study suggests that the common tau genotype AA may interact with APOE e4 in increasing the risk of AD in a subgroup of the AD population.

Investigations of a CA repeat in the oestrogen receptor beta gene in patients with Alzheimer's disease.

Several studies have shown that oestrogen treatment after menopause decreases the risk for Alzheimers disease (AD). It is also known that oestrogen stimulates the outgrowth of nerve cells and that apolipoprotein E (Apo E) synthesis and amyloid precursor protein (APP) metabolism are regulated by oestrogen. Recently a new oestrogen receptor was identified, oestrogen receptor β (ERβ), located at chromosome 14q22-24. Several genes close to this chromosomal region have been implicated in AD, but the results are conflicting. Our hypothesis was that variations in the ERβ gene could be the underlying cause to the positive findings in these genes and we have therefore investigated a CA repeat1 in intron 5 of the ERβ gene. Three hundred and thirty-six AD cases and 110 healthy age-matched controls were included in this study. Fourteen different alleles were found with frequencies between 0.1 and 37%. There was no significant difference between AD cases and controls when all alleles were compared. However, allele 5 was seen in 13.6% of the controls but only in 8.0% of AD cases (P=0.014; odds ratio (OR)=0.55). No AD patient homozygous for this allele was seen but three controls were homozygous. In conclusion, our findings suggest the ERβ allele 5 to be a protective factor. However, this has to be confirmed in a larger population.

Glucose metabolism and PIB binding in carriers of a His163Tyr presenilin 1 mutation

Six young related pre-symptomatic carriers of a His163Tyr mutation in the presenilin 1 gene who will develop early onset familial Alzheimers disease (eoFAD), and a control group of 23 non-carriers underwent (18)F-fluorodeoxyglucose positron emission tomography (FDG PET). The mutation carriers were followed-up after 2 years. Multivariate analysis showed clear separation of carriers from non-carriers on both occasions, with the right thalamus being the region contributing most to group differentiation. Statistical parametric mapping (SPM) revealed in the carriers non-significantly lower thalamic cerebral glucose metabolism (CMRglc) at baseline and significantly decreased CMRglc in the right thalamus at follow-up. One mutation carrier was followed-up with FDG PET 10 years after baseline and showed reductions in cognition and CMRglc in the posterior cingulate and the frontal cortex. This subject was diagnosed with AD 1 year later and assessed with an additional FDG as well as an (11)C-PIB PET scan 12 years after baseline. Global cortical CMRglc and cognition were distinctly decreased. PIB binding was comparable with sporadic AD patterns but showing slightly higher striatal levels.

Genome scan on Swedish Alzheimer's disease families

Alzheimers disease (AD) is an age-related disease, which affects approximately 40% of the population at an age above 90 years. The heritability is estimated to be greater than 60% and there are rare autosomal dominant forms indicating a significant genetic influence on the disease process. Despite the successes in the early 1990s when four genes were identified, which directly cause the disease (APP, PSEN1 and PSEN2) or greatly increase the risk of disease development (APOE), it has proved exceedingly difficult to identify additional genes involved in the pathogenesis. However, several linkage and association studies have repeatedly supported the presence of susceptibility genes on chromosomes (chrms) 9, 10 and 12. The study populations have, however, mostly been of great genetic heterogeneity, and this may have contributed to the meagre successes in identifying the disease associated genetic variants. In this study, we have performed a genome wide linkage study on 71 AD families from the relatively genetically homogeneous Swedish population where it is also possible to study the genetic ancestry in public databases. We have performed nonparametric linkage analyses in the total family material as well as stratified the families with respect to the presence or absence of APOE ɛ4. Our results suggest that the families included in this study are tightly linked to the APOE region, but do not show evidence of linkage to the previously reported linkages on chrms 9, 10 and 12. Instead, we observed the next highest LOD score on chromosome 5q35 in the total material. Further, the data suggest that the major fraction of families linked to this region is APOE ɛ4 positive.

A Follow-Up Study of the Family with the Swedish APP 670/671 Alzheimer’s Disease Mutation

Objective: To study the progression of Alzheimer’s disease (AD) at a very early stage and to evaluate clinical markers of presymptomatic AD. Setting: Longitudinal study at a university hospital. Subjects: A Swedish family harboring a double mutation at codons 670/671 of the APP gene on chromosome 21 was followed longitudinally for 3 years. Both mutation carriers and noncarriers participated. Outcome Measurements: Results from clinical investigations, electroencephalography, neuropsychological and neuroradiological examinations including magnetic resonance imaging, single-photon emission computed tomography and positron emission tomography were assessed and compared on two or more occasions. Main Outcome: During follow-up, 1 initially asymptomatic mutation carrier who was near the expected age of onset for this family, developed cognitive symptoms, and at the end of the follow-up fulfilled the diagnostic criteria for AD. One mutation carrier with cognitive symptoms at the first examination showed clinical deterioration and was diagnosed with AD. One demented mutation carrier died and was shown to have typical AD neuropathology at autopsy. The two remaining asymptomatic mutation carriers, as well as all the noncarriers were asymptomatic. These mutation carriers who were near the expected age of onset of AD but without clinical signs of the disease, did not show changes in either electrophysiological parameters or volumes of the temporal lobes. However, in these 2 individuals the blood flow in the temporal lobe showed intermediate values between the symptomatic mutation carriers and healthy noncarriers. Two neuropsychological tests showed a deterioration that paralleled clinical symptoms in 1 of the mutation carriers who was close to the expected age of onset and who at the end of the follow-up had clinical signs of AD. In the same subject, brain glucose metabolism was pathologically reduced in the temporal lobes before other clinical symptoms were obvious. Conclusion: In this familial form of AD a reduced temporal lobe glucose metabolism was indicative of AD before the expected clinical onset. Reduced glucose metabolism even preceded the development of subjective or objective cognitive dysfunction and might therefore serve as a clinical marker for AD before the onset of clinical symptoms. Reduced cerebral blood flow in the temporal lobes and cognitive deterioration paralleled the clinical decline in the early stage of the disease.