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Genome-wide linkage studies have defined a broad susceptibility region for late-onset Alzheimer's disease on chromosome 12, which contains the Low-Density Lipoprotein Receptor-Related Protein 6 (LRP6) gene, a coreceptor for Wnt signaling. Here, we report the association between common LRP6 variants and late-onset Alzheimer's disease in a multicenter case-control series as well as in a large family-based series ascertained by the National Institute of Mental Health-National Institute on Aging Genetics Initiative. As shown in the genome-wide linkage studies, our association depends mainly on apolipoprotein E-epsilon4 (APOE-epsilon4) carrier status. Haplotype tagging single-nucleotide polymorphisms (SNPs) with a set of seven allelic variants of LRP6 identified a putative risk haplotype, which includes a highly conserved coding sequence SNP: Ile-1062 --> Val. Functional analyses revealed that the associated allele Val-1062, an allele previously linked to low bone mass, has decreased beta-catenin signaling in HEK293T cells. Our study unveils a genetic relationship between LRP6 and APOE and supports the hypothesis that altered Wnt/beta-catenin signaling may be involved in this neurodegenerative disease.

Objective: While the apolipoprotein E (APOE) epsilon allele is a well-established risk factor for late-onset Alzheimer's disease (AD), initial genome scans using microsatellite markers in late-onset AD failed to identify this locus on chromosome 19. Recently developed methods for the simultaneous assessment of hundreds of thousands of single nucleotide polymorphisms (SNPs) promise to help more precisely identify loci that contribute to the risk of AD and other common multigenic conditions. We sought here to demonstrate that more precise identification of loci that are associated with complex, multi-genic genetic disorders can be achieved using ultra-high-density whole-genome associations by demonstrating their ability to identify the APOE locus as a major susceptibility gene for late-onset AD, despite the absence of SNPs within the APOE locus itself, as well as to refine odds ratios (ORs) based on gold-standard phenotyping of the study population., Method: An individualized genome-wide association study using 502,627 SNPs was performed in 1086 his-topathologically verified AD cases and controls to determine the OR associated with genes predisposing to Alzheimer's disease., Results: As predicted, ultra-high-density SNP genotyping, in contrast to traditional microsatellite-based genome screening approaches, precisely identified the APOE locus as having a significant association with late-onset AD. SNP rs4420638 on chromosome 19, located 14 kilobase pairs distal to the APOE epsilon variant, significantly distinguished between AD cases and controls (Bonferroni corrected p value = 5.30 x 10(-34), OR = 4.01) and was far more strongly associated with the risk of AD than any other SNP of the 502,627 tested., Conclusion: This study provides empirical support for the suggestion that the APOE locus is the major susceptibility gene for late-onset AD in the human genome, with an OR significantly greater than any other locus in the human genome. It also supports the feasibility of the ultra-high-density whole-genome association approach to the study of AD and other heritable phenotypes. These whole-genome association studies show great promise to identify additional genes that contribute to the risk of AD.

We report the development and validation of experimental methods, study designs, and analysis software for pooling-based genomewide association (GWA) studies that use high-throughput single-nucleotide-polymorphism (SNP) genotyping microarrays. We first describe a theoretical framework for establishing the effectiveness of pooling genomic DNA as a low-cost alternative to individually genotyping thousands of samples on high-density SNP microarrays. Next, we describe software called "GenePool," which directly analyzes SNP microarray probe intensity data and ranks SNPs by increased likelihood of being genetically associated with a trait or disorder. Finally, we apply these methods to experimental case-control data and demonstrate successful identification of published genetic susceptibility loci for a rare monogenic disease (sudden infant death with dysgenesis of the testes syndrome), a rare complex disease (progressive supranuclear palsy), and a common complex disease (Alzheimer disease) across multiple SNP genotyping platforms. On the basis of these theoretical calculations and their experimental validation, our results suggest that pooling-based GWA studies are a logical first step for determining whether major genetic associations exist in diseases with high heritability.

Human memory is a polygenic trait. We performed a genome-wide screen to identify memory-related gene variants. A genomic locus encoding the brain protein KIBRA was significantly associated with memory performance in three independent, cognitively normal cohorts from Switzerland and the United States. Gene expression studies showed that KIBRA was expressed in memory-related brain structures. Functional magnetic resonance imaging detected KIBRA allele-dependent differences in hippocampal activations during memory retrieval. Evidence from these experiments suggests a role for KIBRA in human memory.

The role of mitochondrial dysfunction in the pathogenesis of Alzheimer's disease (AD) has been well documented. Though evidence for the role of mitochondria in AD seems incontrovertible, the impact of mitochondrial DNA (mtDNA) mutations in AD etiology remains controversial. Though mutations in mitochondrially encoded genes have repeatedly been implicated in the pathogenesis of AD, many of these studies have been plagued by lack of replication as well as potential contamination of nuclear-encoded mitochondrial pseudogenes. To assess the role of mtDNA mutations in the pathogenesis of AD, while avoiding the pitfalls of nuclear-encoded mitochondrial pseudogenes encountered in previous investigations and showcasing the benefits of a novel resequencing technology, we sequenced the entire coding region (15,452 bp) of mtDNA from 19 extremely well-characterized AD patients and 18 age-matched, unaffected controls utilizing a new, reliable, high-throughput array-based resequencing technique, the Human MitoChip. High-throughput, array-based DNA resequencing of the entire mtDNA coding region from platelets of 37 subjects revealed the presence of 208 loci displaying a total of 917 sequence variants. There were no statistically significant differences in overall mutational burden between cases and controls, however, 265 independent sites of statistically significant change between cases and controls were identified. Changed sites were found in genes associated with complexes I (30.2%), III (3.0%), IV (33.2%), and V (9.1%) as well as tRNA (10.6%) and rRNA (14.0%). Despite their statistical significance, the subtle nature of the observed changes makes it difficult to determine whether they represent true functional variants involved in AD etiology or merely naturally occurring dissimilarity. Regardless, this study demonstrates the tremendous value of this novel mtDNA resequencing platform, which avoids the pitfalls of erroneously amplifying nuclear-encoded mtDNA pseudogenes, and our proposed analysis paradigm, which utilizes the availability of raw signal intensity values for each of the four potential alleles to facilitate quantitative estimates of mtDNA heteroplasmy. This information provides a potential new target for burgeoning diagnostics and therapeutics that could truly assist those suffering from this devastating disorder.

The role of iron metabolism in Alzheimer's disease (AD) is well documented. Regulation of the proteins that maintain cellular iron metabolism is mediated by two cytoplasmic RNA-binding proteins, the Iron Regulatory Proteins (IRP1 and IRP2), that function through post-transcriptional interactions with RNA stem loop structures called iron-responsive elements. As the primary mediator of iron homeostasis in neuronal cells, IRP2 is a strong candidate for polymorphisms that could impact AD pathogenesis. Thus, we performed a pilot study to assess polymorphisms in the gene encoding IRP2 (IREB2) on clinically well-characterized, post-mortem samples (50 AD and 50 controls). DNA sequence analysis of the IREB2 gene region revealed 14 polymorphisms. Two (rs2656070 and rs13180) showed statistically significant skewing of allelic and genotypic distributions between AD patients and controls. In silico analyses revealed that rs2656070 lies within a probable promoter and disrupts the binding sites of at least two known transcription factors. Though silent and likely not functionally relevant, rs13180 is in complete LD with rs2656070 (D' > 0.999), creating an IREB2-haplotype that is significantly associated with AD. Confirmation of this association in a larger cohort of cases and controls would further support the role of iron regulation in the pathogenesis of this catastrophic and increasingly common neurodegenerative disorder.

A recent study demonstrated a significant genetic association between the ATP-binding cassette transporter A2 (ABCA2) and the risk for Alzheimer's disease (AD) in a large Caucasian sample. The rare T allele of the synonymous exonic single nucleotide polymorphism (SNP) rs908832 was overrepresented in early-onset AD patients as compared to cognitively healthy controls. Here we confirm the association of rs908832 with AD in a Western European population (n = 291, P = 0.008). In a second sample from Southern Europe, rs908832 was not associated with AD. Interestingly, rs908832 was not polymorphic in a Japanese sample. Furthermore, rs908832 was not associated with either serum cholesterol levels or with the risk for coronary artery disease, but seemed to be related to cholesterol levels in the cerebrospinal fluid. These data suggest that ABCA2 may exert population-dependent effects on the genetic risk for sporadic AD and support a role of ABC lipid transporters in the pathogenesis of this disease., ((c) 2006 Wiley-Liss, Inc.)

Objective: To provide an updated overview of the methods used in genetic, transcriptomic, and proteomic studies in Alzheimer's disease and to demonstrate the importance of those methods for the improvement of the current diagnostic and therapeutic possibilities., Data Sources: MEDLINE-based search of 233 peer-reviewed articles published between 1975 and 2006., Data Synthesis: Alzheimer's disease is a genetically heterogeneous disorder. Rare mutations in the amyloid precursor protein, presenilin 1, and presenilin 2 genes have shown the importance of the amyloid metabolism for its development. In addition, converging evidence from population-based genetic studies, gene expression studies, and protein profile studies in the brain and in the cerebrospinal fluid suggest the existence of several pathogenetic pathways such as amyloid precursor protein processing, beta-amyloid degradation, tau phosphorylation, proteolysis, protein misfolding, neuroinflammation, oxidative stress, and lipid metabolism., Conclusions: The development of high-throughput genotyping methods and of elaborated statistical analyses will contribute to the identification of genetic risk profiles related to the development and course of this devastating disease. The integration of knowledge derived from genetic, transcriptomic, and proteomic studies will greatly advance our understanding of the causes of Alzheimer's disease, improve our capability of establishing an early diagnosis, help define disease subgroups, and ultimately help to pave the road toward improved and tailored treatments.

Experimental work in animals has shown that memory formation depends on a cascade of molecular events. Here we show that variability of human memory performance is related to variability in genes encoding proteins of this signaling cascade, including the NMDA and metabotrobic glutamate receptors, adenylyl cyclase, CAMKII, PKA, and PKC. The individual profile of genetic variability in these signaling molecules correlated significantly with episodic memory performance (P < 0.00001). Moreover, functional MRI during memory formation revealed that this genetic profile correlated with activations in memory-related brain regions, including the hippocampus and parahippocampal gyrus. The present study indicates that genetic variability in the human homologues of memory-related signaling molecules contributes to interindividual differences in human memory performance and memory-related brain activations.

Background: Colony-stimulating factor 1 (CSF1) regulates the proliferation and differentiation of myelomonocytic cells. Microglial cells of CSF1-deficient mice are reduced in number and are functionally impaired. CSF1-deficient mice exhibit subtle neurodevelopmental defects, enhanced neuronal vulnerability. Moreover, it has been reported that these mice may have amyloid-plaque-like depositions in the brain at an early age. The human CSF1 gene maps to chromosome 1p21-p13, a region previously linked to Alzheimer's disease (AD). Thus, CSF1 is a functional and positional candidate gene for AD., Objective: We assessed if genetic variability of CSF1 may influence the risk for AD., Methods: We conducted a population-based case-control association study with 3 single nucleotide polymorphisms (SNPs) across the CSF1 locus in a sample of n = 185 (rs3093054, rs756325) and n = 327 (rs1058885) individuals., Results: None of the 3 investigated SNPs was associated with the risk for AD in our sample., Conclusion: These data do not support the hypothesis that genetic variability of CSF1 influences the risk for AD., (Copyright 2006 S. Karger AG, Basel.)

Human cognitive processes are highly variable across individuals and are influenced by both genetic and environmental factors. Although genetic variations affect short-term memory in humans, it is unknown whether genetic variability has also an impact on long-term memory. Because prion-like conformational changes may be involved in the induction of long-lasting synaptic plasticity, we examined the impact of single-nucleotide polymorphisms (SNPs) of the prion protein gene (PRNP) on long-term memory in healthy young humans. SNPs in the genomic region of PRNP were associated with better long-term memory performance in two independent populations with different educational background. Among the examined PRNP SNPs, the common Met129Val polymorphism yielded the highest effect size. Twenty-four hours after a word list-learning task, carriers of either the 129MM or the 129MV genotype recalled 17% more information than 129VV carriers, but short-term memory was unaffected. These results suggest a role for the prion protein in the formation of long-term memory in humans.

Objective: Polygenic diseases are related to the complex interplay of genetic variations. We evaluated whether clusters of cholesterol- and lipid-related genetic variations are associated with Alzheimer's disease., Method: We analyzed 12 cholesterol-related single nucleotide polymorphisms and 48 control polymorphisms in 545 study participants (Alzheimer's disease group N = 284; control group N = 261). Diagnoses of Alzheimer's disease were made according to the NINCDS-ADRDA criteria. Multi-locus genetic association analysis was done with the set-association method. Dates of data collection were from January 2000 to December 2003., Results: We identified a cluster of polymorphisms in APOE, SOAT1, APOE 5'-untranslated region, OLR1, CYP46A1, LPL, LIPA, and APOA4 conferring significant (p = .0002) susceptibility for Alzheimer's disease. This gene cluster reached a diagnostic accuracy of 74% and correlated significantly (p = .018) with the levels of the brain cholesterol catabolite 24S-hydroxycholesterol in the cerebrospinal fluid., Conclusion: Our results establish a novel approach for the identification of disease-related genetic clusters and demonstrate the need for multi-locus methods in the genetics of complex diseases.

A polymorphism (His452Tyr) of the 5-hydroxytryptamine (5-HT)2a receptor is associated with episodic memory in healthy young humans. Because 5-HT2a-receptor density decreases with increasing age, we tested whether the 5-HT2a receptor genotype effect on memory is influenced by age. We investigated the association of the His452Tyr genotype with memory performance in 622 healthy study participants aged from 18 to 90 years. In young to middle-aged participants, age significantly influenced genotype effects on episodic memory: the His452Tyr genotype exerted a significant influence on memory only in young participants. In the group of elderly cognitively healthy participants, the His452Tyr genotype did not affect memory performance. We conclude that age strongly modulates the effect of the 5-HT2a receptor polymorphism at residue 452 on episodic memory.

A 30 cM broad genomic region on the long arm of chromosome 10 at 80 cM shows significant and consistent linkage with AD and with plasma concentration of the beta-amyloid peptide 1-42 (Abeta42). The PLAU gene, which is involved in the production and degradation of Abeta42, maps to that region and is therefore a strong positional candidate for association with sporadic AD. We analyzed the non-synonymous single nucleotide polymorphism (SNP) rs2227564 in two independent case-control series from Switzerland and Greece and investigated the influence of this SNP on cognition in elderly individuals. Because PLAU modulates the cleavage of the amyloid precursor protein (APP) and the degradation of Abeta, we also determined the levels of Abeta in the brain, plasma and in the cerebrospinal fluid (CSF). We found no evidence for association of this SNP with AD or with AD-related traits such as beta-amyloid load in the medial temporal lobe or Abeta42 concentration in the CSF and in plasma. Our findings do not support a major role of PLAU polymorphisms as susceptibility factors for AD and suggest that large-scale association studies which combine genetic information from populations with similar genetic background might prevent the generation of spurious associations. Although PLAU may be pathophysiologially related to AD, the contribution of common genetic variants of this gene to the risk for developing AD is likely to be low., (Copyright 2004 Wiley-Liss, Inc.)

Alzheimer's disease (AD) is the most common cause of dementia. It is characterized by beta-amyloid (A beta) plaques, neurofibrillary tangles and the degeneration of specifically vulnerable brain neurons. We observed high expression of the cholesterol 25-hydroxylase (CH25H) gene in specifically vulnerable brain regions of AD patients. CH25H maps to a region within 10q23 that has been previously linked to sporadic AD. Sequencing of the 5' region of CH25H revealed three common haplotypes, CH25Hchi2, CH25Hchi3 and CH25Hchi4; CSF levels of the cholesterol precursor lathosterol were higher in carriers of the CH25Hchi4 haplotype. In 1,282 patients with AD and 1,312 healthy control subjects from five independent populations, a common variation in the vicinity of CH25H was significantly associated with the risk for sporadic AD (p = 0.006). Quantitative neuropathology of brains from elderly non-demented subjects showed brain A beta deposits in carriers of CH25Hchi4 and CH25Hchi3 haplotypes, whereas no A beta deposits were present in CH25Hchi2 carriers. Together, these results are compatible with a role of CH25Hchi4 as a putative susceptibility factor for sporadic AD; they may explain part of the linkage of chromosome 10 markers with sporadic AD, and they suggest the possibility that CH25H polymorphisms are associated with different rates of brain A beta deposition., (Copyright 2005 S. Karger AG, Basel.)

We report two 71-year-old female monozygotic twins presenting with advanced hyperostosis frontalis interna, obesity, shortness and cognitive impairment. They both have suffered from generalized seizures since their early adulthood. Moreover, the patients showed some additional conditions only occurring in one individual or the other such as migraine, marked recurrent depressive disorder or polyarthrosis. The symptoms common to both twins appear to correspond to the Morgagni-Stewart-Morel syndrome and indicate a genetic basis of this disorder as these features occur in genetically identical patients., (Copyright 2005 S. Karger AG, Basel.)

Objective: Because elevated cortisol levels inhibit memory retrieval in healthy human subjects, the present study investigated whether cortisol administration might also reduce excessive retrieval of traumatic memories and related symptoms in patients with chronic posttraumatic stress disorder (PTSD)., Method: During a 3-month observation period, low-dose cortisol (10 mg/day) was administered orally for 1 month to three patients with chronic PTSD in a double-blind, placebo-controlled, crossover design., Results: In each patient investigated, there was a significant treatment effect, with cortisol-related reductions of at least 38% in one of the daily rated symptoms of traumatic memories, as assessed by self-administered rating scales. In accordance, Clinician-Administered PTSD Scale ratings assessed after each month showed cortisol-related improvements for reexperiencing symptoms and, additionally, in one patient for avoidance symptoms., Conclusions: The results of this pilot study indicate that low-dose cortisol treatment reduces the cardinal symptoms of PTSD.

P301L mutant tau transgenic mice develop neurofibrillary tangles, a histopathologic hallmark of Alzheimer's disease and frontotemporal dementia (FTDP-17). To identify differentially expressed genes and to gain insight into pathogenic mechanisms, we performed a stringent analysis of the microarray dataset obtained with RNA from whole brains of P301L mutant mice and identified a single up-regulated gene, glyoxalase I. This enzyme plays a critical role in the detoxification of dicarbonyl compounds and thereby reduces the formation of advanced glycation end products. In situ hybridization analysis revealed expression of glyoxalase I in all brain areas analyzed, both in transgenic and control mice. However, levels of glyoxalase I protein were significantly elevated in P301L brains, as shown by Western blot analysis and immunohistochemistry. Moreover, a glyoxalase I-specific antiserum revealed many intensely stained flame-shaped neurons in Alzheimer's disease brain compared with brains from nondemented controls. In addition, we examined a single nucleotide polymorphism predicting a nonconservative amino acid substitution at position 111 (E111A) in ethnically independent populations. We identified significant and consistent deviations from Hardy-Weinberg equilibrium, which points to the presence of selection forces. The E111A single nucleotide polymorphism was not associated with the risk for Alzheimer's disease in the overall population. Together, our data demonstrate the potential of transcriptomics applied to animal models of human diseases. They suggest a previously unidentified role for glyoxalase I in neurodegenerative disease.

Amyloid-beta peptides (Abeta) are major components of amyloid plaques in the Alzheimer's disease (AD) brain and have been proposed as diagnostic markers in cerebrospinal fluid (CSF). Abeta derived from brain may be processed into fragments before emerging in CSF. Therefore, we determined mass profiles of Abeta peptides in CSF of patients with AD and age-matched healthy control subjects (CTR) by using protein biochip technology. Abeta peptides were captured on the chip surfaces (spots) by the specific monoclonal antibody 6E10 and were then analyzed by integrated surface-enhanced laser desorption and ionization time-of-flight mass spectrometry (SELDI-TOF-MS). We found Abeta species with mean molecular masses at 1,583.3 Da (corresponding to Abeta2-14), 2,068.5 Da (Abeta1-17), 2,166.4 Da (Abeta1-18), 3,676.6 Da (Abeta1-33), 3,789.4 Da (Abeta1-34), 4,076.9 Da (Abeta1-37), 4,134.0 Da (Abeta1-38), 4,233.3 Da (Abeta1-39), 4,332.4 Da (Abeta1-40) and 4,516.8 Da (Abeta1-42) in both AD (n = 24) and CTR (n = 24) subjects. Abeta1-38 appeared to be a major Abeta species in human CSF along with Abeta1-40. Quantitation revealed that CSF levels of Abeta1-38 were significantly decreased in AD as compared to CTR subjects. The CSF profile of Abeta peptides may be used for diagnostic and therapeutic purposes in clinical studies., (Copyright 2004 S. Karger AG, Basel.)

Because glucocorticoid excess increases neuronal vulnerability, genetic variations in the glucocorticoid system may be related to the risk for Alzheimer's disease (AD). We analyzed single-nucleotide polymorphisms in 10 glucocorticoid-related genes in a population of 814 AD patients and unrelated control subjects. Set-association analysis revealed that a rare haplotype in the 5' regulatory region of the gene encoding 11beta-hydroxysteroid dehydrogenase type 1 (HSD11B1) was associated with a 6-fold increased risk for sporadic AD. Results of a reporter-gene assay indicated that the rare risk-associated haplotype altered HSD11B1 transcription. HSD11B1 controls tissue levels of biologically active glucocorticoids and thereby influences neuronal vulnerability. Our results indicate that a functional variation in the glucocorticoid system increases the risk for AD, which may have important implications for the diagnosis and treatment of this disease.

Human memory capacity is highly variable across individuals and is influenced by both genetic and environmental factors. A roughly 50% heritability estimate indicates that naturally occurring genetic variations have an important impact on this cognitive ability. Therefore, we investigated a functional variation of a memory-related serotonin receptor in 349 healthy young volunteers, and found 21% poorer memory performance in subjects with the rare variant.

Background: The antemortem diagnosis of Alzheimer disease (AD) requires time-consuming and costly procedures. Therefore, biochemical tests that can direct the physician rapidly to the correct diagnosis are highly desirable. Measurement of single biochemical markers in cerebrospinal fluid (CSF), such as total tau protein and beta-amyloid peptide42 (Abeta42), shows robust alterations that highly correlate with the clinical diagnosis of AD but generally lack sufficient diagnostic accuracy., Objective: To study the combination of CSF phosphorylated tau protein (phospho-tau) and Abeta42 as biochemical markers for AD., Methods: We combined CSF measurements of phospho-tau and Abeta42 in 100 consecutive patients who under-went diagnostic workup for dementia and in 31 healthy control subjects., Results: We found that the calculated ratio of phospho-tau to Abeta42 was significantly increased in patients with AD and provided high diagnostic accuracy in distinguishing patients with AD from healthy control subjects (sensitivity, 86%; specificity, 97%), subjects with non-AD dementias (sensitivity, 80%; specificity, 73%), and subjects with other neurological disorders (sensitivity, 80%; specificity, 89%)., Conclusion: The diagnostic usefulness of the CSF ratio of phospho-tau to Abeta42 is superior to either measure alone and can be recommended as an aid to evaluating individuals suspected of having dementia.

To test whether antibodies against beta-amyloid are effective in slowing progression of Alzheimer's disease, we assessed cognitive functions in 30 patients who received a prime and a booster immunization of aggregated Abeta(42) over a 1 year period in a placebo-controlled, randomized trial. Twenty patients generated antibodies against beta-amyloid, as determined by tissue amyloid plaque immunoreactivity assay. Patients who generated such antibodies showed significantly slower rates of decline of cognitive functions and activities of daily living, as indicated by the Mini Mental State Examination, the Disability Assessment for Dementia, and the Visual Paired Associates Test of delayed recall from the Wechsler Memory Scale, as compared to patients without such antibodies. These beneficial clinical effects were also present in two of three patients who had experienced transient episodes of immunization-related aseptic meningoencephalitis. Our results establish that antibodies against beta-amyloid plaques can slow cognitive decline in patients with Alzheimer's disease.

Increased formation of the beta-amyloid peptide (Abeta) is a central event in the pathogenesis of Alzheimer's disease (AD). High cellular cholesterol load promotes Abeta formation. The ATP-binding cassette transporter A1 (ABCA1) mediates cholesterol efflux from cells. We hypothesized that genetic variability in ABCA1 may influence cholesterol metabolism in the central nervous system (CNS) and, thus, interfere with the development of AD. Healthy elderly carriers of the A allele of a non-synonymous (R219K) single nucleotide polymorphism (SNP) in the ABCA1 gene (rs2234884) had on average 33% lower total cholesterol in cerebrospinal fluid (CSF) than non-carriers. In 169 patients with late onset, sporadic AD, this allele was associated with delayed age at onset of the disease by 1.7 years on average. Rs2234884 and another non-synonymous SNP (R1587K) in ABCA1 (rs2234886) failed to show significant association with the risk for AD. We conclude that genetic variability of ABCA1 influences the development of AD, possibly by interfering with CNS cholesterol homeostasis.

Interleukin-6 (IL-6) plays an important role in the regulation of the inflammatory response in multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE). Previous reports indicated that the C allele of a variable number tandem repeat (vntr) polymorphism located in the 3'flanking region of the IL-6 gene ( IL-6) is associated with reduced activity of IL-6 in vivo. Since disease-modifying genes are likely to contribute to phenotypic differences in MS patients, we tested the hypothesis that the IL-6 C allele is associated with the clinical course of MS. The IL-6 C allele was equally distributed between 217 MS patients of German Caucasian origin and 111 age-mached healthy controls. Stratification of patients according to the course of disease revealed no significant difference of IL-6 C allele distribution between patients with primary progressive and those with either relapsing-remitting or secondary progressive MS although IL-6 C allele was more frequent in patients with RR-MS. Since IL-6 C allele has been associated with a benign course in Sardinian MS patients, we further analysed an independent sample of 125 Sardinian MS patients revealing that IL-6 C allele was much more frequent than in German MS patients. Taken together, a disease-modifying effect of IL-6 C allele could not be demonstrated in MS patients of German Caucasian descent.

The lack of phenotype/genotype association in X-linked adrenoleukodystrophy (X-ALD) has prompted the search for disease modifying factors. We previously demonstrated increased serum antibody responses against myelin oligodendrocyte glycoprotein (MOG) in various clinical phenotypes of X-ALD allowing speculations that myelin specific humoral immune responses might be involved in phenotype generation of X-ALD. In the present study, we investigated the possible association of (1) a naturally occurring variable number tandem repeat (vntr) polymorphism (C allele) in the 3' flanking region of the interleukin-6 gene (IL-6), previously demonstrated to modify the course of Alzheimer's disease, systemic lupus erythematodes and Multiple Sclerosis (MS), (2) a tetranucleotide repeat polymorphism (TAAA)(n) in the 3' flanking region of the MOG gene and (3) HLA class II alleles with adult clinical phenotypes and serum antibody responses to MOG in 70 adult X-ALD patients. HLA class II alleles, (TAAA)(n) MOG gene polymorphisms, and IL-6 C allele were not associated with clinical phenotypes. Anti-MOG antibodies were detectable in 17/54 X-ALD patients (31.5%). Anti-MOG antibodies were associated with the 226 bp (TAAA)(n) MOG gene polymorphism but not with distinct clinical phenotypes.

Interleukin-6 (IL-6) is a multifunctional cytokine involved in the pathogenesis of Alzheimer's disease (AD). The effects of IL-6 are mediated through a specific receptor complex made up of a ligand binding glycoprotein (gp80 or IL-6R) and a signal transducing glycoprotein (gp130). Conflicting results have been reported concerning altered IL-6 or soluble IL-6R (sIL-6R) levels in serum and CSF in AD. This study investigated whether genetic heterogeneity determines the magnitude of the difference in IL-6 and sIL-6R levels in AD. Fifty-eight AD patients and 25 control subjects were included. Plasma and CSF IL-6 and sIL-6R levels were measured and the IL-6 variable number of number repeats ( IL-6vntr) and IL-6 promoter ( IL-6prom) genotypes were determined. sIL-6R levels in plasma and CSF were higher in AD patients than in control subjects. This elevation was striking among non-carriers of the IL-6vntr*C allele and among subjects homozygous for the IL-6prom*C allele whereas no difference in plasma and CSF sIL-6R levels was observed among carriers of the IL-6vntr*C allele and among subjects with the IL-6prom*CG and IL-6prom*GG genotypes. We conclude that plasma and CSF levels of sIL-6R are significantly increased in AD patients and that the magnitude of increase is determined by the IL-6 genotype.

Background: CYP46, the gene encoding cholesterol 24-hydroxylase, plays a key role in the hydroxylation of cholesterol and thereby mediates its removal from brain., Objective: To study the association of polymorphic sites on CYP46 with Alzheimer disease (AD) traits and with the risk of the development of AD., Design: Alzheimer disease traits (beta-amyloid load, beta-amyloid peptides, hyperphosphorylated tau protein) were assessed in brain tissues and in the cerebrospinal fluid of patients with AD and control subjects. Genetic associations were studied in 2 independent populations., Setting: Specialized centers for memory disorders in Switzerland, Greece, and Italy., Participants: Fifty-five brain tissues from nondemented elderly patients for the histopathological studies; 38 patients with AD and 25 control subjects for the cerebrospinal fluid studies; 201 patients with AD and 248 control subjects for the genetic association studies., Results: A polymorphism of CYP46 was associated with increased beta-amyloid load in brain tissues as well as with increased cerebrospinal fluid levels of beta-amyloid peptides and phosphorylated tau protein. Moreover, this CYP46 polymorphism was associated with higher risk of late-onset sporadic AD in 2 independent populations (odds ratio, 2.16; 95% confidence interval [CI], 1.41-3.32; P<.001). The additional presence of 1 or 2 apolipoprotein E epsilon4 alleles synergistically increased the risk of AD to an odds ratio of 9.6 (95% CI, 4.9-18.9; P<.001) as compared with 4.4 for apolipoprotein E epsilon4 alone (95% CI, 2.8-6.8; P<.001)., Conclusion: CYP46 influences brain beta-amyloid load, cerebrospinal fluid levels of beta-amyloid peptides and phosphorylated tau, and the genetic risk of late-onset sporadic AD.

To characterize antibodies produced in humans in response to Abeta42 vaccination, we carried out immunohistochemical examinations of the brains of both transgenic mice and human patients with beta-amyloid pathology. We collected sera from patients with Alzheimer disease who received a primary injection of pre-aggregated Abeta42 followed by one booster injection in a placebo-controlled study. Antibodies in immune sera recognized beta-amyloid plaques, diffuse Abeta deposits and vascular beta-amyloid in brain blood vessels. The antibodies did not cross-react with native full-length beta-amyloid precursor protein or its physiological derivatives, including soluble Abeta42. These findings indicate that vaccination of AD patients with Abeta42 induces antibodies that have a high degree of selectivity for the pathogenic target structures. Whether vaccination to produce antibodies against beta-amyloid will halt the cognitive decline in AD will depend upon clinical assessments over time.

Tissue inhibitor of metalloproteinases 1 (TIMP-1) inhibits several proteinases including a disintegrin and metalloproteinase 10 (ADAM10), a major alpha-secretase that cleaves the beta-amyloid precursor protein within its amyloidogenic Abeta domain. The gene encoding TIMP-1 (TIMP 1) maps to the short arm of the X chromosome, in a region previously suggested as conferring genetic susceptibility for Alzheimer's disease (AD). To determine whether genetic variability of TIMP 1 contributes to the pathogenesis of AD, we analysed one single nucleotide polymorphism within TIMP 1 and one single nucleotide polymorphism in the 5'-untranslated region of TIMP 1 in patients with AD and control subjects from two independent and ethnically different populations. We did not observe any association between TIMP 1 genotypes and the diagnosis of AD in men or women. We also measured TIMP-1 protein levels in the cerebrospinal fluid of patients with AD, healthy control subjects, and patients with other neurological disorders. TIMP-1 levels were similar in all groups. In addition, no significant differences were observed after stratification for TIMP 1 genotypes. Our data show that neither genetic variability nor protein levels of TIMP-1 are associated with AD., (Copyright 2002 Lippincott Williams & Wilkins)

The intracellular aspartyl protease cathepsin D (catD) is involved in such Alzheimer's disease (AD)-related processes as the activation of the endosomal/lysosomal system and the cleavage of the amyloid precursor protein into amyloidogenic components, which may initiate neurodegeneration. A non-synonymous polymorphism (exon 2, C to T exchange leading to ala-->val substitution) of the gene encoding catD (CTSD) was previously associated with AD, in that the T allele increased the risk for AD. To investigate whether the T allele is associated with disease-related traits, we measured the concentration of the amyloid beta-peptide 1-42 (Abeta(42)) and 1-40 (Abeta(40)) in patients and control subjects. The T allele of the CTSD genotype was associated with a 50% decrease in Abeta(42) levels in the cerebrospinal fluid. Thus, we demonstrate a significant impact of the CTSD genotype on Abeta(42) levels in the cerebrospinal fluid of AD patients and underpin the importance of the validation of susceptibility genes by examining their potential pathophysiological relevance.

Cathepsin D (CTSD) is a lysosomal protease involved in the pathogenesis of several diseases such as breast cancer and possibly Alzheimer's disease (AD). Previous findings revealed a significant association between the T allele of the 224 C/T (A58V) polymorphism in exon 2 of the CTSD gene and late onset AD. The exonic regions of the CTSD gene were screened for further polymorphic variations using polymerase chain reaction and single-strand conformation polymorphism analysis. In addition to the known 224 C/T polymorphism and two silent mutations in exons 3 and 4 we detected two new polymorphisms in introns 5 and 8. Combination of these sequence variations results in three different haplotypes; one of these haplotypes is due to the new polymorphism in intron 5. We detected no further missense mutations except for the known 224 C/T polymorphism in exon 2. Thus, if sequence variations within the CTSD gene influence the risk for various diseases, the pathogenic mechanism is likely to be linked to the amino acid substitution in the profragment of CTSD.