For Familial Alzheimer's Disease Research Articles

PSEN1 E280A Cholinergic-like Neurons and Cerebral Spheroids Derived from Mesenchymal Stromal Cells and from Induced Pluripotent Stem Cells Are Neuropathologically Equivalent.

Alzheimer's disease (AD) is a chronic neurological condition characterized by the severe loss of cholinergic neurons. Currently, the incomplete understanding of the loss of neurons has prevented curative treatments for familial AD (FAD). Therefore, modeling FAD in vitro is essential for studying cholinergic vulnerability. Moreover, to expedite the discovery of disease-modifying therapies that delay the onset and slow the progression of AD, we depend on trustworthy disease models. Although highly informative, induced pluripotent stem cell (iPSCs)-derived cholinergic neurons (ChNs) are time-consuming, not cost-effective, and labor-intensive. Other sources for AD modeling are urgently needed. Wild-type and presenilin (PSEN)1 p.E280A fibroblast-derived iPSCs, menstrual blood-derived menstrual stromal cells (MenSCs), and umbilical cord-derived Wharton Jelly's mesenchymal stromal cells (WJ-MSCs) were cultured in Cholinergic-N-Run and Fast-N-Spheres V2 medium to obtain WT and PSEN 1 E280A cholinergic-like neurons (ChLNs, 2D) and cerebroid spheroids (CSs, 3D), respectively, and to evaluate whether ChLNs/CSs can reproduce FAD pathology. We found that irrespective of tissue source, ChLNs/CSs successfully recapitulated the AD phenotype. PSEN 1 E280A ChLNs/CSs show accumulation of iAPPβ fragments, produce eAβ42, present TAU phosphorylation, display OS markers (e.g., oxDJ-1, p-JUN), show loss of ΔΨm, exhibit cell death markers (e.g., TP53, PUMA, CASP3), and demonstrate dysfunctional Ca2+ influx response to ACh stimuli. However, PSEN 1 E280A 2D and 3D cells derived from MenSCs and WJ-MSCs can reproduce FAD neuropathology more efficiently and faster (11 days) than ChLNs derived from mutant iPSCs (35 days). Mechanistically, MenSCs and WJ-MSCs are equivalent cell types to iPSCs for reproducing FAD in vitro.

Rare causes of early-onset dystonia-parkinsonism with cognitive impairment: a de novo PSEN-1 mutation.

Mutations in PSEN1 are responsible for familial Alzheimer's disease (FAD) inherited as autosomal dominant trait, but also de novo mutations have been rarely reported in sporadic early-onset dementia cases. Parkinsonism in FAD has been mainly described in advanced disease stages. We characterized a patient presenting with early-onset dystonia-parkinsonism later complicated by dementia and myoclonus. Brain MRI showed signs of iron accumulation in the basal ganglia mimicking neurodegeneration with brain iron accumulation (NBIA) as well as fronto-temporal atrophy. Whole exome sequencing revealed a novel PSEN1 mutation and segregation within the family demonstrated the mutation arose de novo.We suggest considering PSEN1 mutations in cases of dystonia-parkinsonism with positive DAT-Scan, later complicated by progressive cognitive decline and cortical myoclonus even without a dominant family history.

Visual short-term memory binding deficit in familial Alzheimer's disease

Long-term episodic memory deficits in Alzheimer's disease (AD) are well characterised but, until recently, short-term memory (STM) function has attracted far less attention. We employed a recently-developed, delayed reproduction task which requires participants to reproduce precisely the remembered location of items they had seen only seconds previously. This paradigm provides not only a continuous measure of localization error in memory, but also an index of relational binding by determining the frequency with which an object is misplaced to the location of one of the other items held in memory. Such binding errors in STM have previously been found on this task to be sensitive to medial temporal lobe (MTL) damage in focal lesion cases. Twenty individuals with pathological mutations in presenilin 1 or amyloid precursor protein genes for familial Alzheimer's disease (FAD) were tested together with 62 healthy controls. Participants were assessed using the delayed reproduction memory task, a standard neuropsychological battery and structural MRI.Overall, FAD mutation carriers were worse than controls for object identity as well as in gross localization memory performance. Moreover, they showed greater misbinding of object identity and location than healthy controls. Thus they would often mislocalize a correctly-identified item to the location of one of the other items held in memory. Significantly, asymptomatic gene carriers – who performed similarly to healthy controls on standard neuropsychological tests – had a specific impairment in object-location binding, despite intact memory for object identity and location. Consistent with the hypothesis that the hippocampus is critically involved in relational binding regardless of memory duration, decreased hippocampal volume across FAD participants was significantly associated with deficits in object-location binding but not with recall precision for object identity or localization. Object-location binding may therefore provide a sensitive cognitive biomarker for MTL dysfunction in a range of diseases including AD.

Molecular Pathogenesis of Sporadic Alzheimer's Disease (AD) and Pharmaceutical Research to Develop a Biomarker for AD Diagnosis

Alzheimer's disease (AD) is the most common senile dementia. One of the pathological characteristics of AD is the appearance of senile plaques composed of amyloid-β (Aβ) depositions. Aβ is generated by consecutive cleavages of Aβ precursor protein (APP) by β- and γ-secretases. The common pathogenesis for familial AD (FAD) is believed to involve misprocessing of APP by γ-secretase, resulting in increased Aβ42 peptide deposition. However, little is known about γ-secretase function in sporadic AD (SAD), which is the major type of AD. This may be because Aβ42 peptide has highly aggregative properties; therefore it is not easy to estimate the quantitative alteration of net Aβ42 in SAD patients. Alcadein is a family of neural type I membrane proteins. Processing of Alcadein by APP α- and γ-secretases results in secretion of non-aggregative peptide, p3-Alc, into CSF and blood. The C-terminuses of Aβ and p3-Alc are altered by FAD-linked genetic mutations in catalytic components of γ-secretase, in association with an increase in minor Aβ and p3-Alc species. Thus p3-Alcs are expected to behave as useful indicators of γ-secretase dysfunction in SAD brain. Quantitative and qualitative analyses of p3-Alcs raise the possibility that γ-secretase dysfunction may exist even in the absence of genetic mutations. p3-Alc peptides may be a novel biomarker for AD and an indicator of γ-secretase dysfunction for drug development.

Systematic Characterization of Wild Type and Familial Alzheimer's Disease Mutant Aβ Monomers Through the Convergence of Ensembles Simulated with Different Force Fields

Amyloid β (Aβ) monomers represent the base state in the pathways of aggregation that result in the fibrils and oligomers involved in Alzheimer's disease (AD). The structural properties of these intrinsically disordered peptides remain unclear despite extensive efforts to resolve these through experiment and computation. Comparison of all-atom, explicitly solvated simulations of wild type Aβ monomers simulated with different force fields (OPLS-AA/L and AMBER99sb-ILDN) and water models (TIP3P and TIP4P-Ew) nevertheless demonstrate a convergence in structural properties and good agreement with experimental NMR observables. In Aβ42, antiparallel β-hairpin structure between L17-A21, A30-L34, and V40-I41 is prevalent in these ensembles. While residues 21-30 forms an interceding region in both simulations that rarely interacts with the majority of the protein, the structure of this region and the electrostatic interactions that characterize it are notably different between the two. To further explore these differences, NMR experiments and simulations using both combinations have been conducted for familial AD (FAD) mutations that perturb residues 22 and 23, observed in our wild type Aβ simulation data to be pivotal in determining the structure of this central region. The characterizations made here suggest simulation conditions that best reproduce the experimental data and help clarify how FAD mutations drive Aβ to aberrant aggregation pathways that result in disease phenotypes.

The impact of the availability of prevention studies on the desire to undergo predictive testing in persons at risk for autosomal dominant Alzheimer's disease

Persons at risk for autosomal dominant neurodegenerative diseases provide the opportunity to efficiently test preventive interventions. Only a minority of such persons, however, choose to undergo revealing genetic testing, presenting a challenge to enrollment. Thirty-four preclinical Latinos (n=26) and non-Latinos at risk for familial Alzheimer's disease (FAD) unaware of their genetic status were administered a questionnaire exploring their interest in undergoing revealing genetic testing at baseline and in the context of eligibility for four prevention trials of increasing invasiveness. Forty-four percent of subjects expressed a baseline interest in undergoing revealing testing which increased to 85% in order to be eligible for a study of an oral drug “felt to be very safe.” If there were a 50% chance of receiving placebo, this number dropped to 62% (p=0.02). Among those not interested in a study involving a 50% chance of receiving placebo, a range of 5% to 40% chance of receiving placebo was given as acceptable. For more invasive studies, living in the United States (as opposed to Mexico) positively influenced the likelihood of participating. Our data suggest that clinical trial designs in which persons must confront their genetic status prior to enrollment are feasible. Study designs to minimize the likelihood of being placed on placebo or provide the eventual administration of the drug through open-label extensions should be considered.

Alternative processing of γ‐secretase substrates in common forms of mild cognitive impairment and alzheimer's disease: Evidence for γ‐secretase dysfunction

The most common pathogenesis for familial Alzheimer's disease (FAD) involves misprocessing (or alternative processing) of the amyloid precursor protein (APP) by γ-secretase due to mutations of the presenilin 1 (PS1) gene. This misprocessing/alternative processing leads to an increase in the ratio of the level of a minor γ-secretase reaction product (Aβ42) to that of the major reaction product (Aβ40). Although no PS1 mutations are present, altered Aβ42/40 ratios are also observed in sporadic Alzheimer's disease (SAD), and these altered ratios apparently reflect deposition of Aβ42 as amyloid. Using immunoprecipitation-mass spectrometry with quantitative accuracy, we analyzed in the cerebrospinal fluid (CSF) of various clinical populations the peptide products generated by processing of not only APP but also an unrelated protein, alcadein (Alc). Alc undergoes metabolism by the identical APP α-secretases and γ-secretases, yielding a fragment that we have named p3-Alc(α) because of the parallel genesis of p3-Alc(α) peptides and the p3 fragment of APP. As with Aβ, both major and minor p3-Alc(α) s are generated. We studied the alternative processing of p3-Alc(α) in various clinical populations. We previously reported that changes in the Aβ42/40 ratio showed covariance in a linear relationship with the levels of p3-Alc(α) [minor/major] ratio in media conditioned by cells expressing FAD-linked PS1 mutants. Here we studied the speciation of p3-Alc(α) in the CSF from 3 groups of human subjects (n = 158): elderly nondemented control subjects; mild cognitive impairment (MCI) subjects with a clinical dementia rating (CDR) of 0.5; SAD subjects with CDR of 1.0; and other neurological disease (OND) control subjects. The CSF minor p3-Alc(α) variant, p3-Alc(α) 38, was elevated (p < 0.05) in MCI subjects or SAD subjects, depending upon whether the data were pooled and analyzed as a single cohort or analyzed individually as 3 separate cohorts. These results suggest that some SAD may involve alternative processing of multiple γ-secretase substrates, raising the possibility that the molecular pathogenesis of SAD might involve γ-secretase dysfunction.

Aβ46 Is Processed to Aβ40 and Aβ43, but Not to Aβ42, in the Low Density Membrane Domains

Gamma-secretase cleaves the transmembrane domain of beta-amyloid precursor protein at multiple sites referred to as gamma-, epsilon-, and zeta-cleavage sites. We previously showed that N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester (DAPT), a potent dipeptide gamma-secretase inhibitor, causes differential accumulation of longer amyloid beta-proteins (Abetas) within Chinese hamster ovary cells co-expressing beta C-terminal fragment and wild-type presenilin 1 (C99/wtPS1 cells). In this study, we used sucrose density gradient centrifugation to fractionate the membranes from C99/wtPS1 cells that had been pretreated with DAPT. We found that accumulating Abeta46 localized exclusively to low density membrane (LDM) domains. Incubating the Abeta46-accumulating LDM domains at 37 degrees C produced Abeta40, Abeta42, Abeta43, and beta-amyloid precursor protein intracellular domain. The addition of L685,458 completely prevented beta-amyloid precursor protein intracellular domain generation and resulted in a large decrease in the level of Abeta46 and the concomitant appearance of Abeta40 and Abeta43 but not Abeta42. Further addition of DAPT suppressed the production of Abeta40/43 and abolished the decrease in the amount of Abeta46. These data indicate that preaccumulated Abeta46 is processed by gamma-secretase to Abeta40/43 but not to Abeta42 in the LDM domains. The amount of newly produced Abeta40 and Abeta43 was roughly equivalent to the decrease in the amount of Abeta46. Temporal profiles did not show a maximal concentration for Abeta43, suggesting that Abeta46 is processed to Abeta40 and Abeta43 through a nonsuccessive process.

The association of the regulatory region of the presenilin-2 gene with Alzheimer's disease in the Northern Han Chinese population

Presenilin-2 is one of the causative genes for familial Alzheimer's disease (FAD). Polymorphism of the promoter region of the presenilin-2 gene (PSEN2) has recently been reported in a Russian population to be associated with sporadic Alzheimer's disease (SAD). The purpose of this case-control study was to determine whether SAD is associated with the PSEN2 gene polymorphism in a Chinese population. We examined PSEN2 and APOE genotypes in 200 SAD patients and an equal number of age- and sex-matched controls from the same community, using the PCR-RFLP method. Allelic and genotypic distributions were performed using the Pearson Chi-square test for homogeneity. The interactions between variables were examined by logistic regression. The results revealed no significant differences in the frequency of the +A/-A polymorphism between AD and controls (chi(2)=3.857, p=0.145). However, in the subgroup of APOE epsilon4 non-carriers, there were significant differences in the distributions of both alleles (chi(2)=6.095, p=0.047) and genotypes (chi(2)=4.433, p=0.035) of the PSEN2 promoter in AD compared with controls. In APOE epsilon4 non-carrier group, with +A/+A as a reference, the -A/-A genotype was associated with a 4.657-fold increased risk for AD (chi(2)=5.783, p=0.016, OR=4.657, 95% CI=1.195-18.152). Using logistic analysis, there were no statistical interactions between PSEN2 and APOE genotypes, or between PSEN2 genotypes and age of onset. It is concluded that in the Northern Han Chinese population, the +A/-A polymorphism of the PSEN2 promoter is a moderate genetic risk factor for developing SAD, independent of the APOE epsilon4 allele.

Presenilin-1 mutation E318G and familial Alzheimer's disease in the Italian population

Presenilin-1 (PSEN-1) is a component of the γ-secretase complex involved in β-amyloid precursor protein (βAPP) processing. To date about 140 pathogenic mutations in the PSEN-1 gene have been identified and their main biochemical effect is to increase the production of the fibrillogenic peptide Aβ(1–42). An exception is the PSEN-1 [E318G] mutation that does not alter Aβ(1–42) generation and is generally considered a non-pathogenic polymorphism. Nevertheless, this mutation was reported to be a genetic risk factor for familial Alzheimer's disease (FAD) in the Australian population. To independently confirm this indication, we performed a case-control association study in the Italian population. We found a significant association ( p < 0.05, Fisher's exact test) between the presence of PSEN-1 [E318G] and FAD. In addition, on measuring the Aβ(1–42) and Aβ(1–40) concentrations in fibroblast-conditioned media cultured from PSEN-1 [E318G] carriers and PSEN-1 [ wild type] controls we noted a significant decrease ( p < 0.05, Mann–Whitney test) in the Aβ(1–42)/Aβ(1–40) ratio in PSEN-1 [E318G] carriers, suggesting a peculiar biochemical effect of this mutation.

Interaction of presenilins with FKBP38 promotes apoptosis by reducing mitochondrial Bcl-2

Presenilins 1 and 2 (PS1/2), causative molecules for familial Alzheimer's disease (FAD), are multipass transmembrane proteins localized predominantly in the endoplasmic reticulum (ER) and Golgi apparatus. Heteromeric protein complexes containing PS1/2 are thought to participate in several functions, including intramembrane proteolysis mediated by their gamma-secretase activities. Previous studies have shown that PS1/2 are also involved in the regulation of apoptotic cell death, although the underlying mechanism remains unknown. Here, we demonstrate that FKBP38, an immunophilin family member residing in the mitochondrial membrane, is an authentic PS1/2-interacting protein. PS1/2 and FKBP38 form macromolecular complexes together with anti-apoptotic Bcl-2. PS1/2 promote the degradation of FKBP38 and Bcl-2 and sequester these proteins in the ER/Golgi compartments, thereby inhibiting FKBP38-mediated mitochondrial targeting of Bcl-2 via a gamma-secretase-independent mechanism. Thus, PS1/2 increase the susceptibility to apoptosis by antagonizing the anti-apoptotic function of FKBP38. In contrast, C-terminal fragments of caspase-processed PS1/2 redistribute Bcl-2 to the mitochondria by abrogating the activity of full-length PS1/2, resulting in a dominant-negative anti-apoptotic effect. In cultured cells and mutant PS1-knockin mice brains, FAD-linked PS1/2 mutants enhance the pro-apoptotic activity by causing a more efficient reduction in mitochondrial Bcl-2 than wild-type PS1/2. These results suggest a novel molecular mechanism for the regulation of mitochondria-mediated apoptosis by competition between PS1/2 and FKBP38 for subcellular targeting of Bcl-2. Excessive pro-apoptotic activity of PS1/2 may play a role in the pathogenesis of FAD.

A novel mutation (L250V) in the presenilin 1 gene in a Japanese familial Alzheimer's disease with myoclonus and generalized convulsion

This study reports a novel presenilin 1 (PS1) gene mutation in a Japanese family with Alzheimer's disease (AD). Two patients developed progressive memory disorder with disorientation around 50 years of age and showed myoclonus with frequent tonic–clonic seizures several years later. Direct sequencing of the proband's PS1 gene revealed a novel mis-sense mutation (leucine-to-valine at residue 250 (L250V)). This mutation was found in both patients, but not in a normal family member or normal Japanese control subjects. Thus, L250V is a novel PS1 gene mutation responsible for familial AD (FAD) in Japan.

Presenilin and gamma-secretase: structure meets function.

During the search for the major genes responsible for autosomal-dominant, familial forms of Alzheimer's disease (AD), many thought the encoded proteins would reveal at least one, if not both, of the proteases that cut the amyloid-b peptide (Ab) out of the amyloid-b precursor protein (APP) (Fig. 1). Amyloid-b peptide is the major protein component of the characteristic cerebral plaques of AD (Glenner and Wong 1984), and APP itself had already been identi®ed in 1991 as a locus for familial AD (FAD), with disease-causing missense mutations found immediately near the Ab boundaries (Chartier-Harlin et al. 1991; Goate et al. 1991; Murrell et al. 1991). However, when the search identi®ed presenilin-1 (PS1) and presenilin-2 (PS2) in 1995 (LevyLahad et al. 1995; Sherrington et al. 1995), it was far from clear given the primary structure what the normal function of these proteins might be and why mutant forms cause disease. Ironically, over the past few years the argument has come full circle, and it now appears that presenilins are indeed responsible for the ®nal proteolysis that produces Ab.

Molecular genetic predictive testing for Alzheimer's disease: deliberations and preliminary recommendations.

Forty-one participants representing diverse professional back-grounds attended a workshop on genetic predictive testing for familial Alzheimer's disease (FAD) on January 23, 1993 at Surrey Place Centre in Toronto, Canada. Rapidly emerging molecular genetic findings in AD indicate that predictive testing is now technologically feasible for selected individuals, although defining eligibility criteria remains problematic. Legal, ethical, biomedical, and psychosocial issues related to establishing predictive testing programs for AD were discussed at the workshop. This article reflects these discussions, provides the current biomedical background for them and examines the Huntington's disease (HD) predictive testing experience. Observations concerning molecular genetic predictive testing for AD in light of its genetic heterogeneity and clinical characteristics, such as usual later age of onset than HD, are presented. It is proposed that predictive testing for AD can now be cautiously offered in a research setting primarily according to the recommendations contained within the Ethical Issues Policy Statement on Huntington's Disease Molecular Genetics Predictive Test. However, in their application to AD, some points in the statement are considered to require emphasis, modification, or currently to be of uncertain applicability. This represents an initial step in an on-going process of debate concerning AD that will be required as new advances occur in genetic and clinical research and in bioethics.

A new EcoRI polymorphism at the D21S13 locus

The D21S13 locus has shown linkage to a gene for familial Alzheimer disease (FAD) on chromosome 21 (St. George-Hyslop et al. 1987). The limited informativeness of probes for this locus have hindered precise mapping of the FAD locus and analysis of nonallelic heterogeneity in FAD (Schellenberg et al. 1988; St. George-Hyslop et al. 1987). We describe a new EcoRI polymorphism at the D21S13 locus that may be useful for the further study of FAD families.