Early-onset Familial Alzheimer's Disease Research Articles

Structure and dynamics of γ-secretase with presenilin 2 compared to presenilin 1.

Severe early-onset familial Alzheimer's disease (FAD) is caused by more than 200 different mutations in the genes coding for presenilin, the catalytic subunit of the 4-subunit protease complex γ-secretase, which cleaves the C99 fragment of the amyloid precursor protein (APP) to produce Aβ peptides. γ-Secretase exists with either of two homologues, PS1 and PS2. All cryo-electron microscopic structures and computational work has so far focused on γ-secretase with PS1, yet PS2 mutations also cause FAD. A central question is thus whether there are structural and dynamic differences between PS1 and PS2. To address this question, we use the cryo-electron microscopic data for PS1 to develop the first structural and dynamic model of PS2-γ-secretase in the catalytically relevant mature membrane-bound state at ambient temperature, equilibrated by three independent 500 ns molecular dynamics simulations. We find that the characteristic nicastrin extra-cellular domain breathing mode and major movements in the cytosolic loop between TM6 and TM7 occur in both PS2- and PS1-γ-secretase. The overall structures and conformational states are similar, suggesting similar catalytic activities. However, at the sequence level, charge-controlled membrane-anchoring is extracellular for PS1 and intracellular for PS2, which suggests different subcellular locations. The tilt angles of the TM2, TM6, TM7 and TM9 helices differ in the two forms of γ-secretase, suggesting that the two proteins have somewhat different substrate processing and channel sizes. Our MD simulations consistently indicated that PS2 retains several water molecules near the catalytic site at the bilayer, as required for catalysis. The possible reasons for the differences of PS1 and PS2 are discussed in relation to their location and function.

Risk factors for Alzheimer's disease.

Early reviews identified over 20 risk factors associated with Alzheimer's disease (AD) including age, familial inheritance, exposure to aluminium, traumatic brain injury (TBI), and associated co-morbidities such as vascular disease and infection. In the light of recent evidence, this review reconsiders these risk factors, identifies those currently regarded as important, and discusses various hypotheses to explain how they may cause AD. Rare forms of early-onset familial AD (EO-FAD) are strongly linked to causal gene mutations, viz. mutations in amyloid precursor protein (APP) and presenilin (PSEN1/2) genes. By contrast, late-onset sporadic AD (LO-SAD) is a multifactorial disorder in which age-related changes, genetic risk factors, such as allelic variation in apolipoprotein E (Apo E) and many other genes, vascular disease, TBI and risk factors associated with diet, the immune system, mitochondrial function, metal exposure, and infection are all implicated. These risk factors may act collectively to cause AD pathology: 1) by promoting the liberation of oxygen free radicals with age, 2) via environmental stress acting on regulatory genes early and later in life ('dual hit' hypothesis), or 3) by increasing the cumulative 'allostatic load' on the body over a lifetime. As a consequence, life-style changes which reduce the impact of these factors may be necessary to lower the risk of AD.

Can post-mortem MRI be used as a proxy for in vivo? A case study.

Post-mortem in situ MRI has been used as an intermediate between brain histo(patho)logy and in vivo imaging. However, it is not known how comparable post-mortem in situ is to ante-mortem imaging. We report the unique situation of a patient with familial early-onset Alzheimer’s disease due to a PSEN1 mutation, who underwent ante-mortem brain MRI and post-mortem in situ imaging only 4 days apart. T1-weighted and diffusion MRI was performed at 3-Tesla at both time points. Visual atrophy rating scales, brain volume, cortical thickness and diffusion measures were derived from both scans and compared. Post-mortem visual atrophy scores decreased 0.5–1 point compared with ante-mortem, indicating an increase in brain volume. This was confirmed by quantitative analysis; showing a 27% decrease of ventricular and 7% increase of whole-brain volume. This increase was more pronounced in the cerebellum and supratentorial white matter than in grey matter. Furthermore, axial and radial diffusivity decreased up to 60% post-mortem whereas average fractional anisotropy of white matter increased approximately 10%. This unique case study shows that the process of dying affects several imaging markers. These changes need to be taken into account when interpreting post-mortem MRI to make inferences on the in vivo situation.

Aβ42/Aβ40 Ratios of Presenilin 1 Mutations Correlate with Clinical Onset of Alzheimer's Disease.

Missense mutations in presenilin 1 cause early onset familial Alzheimer's disease in a way that is not understood. Increased Aβ42/Aβ40 ratios are the most consistent biochemical phenotype of such mutations in cultured cells and in vivo, and are thus considered central to the amyloid hypothesis. Previously, an inverse relation has been observed between the Aβ42/Aβ40 ratio of such mutants and the clinical age of symptom onset in patients carrying the mutation. However, a recent extensive study by Sun et al. of assayed presenilin 1 mutants concluded that such a relationship is not evident. To reconcile the disagreement, three different clinical datasets were compared directly with the data by Sun et al. After considering data noise and measurement uncertainty, we find a clear and highly significant inverse correlation between the Aβ42/Aβ40 ratio and the clinical age of onset in all three datasets even without removing noisy single- and double-patient data. With these data removed, the correlation coefficients increase further. The probability that these relationships are coincidental are approximately 0.1%.

Presenilin 1 p. F105L mutation was associated with a Chinese pedigree with early-onset familial Alzheimer's disease

Objective: To investigate the clinical manifestations of an early-onset Alzheimer's family and the novel mutation sites of PSEN1 gene. Methods: Clinical data was collected from 30 members of a family with early onset Alzheimer's disease from Neurology Department of Henan Province People's Hospital in 2016, and high-throughput sequencing and sanger sequencing were used to detect and further validate the PSEN1 gene mutation. At the same time, 100 unrelated healthy people were selected as controls. Results: A total of 3 members of the family carried PSEN1 (p.F105L mutation). The clinical symptoms or imaging of the three people were consistent with the diagnosis of Alzheimer's disease. Conclusion: The p. F105L mutation of the PSEN1 gene has been found in the Chinese population, which may be involved in the pathogenesis of this familial Alzheimer's disease.

The antimicrobial protection hypothesis of Alzheimer's disease

ObjectiveWe explore here a novel model for amyloidogenesis in Alzheimer's disease (AD). This new perspective on AD amyloidosis seeks to provide a rational framework for incorporating recent and seemingly independent findings on the antimicrobial role of β-amyloid and emerging experimental, genetic, and epidemiological data, suggesting innate immune-mediated inflammation propagates AD neurodegeneration. BackgroundAD pathology is characterized by cerebral deposition of amyloid-β protein (Aβ) as β-amyloid. Genetic studies have confirmed the key role of Aβ in AD, revealing that mutation-mediated shifts in the peptides generation lead to early onset familial Alzheimer's disease. However, Aβ generation appears normal for the majority of AD patients, who lack early onset familial Alzheimer's disease mutations. In prevailing models of nonfamilial AD, individual genetics and age-associated changes in brain milieu promote an intrinsically abnormal propensity of Aβ for self-association. However, emerging findings are increasingly inconsistent with characterization of Aβ oligomerization as a nonphysiological and exclusively pathological activity. Recent studies suggest Aβ is an ancient, highly conserved effector molecule of innate immunity. Moreover, Aβ oligomerization and β-amyloid generation appear to be important innate immune pathways that mediate pathogen entrapment and protect against infection. New AD amyloidogenesis modelRecent findings on inflammation-mediated neurodegeneration and the role of Aβ in immunity have led to emergence of the “Antimicrobial Protection Hypothesis” of AD. In this model, β-amyloid deposition is an early innate immune response to genuine, or mistakenly perceived, immunochallenge. Aβ first entraps and neutralizes invading pathogens in β-amyloid. Aβ fibrillization drives neuroinflammatory pathways that help fight the infection and clear β-amyloid/pathogen deposits. In AD, chronic activation of this pathway leads to sustained inflammation and neurodegeneration. Mounting data link elevated brain microbe levels with AD. The Antimicrobial Protection Hypothesis reveals how increased brain microbial burden may directly exacerbate β-amyloid deposition, inflammation, and AD progression. Amyloid cascade hypothesisIn the antimicrobial protection model, the modality of Aβ's pathophysiology is shifted from abnormal stochastic behavior toward dysregulated innate immune response. However, β-amyloid deposition in AD still leads to neurodegeneration. Thus, the new model extends but remains broadly consistent with the Amyloid Cascade Hypothesis and overwhelming data showing the primacy of Aβ in AD pathology.

"In the flesh": Narratives of family caregivers at risk of Early-onset Familial Alzheimer's Disease.

In the growing body of literature dealing with the consequences of family caregiving amongst people with dementia, there are few studies examining the impact of Early-onset Familial Alzheimer's Disease on caregivers. This study exposes the subjective experience of a group of family caregivers who themselves possess a genetic susceptibility to develop this form of dementia. We interviewed and analyzed the accounts of 27 caregivers belonging to family lineages carrying the E280A mutation for Early-onset Alzheimer's Disease. We utilized a phenomenological method to analyze these accounts, initially tracking seven theoretical categories (Anxiety, Depression, Burden, Resilience, Self-efficacy, Social Support, and Coping Strategies) and then subsequently two additional categories which emerged (Conceptions about the Disease and Other Vital Experiences Interfering with Caregiving). The results show that caring for a loved one while simultaneously running the risk of developing the same form of Alzheimer's Disease permeates the caregivers' experience both in a negative and a positive way. The continuous exposition to emotional stress in these caregivers should be seriously considered as they may be at risk of accelerating the onset of symptoms of Alzheimer's Disease, while simultaneously, early psychological symptoms of dementia may be masked by the emotional sequelae of caregiving, interfering with early diagnosis. Certainly, support services for the entire family group are suggested.

Presenilin 1 deficiency suppresses autophagy in human neural stem cells through reducing \u03b3-secretase-independent ERK/CREB signaling

Autophagy impairment is commonly implicated in the pathological characteristic of Alzheimer’s disease (AD). Presenilin 1 (PS1) expression in human brain gradually decreases with age and its mutations account for the most common cases of early-onset familial Alzheimer’s disease (FAD). The dominant autophagy phenotypes occur in PS1-knockout and PS1 mutant neurons; it is still unknown whether PS1 deficiency causes serious autophagy impairment in neural stem cells (NSCs). Herein, we generated the heterozygote and homozygote of PS1 knockout in human induced pluripotent stem cells (iPSCs) via CRISPR/Cas9-based gene editing and differentiated them into human NSCs. In these human PS1-deficient NSCs, reduced autophagosome formation and downregulated expression of autophagy–lysosome pathway (ALP)-related mRNAs, as well as proteins were observed. Mechanistically, ERK/CREB inhibition and GSK3β activation had key roles in reducing TFEB expression in PS1-knockout NSCs. Pharmacological inhibition of GSK3β upregulated the expression of TFEB and ALP-related proteins in PS1-knockout NSCs, whereas this effect could be blocked by CREB inhibition. These findings demonstrate that PS1 deficiency causes autophagy suppression in human NSCs via downregulating ERK/CREB signaling.

Riluzole reduces amyloid beta pathology, improves memory, and restores gene expression changes in a transgenic mouse model of early-onset Alzheimer\u2019s disease

Alzheimer’s disease (AD) represents a major healthcare burden with no effective treatment. The glutamate modulator, riluzole, was shown to reverse many AD-related gene expression changes and improve cognition in aged rats. However, riluzole’s effect on amyloid beta (Aβ) pathology, a major histopathological hallmark of AD, remains unclear. 5XFAD transgenic mice, which harbor amyloid β precursor protein (APP) and presenilin mutations and exhibit early Aβ accumulation, were treated with riluzole from 1 to 6 months of age. Riluzole significantly enhanced cognition and reduced Aβ42, Aβ40, Aβ oligomers levels, and Aβ plaque load in 5XFAD mice. RNA-Sequencing showed that riluzole reversed many gene expression changes observed in the hippocampus of 5XFAD mice, predominantly in expression of canonical gene markers for microglia, specifically disease-associated microglia (DAM), as well as neurons and astrocytes. Central to the cognitive improvements observed, riluzole reversed alterations in NMDA receptor subunits gene expression, which are essential for learning and memory. These data demonstrate that riluzole exerts a disease modifying effect in an Aβ mouse model of early-onset familial AD.

Dysregulation of Neuronal Iron Homeostasis as an Alternative Unifying Effect of Mutations Causing Familial Alzheimer's Disease.

The overwhelming majority of dominant mutations causing early onset familial Alzheimer’s disease (EOfAD) occur in only three genes, PSEN1, PSEN2, and APP. An effect-in-common of these mutations is alteration of production of the APP-derived peptide, amyloid β (Aβ). It is this key fact that underlies the authority of the Amyloid Hypothesis that has informed Alzheimer’s disease research for over two decades. Any challenge to this authority must offer an alternative explanation for the relationship between the PSEN genes and APP. In this paper, we explore one possible alternative relationship – the dysregulation of cellular iron homeostasis as a common effect of EOfAD mutations in these genes. This idea is attractive since it provides clear connections between EOfAD mutations and major characteristics of Alzheimer’s disease such as dysfunctional mitochondria, vascular risk factors/hypoxia, energy metabolism, and inflammation. We combine our ideas with observations by others to describe a “Stress Threshold Change of State” model of Alzheimer’s disease that may begin to explain the existence of both EOfAD and late onset sporadic (LOsAD) forms of the disease. Directing research to investigate the role of dysregulation of iron homeostasis in EOfAD may be a profitable way forward in our struggle to understand this form of dementia.

On the role of sidechain size and charge in the aggregation of Aβ42 with familial mutations

The aggregation of the amyloid-β (Aβ) peptide is linked to the pathogenesis of Alzheimer's disease (AD). In particular, some point mutations within Aβ are associated with early-onset familial Alzheimer's disease. Here we set out to explore how the physical properties of the altered side chains, including their sizes and charges, affect the molecular mechanisms of aggregation. We focus on Aβ42 with familial mutations-A21G (Flemish), E22K (Italian), E22G (Arctic), E22Q (Dutch), and D23N (Iowa)-which lead to similar or identical pathology with sporadic AD or severe cerebral amyloid angiopathy. Through global kinetic analysis, we find that for the E22K, E22G, E22Q, and D23N mutations, the acceleration of the overall aggregation originates primarily from the modulation of the nucleation processes, in particular secondary nucleation on the surface of existing fibrils, whereas the elongation process is not significantly affected. Remarkably, the D23 position appears to be responsible for most of the charge effects during nucleation, while the size of the side chain at the E22 position plays a more significant role than its charge. Thus, we have developed a kinetic approach to determine the nature and the magnitude of the contribution of specific residues to the rate of individual steps of the aggregation reaction, through targeted mutations and variations in ionic strength. This strategy can help rationalize the effect of some disease-related mutations as well as yield insights into the mechanism of aggregation and the transition states of the wild-type protein.

Modeling Late-Onset Sporadic Alzheimer’s Disease through BMI1 Deficiency

Late-onset sporadic Alzheimer's disease (AD) is the most prevalent form of dementia, but its origin remains poorly understood. The Bmi1/Ring1 protein complex maintains transcriptional repression of developmental genes through histone H2A mono-ubiquitination, and Bmi1 deficiency in mice results in growth retardation, progeria, and neurodegeneration. Here, we demonstrate that BMI1 is silenced in AD brains, but not in those with early-onset familial AD, frontotemporal dementia, or Lewy body dementia. BMI1 expression was also reduced in cortical neurons from AD patient-derived induced pluripotent stem cells but not in neurons overexpressing mutant APP and PSEN1. BMI1 knockout in human post-mitotic neurons resulted in amyloid beta peptide secretion and deposition, p-Tau accumulation, and neurodegeneration. Mechanistically, BMI1 was required to repress microtubule associated protein tau (MAPT) transcription and prevent GSK3beta and p53 stabilization, which otherwise resulted in neurodegeneration. Restoration of BMI1 activity through genetic or pharmaceutical approaches could represent a therapeutic strategy against AD.

Impact of late-onset Alzheimer's genetic risk factors on beta-amyloid endocytic production.

The increased production of the 42 aminoacids long beta-amyloid (Aβ42) peptide has been established as a causal mechanism of the familial early onset Alzheimer's disease (AD). In contrast, the causal mechanisms of the late-onset AD (LOAD), that affects most AD patients, remain to be established. Indeed, Aβ42 accumulation has been detected more than 30years before diagnosis. Thus, the mechanisms that control Aβ accumulation in LOAD likely go awry long before pathogenesis becomes detectable. Early on, APOE4 was identified as the biggest genetic risk factor for LOAD. However, since APOE4 is not present in all LOAD patients, genome-wide association studies of thousands of LOAD patients were undertaken to identify other genetic variants that could explain the development of LOAD. PICALM, BIN1, CD2AP, SORL1, and PLD3 are now with APOE4 among the identified genes at highest risk in LOAD that have been implicated in Aβ42 production. Recent evidence indicates that the regulation of the endocytic trafficking of the amyloid precursor protein (APP) and/or its secretases to and from sorting endosomes is determinant for Aβ42 production. Thus, here, we will review the described mechanisms, whereby these genetic risk factors can contribute to the enhanced endocytic production of Aβ42. Dissecting causal LOAD mechanisms of Aβ42 accumulation, underlying the contribution of each genetic risk factor, will be required to identify therapeutic targets for novel personalized preventive strategies.

Comprehensive Characterization of the Pyroglutamate Amyloid-β Induced Motor Neurodegenerative Phenotype of TBA2.1 Mice.

Alzheimer’s disease (AD) is the most common neurodegenerative disorder and is being intensively investigated using a broad variety of animal models. Many of these models express mutant versions of human amyloid-β protein precursor (AβPP) that are associated with amyloid-β protein (Aβ)-induced early onset familial AD. Most of these models, however, do not develop bold neurodegenerative pathology and the respective phenotypes. Nevertheless, this may well be essential for their suitability to identify therapeutically active compounds that have the potential for a curative or at least disease-modifying therapy in humans. In this study, the new transgenic mouse model TBA2.1 was explored in detail to increase knowledge about the neurodegenerative process induced by the presence of pyroglutamate modified human Aβ3-42 (pEAβ3-42). Analysis of the sensorimotor phenotype, motor coordination, Aβ pathology, neurodegeneration, and gliosis revealed formation and progression of severe pathology and phenotypes including massive neuronal loss in homozygous TBA2.1 mice within a few months. In contrast, the start of a slight phenotype was observed only after 21 months in heterozygous mice. These data highlight the role of pEAβ3-42 in the disease development and progression of AD. Based on the findings of this study, homozygous TBA2.1 mice can be utilized to gain deeper understanding in the underlying mechanisms of pEAβ3-42 and might be suitable as an animal model for treatment studies targeting toxic Aβ species, complementary to the well described transgenic AβPP mouse models.

Dysfunctional γ-Secretase in Familial Alzheimer's Disease.

Genetics strongly implicate the amyloid β-peptide (Aβ) in the pathogenesis of Alzheimer's disease. Dominant missense mutation in the presenilins and the amyloid precursor protein (APP) cause early-onset familial Alzheimer's disease (FAD). As presenilin is the catalytic component of the γ-secretase protease complex that produces Aβ from APP, mutation of the enzyme or substrate that produce Aβ leads to FAD. However, the mechanism by which presenilin mutations cause FAD has been controversial, with gain of function and loss of function offered as binary choices. This overview will instead present the case that presenilins are dysfunctional in FAD. γ-Secretase is a multi-functional enzyme that proteolyzes the APP transmembrane domain in a complex and processive manner. Reduction in a specific function-the carboxypeptidase trimming of initially formed long Aβ peptides containing most of the transmembrane domain to shorter secreted forms-is an emerging common feature of FAD-mutant γ-secretase complexes.

Hypermethylation of TRIM59 and KLF14 Influences Cell Death Signaling in Familial Alzheimer's Disease.

Epigenetic mechanisms play an important role in the development and progression of various neurodegenerative diseases. Abnormal methylation of numerous genes responsible for regulation of transcription, DNA replication, and apoptosis has been linked to Alzheimer's disease (AD) pathology. We have recently performed whole transcriptome profiling of familial early-onset Alzheimer's disease (fEOAD) patient-derived fibroblasts. On this basis, we demonstrated a strong dysregulation of cell cycle checkpoints and DNA damage response (DDR) in both fibroblasts and reprogrammed neurons. Here, we show that the aging-correlated hypermethylation of KLF14 and TRIM59 genes associates with abnormalities in DNA repair and cell cycle control in fEOAD. Based on the resulting transcriptome networks, we found that the hypermethylation of KLF14 might be associated with epigenetic regulation of the chromatin organization and mRNA processing followed by hypermethylation of TRIM59 likely associated with the G2/M cell cycle phase and p53 role in DNA repair with BRCA1 protein as the key player. We propose that the hypermethylation of KLF14 could constitute a superior epigenetic mechanism for TRIM59 hypermethylation. The methylation status of both genes affects genome stability and might contribute to proapoptotic signaling in AD. Since this study combines data obtained from various tissues from AD patients, it reinforces the view that the genetic methylation status in the blood may be a valuable predictor of molecular processes occurring in affected tissues. Further research is necessary to define a detailed role of TRIM59 and KLF4 in neurodegeneration of neurons.

Neurons derived from sporadic Alzheimer\u2019s disease iPSCs reveal elevated TAU hyperphosphorylation, increased amyloid levels, and GSK3B activation

BackgroundAlzheimer’s disease (AD) is the most common type of dementia, affecting one in eight adults over 65 years of age. The majority of AD cases are sporadic, with unknown etiology, and only 5% of all patients with AD present the familial monogenic form of the disease. In the present study, our aim was to establish an in vitro cell model based on patient-specific human neurons to study the pathomechanism of sporadic AD.MethodsWe compared neurons derived from induced pluripotent stem cell (iPSC) lines of patients with early-onset familial Alzheimer’s disease (fAD), all caused by mutations in the PSEN1 gene; patients with late-onset sporadic Alzheimer’s disease (sAD); and three control individuals without dementia. The iPSC lines were differentiated toward mature cortical neurons, and AD pathological hallmarks were analyzed by RT-qPCR, enzyme-linked immunosorbent assay, and Western blotting methods.ResultsNeurons from patients with fAD and patients with sAD showed increased phosphorylation of TAU protein at all investigated phosphorylation sites. Relative to the control neurons, neurons derived from patients with fAD and patients with sAD exhibited higher levels of extracellular amyloid-β 1–40 (Aβ1–40) and amyloid-β 1–42 (Aβ1–42). However, significantly increased Aβ1–42/Aβ1–40 ratios, which is one of the pathological markers of fAD, were observed only in samples of patients with fAD. Additionally, we detected increased levels of active glycogen synthase kinase 3 β, a physiological kinase of TAU, in neurons derived from AD iPSCs, as well as significant upregulation of amyloid precursor protein (APP) synthesis and APP carboxy-terminal fragment cleavage. Moreover, elevated sensitivity to oxidative stress, as induced by amyloid oligomers or peroxide, was detected in both fAD- and sAD-derived neurons.ConclusionsOn the basis of the experiments we performed, we can conclude there is no evident difference except secreted Aβ1–40 levels in phenotype between fAD and sAD samples. To our knowledge, this is the first study in which the hyperphosphorylation of TAU protein has been compared in fAD and sAD iPSC-derived neurons. Our findings demonstrate that iPSC technology is suitable to model both fAD and sAD and may provide a platform for developing new treatment strategies for these conditions.

Establishment of induced pluripotent stem cell line (ZZUi010-A) from an Alzheimer's disease patient carrying an APP gene mutation

Alzheimer's disease (AD) is one of the most common neurodegenerative disorders. Previous studies have identified mutations in several genes, such as amyloid precursor protein (APP), presenilin-1 (PSEN1), and presenilin-2 (PSEN2), in patients with early-onset (<65years) familial AD. Recently, a patient with an APP gene mutation was identified; the dermal fibroblasts of the patient were obtained and a line of induced pluripotent stem cells (iPSCs) was successfully generated using the Sendai-virus (SeV) delivery system. The iPSC line will be useful for further study of the pathomechanism and drug screening for AD.

Nature Versus Nurture: Does Proteostasis Imbalance Underlie the Genetic, Environmental, and Age-Related Risk Factors for Alzheimer's Disease?

Aging is a risk factor for a number of “age-related diseases”, including Alzheimer’s disease (AD). AD affects more than a third of all people over the age of 85, and is the leading cause of dementia worldwide. Symptoms include forgetfulness, memory loss, and cognitive decline, ultimately resulting in the need for full-time care. While there is no cure for AD, pharmacological approaches to alleviate symptoms and target underlying causes of the disease have been developed, albeit with limited success. This review presents the age-related, genetic, and environmental risk factors for AD and proposes a hypothesis for the mechanistic link between genetics and the environment. In short, much is known about the genetics of early-onset familial AD (EO-FAD) and the central role played by the Aβ peptide and protein misfolding, but late-onset AD (LOAD) is not thought to have direct genetic causes. Nonetheless, genetic risk factors such as isoforms of the protein ApoE have been identified. Additional findings suggest that air pollution caused by the combustion of fossil fuels may be an important environmental risk factor for AD. A hypothesis suggesting that poor air quality might act by disrupting protein folding homeostasis (proteostasis) is presented.

NOVEL AND KNOWN RARE SORL1 MUTATIONS IN KOREAN AD PATIENTS

Even though APP, PSEN1 and PSEN2 are major causative genes for Alzheimer's disease (AD), they are relatively rare. We are perusing to find other novel genes in the disease progression. Since SORL1 gene was suggested in playing a protective role against amyloid beta secretion, mutation in SORL1 could be involved in the disease progression. We performed a complex genetic screening by NGS for 50 genes, including SORL1 gene. NGS data was confirmed by standard sequencing. We performed PolyPhen2, SIFT and 3D protein structure prediction for the rare mutations. We found several rare probable novel SORL1variants, such as V277I, G511R, D862E, R1159Q, T1483A, G1524R and V2097I. We also detected the common A528T mutation among our patients. Most of them were predicted as possible damaging from the predictions. It is too early to say that these mutations in SORL1 could be involved in disease progression. Mutations in SORL1 may be involved in loss-of-function mechanisms. Previous segregation analyses revealed that rare SORL1 mutations could be also associated with early onset familial AD.