Genetics of Alzheimer's disease

Effectiveness and mechanisms of combined use of antioxidant nutrients in protecting against oxidative stress-induced neuronal loss and related neurological deficits

BACKGROUND

Oxidative stress is a well-known pathological factor driving neuronal loss and age-related neurodegenerative diseases. Melatonin, coenzyme Q10 and lecithin are three common nutrients with an antioxidative capacity. Here, we examined the effectiveness of them administrated individually and in combination in protecting against oxidative stress-induced neuronal death in vitro, and neurodegenerative conditions such as Alzheimer's disease and associated deficits in vivo.

METHODS

Mouse neuroblastoma Neuro-2a (N2a) cells were exposed with H2O2 for 6 h, and subsequently treated with melatonin, coenzyme Q10, and lecithin alone or in combination for further 24 h. Cell viability was assessed using the CCK-8 assay. Eight-week-old male mice were intraperitoneally injected with D-(+)-galactose for 10 weeks and administrated with melatonin, coenzyme Q10, lecithin, or in combination for 5 weeks starting from the sixth week, followed by behavioral tests to assess the effectiveness in mitigating neurological deficits, and biochemical assays to explore the underlying mechanisms.

RESULTS

Exposure to H2O2 significantly reduced the viability of N2a cells and increased oxidative stress and tau phosphorylation, all of which were alleviated by treatment with melatonin, coenzyme Q10, lecithin alone, and, most noticeably, by combined treatment. Administration of mice with D-(+)-galactose-induced oxidative stress and tau phosphorylation, brain aging, impairments in learning and memory, anxiety- and depression-like behaviors, and such detrimental effects were mitigated by melatonin, coenzyme Q10, lecithin alone, and, most consistently, by combined treatment.

CONCLUSIONS

These results suggest that targeting oxidative stress via supplementation of antioxidant nutrients, particularly in combination, is a better strategy to alleviate oxidative stress-mediated neuronal loss and brain dysfunction due to age-related neurodegenerative conditions.

Alzheimer's disease current therapies, novel drug delivery systems and future directions for better disease management

Alzheimer's disease (AD), is a neurodegenerative disorder that escalates with time, exerting a significant impact on physical and mental health and leading to death. The prevalence of AD is progressively rising along with its associated economic burden and necessitates effective therapeutic approaches in the near future. This review paper aims to offer an insightful overview of disease pathogenesis, current FDA-approved drugs, and drugs in different clinical phases. It also explores innovative formulations and drug delivery strategies, focusing on nanocarriers and long-acting medications (LAMs) to enhance treatment efficacy and patient adherence. The review also emphasizes preclinical evidence related to nanocarriers and their potential to improve drug bioavailability, pharmacokinetics, and pharmacodynamics parameters, while also highlighting their ability to minimize systemic side effects. By providing a comprehensive analysis, this review furnishes valuable insights into different pathophysiological mechanisms for future drug development. It aims to inform the development of treatment strategies and innovative formulation approaches for delivering existing molecules in Alzheimer's disease, ultimately striving to improve patient compliance.

Alzheimer's Disease in Lebanon: Exploring Genetic and Environmental Risk Factors-A Comprehensive Review

Alzheimer's disease (AD) is a neurodegenerative condition that displays a high prevalence in Lebanon causing a local burden in healthcare and socio-economic sectors. Unfortunately, the lack of prevalence studies and clinical trials in Lebanon minimizes the improvement of AD patient health status. In this review, we include over 155 articles to cover the different aspects of AD ranging from mechanisms to possible treatment and management tools. We highlight some important modifiable and non-modifiable risk factors of the disease including genetics, age, cardiovascular diseases, smoking, etc. Finally, we propose a hypothetical genetic synergy model between APOE4 and TREM2 genes which constitutes a potential early diagnostic tool that helps in reducing the risk of AD based on preventative measures decades before cognitive decline. The studies on AD in Lebanon and the Middle East are scarce. This review points out the importance of genetic mapping in the understanding of disease pathology which is crucial for the emergence of novel diagnostic tools. Hence, we establish a rigid basis for further research to identify the most influential genetic and environmental risk factors for the purpose of using more specific diagnostic tools and possibly adopting a local management protocol.

The Role of Impaired Receptor Trafficking in Mediating the Pathological Effects of APOE4 in Alzheimer's Disease

BACKGROUND

Apolipoprotein E4 (APOE4) is the most prevalent genetic risk factor of Alzheimer's disease. Several studies suggest that APOE4 binding to its receptors is associated with their internalization and accumulation in intracellular compartments. Importantly, this phenomenon also occurs with other, non-ApoE receptors. Based on these observations, we hypothesized that APOE4 pathological effects are mediated by impairment in the life cycle of distinct receptors (APOER2, LRP1, IR, VEGFR).

OBJECTIVE

To examine the effects of APOE genotype on receptors protein levels and compartmentalization.

METHODS

Primary mouse neurons were prepared from APOE3 or APOE4 targeted replacement mice, or APOE-KO mice. Specific receptors protein levels were evaluated in these neurons, utilizing immunofluorescent staining. Additionally, surface membrane protein levels of those receptors were assessed by cell surface biotinylation assay and ELISA. Receptors' colocalization with intracellular compartments was assessed by double staining and confocal microscopy, followed by colocalization analysis. Finally, LRP1 or APOER2 were knocked-down with CRISPR/Cas9 system to examine their role in mediating APOE4 effects on the receptors.

RESULTS

Our results revealed lower receptors' levels in APOE4, specifically on the membrane surface. Additionally, APOE4 affects the compartmentation of these receptors in two patterns: the first was observed with LRP1 and was associated with decreased receptor levels in numerous intracellular compartments. The second was obtained with the other receptors and was associated with their accumulation in early endosomes and their decrease in the late endosomes.

CONCLUSIONS

These results provide a unifying mechanism, in which APOE4 drives the down regulation of various receptors, which plays important roles in distinct APOE4 related pathological processes.

Advances in the study of the effects of gut microflora on microglia in Alzheimer's disease

Alzheimer's disease (AD) is a central nervous system (CNS) degenerative disorder, is caused by various factors including β-amyloid toxicity, hyperphosphorylation of tau protein, oxidative stress, and others. The dysfunction of microglia has been associated with the onset and advancement of different neurodevelopmental and neurodegenerative disorders, such as AD. The gut of mammals harbors a vast and complex population of microorganisms, commonly referred to as the microbiota. There's a growing recognition that these gut microbes are intrinsically intertwined with mammalian physiology. Through the circulation of metabolites, they establish metabolic symbiosis, enhance immune function, and establish communication with different remote cells, including those in the brain. The gut microbiome plays a crucial part in influencing the development and performance of microglia, as indicated by recent preclinical studies. Dysbiosis of the intestinal flora leads to alterations in the microglia transcriptome that regulate the interconversion of microglia subtypes. This conversation explores recent research that clarifies how gut bacteria, their byproducts, and harmful elements affect the activation and characteristics of microglia. This understanding opens doors to innovative microbial-based therapeutic strategies for early identification and treatment goals in AD.

Transfer Learning for Classification of Alzheimer's Disease Based on Genome Wide Data

Alzheimer's disease (AD) is a type of brain disorder that is regarded as a degenerative disease because the corresponding symptoms aggravate with the time progression. Single nucleotide polymorphisms (SNPs) have been identified as relevant biomarkers for this condition. This study aims to identify SNPs biomarkers associated with the AD in order to perform a reliable classification of AD. In contrast to existing related works, we utilize deep transfer learning with varying experimental analysis for reliable classification of AD. For this purpose, the convolutional neural networks (CNN) are firstly trained over the genome-wide association studies (GWAS) dataset requested from the AD neuroimaging initiative. We then employ the deep transfer learning for further training of our CNN (as base model) over a different AD GWAS dataset, to extract the final set of features. The extracted features are then fed into Support Vector Machine for classification of AD. Detailed experiments are performed using multiple datasets and varying experimental configurations. The statistical outcomes indicate an accuracy of 89% which is a significant improvement when benchmarked with existing related works.

Associations of air pollution with all-cause dementia, Alzheimer's disease, and vascular dementia: a prospective cohort study based on 437,932 participants from the UK biobank

Objective

To prospectively assess whether air pollution, including PM2.5, PM10, and NOx, is associated with the risk of all-cause dementia, Alzheimer's disease (AD), and vascular dementia, and to investigate the potential relationship between air pollution and genetic susceptibility in the development of AD.

Methods and results

Our study included 437,932 participants from the UK Biobank with a median follow-up period of over 10 years. Using a Cox proportional hazards model, we found that participants exposed to PM2.5 levels of ≥10 μg/m3 had a higher risk of developing all-cause dementia (HR = 1.1; 95% CI: 1.05-1.28; p < 0.05) compared to the group exposed to PM2.5 levels of <10 μg/m3. However, there was no significant association between PM10 levels of ≥15 μg/m3 and the risk of all-cause dementia, AD, or vascular dementia when compared to the group exposed to PM10 levels of <15 μg/m3. On the other hand, participants exposed to NOx levels of ≥50 μg/m3 had a significantly higher risk of all-cause dementia (HR = 1.14; 95% CI: 1.02-1.26; p < 0.05) and AD (HR = 1.26; 95% CI: 1.08-1.48; p < 0.05) compared to the group exposed to NOx levels of <50 μg/m3. Furthermore, we examined the combined effect of air pollution (PM2.5, PM10, and NOx) and Alzheimer's disease genetic risk score (AD-GRS) on the development of AD using a Cox proportional hazards model. Among participants with a high AD-GRS, those exposed to NOx levels of ≥50 μg/m3 had a significantly higher risk of AD compared to those in the group exposed to NOx levels of <50 μg/m3 (HR = 1.36; 95% CI: 1.03-1.18; p < 0.05). Regardless of air pollutant levels (PM2.5, PM10, or NOx), participants with a high AD-GRS had a significantly increased risk of developing AD. Similar results were obtained when assessing multiple variables using inverse probability of treatment weighting (IPTW).

Conclusion

Our findings indicate that individuals living in areas with PM2.5 levels of ≥10 μg/m3 or NOx levels of ≥50 μg/m3 are at a higher risk of developing all-cause dementia. Moreover, individuals with a high AD-GRS demonstrated an increased risk of developing AD, particularly in the presence of NOx ≥ 50 μg/m3.

HEBP1 - An early trigger for neuronal cell death and circuit dysfunction in Alzheimer's disease

Alzheimer's Disease (AD) is a progressive neurodegenerative disorder that gradually impairs memory, cognition and the ability to perform simple daily tasks. It is the most prevalent form of dementia in the elderly and its incidence increases exponentially with age. Neuronal and synapse loss, key hallmarks of the disorder, are widely regarded to occur early during the onset of AD, and the extent of this loss closely correlates with the progression of cognitive decline and dysfunction of the underlying neuronal circuity. Nevertheless, the mechanisms driving neuronal and synapse loss during early AD remains poorly understood. This review focuses on Heme-binding protein 1 (HEBP1), a mitochondrial-associated protein that has recently emerged as an important mediator of neuronal cell death during early AD pathogenesis. Acting downstream of Aβ and heme, HEBP1-mediated apoptosis contributes to neuronal loss and neuronal circuit dysfunction. Deleting HEBP1 expression in neurons protects them from heme- and Aβ-induced apoptosis, both of which are mechanisms implicated in neurodegeneration. HEBP1 participates in heme metabolism and binds to heme to modulate mitochondrial dynamics vital to the maintenance of neural circuitry that is affected in AD. HEBP1 elevation is also associated with AGE/RAGE-related neuronal damage, further implicating its involvement in neuronal loss during early AD. Moreover, F2L, a cleavage product of HEBP1 modulates inflammation. Collectively, these findings highlight the importance of HEBP1 in the disruption of neural circuits during early AD.

Neuroprotective Effect of α-Lipoic Acid against Aβ25-35-Induced Damage in BV2 Cells

The prevalence of Alzheimer's disease (AD) is significantly increasing due to the aging world population, and the currently available drug treatments cannot cure or even slow its progression. α-lipoic acid (LA) is a biological factor widely found in spinach and meat and can dissolve in both lipid and aqueous phases. In medicine, LA has been shown to reduce the symptoms of diabetic polyneuropathy, acute kidney injury, cancers, and some metabolism-related diseases. This study to proves that α-lipoic acid (LA) can stabilize the cognitive function of patients with Alzheimer's disease (AD). BV2 cells were divided into control, LA, Aβ_25-35, and LA + Aβ_25-35 groups. Cell growth; IL-6, IL-1β, TNF-α, IFN-γ, SOD, GPx, CAT, ROS, NO, and iNOS secretion; Wnt-related proteins; cell apoptosis; and cell activation were examined. Here, we found that LA could effectively repress apoptosis and changes in the morphology of microglia BV2 cells activated by Aβ_25-35, accompanied by the inhibition of the inflammatory response induced by Aβ_25-35. The Wnt/β-catenin pathway is also involved in preventing Aβ_25-35-induced cytotoxicity in microglia by LA. We found an inhibitory effect of LA on microglia toxicity induced by Aβ_25-35, suggesting that a combination of anti-inflammatory and antioxidant substances may offer a promising approach to the treatment of AD.

Clinical relevance of biomarkers, new therapeutic approaches, and role of post-translational modifications in the pathogenesis of Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disorder that causes progressive loss of cognitive functions like thinking, memory, reasoning, behavioral abilities, and social skills thus affecting the ability of a person to perform normal daily functions independently. There is no definitive cure for this disease, and treatment options available for the management of the disease are not very effective as well. Based on histopathology, AD is characterized by the accumulation of insoluble deposits of amyloid beta (Aβ) plaques and neurofibrillary tangles (NFTs). Although several molecular events contribute to the formation of these insoluble deposits, the aberrant post-translational modifications (PTMs) of AD-related proteins (like APP, Aβ, tau, and BACE1) are also known to be involved in the onset and progression of this disease. However, early diagnosis of the disease as well as the development of effective therapeutic approaches is impeded by lack of proper clinical biomarkers. In this review, we summarized the current status and clinical relevance of biomarkers from cerebrospinal fluid (CSF), blood and extracellular vesicles involved in onset and progression of AD. Moreover, we highlight the effects of several PTMs on the AD-related proteins, and provide an insight how these modifications impact the structure and function of proteins leading to AD pathology. Finally, for disease-modifying therapeutics, novel approaches, and targets are discussed for the successful treatment and management of AD.

Tart Cherry Extract and Omega Fatty Acids Reduce Behavioral Deficits, Gliosis, and Amyloid-Beta Deposition in the 5xFAD Mouse Model of Alzheimer's Disease

Combined treatments using polyphenols and omega fatty acids provide several therapeutic benefits for a variety of age-related disorders, including Alzheimer's disease (AD). Previously, we found a commercial product, Total Body Rhythm (TBR), consisting of tart cherry extract, a potent polyphenol, and omega fatty acids, significantly reduced memory, and neuropathological deficits in the 192 IgG-saporin mouse model of AD. The present study assessed the efficacy of TBR for treating behavioral and neuropathological deficits in the 5xFAD model of AD. Both 6- and 12-month-old 5xFAD mice and age-matched wild-type controls received TBR (60 mg/kg) or the equivalent dose of vehicle (0.5% methylcellulose) via oral administration, every other day for two months. All mice were tested in the open field (OF), novel object recognition (NOR), and the Morris water maze (MWM) tasks. In addition, neuronal morphology, neurodegeneration, Aβ plaque load, and glial activation were assessed. TBR treatment reduced memory deficits in the MWM and NOR tests and lessened anxiety levels in the OF task, mostly in the 6-month-old male mice. TBR also protected against neuron loss, reduced activation of astrocytes and microglia, primarily in 6-month-old mice, and attenuated Aβ deposition. These results suggest that the combination of tart cherry extract and omega fatty acids in TBR can reduce AD-like deficits in 5xFAD mice.

Exploring the Potential of Neuroproteomics in Alzheimer's Disease

Alzheimer's disease (AD) is progressive brain amyloidosis that damages brain regions associated with memory, thinking, behavioral and social skills. Neuropathologically, AD is characterized by intraneuronal hyperphosphorylated tau inclusions as neurofibrillary tangles (NFTs), and buildup of extracellular amyloid-beta (Aβ) peptide as senile plaques. Several biomarker tests capturing these pathologies have been developed. However, for the full clinical expression of the neurodegenerative events of AD, there exist other central molecular pathways. In terms of understanding the unidentified underlying processes for the progression and development of AD, a complete comprehension of the structure and composition of atypical aggregation of proteins is essential. Presently, to aid the prognosis, diagnosis, detection, and development of drug targets in AD, neuroproteomics is elected as one of the leading essential tools for the efficient exploratory discovery of prospective biomarker candidates estimated to play a crucial role. Therefore, the aim of this review is to present the role of neuroproteomics to analyze the complexity of AD.

The neuroprotective effects of alpha-lipoic acid on an experimental model of Alzheimer's disease in PC12 cells

With the growth of the aging population, the prevalence of Alzheimer's disease (AD) has increased and influenced the work and daily life of AD patients, imposing a heavy burden on society and the patients' families. AD is a progressive disease with a long duration, and the pathogenesis is very complicated. Here, we found that alpha-lipoic acid (LA), an endogenous, naturally synthesized compound, could attenuate amyloid beta fragment (Aβ_25-35 )-induced PC12 cell toxicity. Aβ_25-35 treatment largely decreased the viability of PC12 cells, increased reactive oxygen species (ROS) levels, and increased the percentage of apoptotic cells, which were accompanied by changes in the expression of the apoptosis-related genes. Further, the Wnt pathway was inactivated, and the expression of Wnt pathway-related proteins such as Frizzled2, GSK3β, and phosphorylated GSK3β were dysregulated after Aβ_25-35 treatment. LA efficiently attenuated Aβ_25-35 -induced PC12 cell apoptosis and downregulated the phosphorylation-mediated degradation of β-catenin as well as GSK3β. Our results demonstrate that LA rescues Aβ_25-35 -induced neurocytotoxicity through the Wnt-β-catenin pathway.

The Association between Neprilysin gene polymorphisms and Alzheimer's disease in Tibetan population

OBJECTIVES

Alzheimer's disease (AD) is a well-known neurodegenerative disease, of which the hallmark is the disposition of β-amyloid (Aβ) in the form of plaque in the brain. Neprilysin (NEP) is the major enzyme to degrade Aβ and prevent accumulation of Aβ. The present study was undertaken to elucidate the correlation between the NEP gene polymorphisms and AD in Chinese Tibetan population.

METHODS

Ninety-nine sporadic AD Tibetan patients and 113 healthy Tibetan controls were enrolled in this study. The genotype frequencies and allele frequencies of multiple NEP gene loci were analyzed using the case-control association analysis.

RESULTS

No significant correlation was found between polymorphisms of NEP gene loci (rs9829757, rs1816558, rs6776185, rs3736187, rs701109, rs989692) and the occurrence of AD in Tibetan population. However, allele C of NEP gene locus (rs701109) and allele T of gene locus (rs3736187) were possible risk factors of male AD patients in Tibetan population.

CONCLUSIONS

NEP gene loci (rs701109, rs989692, rs9829757, rs3736187, rs1816558, rs6776185) were polymorphic in Tibetan population. No difference was found between these loci but for that male gender combined with allele C of NEP gene locus (rs701109) and T of gene locus (rs3736187) might be risk factors for AD in Tibet.

Molecular Genetics of Early- and Late-Onset Alzheimer's Disease

Alzheimer's disease (AD) is the most common form of dementia in the elderly and this complex disorder is associated with environmental as well as genetic factors. Early-onset AD (EOAD) and late-onset AD (LOAD, more common) are major identified types of AD. The genetics of EOAD is extensively understood, with three gene variants such as APP, PSEN1, and PSEN2 leading to the disease. Some common alleles, including APOE, are effectively associated with LOAD identified, but the genetics of LOAD is not clear to date. It has been accounted that about 5-10% of EOAD patients can be explained through mutations in the three familiar genes of EOAD. The APOE ε4 allele augmented the severity of EOAD risk in carriers, and the APOE ε4 allele was considered as a hallmark of EOAD. A great number of EOAD patients, who are not genetically explained, indicate that it is not possible to identify disease-triggering genes yet. Although several genes have been identified by using the technology of next-generation sequencing in EOAD families, including SORL1, TYROBP, and NOTCH3. A number of TYROBP variants are identified through exome sequencing in EOAD patients and these TYROBP variants may increase the pathogenesis of EOAD. The existence of the ε4 allele is responsible for increasing the severity of EOAD. However, several ε4 allele carriers propose the presence of other LOAD genetic as well as environmental risk factors that are not identified yet. It is urgent to find out missing genetics of EOAD and LOAD etiology to discover new potential genetic facets which will assist in understanding the pathological mechanism of AD. These investigations should contribute to developing a new therapeutic candidate for alleviating, reversing and preventing AD. This article, based on current knowledge, represents the overview of the susceptible genes of EOAD, and LOAD. Next, we represent the probable molecular mechanism that might elucidate the genetic etiology of AD and highlight the role of massively parallel sequencing technologies for novel gene discoveries.

The Role of Nutrition and Inflammation on Cognition in a High-Risk Group for Alzheimer's Disease

Background:

Alzheimer’s disease (AD) is a prevalent neurodegenerative disease. Treatments are necessary to target people at high risk for AD. Inflammation, particularly tumor necrosis factor alpha (TNFα), appears to be an important marker associated with the development of AD pathophysiology. Consuming a high-fat diet induces tissue expression of TNFα.

Objective:

This study investigates the relationship between nutrition, circulating inflammation, and cognition in African American women (age: M = 59.5 (±8.20) [42–73] years) at risk for developing AD.

Methods:

Participants were split into high-fat and low-fat groups based on total dietary fat consumption self-reported on the Lower Mississippi Delta Nutrition Intervention Research Initiative Food Frequency Questionnaire (Delta NIRI FFQ).

Results:

A high-fat diet was associated with increased blood serum TNFα (p = 0.02) compared to the low-fat diet. In addition, global cognition scores were 9.0% better in those who consumed a higher fat diet (p = 0.04). No significant differences across groups were noted for executive function, dual-tasking, and visuospatial performance.

Conclusion:

These results indicate that there may be multiple biological pathways involved in AD development, suggesting the need for more holistic approaches to mitigate AD-development risk.

Gene mutations associated with early onset familial Alzheimer's disease in China: An overview and current status

BACKGROUND

Mutations of three causative genes, namely presenilin 1 (PSEN1), presenilin 2 (PSEN2), and amyloid precursor protein (APP), have been identified as the major causes of early-onset familial Alzheimer's disease (EOFAD). The prevalence of causative gene mutations in patients with EOFAD has been reported in previous studies worldwide but remains unclear in China. The patients with these known mutations always show considerable clinical phenotypic variability. However, to date, there have been no detailed descriptions of the clinical phenotypes associated with these Chinese EOFAD mutations. Thus, the aim of this study was to describe all of the known mutations in three EOFAD causative genes and genotype-phenotype correlations in Chinese patients with EOFAD.

METHOD

We systematically searched the PubMed, MEDLINE, CNKI, VIP, and WAN-FANG databases to find Chinese EOFAD mutations in reports from inception through May 2020.

RESULT

We identified 31 studies reporting mutations of three causative genes in China. 10 mutations in APP gene, 27 mutations in PSEN1 gene and six mutations in PSEN2 were discovered in Chinese EOFAD. This review summarized all these probably pathogenic mutations as well as its clinical features. To the best of our knowledge, this is the first systemic review of causative gene mutations in patients with EOFAD in China.

CONCLUSION

The analysis of the genetic and clinical phenotype correlations in this review supports the idea that the clinical phenotype might be influenced by specific genetic defects. It also suggests genetic testing and genotype-phenotype correlations are important for the accurate diagnosis and for understanding disease-associated pathways and might also improve disease therapy and prevention.

The influence of Aβ-dependent and independent pathways on TDP-43 proteinopathy in Alzheimer's disease: a possible connection to LATE-NC

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that results from the accumulation of plaques by cleaved Aβ₄₂ peptides as well as neurofibrillary tangles of tau proteins. This accumulation triggers a complex cascade of cytotoxic, neuroinflammatory, and oxidative stresses that lead to neuronal death throughout the progression of the disease. Much of research in AD focused on the 2 pathologic proteins. Interestingly, another form of dementia with similar clinical manifestations of AD, but preferentially affected much older individuals, was termed as limbic-predominant age-related transactive response DNA-binding protein 43 (TDP-43) encephalopathy (LATE) and involved the cytotoxic intraneuronal deposition of phosphorylated TDP-43. TDP-43 proteinopathy was also found to be involved in AD pathology leading to the possibility that AD and LATE may share a common upstream etiology. This paper discusses the roles molecular pathways known in AD may have on influencing TDP-43 proteinopathy and the development of AD, LATE, or the 2 being comorbid with each other.

Presenilin 1 and APP Gene Mutations in Early-Onset AD Families from a Southeast Region of China

BACKGROUND

Early-Onset Familial Alzheimer's Disease (EOFAD) has been reported to be associated with Presenilin 1 (PSEN1), Presenilin 2 (PSEN2), and Amyloid Precursor Protein (APP) genes. The spectrum of mutations in Chinese patients with EOFAD was rarely investigated.

OBJECTIVE

To investigate the spectrum of mutations in patients with EOFAD in Chinese population.

METHODS

We performed whole-exome sequencing and described relevant clinical features in a total of 67 subjects from 3 families with EOFAD.

RESULTS

A splice mutation (p.S290C) in PSEN1 and a missense mutation (p.V717I) in APP were identified.

CONCLUSION

The variant p. S290C (c.869-2>G) in PSEN1 in Chinese EOAD family revealed different clinical phenotypes when compared with that of Europeans.

Canine Models of Inherited Musculoskeletal and Neurodegenerative Diseases

Mouse models of human disease remain the bread and butter of modern biology and therapeutic discovery. Nonetheless, more often than not mouse models do not reproduce the pathophysiology of the human conditions they are designed to mimic. Naturally occurring large animal models have predominantly been found in companion animals or livestock because of their emotional or economic value to modern society and, unlike mice, often recapitulate the human disease state. In particular, numerous models have been discovered in dogs and have a fundamental role in bridging proof of concept studies in mice to human clinical trials. The present article is a review that highlights current canine models of human diseases, including Alzheimer's disease, degenerative myelopathy, neuronal ceroid lipofuscinosis, globoid cell leukodystrophy, Duchenne muscular dystrophy, mucopolysaccharidosis, and fucosidosis. The goal of the review is to discuss canine and human neurodegenerative pathophysiologic similarities, introduce the animal models, and shed light on the ability of canine models to facilitate current and future treatment trials.

Prospects for the application of mesenchymal stem cells in Alzheimer's disease treatment

Alzheimer's disease (AD) as a dementia and neurodegenerative disease, is mostly prevalent among people more than 65 years. AD is mostly manifested in the form of degraded mental function, such as losing memory and impaired cognitive function. Due to inefficiency of traditional pharmacological therapeutic approaches with no long-term cure, cell therapy can be considered as a capable approach in AD management. Therapies based on mesenchymal stem cells (MSCs) have provided hopeful results in experimental models regarding several disorders. MSCs enhance the levels of functional recoveries in pathologic experimental models of central nervous system (CNS) and are being investigated in clinical trials in neurological disorders. However, there is limited knowledge on the protective capabilities of MSCs in AD management. Almost, several experiments have suggested positive effects of MSCs and helped to better understand of AD-related dementia mechanism. MSCs have the potential to be used in AD treatment through amyloid-β peptide (AB), Tau protein and cholinergic system. This review aimed to clarify the promising perspective of MSCs in the context of AD.

Systematic analysis of dark and camouflaged genes reveals disease-relevant genes hiding in plain sight

BACKGROUND

The human genome contains "dark" gene regions that cannot be adequately assembled or aligned using standard short-read sequencing technologies, preventing researchers from identifying mutations within these gene regions that may be relevant to human disease. Here, we identify regions with few mappable reads that we call dark by depth, and others that have ambiguous alignment, called camouflaged. We assess how well long-read or linked-read technologies resolve these regions.

RESULTS

Based on standard whole-genome Illumina sequencing data, we identify 36,794 dark regions in 6054 gene bodies from pathways important to human health, development, and reproduction. Of these gene bodies, 8.7% are completely dark and 35.2% are ≥ 5% dark. We identify dark regions that are present in protein-coding exons across 748 genes. Linked-read or long-read sequencing technologies from 10x Genomics, PacBio, and Oxford Nanopore Technologies reduce dark protein-coding regions to approximately 50.5%, 35.6%, and 9.6%, respectively. We present an algorithm to resolve most camouflaged regions and apply it to the Alzheimer's Disease Sequencing Project. We rescue a rare ten-nucleotide frameshift deletion in CR1, a top Alzheimer's disease gene, found in disease cases but not in controls.

CONCLUSIONS

While we could not formally assess the association of the CR1 frameshift mutation with Alzheimer's disease due to insufficient sample-size, we believe it merits investigating in a larger cohort. There remain thousands of potentially important genomic regions overlooked by short-read sequencing that are largely resolved by long-read technologies.

Association study of rs3846662 with Alzheimer's disease in a population-based cohort: the Cache County Study

3-Hydroxy-3-methylglutaryl coenzyme A reductase is associated with monitoring cholesterol levels. The presence of the single-nucleotide polymorphism rs3846662 introduces alternative splicing at exon 13; the exclusion of this exon leads to a reduction in total cholesterol levels. Lower cholesterol levels are linked to a reduction in Alzheimer's disease (AD) risk. The major allele of rs3846662, which encourages the splicing of exon 13, has recently been shown to act as a preventative allele for AD, especially in women. The purpose of our research was to replicate and confirm this finding. Using logistic regressions and survival curves, we found a significant association between AD and rs3846662, with a stronger association in individuals who carry the APOE e4 allele, supporting previously published work. The effect of rs3846662 on women is insignificant in our cohort. We confirmed that rs3846662 is associated with reduced risk for AD without gender differences; however, we failed to detect association between rs3846662 and delayed mild cognitive impairment conversion to AD for either of the APOE e4 allelic groups.

Population genealogy resource shows evidence of familial clustering for Alzheimer disease

OBJECTIVE

To show the potential of a resource consisting of a genealogy of the US record linked to National Veterans Health Administration (VHA) patient data for investigation of the genetic contribution to health-related phenotypes, we present an analysis of familial clustering of VHA patients diagnosed with Alzheimer disease (AD).

METHODS

Patients with AD were identified by the International Classification of Diseases code. The Genealogical Index of Familiality method was used to compare the average relatedness of VHA patients with AD with expected relatedness. Relative risks for AD were estimated in first- to fifth- degree relatives of patients with AD using population rates for AD.

RESULTS

Evidence for significant excess relatedness and significantly elevated risks for AD in relatives was observed; multiple pedigrees with a significant excess of VHA patients with AD were identified.

CONCLUSIONS

This analysis of AD shows the nascent power of the US Veterans Genealogy Resource, in early stages, to provide evidence for familial clustering of multiple phenotypes, and shows the utility of this VHA genealogic resource for future genetic studies.

Low expression of aging-related NRXN3 is associated with Alzheimer disease: A systematic review and meta-analysis

BACKGROUND

Alzheimer disease (AD) is a common neurodegenerative disorder with distinct pathological features, with aging considered the greatest risk factor. We explored how aging contributes to increased AD risk, and determined concurrent and coordinate changes (including genetic and phenotypic modifications) commonly exhibited in both normal aging and AD.

METHODS

Using the Gene Expression Omnibus (GEO) database, we collected 1 healthy aging-related and 3 AD-related datasets of the hippocampal region. The normal aging dataset was divided into 3 age groups: young (20-40 years old), middle-aged (40-60 years old), and elderly (>60 years old). These datasets were used to analyze the differentially expressed genes (DEGs). The Gene Ontology (GO) terms, pathways, and function network analysis of these DEGs were analyzed.

RESULTS

One thousand two hundred ninety-one DEGs were found to be shared in the natural aging groups and AD patients. Among the shared DEGs, ATP6V1E1, GNG3, NDUFV2, GOT1, USP14, and NAV2 have been previously found in both normal aging individuals and AD patients. Furthermore, using Java Enrichment of Pathways Extended to Topology (JEPETTO) analysis based on Kyoto Encyclopedia of Genes and Genomes (KEGG) database, we determined that changes in aging-related KEGG annotations may contribute to the aging-dependence of AD risk. Interestingly, NRXN3, the second most commonly deregulated gene identified in the present study, is known to carry a mutation in AD patients. According to functional network analysis, NRXN3 plays a critical role in synaptic functions involved in the cognitive decline associated with normal aging and AD.

CONCLUSION

Our results indicate that the low expression of aging-related NRXN3 may increase AD risk, though the potential mechanism requires further clarification.

Genetic variation affecting exon skipping contributes to brain structural atrophy in Alzheimer's disease

Genetic variation in cis-regulatory elements related to splicing machinery and splicing regulatory elements (SREs) results in exon skipping and undesired protein products. We developed a splicing decision model to identify actionable loci among common SNPs for gene regulation. The splicing decision model identified SNPs affecting exon skipping by analyzing sequence-driven alternative splicing (AS) models and by scanning the genome for the regions with putative SRE motifs. We used non-Hispanic Caucasians with neuroimaging, and fluid biomarkers for Alzheimer's disease (AD) and identified 17,088 common exonic SNPs affecting exon skipping. GWAS identified one SNP (rs1140317) in HLA-DQB1 as significantly associated with entorhinal cortical thickness, AD neuroimaging biomarker, after controlling for multiple testing. Further analysis revealed that rs1140317 was significantly associated with brain amyloid-f deposition (PET and CSF). HLA-DQB1 is an essential immune gene and may regulate AS, thereby contributing to AD pathology. SRE may hold potential as novel therapeutic targets for AD.

Assembly of 809 whole mitochondrial genomes with clinical, imaging, and fluid biomarker phenotyping

INTRODUCTION

Mitochondrial genetics are an important but largely neglected area of research in Alzheimer's disease. A major impediment is the lack of data sets.

METHODS

We used an innovative, rigorous approach, combining several existing tools with our own, to accurately assemble and call variants in 809 whole mitochondrial genomes.

RESULTS

To help address this impediment, we prepared a data set that consists of 809 complete and annotated mitochondrial genomes with samples from the Alzheimer's Disease Neuroimaging Initiative. These whole mitochondrial genomes include rich phenotyping, such as clinical, fluid biomarker, and imaging data, all of which is available through the Alzheimer's Disease Neuroimaging Initiative website. Genomes are cleaned, annotated, and prepared for analysis.

DISCUSSION

These data provide an important resource for investigating the impact of mitochondrial genetic variation on risk for Alzheimer's disease and other phenotypes that have been measured in the Alzheimer's Disease Neuroimaging Initiative samples.

Mitochondria and Alzheimer's Disease: the Role of Mitochondrial Genetic Variation

Purpose of Review

Alzheimer’s disease (AD) is the most common form of dementia, affects an increasing number of people worldwide, has a rapidly increasing incidence, and is fatal. In the past several years, significant progress has been made towards solving the genetic architecture of AD, but our understanding remains incomplete and has not led to treatments that either cure or slow disease. There is substantial evidence that mitochondria are involved in AD: mitochondrial functional declines in AD, mitochondrial encoded gene expression changes, mitochondria are morphologically different, and mitochondrial fusion/fission are modified. While a majority of mitochondrial proteins are nuclear encoded and could lead to malfunction in mitochondria, the mitochondrial genome encodes numerous proteins important for the electron transport chain, which if damaged could possibly lead to mitochondrial changes observed in AD. Here, we review publications that describe a relationship between the mitochondrial genome and AD and make suggestions for analysis approaches and data acquisition, from existing datasets, to study the mitochondrial genetics of AD.

Recent Findings

Numerous mitochondrial haplogroups and SNPs have been reported to influence risk for AD, but the majority of these have not been replicated, nor experimentally validated.

Summary

The role of the mitochondrial genome in AD remains elusive, and several impediments exist to fully understand the relationship between the mitochondrial genome and AD. Yet, by leveraging existing datasets and implementing appropriate analysis approaches, determining the role of mitochondrial genetics in risk for AD is possible.

Molecular Insights into the Roles of Rab Proteins in Intracellular Dynamics and Neurodegenerative Diseases

In eukaryotes, the cellular functions are segregated to membrane-bound organelles. This inherently requires sorting of metabolites to membrane-limited locations. Sorting the metabolites from ribosomes to various organelles along the intracellular trafficking pathways involves several integral cellular processes, including an energy-dependent step, in which the sorting of metabolites between organelles is catalyzed by membrane-anchoring protein Rab-GTPases (Rab). They contribute to relaying the switching of the secretory proteins between hydrophobic and hydrophilic environments. The intracellular trafficking routes include exocytic and endocytic pathways. In these pathways, numerous Rab-GTPases are participating in discrete shuttling of cargoes. Long-distance trafficking of cargoes is essential for neuronal functions, and Rabs are critical for these functions, including the transport of membranes and essential proteins for the development of axons and neurites. Rabs are also the key players in exocytosis of neurotransmitters and recycling of neurotransmitter receptors. Thus, Rabs are critical for maintaining neuronal communication, as well as for normal cellular physiology. Therefore, cellular defects of Rab components involved in neural functions, which severely affect normal brain functions, can produce neurological complications, including several neurodegenerative diseases. In this review, we provide a comprehensive overview of the current understanding of the molecular signaling pathways of Rab proteins and the impact of their defects on different neurodegenerative diseases. The insights gathered into the dynamics of Rabs that are described in this review provide new avenues for developing effective treatments for neurodegenerative diseases-associated with Rab defects.

Gene Expression of Quaking in Sporadic Alzheimer's Disease Patients is Both Upregulated and Related to Expression Levels of Genes Involved in Amyloid Plaque and Neurofibrillary Tangle Formation

Quaking (QKI) is a gene exclusively expressed within glial cells. QKI has previously been implicated in various neurological disorders and diseases, including Alzheimer’s disease (AD), a condition for which increasing evidence suggests a central role of glia cells. The objective of the present study was to investigate the expression levels of QKI and three QKI isoforms (QKI5, QKI6, and QKI7) in AD. Genes that have previously been related to the ontogeny and progression of AD, specifically APP, PSEN1, PSEN2, and MAPT, were also investigated. A real-time PCR assay of 123 samples from human postmortem sporadic AD patients and control brains was performed. The expression values were analyzed with an analysis of covariance model and subsequent multiple regressions to explore the possibility of related expression values between QKI, QKI isoforms, and AD-related genes. Further, the sequences of AD-related genes were analyzed for the presence of QKI binding domains. QKI and all measured QKI isoforms were found to be significantly upregulated in AD samples, relative to control samples. However, APP, PSEN1, PSEN2, and MAPT were not found to be significantly different. QKI and QKI isoforms were found to be predictive for the variance of APP, PSEN1, PSEN2, and MAPT, and putative QKI binding sites suggests an interaction with QKI. Overall, these results implicate a possible role of QKI in AD, although the exact mechanism by which this occurs remains to be uncovered.

Role of the peripheral innate immune system in the development of Alzheimer's disease

Alzheimer's disease is one of the most devastating neurodegenerative diseases. The exact cause of the disease is still not known although many scientists believe in the beta amyloid hypothesis which states that the accumulation of the amyloid peptide beta (Aβ) in brain is the initial cause which consequently leads to pathological neuroinflammation. However, it was recently shown that Aβ may have an important role in defending the brain against infections. Thus, the balance between positive and negative impact of Aβ may determine disease progression. Microglia in the brain are innate immune cells, and brain-initiated inflammatory responses reflected in the periphery suggests that Alzheimer's disease is to some extent also a systemic inflammatory disease. Greater permeability of the blood brain barrier facilitates the transport of peripheral immune cells to the brain and vice versa so that a vicious circle originating on the periphery may contribute to the development of overt clinical AD. Persistent inflammatory challenges by pathogens in the periphery, increasing with age, may also contribute to the central propagation of the pathological changes seen clinically. Therefore, the activation status of peripheral innate immune cells may represent an early biomarker of the upcoming impact on the brain. The modulation of these cells may thus become a useful mechanism for modifying disease progression.

Navβ2 knockdown improves cognition in APP/PS1 mice by partially inhibiting seizures and APP amyloid processing

Voltage-gated sodium channels beta 2 (Navβ2, encoded by SCN2B) is a substrate of β-site amyloid precursor protein cleaving enzyme 1 (BACE1) and regulates cell surface expression of channels in neurons. Previous studies reported enhanced Navβ2 processing by BACE1 in Alzheimer’s disease (AD) model and patients. We investigated whether changes in Navβ2 expression affect neuronal seizure and amyloid precursor protein (APP) processing in an AD mouse model. Our study used eight-month-old APP/presenilin 1 (PS1) mice and transgenic Navβ2 knockdown [by 61% vs. wild type (WT)] APP/PS1 mice (APP/PS1/Navβ2-kd), with age-matched WT and Navβ2 knockdown (Navβ2-kd) mice as controls. We found that Navβ2 knockdown in APP/PS1 mice partially reversed the abnormal Navβ2 cleavage and the changes in intracellular and total Nav1.1α expression. It also restored sodium currents density in hippocampal neurons and neuronal activity, as indicated by EEG tracing; improved Morris water maze performance; and shifted APP amyloidogenic metabolism towards non-amyloidogenic processing. There were no differences in these indicators between WT and Navβ2-kd mice. These results suggest Navβ2 knockdown may be a promising strategy for treating AD.

Overview and Current Status of Alzheimer's Disease in Bangladesh

Alzheimer’s disease (AD) is a complex neurological disorder with economic, social, and medical burdens which is acknowledged as leading cause of dementia marked by the accumulation and aggregation of amyloid-β peptide and phosphorylated tau (p-tau) protein and concomitant dementia, neuron loss and brain atrophy. AD is the most prevalent neurodegenerative brain disorder with sporadic etiology, except for a small fraction of cases with familial inheritance where familial forms of AD are correlated to mutations in three functionally related genes: the amyloid-β protein precursor and presenilins 1 and 2, two key γ-secretase components. The common clinical features of AD are memory impairment that interrupts daily life, difficulty in accomplishing usual tasks, confusion with time or place, trouble understanding visual images and spatial relationships. Age is the most significant risk factor for AD, whereas other risk factors correlated with AD are hypercholesterolemia, hypertension, atherosclerosis, coronary heart disease, smoking, obesity, and diabetes. Despite decades of research, there is no satisfying therapy which will terminate the advancement of AD by acting on the origin of the disease process, whereas currently available therapeutics only provide symptomatic relief but fail to attain a definite cure and prevention. This review also represents the current status of AD in Bangladesh.

Microglia-Synapse Pathways: Promising Therapeutic Strategy for Alzheimer's Disease

The main hallmarks of Alzheimer's disease (AD) are extracellular deposits of amyloid plaques and intracellular accumulation of hyperphosphorylated neurofibrillary tangles (tau). However, the mechanisms underlying these neuropathological changes remain largely unclear. To date, plenty of studies have shown that microglia-mediated neuroinflammation contributes to the pathogenesis of AD, and the microglia-synapse pathways have been repeatedly identified as the crucial factor in the disease process. In this review, evidences from microglia and synapse studies are presented, and the role of microglia in the pathogenesis of AD, the contributing factors to synapse dysfunction, and the role and mechanisms of microglia-synapse pathways will be discussed.

Old age potentiates cold-induced tau phosphorylation: linking thermoregulatory deficit with Alzheimer's disease

Thermoregulatory deficits coincide with a rise in the incidence of Alzheimer's disease (AD) in old age. Lower body temperature increases tau phosphorylation, a neuropathological hallmark of AD. To determine whether old age potentiates cold-induced tau phosphorylation, we compared the effects of cold exposure (4 °C, 24 hours) in 6- and 18-month-old mice. Cold-induced changes in body temperature, brown adipose tissue activity, and phosphorylation of tau at Ser202 were not different between 6- and 18-month-old mice. However, following cold exposure, only old mice displayed a significant rise in soluble tau pThr181 and pThr231, which was correlated with body temperature. Inactivation of glycogen synthase kinase 3β was more prominent in young mice, suggesting a protective mechanism against cold-induced tau phosphorylation. These results suggest that old age confers higher susceptibility to tau hyperphosphorylation following a change in body temperature, thereby contributing to an enhanced risk of developing AD.

Genetic alterations of δ-catenin/NPRAP/Neurojungin (CTNND2): functional implications in complex human diseases

Some genes involved in complex human diseases are particularly vulnerable to genetic variations such as single nucleotide polymorphism, copy number variations, and mutations. For example, Ras mutations account for over 30 % of all human cancers. Additionally, there are some genes that can display different variations with functional impact in different diseases that are unrelated. One such gene stands out: δ-catenin/NPRAP/Neurojungin with gene designation as CTNND2 on chromosome 5p15.2. Recent advances in genome wide association as well as molecular biology approaches have uncovered striking involvement of δ-catenin gene variations linked to complex human disorders. These disorders include cancer, bipolar disorder, schizophrenia, autism, Cri-du-chat syndrome, myopia, cortical cataract-linked Alzheimer's disease, and infectious diseases. This list has rapidly grown longer in recent years, underscoring the pivotal roles of δ-catenin in critical human diseases. δ-Catenin is an adhesive junction-associated protein in the delta subfamily of the β-catenin superfamily. δ-Catenin functions in Wnt signaling to regulate gene expression and modulate Rho GTPases of the Ras superfamily in cytoskeletal reorganization. δ-Catenin likely lies where Wnt signaling meets Rho GTPases and is a unique and vulnerable common target for mutagenesis in different human diseases.

Therapies for Prevention and Treatment of Alzheimer's Disease

Alzheimer's disease (AD) is the most common cause of dementia associated with a progressive neurodegenerative disorder, with a prevalence of 44 million people throughout the world in 2015, and this figure is estimated to double by 2050. This disease is characterized by blood-brain barrier disruption, oxidative stress, mitochondrial impairment, neuroinflammation, and hypometabolism; it is related to amyloid-β peptide accumulation and tau hyperphosphorylation as well as a decrease in acetylcholine levels and a reduction of cerebral blood flow. Obesity is a major risk factor for AD, because it induces adipokine dysregulation, which consists of the release of the proinflammatory adipokines and decreased anti-inflammatory adipokines, among other processes. The pharmacological treatments for AD can be divided into two categories: symptomatic treatments such as acetylcholinesterase inhibitors and N-methyl-D-aspartate (NMDA) receptor antagonists and etiology-based treatments such as secretase inhibitors, amyloid binders, and tau therapies. Strategies for prevention of AD through nonpharmacological treatments are associated with lifestyle interventions such as exercise, mental challenges, and socialization as well as caloric restriction and a healthy diet. AD is an important health issue on which all people should be informed so that prevention strategies that minimize the risk of its development may be implemented.

A novel approach for multi-SNP GWAS and its application in Alzheimer's disease

BACKGROUND

Genome-wide association studies (GWAS) have effectively identified genetic factors for many diseases. Many diseases, including Alzheimer's disease (AD), have epistatic causes, requiring more sophisticated analyses to identify groups of variants which together affect phenotype.

RESULTS

Based on the GWAS statistical model, we developed a multi-SNP GWAS analysis to identify pairs of variants whose common occurrence signaled the Alzheimer's disease phenotype.

CONCLUSIONS

Despite not having sufficient data to demonstrate significance, our preliminary experimentation identified a high correlation between GRIA3 and HLA-DRB5 (an AD gene). GRIA3 has not been previously reported in association with AD, but is known to play a role in learning and memory.

Identification of the PS1 Thr147Ile Variant in a Family with Very Early Onset Dementia and Expressive Aphasia

BACKGROUND

Early onset dementias have variable clinical presentations and are often difficult to diagnose. We established a family pedigree that demonstrated consistent recurrence of very early onset dementia in successive generations.

OBJECTIVE AND METHOD

In order to refine the diagnosis in this family, we sequenced the exomes of two affected family members and relied on discrete filtering to identify disease genes and the corresponding causal variants.

RESULTS

Among the 720 nonsynonymous single nucleotide polymorphisms (SNPs) shared by two affected members, we found a C to T transition that gives rise to a Thr147Ile missense substitution in the presenilin 1 (PS1) protein. The presence of this same mutation in a French early-onset Alzheimer's disease family, other affected members of the family, and the predicted high pathogenicity of the substitution strongly suggest that it is the causal variant. In addition to exceptionally young age of onset, we also observed significant limb spasticity and early loss of speech, concurrent with progression of dementia in affected family members. These findings extend the clinical presentation associated with the Thr147Ile variant. Lastly, one member with the Thr147Ile variant was treated with the PKC epsilon activator, bryostatin, in a compassionate use trial after successful FDA review. Initial improvements with this treatment were unexpectedly clear, including return of some speech, increased attentional focus, ability to swallow, and some apparent decrease in limb spasticity.

CONCLUSIONS

Our findings confirm the role of the PS1 Thr147Ile substitution in Alzheimer's disease and expand the clinical phenotype to include expressive aphasia and very early onset of dementia.

Crowdsourced estimation of cognitive decline and resilience in Alzheimer's disease

Identifying accurate biomarkers of cognitive decline is essential for advancing early diagnosis and prevention therapies in Alzheimer's disease. The Alzheimer's disease DREAM Challenge was designed as a computational crowdsourced project to benchmark the current state-of-the-art in predicting cognitive outcomes in Alzheimer's disease based on high dimensional, publicly available genetic and structural imaging data. This meta-analysis failed to identify a meaningful predictor developed from either data modality, suggesting that alternate approaches should be considered for prediction of cognitive performance.

Assessment of the genetic variance of late-onset Alzheimer's disease

Alzheimer's disease (AD) is a complex genetic disorder with no effective treatments. More than 20 common markers have been identified, which are associated with AD. Recently, several rare variants have been identified in Amyloid Precursor Protein (APP), Triggering Receptor Expressed On Myeloid Cells 2 (TREM2) and Unc-5 Netrin Receptor C (UNC5C) that affect risk for AD. Despite the many successes, the genetic architecture of AD remains unsolved. We used Genome-wide Complex Trait Analysis to (1) estimate phenotypic variance explained by genetics; (2) calculate genetic variance explained by known AD single nucleotide polymorphisms (SNPs); and (3) identify the genomic locations of variation that explain the remaining unexplained genetic variance. In total, 53.24% of phenotypic variance is explained by genetics, but known AD SNPs only explain 30.62% of the genetic variance. Of the unexplained genetic variance, approximately 41% is explained by unknown SNPs in regions adjacent to known AD SNPs, and the remaining unexplained genetic variance outside these regions.

Impaired thermoregulation and beneficial effects of thermoneutrality in the 3×Tg-AD model of Alzheimer's disease

The sharp rise in the incidence of Alzheimer's disease (AD) at an old age coincides with a reduction in energy metabolism and core body temperature. We found that the triple-transgenic mouse model of AD (3×Tg-AD) spontaneously develops a lower basal body temperature and is more vulnerable to a cold environment compared with age-matched controls. This was despite higher nonshivering thermogenic activity, as evidenced by brown adipose tissue norepinephrine content and uncoupling protein 1 expression. A 24-hour exposure to cold (4 °C) aggravated key neuropathologic markers of AD such as: tau phosphorylation, soluble amyloid beta concentrations, and synaptic protein loss in the cortex of 3×Tg-AD mice. Strikingly, raising the body temperature of aged 3×Tg-AD mice via exposure to a thermoneutral environment improved memory function and reduced amyloid and synaptic pathologies within a week. Our results suggest the presence of a vicious cycle between impaired thermoregulation and AD-like neuropathology, and it is proposed that correcting thermoregulatory deficits might be therapeutic in AD.

Next Generation Sequencing in Alzheimer's Disease

For the first time in the history of human genetics research, it is now both technically feasible and economically affordable to screen individual genomes for novel disease-causing mutations at base-pair resolution using "next-generation sequencing" (NGS). One popular aim in many of today's NGS studies is genome resequencing (in part or whole) to identify DNA variants potentially accounting for the "missing heritability" problem observed in many genetically complex traits. Thus far, only relatively few projects have applied these powerful new technologies to search for novel Alzheimer's disease (AD) related sequence variants. In this review, I summarize the findings from the first NGS-based resequencing studies in AD and discuss their potential implications and limitations. Notable recent discoveries using NGS include the identification of rare susceptibility modifying alleles in APP, TREM2, and PLD3. Several other large-scale NGS projects are currently underway so that additional discoveries can be expected over the coming years.