Alzheimer's disease: insights from Drosophila melanogaster models.
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ABSTRACT:
SUBMITTER: Moloney A
PROVIDER: S-EPMC2856915 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Alzheimer's disease (AD) is the most widespread neurodegenerative disorder worldwide. Its pathogenesis involves two hallmarks: aggregation of amyloid beta (A?) and occurrence of neurofibrillary tangles (NFTs). The mechanism behind the disease is still unknown. This has prompted the use of animal models to mirror the disease. The fruit fly, Drosophila melanogaster has garnered considerable attention as an organism to recapitulate human disorders. With the ability to monopolise a multitude of traditional and novel genetic tools, Drosophila is ideal for studying not only cellular aspects but also physiological and behavioural traits of human neurodegenerative diseases. Here, we discuss the use of the Drosophila model in understanding AD pathology and the insights gained in discovering drug therapies for AD.
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Project description:Reactive oxygen species (ROS) play an important role as endogenous mediators in several cellular signalling pathways. However, at high concentrations they can also exert deleterious effects by reacting with many macromolecules including DNA, proteins and lipids. The precise balance between ROS production and their removal via numerous enzymatic and nonenzymatic molecules is of fundamental importance for cell survival. Accordingly, many neurodegenerative disorders, including Parkinson's disease (PD), are associated with excessive levels of ROS, which induce oxidative damage. With the aim of coping with the progression of PD, antioxidant compounds are currently receiving increasing attention as potential co-adjuvant molecules in the treatment of these diseases, and many studies have been performed to evaluate the purported protective effects of several antioxidant molecules. In the present review, we present and discuss the relevance of the use of Drosophila melanogaster as an animal model with which to evaluate the therapeutic potential of natural and synthetic antioxidants. The conservation of most of the PD-related genes between humans and D. melanogaster, along with the animal's rapid life cycle and the versatility of genetic tools, makes fruit flies an ideal experimental system for rapid screening of antioxidant-based treatments.
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Project description:Genetic polymorphisms of immune genes that associate with higher risk to develop Alzheimer's disease (AD) have led to an increased research interest on the involvement of the immune system in AD pathogenesis. A link between amyloid pathology and immune gene expression was suggested in a genome-wide gene expression study of transgenic amyloid mouse models. In this study, the gene expression of lysozyme, a major player in the innate immune system, was found to be increased in a comparable pattern as the amyloid pathology developed in transgenic mouse models of AD. A similar pattern was seen at protein levels of lysozyme in human AD brain and CSF, but this lysozyme pattern was not seen in a tau transgenic mouse model. Lysozyme was demonstrated to be beneficial for different Drosophila melanogaster models of AD. In flies that expressed A?1-42 or A?PP together with BACE1 in the eyes, the rough eye phenotype indicative of toxicity was completely rescued by coexpression of lysozyme. In Drosophila flies bearing the A?1-42 variant with the Arctic gene mutation, lysozyme increased the fly survival and decreased locomotor dysfunction dose dependently. An interaction between lysozyme and A?1-42 in the Drosophila eye was discovered. We propose that the increased levels of lysozyme, seen in mouse models of AD and in human AD cases, were triggered by A?1-42 and caused a beneficial effect by binding of lysozyme to toxic species of A?1-42 , which prevented these from exerting their toxic effects. These results emphasize the possibility of lysozyme as biomarker and therapeutic target for AD.
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Project description:Recent studies indicate that physical activity can slow down progression of neurodegeneration in humans. To date, automated ways to induce activity have been predominantly described in rodent models. To study the impact of activity on behavior and survival in adult Drosophila melanogaster, we aimed to develop a rotating tube device "swing boat" which is capable of monitoring activity and sleep patterns as well as survival rates of flies. For the purpose of a first application, we tested our device on a transgenic fly model of Alzheimer's disease (AD). Activity of flies was recorded in a climate chamber using the Drosophila Activity Monitoring (DAM) System connected to data acquisition software. Locomotor activity was induced by a rotating tube device "swing boat" by repetitively tilting the tubes for 30 min per day. A non-exercising group of flies was used as control and activity and sleep patterns were obtained. The GAL4-/UAS system was used to drive pan-neuronal expression of human A?42 in flies. Immunohistochemical stainings for A?42 were performed on paraffin sections of adult fly brains. Daily rotation of the fly tubes evoked a pronounced peak of activity during the 30 min exercise period. Pan-neuronal expression of human A?42 in flies caused abnormalities in locomotor activity, reduction of life span and elevated sleep fragmentation in comparison to wild type flies. Furthermore, the formation of amyloid accumulations was observed in the adult fly brain. Gently induced activity over 12 days did not evoke prominent effects in wild type flies but resulted in prolongation of median survival time by 7 days (32.6%) in A?42-expressing flies. Additionally, restoration of abnormally decreased night time sleep (10%) and reduced sleep fragmentation (28%) were observed compared to non-exercising A?42-expressing flies. On a structural level no prominent effects regarding prevalence of amyloid aggregations and A?42 RNA expression were detected following activity induction. The rotating tube device successfully induced activity in flies shown by quantitative activity analysis. Our setup enabled quantitative analysis of activity and sleep patterns as well as of survival rates. Induced activity in a Drosophila model of Alzheimer's disease improved survival and ameliorated sleep phenotypes.
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Project description:Alzheimer's disease (AD) is the most common form of dementia, affecting millions of people and currently lacking available disease-modifying treatments. Appropriate disease models are necessary to investigate disease mechanisms and potential treatments. Drosophila melanogaster models of AD include the Aβ fly model and the AβPP-BACE1 fly model. In the Aβ fly model, the Aβ peptide is fused to a secretion sequence and directly overexpressed. In the AβPP-BACE1 model, human AβPP and human BACE1 are expressed in the fly, resulting in in vivo production of Aβ peptides and other AβPP cleavage products. Although these two models have been used for almost two decades, the underlying mechanisms resulting in neurodegeneration are not yet clearly understood. In this study, we have characterized toxic mechanisms in these two AD fly models. We detected neuronal cell death and increased protein carbonylation (indicative of oxidative stress) in both AD fly models. In the Aβ fly model, this correlates with high Aβ1-42 levels and down-regulation of the levels of mRNA encoding lysosomal-associated membrane protein 1, lamp1 (a lysosomal marker), while in the AβPP-BACE1 fly model, neuronal cell death correlates with low Aβ1-42 levels, up-regulation of lamp1 mRNA levels and increased levels of C-terminal fragments. In addition, a significant amount of AβPP/Aβ antibody (4G8)-positive species, located close to the endosomal marker rab5, was detected in the AβPP-BACE1 model. Taken together, this study highlights the similarities and differences in the toxic mechanisms which result in neuronal death in two different AD fly models. Such information is important to consider when utilizing these models to study AD pathogenesis or screening for potential treatments.
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Project description:The gut-brain-axis (GBA) describing the bidirectional communication between the gut microbiota and brain was recently implicated in Alzheimer's disease (AD). The current study describes a novel synbiotic containing three metabolically active probiotics and a novel polyphenol-rich prebiotic which has beneficial impacts on the onset and progression of AD. In a transgenic humanized Drosophila melanogaster model of AD, the synbiotic increased survivability and motility and rescued amyloid beta deposition and acetylcholinesterase activity. Such drastic effects were due to the synbiotic's combinatorial action on GBA signaling pathways including metabolic stability, immune signaling, oxidative and mitochondrial stress possibly through pathways implicating PPARγ. Overall, this study shows that the therapeutic potential of GBA signaling is best harnessed in a synbiotic that simultaneously targets multiple risk factors of AD.
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Project description:Alzheimer’s disease (AD) is a neurodegenerative disease displaying plaques formed by the neurotoxic amyloid β-peptide (Aβ) and intracellular neurofibrillary tangles consisting of protein tau. However, how these pathologies relates to the massive neuronal death that occurs in AD brains remain elusive. To identify proteins, the levels of which are affected by increased Aβ levels, we performed a proteomic analysis of the AD mouse model APPsw and compared it to that of APPsw mice lacking the major Aβ degrading enzyme neprilysin. This was achieved by establishing an LC-MS/MS method to analyze brain homogenate, using an 18O-labeled internal standard to accurately quantify the protein levels. By this approach we identified approximately 600 proteins and could quantify the levels of 300 of these. Interestingly, several proteins, including some not previously reported to be associated with AD, were identified. The relevance of these proteins for AD warrants further research.
2015-07-29 | PXD000968 | Pride
Project description:Dietary restriction (DR) extends lifespan in diverse organisms and, in animal and cellular models, can delay a range of aging-related diseases including Alzheimer's disease (AD). A better understanding of the mechanisms mediating these interactions, however, may reveal novel pathways involved in AD pathogenesis, and potential targets for disease-modifying treatments and biomarkers for disease progression. Drosophila models of AD have recently been developed and, due to their short lifespan and susceptibility to genetic manipulation, we have used the fly to investigate the molecular connections among diet, aging and AD pathology. DR extended lifespan in both Arctic mutant A?42 and WT 4R tau over-expressing flies, but the underlying molecular pathology was not altered and neuronal dysfunction was not prevented by dietary manipulation. Our data suggest that DR may alter aging through generalised mechanisms independent of the specific pathways underlying AD pathogenesis in the fly, and hence that lifespan-extending manipulations may have varying effects on aging and functional declines in aging-related diseases. Alternatively, our analysis of the specific effects of DR on neuronal toxicity downstream of A? and tau pathologies with negative results may simply confirm that the neuro-protective effects of DR are upstream of the initiating events involved in the pathogenesis of AD.
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Project description:Insecticide resistance is considered a classic model of microevolution, where a strong selective agent is applied to a large natural population, resulting in a change in frequency of alleles that confer resistance. While many insecticide resistance variants have been characterized at the gene level, they are typically single genes of large effect identified in highly resistant pest species. In contrast, multiple variants have been implicated in DDT resistance in Drosophila melanogaster; however, only the Cyp6g1 locus has previously been shown to be relevant to field populations. Here we use genome-wide association studies (GWAS) to identify DDT-associated polygenes and use selective sweep analyses to assess their adaptive significance. We identify and verify two candidate DDT resistance loci. A largely uncharacterized gene, CG10737, has a function in muscles that ameliorates the effects of DDT, while a putative detoxifying P450, Cyp6w1, shows compelling evidence of positive selection.
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Project description:In the past decade, genome-sequencing projects have yielded a great amount of information on DNA sequences in several organisms. The release of the Drosophila melanogaster heterochromatin sequence by the Drosophila Heterochromatin Genome Project (DHGP) has greatly facilitated studies of mapping, molecular organization, and function of genes located in pericentromeric heterochromatin. Surprisingly, genome annotation has predicted at least 450 heterochromatic gene models, a figure 10-fold above that defined by genetic analysis. To gain further insight into the locations and functions of D. melanogaster heterochromatic genes and genome organization, we have FISH mapped 41 gene models relative to the stained bands of mitotic chromosomes and the proximal divisions of polytene chromosomes. These genes are contained in eight large scaffolds, which together account for approximately 1.4 Mb of heterochromatic DNA sequence. Moreover, developmental Northern analysis showed that the expression of 15 heterochromatic gene models tested is similar to that of the vital heterochromatic gene Nipped-A, in that it is not limited to specific stages, but is present throughout all development, despite its location in a supposedly "silent" region of the genome. This result is consistent with the idea that genes resident in heterochromatin can encode essential functions.
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