Translational Research

Discover what the previously known Alzheimer’s genes can teach us about Alzheimer’s disease pathology and identify the role of the newly identified genes.

Antibody Signature of Alzheimer’s Disease: Promise of an Early Diagnostic Test

Funding year(s): 
2012
Funding to date: 
$100,000

A physician can’t cure what he can’t diagnose. The diagnosis of Alzheimer's disease is based on the exclusion of several neurological syndromes, rather than directly testing for the disease of interest. This can be an inaccurate exercise in up to 20% of the cases. Promising biomarkers are being developed, such as the cerebrospinal fluid profile of beta amyloid and tau proteins, as well as amyloid imaging with positron-emission tomography. However, these tests are not universally available and have some disadvantages, including the need for a spinal tap or the injection of radioactive material. A plasma biomarker capable of identifying asymptomatic individuals developing Alzheimer's-type pathology is needed, as they are ideal targets for intervention (i.e., amyloid-binding therapies) to prevent dementia or delay its onset. PSEN-1 mutations cause a predictable onset of mild cognitive dysfunction by age 40, followed by frank dementia a few years later. If characteristic biomarkers accompany different disease stages, these patterns could guide clinicians in the future to decide when to pursue more elaborate tests such a spinal tap and PET scans.  Immunosignaturing, a technology that employs antibody binding to a random-peptide microarray, is capable of generating profiles that distinguish transgenic mice engineered with familial Alzheimer’s disease mutations (APPswe and PSEN1-dE9) from non-transgenic littermates. The signature is distinguishable in transgenic mice as early as 2 months of age and intensifies as animals grow older. Immunosignatures can also distinguish individuals with non-genetic Alzheimer’s disease from non-demented elderly controls. In this project, we will evaluate whether late-stage Alzheimer’s disease patients with presenilin-1 (PSEN-1) mutations have a different signature as compared to young non-demented PSEN-1 carriers. In addition, we will assess the differences between the signature of demented patients with PSEN-1 mutations and elderly Alzheimer’s disease patients without PSEN-1 mutations. We will also investigate whether age-matched individuals without the mutation can be distinguished from asymptomatic carriers. Finally, we will determine if patients with different PSEN-1mutations born and raised in different continents (North America and South America) have similar signatures. This will be a collaborative project between 4 institutions: Arizona State University (Tempe, AZ), Banner Alzheimer’s Institute (Phoenix, AZ), Universidad de Antioquia (Medellin, Columbia) and UCLA Medical Center.

iPS-derived and trans-differentiated human neurons as models to study Alzheimer’s disease

Funding year(s): 
2012
Funding to date: 
$100,000

Recent groundbreaking work in stem cell biology has made it possible to reprogram non-neuronal cells obtained from Alzheimer’s diseased patients into neurons. For the first time, the research community has the means to study diseased human neurons from Alzheimer’s patients. These models have already yielded novel insights into the disease. However, different reprogramming techniques and various sources of cell material have been used to generate these models, and it is currently unclear whether one approach provides an advantage over the other (in terms of phenotype robustness and disease-relevance). Here, we propose to derive PSEN1-mutant neurons in two distinct ways, i.e., from induced pluripotent stem cells (iPSCs) or directly from fibroblasts by trans-differentiation. We will then characterize the epigenetic signatures of these neurons and determine if the two reprogramming techniques yield phenotypically similar neurons or if one set more closely resembles adult, aged neurons from diseased patients.

The Putative Role of Red Blood Cell CR1 levels in Amyloid Beta Clearance and Alzheimer’s Disease Pathogenesis.

Researchers: 
Funding year(s): 
2012
Funding to date: 
$100,000

The immune system uses complement proteins and receptors to “coat and clear” pathogens and proteins from the body. Complement Receptor 1 (CR1/CD35) is found on the surface of red blood cells in humans and helps shuttle cellular debris to the liver for degradation. Recently, specific genetic variations, called polymorphisms, in the CR1 gene were found to be associated with an increased risk of late-onset Alzheimer’s disease. We hypothesize that people with AD-risk CR1polymorphisms have low levels of CR1 protein on their red blood cells and therefore, are less efficient at clearing amyloid-â protein (Aâ) throughout life, gradually leading to Aâ aggregation and deposition in the brain. To test this hypothesis, we will examine Aâ and CR1 in archived human brain and measure the amount of CR1 molecules on red blood cells in individuals with and without AD-risk CR1polymorphisms.

The role of PICALM in vascular clearance of amyloid-β

Funding year(s): 
2012
Funding to date: 
$100,000

PICALM, the gene encoding phosphatidylinositol binding clathrin assembly (picalm) protein, plays a key role in endocytosis, a process which regulates the function of cell receptors and synaptic transmission. PICALM is one of the most highly validated Alzheimer’s disease (AD) risk factors. Its role in AD, however, is unknown. A recent genome-wide screen for modifiers of amyloid-b peptide (Aβ) toxicity in yeast has identified the key role of the yeast homologue of PICALM. This study has shown that PICALM efficiently controls Aβ toxicity in yeast, nematode models and mammalian neurons by regulating endocytosis-dependent cell vulnerability to Aβ. Our preliminary data in human and mouse brain show that picalm protein is most abundantly expressed in blood vessels which have been shown to provide a major pathway for Aβ removal from brain into the bloodstream. Therefore, picalm in brain endothelium is ideally situated to participate in Aβ clearance from brain. Interestingly, our pilot data also show significantly reduced picalm expression in brain vessels in AD. Previous findings have established that low density lipoprotein receptor (LRP) in brain endothelium mediates vascular clearance of Aβ from brain via transport across the brain capillary endothelium, a site of the blood-brain barrier (BBB) in vivo. Our preliminary data using human brain endothelial cells show that PICALM is required for rapid endothelial internalization of Aβ after its initial binding to LRP. The current proposal will determine the role of PICALM in regulating internalization and transcellular transport (transcytosis) of LRP-bound Aβ across the endothelial cell wall of the BBB in vitro and in vivo. To test our hypotheses we will use a human model of the BBB and a mouse model of Aβ clearance, both developed in our laboratory. In collaboration with Dr Tanzi we will study the effects of novel PICALM mutations on amyloid-β vascular clearance once the sequence of these functional variants/mutations becomes available. The proposed studies will represent a novel advance in our understanding of the molecular regulation of CNS Aβ homeostasis and will demonstrate a pivotal role of PICALM in controlling brain Aβ.

General Anesthetics and Alzheimer’s Disease

Funding year(s): 
2012
Funding to date: 
$100,000

The goal of this project is to test the hypothesis that desflurane is a safer anesthetic than isoflurane for AD patients in order to find safer anesthetics that won’t worsen AD symptoms.

Age is one of the most important risk factors for Alzheimer’s Disease (AD), with an incidence of 6.8 percent in people older than 65 years. One-third of all anesthetics are administered to people older than 65. Therefore, it is inevitable that many older patients who present to anesthesiologists will have AD. Just as the anesthesia specialty became intimately involved with the management of coronary artery disease (CAD), it is time for the anesthesiology specialty to develop guidelines for safer anesthesia care for AD patients. As the first step of these efforts, Dr. Zhongcong Xie and his fellow researchers will set out to identify anesthetics that will exacerbate the AD pathology, such as neuronal death, increases of Abeta levels, learning/memory impairment and synapse loss.

In their preliminary studies, they found the inhalation anesthetic isoflurane, but not desflurane, can induce cell death and increase Abeta levels in the cultured cells. In this application they will repeat these experiments in the mice having AD pathology (Aim #1) and in real human AD patients (Aim #3). In addition, they will study the up-stream mechanism of the anesthetics-induced cell death and increases in Abeta levels (Aim #2). The hypothesis they will test is desflurane is a safer anesthetic than isoflurane for both AD patients and normal patients. The anticipated results from the proposed studies will finally help them find safer anesthetics, which may not worsen the AD symptoms (e.g., learning/memory impairment). These efforts are consistent with the goals of Cure Alzheimer’s Fund research grant program in identifying the risk factors of AD and in finding the prospects and strategies for the prevention of AD, which, ultimately, will help AD patients.

Understand the Role of ADAM10 in the Pathogenesis of Alzheimer's Disease After Head Trauma

Funding year(s): 
2011
Funding to date: 
$100,000

The goal of this project is to determine whether increased sAPPα levels are capable of reducing the production of neurotoxic Abeta following head trauma in order to reduce the risk of developing Alzheimer’s disease following brain injury.

Traumatic brain injury (TBI) is the strongest environmental risk factor for the development of Alzheimer’s disease (AD). AD is characterized by the accumulation and deposition of Abeta in the form of senile plaques. Abeta is a neurotoxic peptide (small protein) derived by the sequential cleavage of the amyloid precursor protein (APP) by beta and gamma secretase enzymes. In addition to the amyloidgenic processing of APP, which gives rise to the production of Abeta, an alternative non-amyloidgenic pathway exists in which APP is cleaved by α-secretase, which inhibits the production of the neurotoxic Abeta. In addition, cleavage of APP by α-secretase gives rise to the production of the secreted alpha cleaved APP fragment (sAPPα), which has been shown to have neuroprotective properties. A recent study has shown that when synthetic sAPPα is administered to mice following experimental head trauma, it appears to be protective, reducing neuronal death and axonal injury. If the neuroprotective properties of sAPPα following head trauma can be confirmed, this provides a potential therapeutic strategy for improving a patient’s clinical outcome and reducing the potential for the development of AD following head trauma. More importantly, mutations in the gene ADAM10 have been associated with an increased risk of developing AD by reducing the production of sAPPα. This project aims to prove whether increased production of sAPPα is protective following experimental traumatic brain injury by using genetically engineered mice that overexpress the α-secretase gene (ADAM10) and whether reduced levels sAPPα in mice expressing ADAM10 AD-associated mutations results in a worse functional outcome following levels of head trauma. These mice will be bred with a well-characterized mouse model of AD to generate mice that express increased levels of sAPPα and also develop key characteristics of AD, such as amyloid plaques and impaired learning and memory. These mice will be subjected to experimental traumatic brain injury at 3 months of age (young adult mice). One group of mice will be analyzed shortly after injury to determine whether increased expression of α-secretase and hence sAPPα reduces the production of neurotoxic Aβ and improves learning and memory compared with control mice that have decreased levels of sAPPα. A second group of mice will be allowed to age following TBI and will be analyzed at 12 months of age (when they would normally develop symptoms of AD, such as amyloid plaques and impaired memory) to determine whether the increased levels of sAPPα are protective against AD by reducing the number and size of amyloid plaques and improving learning and memory compared with a control group of mice that have decreased levels of sAPPα. If they are able to prove that over-expression of α-secretase and hence increased sAPPα levels are capable of reducing the production of neurotoxic Aβ peptides and Aβ plaques and improving learning and memory in these mice following head trauma, this provides an important therapeutic strategy to pursue to reduce the risk of developing AD following brain injury.

Published papers: 

Metallomic Mapping of the Aging Brain in Trg2576 Transgenic Mouse Model

Funding year(s): 
2011
Funding to date: 
$100,000

The goal of this project is to perform the first high-resolution metallomic brain maps of key biometals (copper, zinc, iron) during normal brain aging and in Alzheimer’s disease in order to develop disease-modifying treatments that target normalization of biometal distribution and metal-protein interactions in the brain.

In this project, Dr. Lee Goldstein’s lab will deploy unique analytical resources at the Boston University Center for Biometals & Metallomics studying zinc and other key brain biometals and show how they play a critical role in normal brain function and, when altered, lead to the development of Alzheimer’s disease. Recent clinical trials strongly support developing drugs targeting brain biometals and metal-protein interactions as a promising therapeutic strategy for this devastating neurodgenerative disease. However, little is known about the role and distribution of key biometals and essential micronutrients (including copper, zinc and iron) in brain aging and Alzheimer’s disease. This information is critical for rational development of disease-modifying treatments that target normalization of biometal distribution and metal- protein interactions in the brain. In this project, Goldstein and his colleagues will deploy unique analytical resources at the Boston University Center for Biometals & Metallomics to perform the first high-resolution metallomic brain maps of key biometals (copper, zinc, iron) during normal brain aging and in Alzheimer’s disease. These studies will be performed in a well-characterized Alzheimer’s disease transgenic mouse model and validated in human brain specimens.

Cellular and Animal Models of Amyloid Pathology in Early Alzheimer's Disease

Researchers: 
Funding year(s): 
2011
Funding to date: 
$100,000

The goal of this project is to evaluate the pathological significance of a new type of Abeta deposits in the brain (at the onset of Alzheimer’s disease) in order to develop a novel mechanism for amyloid pathogenesis to help convince the FDA to approve and support early clinical trials.

Although the genetics of Alzheimer’s disease (AD) implicates Abeta as a causal agent of pathology, the potential mechanisms of amyloid pathology are numerous, and there is no consensus about which mechanisms are critically important. The simple formulations of the “amyloid hypothesis” have a number of weaknesses, including the fact that amyloid plaques do not correlate well with disease and that cognitively normal individuals can have the same amount of plaque amyloid as patients with dementia. This has led to a reformulation of the amyloid hypothesis where other types of amyloid aggregates, such as soluble oligomers, are postulated to be the primary pathogenic species. If this is the case, there is considerable disagreement about which specific oligomers are toxic and why they are pathological. Dr. Charles Glabe’s previous work established that Abeta can form a variety of structurally and immunologically different types of oligomers. In work that was partially funded by Cure Alzheimer’s Fund, he and his team have recently produced a battery of monoclonal antibodies by immunizing rabbits with Abeta. The goal of this effort was to obtain as many different antibodies as possible with the hope they might reveal new types of amyloid aggregates in the brain. Most of these antibodies are conformation dependent and specifically recognize Abeta aggregates and not Abeta monomer or the amyloid precursor protein, APP. One of these antibodies, Mab78, identified a new type of Abeta pathology in an aged human and AD brain. Analysis of more than 20 different human brain samples suggests this new pathological accumulation of Abeta is a very early event in aging of AD pathogenesis and disappears as plaques accumulate in later stages of AD.

In order to experimentally evaluate this relationship and the pathological significance of this new type of Abeta deposits, researchers need a living system they can study over time and manipulate experimentally. The potential significance of this work may be the identification of the earliest type of amyloid pathology at the onset of the disease and the discovery of a novel mechanism for amyloid pathogenesis. This may provide a new target for therapeutic development and provide evidence for the early initiation of the disease before cognitive impairments. This evidence could be instrumental in convincing the FDA to approve and support early clinical trials, which may have a much better chance of preventing or curing the disease.

Structural and Functional Analysis of Novel Abeta and Tau Oligomers Using Conformation-Specific Monoclonal Antibodies

Researchers: 
Funding year(s): 
2011
Funding to date: 
$100,000

The goal of this project is to determine which oligomers of Abeta and Tau are most damaging and whether specific antibodies can prevent formation of those oligomers.

Two types of abnormal structures, amyloid plaques and neurofibrillary tangles, have long been known to accumulate in the brains of Alzheimer’s disease (AD) patients, but recent advances point to the building blocks of these structures as the actual disease-causing agents. The building blocks of plaques are small clusters, or “oligomers” of Abeta peptides, which represent small pieces of a larger protein and are aggregated into densely packed, insoluble fibers in the plaques. Tangles arise by an analogous process and also comprise densely packed, insoluble fibers, but their building blocks are oligomers of the protein known as Tau. There are many structurally distinct versions of both Abeta and Tau, and the oligomers they form vary in size and shape. It follows naturally that development of procedures for early diagnosis and effective treatment of AD depend on learning exactly which oligomers of Abeta and Tau are most damaging.

This project builds on recent discoveries made in the labs of Dr. George Bloom at the University of Virginia and Dr. Charles Glabe of the University of California, Irvine. Bloom’s lab identified a new class of exceptionally toxic Abeta oligomers that are self-propagating, like the infectious particles that cause mad cow disease, and they also have been studying how Abeta oligomers can seed formation of Tau oligomers. Concurrently, the Glabe lab developed a new and intriguing collection of antibodies that were made by immunizing rabbits with Abeta. Collectively, these antibodies stain a variety of abnormal structures in post-mortem brain tissue removed from the brains of AD patients and mice that are genetically engineered to develop AD. Most notable among these structures are “aggrodegrosomes,” or “ADsomes,” which were seen in the human tissue, had never been observed earlier and represent a brand new type of brain lesion associated with AD. Remarkably, several of the Glabe lab antibodies recognize multiple proteins in addition to Abeta. We will see if any of the Glabe lab antibodies recognize the Abeta or Tau oligomers that the Bloom lab is studying, and whether the antibodies can prevent formation of those oligomers. Completion of this work could lead eventually to new diagnostic and therapeutic tools for AD.

Selective Cell Vulnerability in Alzheimer's Disease

Researchers: 
Funding year(s): 
2011
Funding to date: 
$100,000

The goal of this project is to identify cells that are both most vulnerable and most resistant to Alzheimer’s disease in order to develop drugs that will protect the most vulnerable.

At the early stages of Alzheimer’s disease (AD), neurofibrillary tangles (NFT) and neurodegeneration occur only in very specific regions, while many regions remain virtually unaffected. Paul Greengard’s lab at the Rockefeller University recently developed a new procedure to compare the molecular profiles of very specific cell types inside the brain. They will apply this technology to mice in order to compare vulnerable regions with more resistant regions that don’t show any pathology until late stages of the disease. They will establish the molecular profiles of the different regions of interest, try to find genes that are common to all vulnerable regions or to all resistant regions and verify the region-specific expression of these genes in human brain tissue. Important differences between vulnerable and resistant cells might not be obvious at a normal physiological state,
but might become obvious only in a pathological environment. They will apply the bacTRAP technology (a platform to identify novel targets in specific cell types) to different AD mouse models, and study the molecular profile of the different regions in an AD-like environment. Then they will try to find genes that are modulated region-specifically in the context of AD and verify their findings in brain tissue of patients at different stages of AD.

These comparisons will yield lists of vulnerability genes that could potentially explain why vulnerable cells are vulnerable, or why resistance genes protect resistant cells from the pathology. By comparing these genes with AD susceptibility genes, they have the potential to identify genes that are crucial for AD pathogenesis. In future studies, they will modulate the expression level of the best candidates in neurons, and test the vulnerability of the cells thereafter. If these genes are indeed vulnerable or resistance genes, they could be very good drug targets aimed at protecting vulnerable cells.