Stem cells are the least mature cells in the body. Because these cells are so immature, they can be treated with a defined cocktail of factors and, depending on which factors are used and in what sequence, those factors can cause maturation of cells along discrete cell types. With a new tool called induced pluripotent stem cells, it now is possible to take skin cells from adults and return them to this immature state. By redirecting skin cells from Alzheimer’s patients and turning them into nerve cells, we are able to study adult Alzheimer’s neurons (nerve cells) in the lab. These Alzheimer’s neurons can be studied either in a dish or by transplanting them into the brains of host mice.
Together the Cure Alzheimer’s Fund Stem Cell Consortium team—Drs. Scott Noggle, Kevin Eggan, Sam Gandy, Doo Kim, Rudy Tanzi, Tamir Ben-Hur and Marc Tessier-Lavigne—will develop, study and maintain Alzheimer’s neurons that will be used to screen for new drugs. This “Stem Cell Bank” can be used by these and other researchers around the world to advance drug screening much more rapidly. The first targets for such screening will be drugs that already have been proven safe in humans. Other targets will include compounds developed specifically for interruption of Alzheimer’s pathology. Most excitingly, new drugs will be based on new clues that will arise only from the study of these human Alzheimer’s neurons.
Genetic approaches have provided major insights into the molecular pathogenesis of Alzheimer’s disease (AD). However, only about 3 percent of all AD is due to genetic mutations in either amyloid precursor protein (APP), or presenilin 1 or 2 (PSEN1, PSEN2). About 25 to 33 percent of all AD is associated with a polymorphism in the apolipoprotein E (APOE) gene, yet there is little consensus surrounding the molecular pathway(s) leading from APOEε4 alleles to an enhanced risk for AD. A particular promise for the recent success in differentiating skin fibroblasts into phenotypes of brain neurons provides an unprecedented and unequaled cell system for exploring AD pathogenesis in both familial and sporadic AD. We propose to generate a human in vitro model using induced pluripotent stem (iPS) cells, in which the genetic and developmental aspects of familial and sporadic AD can be studied more accurately and therapeutic targets can be identified for subsequent drug discovery. The cell-type-specificity of key AD risk molecules (e.g., APOE and astrocytes) dictates that the complete modeling of the AD brain in culture will require the generation of neurons and glia and the study of these cells in mixed cultures. Ultimately, we will transplant these neurons into mouse brain in order to study their molecular and physiological properties in vivo.
Gandy and Noggle Year 2 Specific Aims
Genetic approaches have provided major insights into the molecular pathogenesis of Alzheimer's disease (AD). However. only about 3% of all of AD is due to genetic mutations in either amyloid precursor protein (APP), or presenilin 1 or 2 (PSEN1. PENS2). A particular promise for the recent success in differentiating skin fibroblasts into phenotypes of brain neurons provides an unprecedented and unequaled cell system for exploring AD pathogenesis in both familial and sporadic AD. We propose to generate a human in vitromodel using induced pluripotent stem (iPS) cells, in which the genetic and developmental aspects of familial and sporadic AD can be studied more accurately and therapeutic targets can be identified for subsequent drug discovery. The cell-type-specificity of key AD risk molecules (e.g., apoE and astrocytes) dictates that the complete modeling of the AD brain in culture will require the generation of neurons and glia and the study of these cells in mixed cultures. Ultimately, we will transplant these neurons into mouse brain in order to study their molecular and physiological properties in vivo.
Kim and Tanzi Year 2 Specific Aims
To evaluate the impact of candidate AD drugs on beta-amyloid and tau pathology in human cellular AD models. In collaboration with Dr. Tanzi's laboratory (Massachusetts General Hospital), we will test the impact of select candidate AD drugs on both beta-amyloid and tau pathology in the 30 human neural cell culture models developed in Aim 4. In the first year, we found that SGSM41i a candidate AD drug designed to specifically decrease the toxic Abeta42 generation, decreases not only the beta-amyloid plaques but also the tau pathology in the 30 human cellular AD models. In the second year, we will test additional anti-beta-amyloid drugs including SGSM36, SGSM46, and SGSM49, which showed the higher potency in decreasing toxic Abeta species in vitro. We will test additional candidate AD drugs designed to block beta-amyloid or beta-amyloid-induced neuronal toxicity in the 30 human neural cell culture models. The overarching goal of this aim is to setup a unified platform that can be used for both studying the pathogenic mechanism of AD and evaluating target based candidate AD drugs before human clinical trials.
Ben-Hur Year 2 Specific Aims
1. Continue and complete the characterization of the protective effects of NPC Transplantation in E200K mice.
2. To examine the effect of NPC transplantation on progression of disease in 5xFAD mice.
We will characterize various pathological features of disease, rate of neurodegeneration and behavioral tests. These experiments may show for the first time whether it is possible to slow down neurodegeneration, and in particular in models that are relevant to human AD.
3.To compare the functional properties of NPS’s from wild type versus 5xFAD mice invivo and in vitro:
a. Examine the response of resident adult NPC’s to injury in vivo, and compare that of 5xFAD to wt mice
b. Compare the immune-modulatory and neuro-trophic properties of NPC’s from 5xFAD and wild type mice in vitro (by co-culture and gene expression assays) and in vivo (by their effect of neurogenesis)
These experiments will indicate whether NPC’s from AD mice display defective functional properties.
4. To study the therapeutic functions of NPC’s from human familial AD background so compared to normal NPC’s (to be provided by Dr. Noggle). We will examine human NPC properties using both in vitro and in vivo assays, as described above.
Tessier-Lavigne Year 2 Specific Aims
Alzheimer's disease is the most common form of dementia, affecting over 5 million people in the United States alone; it is the sixth-leading cause of death and is expected to cost the nation over$200 billion in 2013, with costs projected to exceed $1 trillion by 2050. Currently, there is no cure for Alzheimer's disease, nor are there effective treatments that delay or improve symptoms. Progress in understanding the underlying etiology and molecular mechanisms that cause progressive neuronal cell death has been hampered by a lack of research models that faithfully recapitulate the disease, including mouse models carrying genetic mutations that predispose humans to Alzheimer's disease. The brief lifespan of mice (age of onset for Alzheimer's is usually over 65) and intrinsic differences between mouse and human neuron physiology are two factors that likely contribute to the failure of mouse models. These obstacles were particularly difficult, or impossible, to overcome until recently.
Advances in stem cell technology have given researchers new hope by making it possible to study cultured human neurons derived from Alzheimer's patient fibroblasts. Here, we will take advantage of these technological advances to examine neurons from patients carrying mutations in MAPT (Microtubule-Associated Protein Tau), which encodes the tau protein. Postmortem brains from a broad range of dementia patients, including Alzheimer's and frontotemporal dementia (FTD) patients, show altered tau biology that includes tau tangles and elevated levels of hyperphosphorylated tau. To determine how tau misregulation perturbs normal neuronal function and leads to neurodegeneration, we will perform a comprehensive biochemical and cell biological analysis of tau-mutant human neurons and compare to gene-edited isogenic controls. In addition to examining neurons longitudinally, we will assess changes that may occur in response to premature aging. Finally, we aim to determine whether tau is required for AP-induced toxicity in human neurons, as has been reported for mouse neurons, and whether MAPT mutations sensitize neurons to AP-induced degeneration . We expect this research to provide new insights into tau biology in Alzheimer's disease and to potentially reveal novel disease mechanisms that could be beneficial for developing therapeutics for treating dementia.