Recent advances in stem cell biology provide a unique opportunity for researchers to investigate the molecular mechanisms underlying developmental diseases of the nervous system in living neurons derived from the cells of the affected subject. Several laboratories around the world are generating induced pluripotent stem (iPS) cell lines from hundreds of individuals with neurological disease. In some cases the subject has a known causal genetic mutation, while others express genetic risk alleles, and still others have no known genetic predisposition. While iPS cell technology provides an exciting inroad to study the effects of genetic alterations in the cells of interest, it is important to determine the feasibility of creating model systems to study genetic variation using this technology. Here, we aim to establish assays to investigate the mechanistic consequences of both a strong, dominantly inherited familial Alzheimer's disease (fAD) mutation and an allelic variant in APOE that increases risk for AD. We propose to take advantage of the pluripotency of stem cells, and direct the differentiation of these cells to specific neural fates.
In Aim 1, iPS clls will be directed to differentiate to the cell type most affected in AD, excitatory pyramidal neuron of the hippocampus and cerebral cortex. Certain features key to AD pathogenesis will be examined, namely, generation and secretion of A?, phosphorylation of Tau, and neuritic integrity. In addition to examining the intrinsically programmed presentation of these phenotypes in neuronal cells with varied genetic background, we also will examine the responses of these cells to exogenously added A? purified from postmortem human AD brain. In the second aim, we will direct the cells to a glial fate, and examine the effects of APOE genotype on clearance of A? by these cells. In the third aim, iPS cells will be directed to dopaminergic and motor neuron fates, which are less vulnerable in AD. Similar to Aim 1, cells with these fates will be analyzed for A? generation and clearance, Tau phosphorylation, and neuritic integrity. By comparing the results in different cell types with the same genetic background, we aim to begin to address the mechanisms of selective vulnerability in the AD brain.
Understanding how genetic alterations lead to molecular changes that ultimately lead to disease is key for the identification of novel therapeutic targets. These studies aim to utilize stem cells to establish a human neuronal model to study key features of Alzheimer's disease pathogenesis.