Reprogramming of primary dermal fibroblasts into induced pluripotent stem cells (iPSCs) has recently proven to be instrumental for the generation of viable neurons derived from patients with neurodegenerative disorders. This technology holds tremendous promise for the creation of in vitro models to study disease pathophysiology in relevant human cell types that would otherwise be impossible to obtain. Familial British and Danish dementias (FBD and FDD, respectively) are autosomal dominant conditions that closely resemble many clinical and neuropathological features of Alzheimer's disease (AD) including parenchymal amyloid and pre- amyloid lesions, widespread cerebral amyloid angiopathy and neurofibrillary tangles morphologically and immunochemically indistinguishable from those in AD. Notably, the amyloid subunits isolated from FBD deposits -ABri- and FDD lesions -ADan- are structurally unrelated to the Alzheimer's A¿, a clear indication that different amyloid peptides could trigger similar neuropathological changes leading to the same scenario: CAA-related microvascular dysfunction, neuronal loss and dementia. Thus, these familial disorders constitute promising alternative paradigms to better understand the role of amyloid in the complex mechanisms of disease pathogenesis. In view of the many clinical and neuropathological similarities between AD, FBD and FDD, we are proposing i) to generate and characterize iPSC lines from dermal fibroblasts obtained from a cohort of FBD and FDD patients as well as from non-carrier siblings of both disorders using repetitive mRNA transfections, a safer non- DNA-integrating technology successfully used by the research team; and ii) to further differentiate the newly generated iPSCs into viable and functional neurons and endothelial cells characterized through well- established morphological, molecular and biological criteria. We anticipate that these iPSC-derived mature cells will constitute excellent candidates to study specific molecular and temporal aspects linked to FBD and FDD disease phenotypes. Moreover, they will have a broader impact in the field of neurodegenerative disorders, extending beyond these rare diseases into the field of AD, providing invaluable options for a better understanding of the mechanisms that modulate APP processing, A¿ homeostasis and the process of tau hyperphosphorylation, serving as alternative paradigms for high throughput drug screening platforms, and assisting with the identification of cross-talk pathways connecting CAA-associated blood brain barrier dysfunction and development of microhemorrhages with changes in the neurovascular unit and cognitive impairment. This proposal represents a collaborative effort from investigators of New York University School of Medicine and the University of California, Irvine and builds on the complementary expertise of the participating researchers and their long-standing interest in the molecular pathogenesis of cerebral amyloid disorders.

Studies aiming to elucidate the pathogenesis of human neurological diseases have traditionally utilized postmortem tissues, genetically manipulated animal models and transfected cells, with each of these approaches exhibiting their own caveats. The recent availability of technology that allows somatic cells (e.g. skin fibroblasts) to be reprogrammed into inducible pluripotent stem cells (iPSC) offers the unique opportunity to generate cellular models that otherwise are impossible to obtain. We are proposing to reprogram fibroblasts obtained from patients with familial British and Danish dementias -two disorders that closely mimic clinical, neuropathological, and cerebral microvascular features of Alzheimer's disease- and further generate iPSCs- derived neurons and endothelial cells. These new tools will constitute excellent cellular models to study disease mechanisms common to neurodegenerative disorders that share striking similarities with Alzheimer's disease and will also provide excellent paradigms for high throughput drug screening platforms.