Alzheimer’s disease (AD) is the most common age-related neurodegenerative disorder. It is characterized by an irreversible loss of neurons accompanied by the accumulation of extracellular amyloid plaques and intraneuronal neurofibrillary tangles. Currently, 5.3 million Americans are afflicted with this insidious disorder, including over 588,000 in the State of California alone. Mouse models of AD have contributed significantly to our understanding of the proteins and factors involved in the pathology of AD. However, there are critical differences between mouse and human cell physiology that likely dramatically influence the development of AD-related pathologies. Hence, there is an urgent need to develop novel human neuronal cell-based models of AD.
To achieve this goal, we have generated stable human embryonic stem cell (hES) lines over-expressing the gene for human amyloid precursor protein (APP). We succeeded in creating several lines of hES cells that stably express either wild-type (unaltered) APP or APP that includes rare familial mutations known to cause early-onset cases of AD. In each line, transgene expression is driven under control of the human APP proximal promoter. Mutant versions of APP utilized include the “Swedish” mutation which increases production of Aß and the “Arctic” mutation which increases the assembly and accumulation of synaptotoxic Aß oligomers and protofibrils. The generation of lines that harbor familial mutations in APP both provides an aggressive model of AD, to facilitate the identification of targets that modulate not only Aß production but also the assembly of toxic oligomeric species.
In addition to generating stable HUES7 and H9 cell lines over-expressing mutant and wild type forms of APP, we also succeeded in establishing a neuronal differentiation protocol which results in 80% of cells adopting a mature neuronal fate. Importantly, we have also verified by biochemical measures that APP-overexpressing cells produce significantly elevated levels of Aß. As a result we are now preparing to utilize these novel cell lines to identify and examine genes that regulate Aß production and hence the development of AD.