Impaired APP activity and altered tau splicing in embryonic stem cell-derived astrocytes derived from the APPsw transgenic minipig

Abstract

Animal models of familial juvenile onset of Alzheimer's disease (AD) often fail to produce diverse pathological features of the disease by modification of single gene mutations that are responsible for the disease and hence can be poor models for testing and development of novel drugs. Here we analyze in vitro produced stem cells and their derivatives from a large mammalian model of the disease created by overexpression of a single mutant human gene (APPsw). We produced hemizygous and homozygous radial glial-like cells following culture and differentiation of embryonic stem cells (ESCs) isolated from embryos obtained from mated hemizygous minipigs. These cells were confirmed to co-express varying neural markers including Nestin, GFAP and BLBP, typical of type one radial glial cells (RG) from the subgranular zone. These cells had altered expression of Cyclin D1 and NOTCH and decreased expression of several ribosomal RNA genes. We found these cells were able to differentiate into astrocytes upon directed differentiation. The astrocytes produced had decreased α–secretase and β–secretase activity, increased γ–secretase activity and altered splicing of tau. This points to novel aspects of early onset mechanisms related to cell renewal and function in familial AD astrocytes. These outcomes also point out that radial glia could be a potentially useful population of cells for drug discovery and that altered APP expression and altered tau phosphorylation can be detected in an in vitro model of the disease. Finally it may be possible to use large mammal models to model familial AD by insertion of only a single mutation.