APP and its intracellular domain modulate Alzheimer's disease risk gene networks in transgenic APPsw and PSEN1M146I porcine models [fibroblasts]
Alzheimer's disease (AD) is a progressive neurodegenerative disorder and the most frequent cause of dementia. The disease has a substantial genetic component comprising both highly penetrant familial mutations (APP, PSEN1 and PSEN2) and sporadic cases with complex genetic etiology. Mutations in APP and PSEN1/2 alter the proteolytic processing of APP to its metabolites, including Ab and APP Intracellular Domain (AICD). In this study, we use transgenic porcine models carrying the human APPsw and PSEN1M146I transgenes to demonstrate the pathobiological relevance of transcriptional regulation facilitated by APP and its AICD domain. Through molecular characterization of hippocampal tissue, we describe the differential expression of gene sets that cluster in molecular pathways with translational relevance to AD. We further identify phosphorylated and unphosphorylated AICD in differential complexes with proteins implicated in signal transduction and transcriptional regulation. Integrative genomic analysis of transcriptional changes in somatic cell cultures derived from pigs treated with g-secretase inhibitor demonstrates the importance of g-secretase APP processing in transcriptional regulation. Collectively, our data supports a model in which APP, and in particular its AICD domain, modulates gene networks associated with AD pathobiology through interaction with signaling proteins. Overall design: Fibroblasts derived from wild type (WT) and transgenic Göttingen minipigs, carrying  copies of human APP695 cDNA with the Lys670Asn/Met671Leu (APP) double-mutation and/or one copy of human PSEN1 cDNA with the Met146Ile (genotype PS1) mutation were subjected to transcriptomic profiling using RNAseq. Fibroblasts were treated with 50?M  LY294002 (in DMSO; Cell Signaling) or 2???L-685-458 (??secretase inhibitor in DMSO; Merck Millipore),???????-Secretase Inhibitor IV?(in DMSO; Merck Millipore),?or?DMSO (Sigma Aldrich) for 24hrs.