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Comparative transcriptome analysis of APPsα-DM and APLP2-KO brains

ABSTRACT: Despite its key role in Alzheimer pathogenesis, the physiological function(s) of the amyloid precursor protein (APP) and of its proteolytic fragments are still poorly understood. The secreted APPsα ectodomain has been shown to be involved in neuroprotection and synaptic plasticity. The γ-secretase generated APP intracellular domain, AICD, functions as a transcriptional regulator in heterologous reporter assays although its role for endogenous gene regulation has remained controversial. Previously, we have generated APPsα knockin (KI) mice expressing solely the secreted ectodomain APPsα. Here, we generated double mutants (APPsα-DM) by crossing APPsα-KI mice onto an APLP2-deficient background and show that APPsα rescues the postnatal lethality of the majority of APP/APLP2 double knockout mice. Despite normal CNS morphology and unaltered basal synaptic transmission, young APPsα-DM mice already showed pronounced hippocampal dysfunction, impaired spatial learning and a deficit in LTP. To gain further mechanistic insight into which domains/proteolytic fragments are crucial for hippocampal APP/APLP2 mediated functions, we performed a DNA microarray transcriptome profiling of prefrontal cortex and hippocampus of adult APLP2-KO (APLP2-/-) and APPsα-DM mice (APPα/αAPLP2-/- mice).Interestingly, this analysis failed to reveal major genotype-related transcriptional differences. Expression differences between cortex and hippocampus were, however, readily detectable.

ORGANISM(S): Mus musculus

PROVIDER: GSE27888 | GEO | 2011/05/10

SECONDARY ACCESSION(S): PRJNA138003

REPOSITORIES: GEO

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Project description:The Î²-amyloid precursor protein APP and the related APLPs, undergo complex proteolytic processing giving rise to several fragments. Whereas it is well established that AÎ² accumulation is a central trigger for Alzheimer disease (AD), the physiological role of APP family members and their diverse proteolytic products is still largely unknown. The secreted APPsÎ± ectodomain has been shown to be involved in neuroprotection and synaptic plasticity. The Î³-secretase generated APP intracellular domain AICD, functions as a transciptional regulator in heterologous reporter assays, although its role for endogenous gene regulation has remained controversial. To gain further insight into the molecular changes associated with knockout phenotypes and to elucidate the physiological functions of APP family members including their proposed role as transcriptional regulators we performed a DNA microarray transcriptome profiling of the frontal cortex of adult wild type, APP-/-, APLP2-/- and APPsÎ± knockin (KI) mice, APPÎ±/Î±, expressing solely the secreted APPsÎ± ectodomain. Biological pathways affected by the lack of APP family members included regulation of neurogenesis, regulation of transcription and regulation of neuron projection development. Comparative analysis of transcriptome changes and qPCR validation identified co-regulated gene sets. Interestingly, these included heat shock proteins and plasticity related genes that were down-regulated in knock-out cortices. In contrast, we failed to detect significant differences in expression of previously proposed AICD target genes including Bace1, Kai1, Gsk3b, p53, Tip60 and Vglut2. Only Egfr was slightly up-regulated in APLP2-/- mice. Comparison of APP-/- and APPÎ±/Î± with wild-type mice revealed a high proportion of co-regulated genes indicating an important role of the C-terminus for cellular signaling. Finally, comparison of APLP2-/- on different genetic backgrounds revealed that background related transcriptome changes may dominate over changes due to the knockout of a single gene. Shared transcriptome profiles corroborated closely related physiological functions of APP family members in the adult central nervous system. As expression of proposed AICD target genes was not altered in adult cortex, this may indicate that these genes are not affected by lack of APP under resting conditions or only in a small subset of cells. Prefrontal cortices of adult male mice (24 - 28 weeks) of the following genotypes were analyzed: WT (n=3), APP-/- (n=3), APPÎ±/Î± (n=3), APLP2-/- (n=3), APLP2(R1)-/- (n=3). WT, APP-/-, APPÎ±/Î±, APLP2-/- had been backcrossed for six generations to C57BL/6 mice. APLP2(R1)-/- harbors the identical knockout allele as APLP2-/- but was back-crossed only once.

Project description:The β-amyloid precursor protein APP and the related APLPs, undergo complex proteolytic processing giving rise to several fragments. Whereas it is well established that Aβ accumulation is a central trigger for Alzheimer disease (AD), the physiological role of APP family members and their diverse proteolytic products is still largely unknown. The secreted APPsα ectodomain has been shown to be involved in neuroprotection and synaptic plasticity. The γ-secretase generated APP intracellular domain AICD, functions as a transciptional regulator in heterologous reporter assays, although its role for endogenous gene regulation has remained controversial. To gain further insight into the molecular changes associated with knockout phenotypes and to elucidate the physiological functions of APP family members including their proposed role as transcriptional regulators we performed a DNA microarray transcriptome profiling of the frontal cortex of adult wild type, APP-/-, APLP2-/- and APPsα knockin (KI) mice, APPα/α, expressing solely the secreted APPsα ectodomain. Biological pathways affected by the lack of APP family members included regulation of neurogenesis, regulation of transcription and regulation of neuron projection development. Comparative analysis of transcriptome changes and qPCR validation identified co-regulated gene sets. Interestingly, these included heat shock proteins and plasticity related genes that were down-regulated in knock-out cortices. In contrast, we failed to detect significant differences in expression of previously proposed AICD target genes including Bace1, Kai1, Gsk3b, p53, Tip60 and Vglut2. Only Egfr was slightly up-regulated in APLP2-/- mice. Comparison of APP-/- and APPα/α with wild-type mice revealed a high proportion of co-regulated genes indicating an important role of the C-terminus for cellular signaling. Finally, comparison of APLP2-/- on different genetic backgrounds revealed that background related transcriptome changes may dominate over changes due to the knockout of a single gene. Shared transcriptome profiles corroborated closely related physiological functions of APP family members in the adult central nervous system. As expression of proposed AICD target genes was not altered in adult cortex, this may indicate that these genes are not affected by lack of APP under resting conditions or only in a small subset of cells.

Project description:RNAseq differential gene expression profiling of olfactory mucosa in young wild type, aged wild type, APP deficient, APLP2 deficient and PSEN2 deficient mice. Purpose: Next-generation gene expression profiling has revolutionized analysis of molecular pathways. The goals of this study were to compare NGS-derived olfactory mucosa transcriptome profiles (RNAseq) of aged wild-type mice, APP knockout mice, APLP2 knockout mice and PSEN2 knockout mice with young wild-type controls. Selected genes and pathways will be analyze further by low-throughput techniques such as real-time RT-PCR. Methods: Olfactory mucosa mRNA profiles of 2 months old wild-type (WT), 2 years old wild-type, APP knockout, APLP2 knockout and PSEN2 knockout mice were generated by deep sequencing, in triplicate, using Illumina NovaSeq6000 . For inspecting the quality of RNA-Seq data, the 100 most abundant genes are taken from all the samples and heatmaps were generated to observe the relation between samples/conditions. The sequence reads that passed the quality filters were analyzed at the transcript isoform level with TopHat followed by Cufflinks. Results: Using our data analysis workflow, we mapped at least 30 million sequence reads per sample to the mouse genome (build mm10) and identified approximately 25,867 transcripts in the olfactory epithelium of WT and genetically modified mice with TopHat workflow. RNAseq data confirmed stable expression of 20 known housekeeping genes, and 3 of them were validated with qRT-PCR. Approximately 20% of transcripts showed differential expression between WT and aged samples and 0.1-1.0 % showed differential expression between WT and genetically modified lines (fold change >1.5; p value < 0.05). Altered expression of 20 genes for aged samples and 10 genes for PS-deficient samples was confirmed by qRT-PCR, demonstrating the high degree of sensitivity of RNAseq approach. Conlusion: Our study represent the first detailed analysis of differential gene expression by RNAseq technology in murine olfactory mucosa in aged animals. It is also the first study examining effects of gene knockout for APP, APLP2 and PSEN2 on gene expression profile in murine olfactory mucosa. We conclude that these data would help future studies in olfactory mucosa cells aimed to reveal molecular mechanisms associated with aging and biological function of APP, APLP2 and PSEN2 genes. RNAseq differential gene expression profiling of olfactory mucosa in young wild type, aged wild type, APP deficient, APLP2 deficient and PSEN2 deficient mice. Purpose: Next-generation gene expression profiling has revolutionized analysis of molecular pathways. The goals of this study were to compare NGS-derived olfactory mucosa transcriptome profiles (RNAseq) of aged wild-type mice, APP knockout mice, APLP2 knockout mice and PSEN2 knockout mice with young wild-type controls. Selected genes and pathways will be analyze further by low-throughput techniques such as real-time RT-PCR. Methods: Olfactory mucosa mRNA profiles of 2 months old wild-type (WT), 2 years old wild-type, APP knockout, APLP2 knockout and PSEN2 knockout mice were generated by deep sequencing, in triplicate, using Illumina NovaSeq6000 . For inspecting the quality of RNA-Seq data, the 100 most abundant genes are taken from all the samples and heatmaps were generated to observe the relation between samples/conditions. The sequence reads that passed the quality filters were analyzed at the transcript isoform level with TopHat followed by Cufflinks. Results: Using our data analysis workflow, we mapped at least 30 million sequence reads per sample to the mouse genome (build mm10) and identified approximately 24,000 transcripts in the olfactory epithelium of WT and genetically modified mice with TopHat workflow. RNAseq data confirmed stable expression of 20 known housekeeping genes, and 3 of them were validated with qRT-PCR. Approximately 20% of transcripts showed differential expression between WT and aged samples and 0.1-1.0 % showed differential expression between WT and genetically modified lines (fold change >1.5; p value < 0.05). Altered expression of 20 genes for aged samples and 10 genes for PS-deficient samples was confirmed by qRT-PCR, demonstrating the high degree of sensitivity of RNAseq approach. Conlusion: Our study represent the first detailed analysis of differential gene expression by RNAseq technology in murine olfactory mucosa in aged animals. It is also the first study examining effects of gene knockout for APP, APLP2 and PSEN2 on gene expression profile in murine olfactory mucosa. We conclude that these data would help future studies in olfactory mucosa cells aimed to reveal molecular mechanisms associated with aging and biological function of APP, APLP2 and PSEN2 genes. This RNAseq project has been supported by a grant of Polish National Science Centre (UMO-2013/09/NZ3/02359).

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Comparative transcriptome analysis of APPsα-DM and APLP2-KO brains

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