Project description:The aim of this experiment was to assess the on- and off-target effects of MAPT-AS1 expression, and whether mutations/deletions to MAPT-AS1 alter these effects. SHSY5Y cells stably expressing variants of MAPT-AS1 were analyzed by Riboseq and Quantseq.
Project description:Lysosomal failure underlies pathogenesis of numerous congenital neurodegenerative disorders and is an early and progressive feature of Alzheimer’s disease (AD) pathogenesis. Here, we report that lysosomal dysfunction in Down Syndrome (Trisomy 21) requires the extra gene copy of amyloid precursor protein (APP) and is mediated by the beta cleaved carboxy terminal fragment of APP (APP-βCTF, C99). In primary fibroblasts from individuals with Down Syndrome (DS), lysosomal degradation of autophagic and endocytic substrates is selectively impaired causing them to accumulate in enlarged autolysosomes/lysosomes. Direct measurements of lysosomal pH uncovered a significant elevation (0.6 units) associated with slowed LC3 turnover and the inactivation of cathepsin D (CTSD) and other lysosomal hydrolases known to be unstable or less active when lysosomal pH is persistently elevated. RNA sequencing analysis excluded a transcriptional contribution to hydrolase declines. Normalizing lysosome pH by delivering acidic nanoparticles to lysosomes ameliorated lysosomal deficits, implicating pH elevation as their primary basis. Cortical neurons cultured from the Ts2 mouse model of DS exhibited lysosomal deficits similar to those in DS cells. Lowering APP expression with siRNA or BACE1 inhibition reversed cathepsin deficits in both fibroblasts and neurons. Deleting one BACE1 allele from adult Ts2 mice had similar rescue effects in vivo. The modest elevation of endogenous APP-βCTF needed to disrupt lysosomal function in DS is relevant to sporadic AD where APP-βCTF, but not APP, is also elevated. Our results extend evidence that impaired lysosomal acidification drives progressive lysosomal failure in multiple forms of AD.
Project description:Mapttm1(EGFP)Klt/J mice (Mapt-EGFP; The Jackson Laboratory, Bar Harbor, ME, USA; stock 004779) carry a knock-in of the EGFP coding sequence in the first exon of the microtubule-associated protein tau (Mapt) gene producing a cytoplasmic EGFP fused to the first 31 amino acids of MAPT. EGFP expression marks neurons including enteric neurons regardless of their lineage, closely patterning the expression of neuron-specific beta-tubulin III (TUBB3). Mapt-EGFP ice were backcrossed to C57BL/6J (Jackson Laboratory strain #:000664) for three to five generations at Mayo Clinic. Six male and six female Mapt-EGFP mice (54-98 days of age) underwent surgical laparotomy in 3 groups (surgery #1: 1 male and 1 female, surgery #2: 3 males and 1 female, surgery #3: 2 males and 4 females) under pentobarbital (50mg/kg) anesthesia. The celiac ganglion of each mouse was injected with 3-5 μL of 25 mg/mL Alexa Fluor 647-labeled cholera toxin subunit B (CTB-AF647; Thermo Fisher Scientific, Waltham, MA, USA) with the intention of labeling the cell soma of intestinofugal neurons in the myenteric plexus of the colon. The animals were killed 3-4 days after surgery. The muscularis externa of the colon from each Mapt-EGFP mouse was pooled together between all mice of the same surgery date (2, 4, and 6 mice) and mechanically and enzymatically dissociated into single cells with a two-step process that first enriches for cells within myenteric ganglia (PMCID: PMC8114175). The pooled cells from each group of mice formed one biological replicate and subjected to FACS immediately after dissociation to generate populations of Mapt-EGFP+ neurons with or without the CTB-AF647 tracer and Mapt-EGFP− non-neuronal cells. The frequency of Mapt-EGFP+CTB-AF647+ neurons was approximately 125-fold lower than that of Mapt-EGFP+CTB-AF647− neurons and RNA from these preparations did not pass quality control. Therefore, only data from Mapt-EGFP+CTB-AF647− neurons were analyzed and referred to as Mapt-EGFP+ cells. Total RNA was isolated from Mapt-EGFP+ colonic neurons and Mapt-EGFP− myenteric cells using RNA-Bee (AMSBIO, Cambridge, MA, USA) and purified with RNeasy Mini Kit (Qiagen, Germantown, MD, USA). RNA quality was tested using Agilent Electropherogram (Agilent Technologies, Santa Clara, CA, USA) and hybridized to Affymetrix Mouse Genome 430.2 gene expression microarrays (Thermo Fisher Scientific, Waltham, MA, USA). This study utilized Affymetrix Mouse Genome 430.2 oligonucleotide microarray analysis to charaterize the transcriptome of Mapt-EGFP+ neurons and Mapt-EGFP- non-neuronal myenteric cells isolated from the colon of Mapttm1(EGFP)Klt/J mice.
Project description:Analysis of murine cerebrospinal fluid (CSF) by quantitative mass spectrometry is challenging due to low CSF volume, low total protein concentration and the presence of highly abundant proteins such as albumin. We demonstrate that the CSF proteome of individual mice can be analyzed in a quantitative manner to a depth of several hundred proteins in a robust and simple workflow consisting of single ultra HPLC runs on a benchtop mass spectrometer. The workflow is validated by a comparative analysis of BACE1-/- and wild type mice using label-free quantification. The protease BACE1 cleaves the amyloid precursor protein (APP) as well as several other substrates and is a major drug target in Alzheimer’s disease. We identified a total of 715 proteins with at least 2 unique peptides and quantified 522 of those proteins in CSF from BACE1-/- and wild type mice. Several proteins, including the known BACE1 substrates APP, APLP1, CHL1 and contactin-2 showed lower abundance in the CSF of BACE1-/- mice, demonstrating that BACE1 substrate identification is possible from CSF. Additionally, ectonucleotide pyrophosphatase 5 was identified as a novel BACE1 substrate and validated by immunoblot and in vitro BACE1 protease assay. Taken together, our study shows the deepest characterization of the mouse CSF proteome to date and the first quantitative analysis of the CSF proteome of individual mice. The BACE1 substrates identified in CSF may serve as biomarkers to monitor BACE1 activity in Alzheimer patients treated with BACE inhibitors.
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. Prefrontal cortices of adult male mice (24 - 28 weeks) of the following genotypes were analyzed: WT (n=3), APP-/- (n=3), APPα/α (n=3), APLP2-/- (n=3), APLP2(R1)-/- (n=3). WT, APP-/-, APPα/α, 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:We found that β-amyloid accumulation is modulated in HAOEC cells by overexpression or blocking of lncRNA BACE1-AS, which in turn regulates both BACE1 mRNA and protein expression. BACE1 is key-enzyme in the synthesis of β-amyloid from Amyloid Precursor Protein (APP). The transcriptomic changes mediated by 400nM β-amyloid was investigated in HAOEC cells.
Project description:Tau (MAPT) is a microtubule-associated protein causing frequent neurodegenerative diseases or inherited frontotemporal lobar degenerations. Emerging evidence for non-canonical functions of Tau in DNA protection and P53 regulation suggests its involvement in cancer. Indeed, Tau expression correlates with cancer-specific survival or response to microtubule therapeutics. These data may imply common molecular pathways involved in the pathogenesis of neurodegenerative disorders and cancer. To bring new evidence that Tau represents a key protein in cancer, we present an in silico pan-cancer analysis of MAPT transcriptomic profile in over 11000 clinical samples and over 1300 pre-clinical samples provided by the TCGA and the DEPMAP datasets respectively. We completed this analysis by exploring a possible interplay of MAPT with wild-type or mutated P53. Then, we calculated the impact of MAPT expression on clinical outcome and drug response. Overall, the results support a relevant role of the MAPT gene in several cancer types, although the contribution of Tau to cancer appears to very much depend on the cellular context.