8 research outputs found
Epigenetic Small Molecules Rescue Nucleocytoplasmic Transport and DNA Damage Phenotypes in C9ORF72 ALS/FTD
Amyotrophic lateral sclerosis (ALS) is a progressive and fatal neurodegenerative disease with available treatments only marginally slowing progression or improving survival. A hexanu-cleotide repeat expansion mutation in the C9ORF72 gene is the most commonly known genetic cause of both sporadic and familial cases of ALS and frontotemporal dementia (FTD). The C9ORF72 expansion mutation produces five dipeptide repeat proteins (DPRs), and while the mechanistic determinants of DPR-mediated neurotoxicity remain incompletely understood, evidence suggests that disruption of nucleocytoplasmic transport and increased DNA damage contributes to pathology. Therefore, characterizing these disturbances and determining the relative contribution of different DPRs is needed to facilitate the development of novel therapeutics for C9ALS/FTD. To this end, we generated a series of nucleocytoplasmic transport “biosensors”, composed of the green fluorescent protein (GFP), fused to different classes of nuclear localization signals (NLSs) and nuclear export signals (NESs). Using these biosensors in conjunction with automated microscopy, we investigated the role of the three most neurotoxic DPRs (PR, GR, and GA) on seven nuclear import and two export pathways. In addition to other DPRs, we found that PR had pronounced inhibitory effects on the classical nuclear export pathway and several nuclear import pathways. To identify compounds capable of counteracting the effects of PR on nucleocytoplasmic transport, we developed a nucleocy-toplasmic transport assay and screened several commercially available compound libraries, totaling 2714 compounds. In addition to restoring nucleocytoplasmic transport efficiencies, hits from the screen also counteract the cytotoxic effects of PR. Selected hits were subsequently tested for their ability to rescue another C9ALS/FTD phenotype—persistent DNA double strand breakage. Overall, we found that DPRs disrupt multiple nucleocytoplasmic transport pathways and we identified small molecules that counteract these effects—resulting in increased viability of PR-expressing cells and decreased DNA damage markers in patient-derived motor neurons. Several HDAC inhibitors were validated as hits, supporting previous studies that show that HDAC inhibitors confer therapeutic effects in neurodegenerative models
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A Pharmacological Approach to Identify Small Molecules Capable of Rescuing Nucleocytoplasmic Transport and DNA Damage Phenotypes in C9ORF72 ALS/FTD
Amyotrophic lateral sclerosis (ALS) is a progressive and fatal neurodegenerative disease with available treatments only marginally slowing progression or improving survival. A hexanucleotide repeat expansion mutation in the C9ORF72 gene is the most common known genetic cause of both sporadic and familial cases of ALS and frontotemporal dementia (FTD). The C9ORF72 expansion mutation produces five dipeptide-repeat proteins (DPRs), and while the mechanistic determinants of DPR-mediated neurotoxicity remain incompletely understood, evidence suggests that disruption of nucleocytoplasmic transport and increased DNA damage contributes to pathology. Therefore, characterizing these disturbances and determining the relative contribution of different DPRs is needed to facilitate the development of novel therapeutics for C9ALS/FTD. To this end, we generated a series of nucleocytoplasmic transport biosensors composed of the green fluorescent protein (GFP) fused to different classes of nuclear localization signals (NLSs) and nuclear export signals (NESs). Using these biosensors in conjunction with automated microscopy, we investigated the role of the three most neurotoxic DPRs (PR, GR, and GA) on 7 nuclear import and 2 export pathways. In addition to other DPRs, we found that PR had pronounced inhibitory effects on the classical nuclear export pathway and several nuclear import pathways. To identify compounds capable of counteracting the effects of PR on nucleocytoplasmic transport, we developed a nucleocytoplasmic transport assay and screened several commercially-available compound libraries totaling 2,714 compounds. In addition to restoring nucleocytoplasmic transport efficiencies, hits from the screen also counteract the cytotoxic effects of PR. Selected hits were subsequently tested for their ability to rescue another C9ALS/FTD phenotype, persistent DNA double strand breakage. Overall, we found that DPRs disrupt multiple nucleocytoplasmic transport pathways and identified small molecules that counteract these effects.</p
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Emerging Technologies for Genome-Wide Profiling of DNA Breakage
Genome instability is associated with myriad human diseases and is a well-known feature of both cancer and neurodegenerative disease. Until recently, the ability to assess DNA damage—the principal driver of genome instability—was limited to relatively imprecise methods or restricted to studying predefined genomic regions. Recently, new techniques for detecting DNA double strand breaks (DSBs) and single strand breaks (SSBs) with next-generation sequencing on a genome-wide scale with single nucleotide resolution have emerged. With these new tools, efforts are underway to define the “breakome” in normal aging and disease. Here, we compare the relative strengths and weaknesses of these technologies and their potential application to studying neurodegenerative diseases
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Dipeptide repeat proteins inhibit homology-directed DNA double strand break repair in C9ORF72 ALS/FTD
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Abstract MP257: Dual Actions Of β 2 Ar-agonism Confer Protection Against Heart Failure And Renal Dysfunction Via Inotropic And Lusitropic Effects And Normalized Cholesterol Homeostasis In A Mouse Model Of Alport Syndrome
Background:
Col4a3
-/-
Alport mice present a model of heart failure with preserved ejection fraction (HFpEF) secondary to chronic kidney disease (CKD) wherein etiological relationships have been established between hypertension, pulmonary edema, inflammation, cardiac hypertrophy and fibrosis, diastolic dysfunction and underlying abnormalities of elevated low-density lipoprotein receptor (LDLR) expression, excess LDL-cholesterol (LDL-C) accumulation, and mitochondrial dysfunction in renal tubules. HFpEF is characteristically unresponsive to pharmacological intervention. Here, we tested the hypothesis that selective β
2
-Adrenoceptor (β
2
AR) modulation with salbutamol, a short-acting β
2
AR agonist, could alleviate symptoms of CKD and simultaneously augment cardiac function. Secondarily, we investigated the mechanism of actions of such β
2
AR-mediated therapeutics on cardiac and renal functions.
Methods:
Alport mice were injected intraperitoneally with salbutamol or DMSO vehicle as a single bolus of 200μg/dose in short-term studies or daily with 100 μg/dose for 2 weeks long-term. Cardiac and renal functions, cAMP levels,
in vivo
renal tubular LDL-C uptake and renal histology were evaluated post-injection.
In vitro
mechanistic studies were performed in HK-2, Alport dog smooth muscle and tubular epithelial cells differentiated from Alport patient-derived iPSCs. Protein-protein interactions were studied using co-immunoprecipitation experiments and LDL-C uptake was measured by live-cell imaging.
Results:
Short-term, salbutamol improved renal function in parallel with decreased LDLR levels and reduced uptake of LDL-C into renal tubules. Long-term, cardiac diastolic function assessed by isovolumetric relaxation time (IVRT), filling pressures (E/E’), and myocardial performance index, and systolic function reflected by ejection fraction, stroke volume and cardiac output improved significantly in parallel with increased cardiac cAMP. Mechanistically, in the kidney, salbutamol activated IDOL and hence lysosomal ubiquitination and degradation of LDLR via a novel β
2
AR-mediated, cAMP-independent pathway involving the Rac1/Cdc42 β
1
PixGEF. β
1
Pix reversibly sequesters IDOL into a complex with LDLR, thereby blocking the degradation pathway. β
2
AR stimulation dissipates the complex reactivating IDOL-mediated LDLR degradation thereby re-establishing LDL-C homeostasis and renal function. Using flow cytometry in HEK293T cells, ectopic expression of bPix stabilized membrane LDLR, sensitive to IDOL- but not PCSK-mediated degradation.
Conclusions:
β
2
AR agonism represents a potential treatment strategy to alleviate progression of CKD and heart failure associated with HFpEF phenogroup 3
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Abstract 12089: Dual Actions of β 2 AR-Agonism Confer Protection Against Heart Failure and Renal Dysfunction via Inotropic and Lusitropic Effects and Normalized Cholesterol Homeostasis in a Mouse Model of Alport Syndrome
Introduction:
Col4a3-/- Alport mice present a model of heart failure with preserved ejection fraction (HFpEF) secondary to chronic kidney disease(CKD) wherein etiological relationships have been established between hypertension, pulmonary edema, inflammation, cardiac hypertrophy and fibrosis, diastolic dysfunction and underlying abnormalities of elevated low-density lipoprotein receptor (LDLR) expression, excess LDL-cholesterol(LDL-C) accumulation, and mitochondrial dysfunction in renal tubules.
Hypothesis:
We tested the hypothesis that selective β2-Adrenoceptor (β2AR) modulation with salbutamol, a short-acting β2AR agonist, could alleviate symptoms of CKD and simultaneously augment cardiac function.
Methods:
Alport mice were injected i.p.with salbutamol or DMSO vehicle as a single bolus of 200μg/dose in short-term studies or daily with 100 μg/dose for 2 wks long-term. Cardiac and renal functions, cAMP levels, in vivo renal tubular LDL-C uptake and renal histology were evaluated post-injection. N=3-8 for all experiments.
Results:
Short-term, salbutamol improved renal function in parallel with decreased LDLR levels and reduced uptake of LDL-C into renal tubules. Long-term, cardiac diastolic function assessed by isovolumetric relaxation time, filling pressures, and myocardial performance index, and systolic function reflected by ejection fraction, stroke volume and cardiac output improved significantly in parallel with increased cardiac cAMP (p<.05). Mechanistically, in the kidney, salbutamol activated IDOL and hence lysosomal ubiquitination and degradation of LDLR via a novel β2AR-mediated, cAMP-independent pathway involving the Rac1/Cdc42 β1PixGEF. β1Pix reversibly sequesters IDOL into a complex with LDLR, thereby blocking the degradation pathway. β2AR stimulation dissipates the complex reactivating IDOL-mediated LDLR degradation thereby re-establishing LDL-C homeostasis and renal function. Using flow cytometry in 293T cells, ectopic expression of bPix stabilized membrane LDLR, sensitive to IDOL- but not PCSK-mediated degradation.
Conclusions:
β2AR agonism represents a potential treatment strategy to alleviate progression of CKD and HF associated with HFpEF phenogroup 3
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CRISPR/Cas9-mediated excision of ALS/FTD-causing hexanucleotide repeat expansion in C9ORF72 rescues major disease mechanisms in vivo and in vitro
A GGGGCC
hexanucleotide repeat expansion (HRE) in the C9ORF72 gene is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), fatal neurodegenerative diseases with no cure or approved treatments that substantially slow disease progression or extend survival. Mechanistic underpinnings of neuronal death include C9ORF72 haploinsufficiency, sequestration of RNA-binding proteins in the nucleus, and production of dipeptide repeat proteins. Here, we used an adeno-associated viral vector system to deliver CRISPR/Cas9 gene-editing machineries to effectuate the removal of the HRE from the C9ORF72 genomic locus. We demonstrate successful excision of the HRE in primary cortical neurons and brains of three mouse models containing the expansion (500-600 repeats) as well as in patient-derived iPSC motor neurons and brain organoids (450 repeats). This resulted in a reduction of RNA foci, poly-dipeptides and haploinsufficiency, major hallmarks of C9-ALS/FTD, making this a promising therapeutic approach to these diseases