Article

Genetic Correction of Huntington's Disease Phenotypes in Induced Pluripotent Stem Cells

The Buck Institute for Research on Aging, Novato, CA 94945, USA.
Cell stem cell (Impact Factor: 22.27). 06/2012; 11(2):253-63. DOI: 10.1016/j.stem.2012.04.026
Source: PubMed

ABSTRACT

Huntington's disease (HD) is caused by a CAG expansion in the huntingtin gene. Expansion of the polyglutamine tract in the huntingtin protein results in massive cell death in the striatum of HD patients. We report that human induced pluripotent stem cells (iPSCs) derived from HD patient fibroblasts can be corrected by the replacement of the expanded CAG repeat with a normal repeat using homologous recombination, and that the correction persists in iPSC differentiation into DARPP-32-positive neurons in vitro and in vivo. Further, correction of the HD-iPSCs normalized pathogenic HD signaling pathways (cadherin, TGF-β, BDNF, and caspase activation) and reversed disease phenotypes such as susceptibility to cell death and altered mitochondrial bioenergetics in neural stem cells. The ability to make patient-specific, genetically corrected iPSCs from HD patients will provide relevant disease models in identical genetic backgrounds and is a critical step for the eventual use of these cells in cell replacement therapy.

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    • "Undifferentiated and Differentiated HD Induced Pluripotent Stem Cell Models Previously, we characterized the genetically corrected lines of HD patient-derived iPSCs and found that a phenotype was apparent in the differentiated NSC stage but absent at the pluripotent stem cell state (Figure 1A) (An et al., 2012). We aimed to use this neural-specific correlation between disease genotype and disease phenotype to inform our global analysis of transcriptional changes that occur as a result of mHTT in our established human HD isogenic stem cell model (Figure 1A). "
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    ABSTRACT: We utilized induced pluripotent stem cells (iPSCs) derived from Huntington’s disease (HD) patients as a human model of HD and determined that the disease phenotypes only manifest in the differentiated neural stem cell (NSC) stage, not in iPSCs. To understand the molecular basis for the CAG repeat expansion-dependent disease phenotypes in NSCs, we performed transcriptomic analysis of HD iPSCs and HD NSCs compared to isogenic controls. Differential gene expression and pathway analysis pointed to transforming growth factor β (TGF-β) and netrin-1 as the top dysregulated pathways. Using data-driven gene coexpression network analysis, we identified seven distinct coexpression modules and focused on two that were correlated with changes in gene expression due to the CAG expansion. Our HD NSC model revealed the dysregulation of genes involved in neuronal development and the formation of the dorsal striatum. The striatal and neuronal networks disrupted could be modulated to correct HD phenotypes and provide therapeutic targets.
    Full-text · Article · Dec 2015 · Stem Cell Reports
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    • "Symptoms of early and late HD have been demonstrated in the YAC128 HD mouse model, including early susceptibility and later resistance to excitotoxicity induced by quinolinic acid as well as early hyperactivity and later decreases in activity (Slow et al., 2003). Mutant huntingtin is known to affect the activation of the MAPK signaling pathway (Bodai and Marsh, 2012), and the dysregulation pattern is biphasic, depending on the stage of HD. Young YAC128 mice show decreased phosphorylation of ERK, whereas 1-year-old YAC128 mice show an increased level of p-ERK (Gladding et al., 2014). "
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    ABSTRACT: Huntington disease (HD) is an incurable brain disorder characterized by the late onset of motor and cognitive symptoms, even though the neurons in the brain begin to suffer dysfunction and degeneration long before symptoms appear. Several molecular and developmental effects of HD have been identified using neural stem cells (NSCs) and differentiated cells, such as neurons and astrocytes. Still, little is known regarding the molecular pathogenesis of HD in pluripotent cells, such as embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs). Therefore, we examined putative signaling pathways and processes involved in HD pathogenesis in pluripotent cells. We tested naïve mouse HD YAC128 iPSCs and two types of human HD iPSCs that were generated from HD and juvenile HD patients. Surprisingly, we found that a number of changes affecting cellular processes in HD were also present in undifferentiated pluripotent HD iPSCs, including the deregulation of the MAPK and Wnt signaling pathways and the deregulation of the expression of genes related to oxidative stress, such as Sod1. Interestingly, a common protein interactor of the huntingtin protein and the proteins in the above pathways is p53, and the expression of the p53 gene was deregulated in HD YAC128 iPSCs and human HD iPSCs. In summary, our findings demonstrate that multiple molecular pathways that are characteristically deregulated in HD are already altered in undifferentiated pluripotent cells and that the pathogenesis of HD may begin during the early stages of life. © 2015. Published by The Company of Biologists Ltd.
    Full-text · Article · Jun 2015 · Disease Models and Mechanisms
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    • "It also allows designing of new treatment strategies for HD. Moreover, if to be used in cell replacement therapy, it is essential to correct mutation of the HTT in HD iPSCs as reported recently using the replacement of the expanded CAG repeat with a normal repeat via homologous recombination [22] "
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    ABSTRACT: Huntington's disease is the most common inherited neurodegenerative disorder among polyglutamine diseases caused by CAG repeat expansion in exon 1 of the huntingtin gene whose translation results in polyQ stretch in the N-terminus of the huntingtin protein. This mutation significantly affects huntingtin conformation, proteolysis, post-translational modifications, as well as its ability to bind interacting proteins. As a consequence, a variety of cellular mechanisms such as transcription, mitochondrial energy metabolism, axonal transport, neuronal vulnerability to oxidative stress, neurotransmission, and immune response are altered and involved in the pathogenesis of Huntington's disease. Promising candidate molecular biomarkers of HD have emerged from proteomic studies. Recent analyses focused on huntingtin protein itself, its post-translational modification and interacting proteins, which are of great importance for disease course. Furthermore, brain, body fluids and immune system are intensively studied in order to search for additional proteins with a view to their use as a biomarker(s) or set of biomarkers in clinical trials in HD translational research. This article is protected by copyright. All rights reserved.
    Full-text · Article · Feb 2015 · Proteomics. Clinical applications
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