Human Trisomic iPSCs from Down Syndrome Fibroblasts Manifest Mitochondrial Alterations Early during Neuronal Differentiation (original) (raw)
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Mitochondrial Abnormalities in Down Syndrome: Pathogenesis, Effects and Therapeutic Approaches
Advances in Research on Down Syndrome, 2018
Down syndrome (DS) consists of a complex phenotype with constant features, such as mental retardation and hypotonia, and variable features, including heart defects and susceptibility to Alzheimer's disease, type 2 diabetes, obesity and immune disorders. Overexpression of genes mapping to chromosome 21 (Hsa21) is directly or indirectly responsible for pathogenesis of DS phenotypic features, as overexpressed Hsa21 genes dysregulate several other genes mapping to different chromosomes. Many of these genes are involved in mitochondrial function. Recent studies highlight a link between mitochondrial dysfunction, consistently observed in DS subjects, and DS phenotype. In this review, we first provide a basic overview of mitochondrial alterations in DS in terms of mitochondrial bioenergetics, biogenesis and morphology. We then discuss how mitochondrial malfunction may contribute to the pathogenesis of clinical manifestations and how specific Hsa21 genes may cause the disruption of mitochondrial phenotype. Finally, we focus on drugs, which affect mitochondrial function and network to propose possible therapeutic approaches aimed at improving and/or preventing various aspects of the DS phenotype. Our working hypothesis is that correcting the mitochondrial defect might improve the neurological phenotype and prevent DS-associated pathologies, thus providing a better quality of life for DS individuals and their families.
Mitochondrial dysfunction in down syndrome: molecular mechanisms and therapeutic targets
Molecular Medicine
Trisomy of chromosome 21 (TS21) is the most common autosomal aneuploidy compatible with postnatal survival with a prevalence of 1 in 700 newborns. Its phenotype is highly complex with constant features, such as mental retardation, dysmorphic traits and hypotonia, and variable features including heart defects, susceptibility to Alzheimer's disease (AD), type 2 diabetes, obesity and immune disorders. Overexpression of genes on chromosome-21 (Hsa21) is responsible for the pathogenesis of Down syndrome (DS) phenotypic features either in a direct or in an indirect manner since many Hsa21 genes can affect the expression of other genes mapping to different chromosomes. Many of these genes are involved in mitochondrial function and energy conversion, and play a central role in the mitochondrial dysfunction and chronic oxidative stress, consistently observed in DS subjects. Recent studies highlight the deep interconnections between mitochondrial dysfunction and DS phenotype. In this short review we first provide a basic overview of mitochondrial phenotype in DS cells and tissues. We then discuss how specific Hsa21 genes may be involved in determining the disruption of mitochondrial DS phenotype and biogenesis. Finally we briefly focus on drugs that affect mitochondrial function and mitochondrial network suggesting possible therapeutic approaches to improve and/or prevent some aspects of the DS phenotype.
Adaptive Downregulation of Mitochondrial Function in Down Syndrome
Cell Metabolism, 2013
Mitochondrial dysfunction and oxidative stress are common features of Down syndrome (DS). However, the underlying mechanisms are not known. We investigated the relationship between abnormal energy metabolism and oxidative stress with transcriptional and functional changes in DS cells. Impaired mitochondrial activity correlated with altered mitochondrial morphology. Increasing fusion capacity prevented morphological but not functional alterations in DS mitochondria. Sustained stimulation restored mitochondrial functional parameters but increased reactive oxygen species production and cell damage, suggesting that reduced DS mitochondrial activity is an adaptive response for avoiding injury and preserving basic cellular functions. Network analysis of genes overexpressed in DS cells demonstrated functional integration in pathways involved in energy metabolism and oxidative stress. Thus, although preventing extensive oxidative damage, mitochondrial downregulation may contribute to increased susceptibility of individuals with DS to clinical conditions in which altered energy metabolism may play a role, such as Alzheimer's disease, diabetes, and some types of autistic spectrum disorders.
Neuronal dysfunction in Down syndrome: Contribution of neuronal models in cell culture
Journal of Physiology-Paris, 2006
Down syndrome (DS) in humans, or trisomy of autosome 21, represents the hyperdiploidy that most frequently survives gestation, reaching an incidence of 1 in 700 live births. The condition is associated with multisystemic anomalies, including those affecting the central nervous system (CNS), determining a characteristic mental retardation. At a neuronal level, our group and others have shown that the condition determines marked alterations of action potential and ionic current kinetics, which may underlie abnormal processing of information by the CNS.
STEM CELLS, 2015
Trisomy 21 (T21), Down Syndrome (DS) is the most common genetic cause of dementia and intellectual disability. Modelling DS is beginning to yield pharmaceutical therapeutic interventions for amelioration of intellectual disability, which are currently being tested in clinical trials. DS is also a unique genetic system for investigation of pathological and protective mechanisms for accelerated ageing, neurodegeneration, dementia, cancer and other important common diseases. New drugs could be identified and disease mechanisms better understood by establishment of well controlled cell model systems. We have developed a first non-integrationreprogrammed isogenic human induced-pluripotent-stem-cells (iPSC) model of DS by reprogramming the skin fibroblasts from an adult individual with constitutional mosaicism for DS, and separately cloned multiple isogenic T21 and euploid (D21) iPSC lines. Our model shows a very low number of reprogramming rearrangements as assessed by a high-resolution whole genome CGH-array hybridisation and it reproduces several cellular pathologies seen in primary human DS cells, as assessed by automated high-content microscopic analysis. Early differentiation shows an imbalance of the lineage-specific stem/progenitor cell compartments: T21 causes slower proliferation of neural and faster expansion of hematopoietic lineage. T21 iPSC-derived neurons show increased production of amyloid peptide-containing material, a decrease in mitochondrial membrane potential, and an increased number and abnormal appearance of mitochondria. Finally, T21-derived neurons show significantly higher number of DNA double-strand breaks than isogenic D21 controls. Our fully isogenic system therefore opens possibilities for modelling mechanisms of developmental, accelerated ageing, and neurodegenerative pathologies caused by T21.
Experimental Cell Research, 2013
Trisomy 21 Neurogenesis impairment Induced pluripotent stem cells miRNA a b s t r a c t Down syndrome (DS), or Trisomy 21 (T21) syndrome, one of the most common chromosomal abnormalities, is caused by an extra duplication of chromosome 21. In studies of neuron development, experimental models based on human cells are considered to be the most desired and accurate for basic research. The generation of diseased induced pluripotetn stem (iPS) cell is a critical step in understanding the developmental stages of complex neuronal diseases. Here, we generated human DS iPS cell lines from second trimester amniotic fluid (AF) cells with T21 by co-expressing Yamanaka factors through lentiviral delivery and subsequently differentiated them into neuronal progenitor cells (NPCs) for further analyses. T21 AF-iPS cells were characterized for the expression of pluripotent markers and for their ability to differentiate into all three germ layers by forming embryoid bodies in vitro and teratomas in vivo. The T21 AF-iPS cells maintained their unique pattern of chromosomal karyotypes: three pairs of chromosome 21. The level of amyloid precursor protein was significantly increased in NPCs derived from T21 AF-iPS cells compared with NPCs from normal AF-iPS cells. The expression levels of miR-155 and miR-802 in T21 AF-iPS-NPCs were highly elevated in the presence of low expression of MeCP2. We observed that T21 iPS-NPCs generated fewer neurons compared with controls. T21 iPS-NPCs exhibit developmental defects during neurogenesis. Our findings suggest that T21 AF-iPS cells serve as a good source to further elucidate the impairment neurogenesis of DS and the onset of Alzheimer's disease.
Targeting Mitochondrial Network Architecture in Down Syndrome and Aging
International Journal of Molecular Sciences
Mitochondria are organelles that mainly control energy conversion in the cell. In addition, they also participate in many relevant activities, such as the regulation of apoptosis and calcium levels, and other metabolic tasks, all closely linked to cell viability. Functionality of mitochondria appears to depend upon their network architecture that may dynamically pass from an interconnected structure with long tubular units, to a fragmented one with short separate fragments. A decline in mitochondrial quality, which presents itself as an altered structural organization and a function of mitochondria, has been observed in Down syndrome (DS), as well as in aging and in age-related pathologies. This review provides a basic overview of mitochondrial dynamics, from fission/fusion mechanisms to mitochondrial homeostasis. Molecular mechanisms determining the disruption of the mitochondrial phenotype in DS and aging are discussed. The impaired activity of the transcriptional co-activator PGC...
EMBO molecular medicine, 2013
Down syndrome (trisomy 21) is the most common viable chromosomal disorder with intellectual impairment and several other developmental abnormalities. Here, we report the generation and characterization of induced pluripotent stem cells (iPSCs) derived from monozygotic twins discordant for trisomy 21 in order to eliminate the effects of the variability of genomic background. The alterations observed by genetic analysis at the iPSC level and at first approximation in early development illustrate the developmental disease transcriptional signature of Down syndrome. Moreover, we observed an abnormal neural differentiation of Down syndrome iPSCs in vivo when formed teratoma in NOD-SCID mice, and in vitro when differentiated into neuroprogenitors and neurons. These defects were associated with changes in the architecture and density of neurons, astroglial and oligodendroglial cells together with misexpression of genes involved in neurogenesis, lineage specification and differentiation. Furthermore, we provide novel evidence that dual-specificity tyrosine-(Y)-phosphorylation regulated kinase 1A (DYRK1A) on chromosome 21 likely contributes to these defects. Importantly, we found that targeting DYRK1A pharmacologically or by shRNA results in a considerable correction of these defects.