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Molecular Characterization of Down Syndrome Embryonic Stem Cells Reveals a Role for RUNX1 in Neural Differentiation

ABSTRACT: Down syndrome (DS) is the leading genetic cause of mental retardation and is caused by a third copy of human chromosome 21. The different pathologies of DS involve many tissues with a distinct array of neural phenotypes. Here we characterize new embryonic stem cell lines with DS (DS-ESCs), and focus on the neural aspects of the diease. Our results show that neural progenitor cells (NPCs) differentiated from five independent DS-ESC lines display increased apoptosis and down-regulation of forehead developmental genes. Analysis of differentially expressed genes suggested RUNX1 as a key transcription regulator in DS-NPCs. Using genome editing we were able to disrupt all three copies of RUNX1 in DS-ESCs, leading to down-regulation of several RUNX1 target developmental genes accompanied by reduced apoptosis and neuron migration. Our work sheds new light on the role of RUNX1 and the importance of dosage balance in the development of neural phenotypes in DS.

ORGANISM(S): Homo sapiens

PROVIDER: GSE84887 | GEO | 2016/09/24

SECONDARY ACCESSION(S): PRJNA335552

REPOSITORIES: GEO

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Project description:Down syndrome (DS) is the most frequent cause of human congenital mental retardation. Cognitive deficits in DS result from perturbations of normal cellular processes both during development and in adult tissues, but the mechanisms underlying DS etiology remain poorly understood. To assess the ability of iPSCs to model DS phenotypes, as a prototypical complex human disease, we generated bona-fide DS and wild-type (WT) non-viral iPSCs by episomal reprogramming. DS iPSCs selectively overexpressed chromosome 21 genes, consistent with gene dosage, which was associated with deregulation of thousands of genes throughout the genome. DS and WT iPSCs were neurally converted at >95% efficiency, and had remarkably similar lineage potency, differentiation kinetics, proliferation and axon extension at early time points. However, at later time points DS cultures showed a two-fold bias towards glial lineages. Moreover, DS neural cultures were up to two times more sensitive to oxidative stress induced apoptosis, and this could be prevented by the anti-oxidant N-acetylcysteine. Our results reveal a striking complexity in the genetic alterations caused by trisomy-21 that are likely to underlie DS developmental phenotypes, and indicate a central role for defective early glial development in establishing developmental defects in DS brains. Furthermore, oxidative stress sensitivity is likely to contribute to the accelerated neurodegeneration seen in DS, and we provide proof of concept for screening corrective therapeutics using DS iPSCs and their derivatives. Non-viral DS iPSCs can therefore recapitulate features of complex human disease in vitro, and provide a renewable and ethically unencumbered discovery platform. Control (WT) and Down Syndrome iPSC lines were generated via episomal reprogramming of human donor fibroblasts. Two iPSC clones conforming to iPS criteria (determined by immunocytochemistry detection of pluripotency markers) were developed from each fibroblast donor. Two control (WT) and DS lines each were further characterized and underwent neural differentiation. Multiple biological replicates of donor fibroblast and iPSC from both control (WT) and DS lines, including 3 euploid DS samples and 3 MEL1 hESC controls (total 54 samples) were hybridized to Illumina HT-12 v4 microarray for gene expression analysis.

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Molecular Characterization of Down Syndrome Embryonic Stem Cells Reveals a Role for RUNX1 in Neural Differentiation

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