Unknown,Transcriptomics,Genomics,Proteomics

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Netrin-1 facilitates somatic cell reprogramming by limiting Dcc pro-apoptotic activity.

ABSTRACT: The generation of induced pluripotent stem (iPS) cells holds great promise in regenerative medicine. However, the relative flaws in the understanding of the molecular mechanisms promoting or limiting reprogramming still hinder the efficient generation of high quality iPS cells. Whereas modulation of the initial Oct4, Sox2, Klf4 and c-Myc (OSKM) cocktail with new transcription factors has been extensively documented, comparatively little is known about soluble molecules promoting the process, even if such recombinant factors could be highly valuable for therapeutic applications. In this study we developed a large-scale identification method to uncover novel programmed cell death (PCD)-related mechanisms limiting somatic cell reprogramming to pluripotency (SCRP). We identified Netrin-1 and its dependence receptor Dcc (Deleted in Colorectal Carcinoma), previously described for their respective survival/death functions both in normal and oncogenic contexts, as novel key SCRP modulators. We show that the early phase of SCRP is accompanied with a strong Netrin-1 deficiency, due to the improper epigenetic regulation of the Ntn1 promoter by OSKM. Mechanistically, we demonstrate that such Netrin-1 imbalance induces apoptosis mediated by the dependence receptor Dcc in a p53-independent manner. Correction of the Netrin-1/Dcc equilibrium by gain-of-ligand and loss-of-receptor experiments constrains apoptosis and improves reprogramming. As a consequence, we propose a novel iPS derivation protocol including a sequential treatment with recombinant Netrin1 that greatly facilitates the generation of mouse and human iPS cells. RNA-sequencing of mouse embryonic fibroblasts (passage 2 and passage 4), mouse pre-iPS cells (passage 5 and passage 25), 1 clone of control iPS (passage 5 and passage 25) and 2 independent clones of "Netrin-1 derived" iPS cells (passage 5 and passage 25). For this analysis, mouse iPS cell lines were grown in KSR+LIF media.

ORGANISM(S): Mus musculus

SUBMITTER: Fabrice Lavial

PROVIDER: E-GEOD-54107 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Reprogramming of somatic cells is a valuable tool to understand the mechanisms of regaining pluripotency and further opens up the possibility to generate patient-specific pluripotent stem cells. Reprogramming of mouse and human somatic cells into pluripotent stem cells, designated as induced pluripotent stem (iPS) cells, has been possible with the expression of the transcription factor quartet Oct4, Sox2, c-Myc, and Klf4. Considering that ectopic expression of c-Myc causes tumourigenicity in offspring and retroviruses themselves can cause insertional mutagenesis, the generation of iPS cells with a minimal number of factors may hasten the clinical application of this approach. Here, we show that adult mouse neural stem cells (NSCs) express higher endogenous levels of Sox2 and c-Myc than ES cells and that exogenous Oct4 together with either Klf4 or c-Myc are sufficient to generate iPS cells from NSCs. These two-factor (2F) iPS cells are similar to embryonic stem cells at the molecular level, contribute to development of the germline, and form chimeras. We propose that, in inducing pluripotency, the number of reprogramming factors can be reduced when using somatic cells that endogenously express appropriate levels of complementing factors. Experiment Overall Design: 8 hybridizations in total. Experiment Overall Design: NSC derived iPS cells by 2 factors (Oct4 and Klf4) in triplicate: Experiment Overall Design: - iPS cell_2F_1 Experiment Overall Design: - iPS cell_2F_2 Experiment Overall Design: - iPS cell_2F_3 Experiment Overall Design: Embryonic Stem cells (ESC) in triplicate: Experiment Overall Design: - ESC_1 Experiment Overall Design: - ESC_2 Experiment Overall Design: - ESC_3 Experiment Overall Design: NSC cultures in duplicates: Experiment Overall Design: - NSC_2 Experiment Overall Design: - NSC_3 Experiment Overall Design: NSC derived iPS cells by 4 factors (Oct4, Sox2, c-Myc and Klf4) in triplicate: Experiment Overall Design: - iPS cell_4F_1 Experiment Overall Design: - iPS cell_4F_2 Experiment Overall Design: - iPS cell_4F_3

Project description:In the context of most induced pluripotent stem (iPS) cell reprogramming methods, heterogeneous populations of nonproductive and staggered productive intermediates arise at different reprogramming time points1-11. Despite recent reports claiming substantially increased reprogramming efficiencies using genetically modified donor cells12,13 prospectively isolating distinct reprogramming intermediates remains an important goal to decipher reprogramming mechanisms. Previous attempts to identify surface markers of intermediate cell populations were based on the assumption that during reprogramming the cells progressively lose donor cell identity and gradually acquire iPS cell properties1,2,7,8,10. Here, we report that iPS cell and epithelial markers, such as SSEA1 and EpCAM, respectively, are not predictive of reprogramming during early phases. Instead, in a systematic functional surface marker screen we find that early reprogramming-prone cells express a unique set of surface markers, including CD73, CD49d and CD200 that are absent in fibroblasts and iPS cells. Single cell mass cytometry and prospective isolation show that these distinct intermediates are transient and bridge the gap between donor cell silencing and pluripotency marker acquisition during the early, presumably stochastic reprogramming phase2. Expression profiling revealed that the transcriptional regulators Nr0b1 and Etv5 are specifically expressed in this early reprogramming state, preceding activation of key pluripotency regulators such as Rex1, Dppa2, Nanog and Sox2. Both factors are required for the generation of the early intermediate state and fully reprogrammed iPS cells, and thus mark some of the earliest known regulators of iPS cell induction. Our study shows an ordered sequence of transitions during the earliest steps of iPS cell reprogramming that deconvolutes the first steps in a hierarchical series of events that lead to pluripotency acquisition. Samples for poised (CD73+ or CD49d+) and non-poised (CD73-) reprogramming samples were FACS sorted 6 and 9 days after induction of Klf4, Oct4, Sox2 and cMyc in Rosa-rtTA +/- mouse embryonic fibroblasts (MEFs). 'Total' populations are expression analyses for unsorted populations analyzed at the same time points. Control populations were also sampled: mouse embryonic fibroblasts (MEFs), partially reprogrammed cells (SC4) and mouse embryonic stem cell (ESC).

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Netrin-1 facilitates somatic cell reprogramming by limiting Dcc pro-apoptotic activity.

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