Transcriptional analysis of pluripotency reveals the Hippo pathway as a barrier to reprogramming.

Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, and Diabetes Center, South San Francisco, CA, USA.
Human Molecular Genetics (Impact Factor: 6.68). 02/2012; 21(9):2054-67. DOI: 10.1093/hmg/dds023
Source: PubMed

ABSTRACT Pluripotent stem cells are derived from culture of early embryos or the germline and can be induced by reprogramming of somatic cells. Barriers to reprogramming that stabilize the differentiated state and have tumor suppression functions are expected to exist. However, we have a limited understanding of what such barriers might be. To find novel barriers to reprogramming to pluripotency, we compared the transcriptional profiles of the mouse germline with pluripotent and somatic cells, in vivo and in vitro. There is a remarkable global expression of the transcriptional program for pluripotency in primordial germ cells (PGCs). We identify parallels between PGC reprogramming to pluripotency and human germ cell tumorigenesis, including the loss of LATS2, a tumor suppressor kinase of the Hippo pathway. We show that knockdown of LATS2 increases the efficiency of induction of pluripotency in human cells. LATS2 RNAi, unlike p53 RNAi, specifically enhances the generation of fully reprogrammed iPS cells without accelerating cell proliferation. We further show that LATS2 represses reprogramming in human cells by post-transcriptionally antagonizing TAZ but not YAP, two downstream effectors of the Hippo pathway. These results reveal transcriptional parallels between germ cell transformation and the generation of iPS cells and indicate that the Hippo pathway constitutes a barrier to cellular reprogramming.

Download full-text


Available from: Laure Blouin, Sep 26, 2014
  • Source
    • "Importantly, the somatic cell is not a tabula rasa and expresses genes that antagonize reprogramming, as has been shown for tumor suppressors (p53, INK4a/ARF, LATS2) (Kawamura et al., 2009; Qin et al., 2012; Zhao et al., 2008) and H3K9 methyltransferases (SETDB1, SUV39H, EHMT2) (Chen et al., 2013). In addition, focused RNAi screens have revealed other pathways that act as barriers to reprogramming, such as TGF-b signaling (Samavarchi-Tehrani et al., 2010), H3K79 methylation by DOT1L (Onder et al., 2012), or protein ubiquitination (Buckley et al., 2012). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Reprogramming of somatic cells to induced pluripotent stem cells (iPSCs) holds enormous promise for regenerative medicine. To elucidate endogenous barriers limiting this process, we systematically dissected human cellular reprogramming by combining a genome-wide RNAi screen, innovative computational methods, extensive single-hit validation, and mechanistic investigation of relevant pathways and networks. We identify reprogramming barriers, including genes involved in transcription, chromatin regulation, ubiquitination, dephosphorylation, vesicular transport, and cell adhesion. Specific a disintegrin and metalloproteinase (ADAM) proteins inhibit reprogramming, and the disintegrin domain of ADAM29 is necessary and sufficient for this function. Clathrin-mediated endocytosis can be targeted with small molecules and opposes reprogramming by positively regulating TGF-β signaling. Genetic interaction studies of endocytosis or ubiquitination reveal that barrier pathways can act in linear, parallel, or feedforward loop architectures to antagonize reprogramming. These results provide a global view of barriers to human cellular reprogramming.
    Cell 07/2014; 158(2):449-61. DOI:10.1016/j.cell.2014.05.040 · 33.12 Impact Factor
  • Source
    • "By comparing somatic cells with iPSCs, the Hippo pathway gene Lats2 was found to be significantly repressed during reprogramming , and may therefore represent such a barrier (Qin et al., 2012). Indeed, knockdown of Lats2 increased efficiency of human iPSC generation about three fold without accelerating cell proliferation (Qin et al., 2012). The elevated reprogramming efficiency depends on TAZ because concomitant knockdown of TAZ blocked the effect of Lats2 knockdown. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Stem cells and progenitor cells are the cells of origin for multi-cellular organisms and organs. They play key roles during development and their dysregulation gives rise to human diseases such as cancer. The recent development of induced pluripotent stem cell (iPSC) technology which converts somatic cells to stem-like cells holds great promise for regenerative medicine. Nevertheless, the understanding of proliferation, differentiation, and self-renewal of stem cells and organ-specific progenitor cells is far from clear. Recently, the Hippo pathway was demonstrated to play important roles in these processes. The Hippo pathway is a newly established signaling pathway with critical functions in limiting organ size and suppressing tumorigenesis. This pathway was first found to inhibit cell proliferation and promote apoptosis, therefore regulating cell number and organ size in both Drosophila and mammals. However, in several organs, disturbance of the pathway leads to specific expansion of the progenitor cell compartment and manipulation of the pathway in embryonic stem cells strongly affects their self-renewal and differentiation. In this review, we summarize current observations on roles of the Hippo pathway in different types of stem cells and discuss how these findings changed our view on the Hippo pathway in organ development and tumorigenesis.
    Protein & Cell 04/2012; 3(4):291-304. DOI:10.1007/s13238-012-2919-3 · 2.85 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Stem cell (SC) activity fluctuates throughout an organism's lifetime to maintain homeostatic conditions in all tissues. As animals develop and age, their organs must remodel and regenerate themselves in response to environmental and physiological demands. Recently, the highly conserved Hippo signaling pathway, discovered in Drosophila melanogaster, has been implicated as a key regulator of organ size control across species. Deregulation is associated with substantial overgrowth phenotypes and eventual onset of cancer in various tissues. Importantly, emerging evidence suggests that the Hippo pathway can modulate its effects on tissue size by the direct regulation of SC proliferation and maintenance. These findings provide an attractive model for how this pathway might communicate physiological needs for growth to tissue-specific SC pools. In this review, we summarize the current and emerging data linking Hippo signaling to SC function.
    Trends in cell biology 05/2012; 22(7):339-46. DOI:10.1016/j.tcb.2012.04.006 · 12.31 Impact Factor
Show more