Embryonic stem cells (ESCs) are pluripotent and have therapeutic potential in regenerative medicine. The pluripotent ESC identity is governed by a set of transcription factors centered on Oct4, Sox2 and Nanog together with a number of epigenetic regulators. To dissect the molecular basis for the pluripotency of ESCs, we have developed an in vivo biotinylation strategy for affinity purification of protein complexes (dubbed bioSAIP) and chromatin immunoprecipitation (dubbed bioChIP). These approaches have allowed us to delineate a protein interaction network surrounding Nanog, i.e., the Nanog interactome. The Nanog interactome is highly enriched for transcription factors including Oct4, which plays critical roles in stem cell pluripotency, somatic cell reprogramming and early development. It also encompasses several epigenetic regulatory pathways including Polycomb-repressive complex 1 (PRC1). Our preliminary data confirmed endogenous interaction between Oct4 and PRC1 proteins and uncovered unique PRC1 complexes in ESCs that comprise Rybp but not chromobox proteins (Cbxs). The overall objective of the proposed research is to use our well-established proteomics approaches coupled with mass spectrometry to establish the Oct4-centered """"""""epigenetic interactome"""""""" encompassing the PRC1 interactome in mouse ESCs, and to elucidate molecular mechanism of PRC1 repression for stem cell maintenance. Our hypothesis is that the Oct4-centered """"""""epigenetic interactome"""""""" links multiple critical epigenetic pathways to the Nanog interactome and comprises a unique PRC1 repression to maintain ESC identity. The proposed studies are: 1) to dissect the biochemical basis for epigenetic regulation of stem cell pluripotency;2) to establish the PRC1 interactome in ESCs;and 3) to decipher the mechanism of PRC1 function for target gene regulation and stem cell maintenance. These studies will not only lead to the discovery of novel pluripotency factors, but also illuminate the fundamental properties of stem cell pluripotency and the process of somatic cell reprogramming. Furthermore, it will provide a framework for exploring epigenetic mechanisms for stem cell pluripotency and finding ways to perturb epigenetic pathways for cell fate changes.

Public Health Relevance

Embryonic stem cells (ESCs) can self renew indefinitely and differentiate into different cell types of a body, and are thus considered an unlimited, renewable source for cell-based therapies in regenerative medicine. We will dissect the biochemical basis for Oct4-centered epigenetic regulation of stem cell pluripotency, and decipher the mechanism of PRC1 function for target gene regulation and stem cell maintenance. This will provide a framework for understanding the epigenetic mechanisms of pluripotency (and cancer), and for exploring perturbation of epigenetic pathways to manipulate ESC fate changes for clinical application.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
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Development - 2 Study Section (DEV2)
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Haynes, Susan R
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Icahn School of Medicine at Mount Sinai
Schools of Medicine
New York
United States
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Saunders, Arven; Huang, Xin; Fidalgo, Miguel et al. (2017) The SIN3A/HDAC Corepressor Complex Functionally Cooperates with NANOG to Promote Pluripotency. Cell Rep 18:1713-1726
Saunders, Arven; Li, Dan; Faiola, Francesco et al. (2017) Context-Dependent Functions of NANOG Phosphorylation in Pluripotency and Reprogramming. Stem Cell Reports 8:1115-1123
Huang, Xin; Balmer, Sophie; Yang, Fan et al. (2017) Zfp281 is essential for mouse epiblast maturation through transcriptional and epigenetic control of Nodal signaling. Elife 6:
Faiola, Francesco; Yin, Nuoya; Fidalgo, Miguel et al. (2017) NAC1 Regulates Somatic Cell Reprogramming by Controlling Zeb1 and E-cadherin Expression. Stem Cell Reports 9:913-926
Guallar, Diana; Wang, Jianlong (2016) Taking the RISC of exiting naïve pluripotency. Genome Biol 17:104
Fidalgo, Miguel; Huang, Xin; Guallar, Diana et al. (2016) Zfp281 Coordinates Opposing Functions of Tet1 and Tet2 in Pluripotent States. Cell Stem Cell 19:355-69
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Ding, Junjun; Huang, Xin; Shao, Ningyi et al. (2015) Tex10 Coordinates Epigenetic Control of Super-Enhancer Activity in Pluripotency and Reprogramming. Cell Stem Cell 16:653-68
Gingold, Julian A; Fidalgo, Miguel; Guallar, Diana et al. (2014) A genome-wide RNAi screen identifies opposing functions of Snai1 and Snai2 on the Nanog dependency in reprogramming. Mol Cell 56:140-52
Faiola, Francesco; Saunders, Arven; Dang, Baoyen et al. (2014) An improved in vivo biotinylation strategy combined with FLAG and antibody based approaches for affinity purification of protein complexes in mouse embryonic stem cells. Methods Mol Biol 1177:135-49

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