Mouse Preimplantation Development Laboratory
Guangming Wu, PhD, DVM
Following fertilization, the genomes of the differentiated oocyte and spermatozoon are epigenetically reprogrammed to instruct the zygote to differentiate into all types of somatic cells in a highly organized fashion and form an entire organism, a feature referred to as totipotency. The totipotency of mouse embryos could be retained up until the 8-cell or 16-cell stage. After this stage, early embryos differentiate into the first two lineages—the pluripotent inner cell mass (ICM) and the trophectoderm (TE). The ICM gives rise to the entire embryo proper—i.e., all cell types except for the TE, in an ability referred to as pluripotency. Currently, the molecular signals governing the reprogramming process and the establishment of pluripotency remain largely unknown, particularly in vivo. It has long been considered that totipotency-related factors are stored in the cytoplasm of the metaphase II (MII) oocyte. These factors include maternally expressed RNA, which peaks at the 8-cell stage but declines thereafter during embryonic development. Activation of zygotic transcripts mediated by maternal regulatory factors provides the first step in the establishment of totipotency/pluripotency.
The identification of a large number of genes and multiple signaling pathways involved at each developmental stage of embryonic development by global gene expression profiling has been done to enhance our understanding of the molecular mechanisms underlying totipotency/pluripotency and the programs of early mammalian development.
The main focus of our lab is on how totipotency is established and transformed into pluripotency during development—i.e., in vivo.
Oct4 (Pou5f1), a POU family transcription factor expressed specifically in germ cells, the ICM, and embryonic stem (ES) cells, is a transcription factor that plays a key role in the maintenance of cellular pluripotency in the ICM. On the other hand, Cdx2, a Class I homeobox gene, is required for differentiation of the TE, and its deficiency results in peri-implantation lethality. In our lab, using an efficient Eppendorf Femtojet microinjection system, we are screening for candidate factors regulating Oct4 expression by injecting siRNAs into mouse zygotes. Additionally, as Tead4—a protein regulated by Yap1 involving the Hippo pathway—has been identified as an upstream activator of Cdx2, we are studying the effects of Hippo pathway components, KIBRA and Wwc2, by conditional knockout in order to study their function in the oocyte-embryo transition, embryogenesis, and development. Identification of upstream regulators of these genes will lead us to a better understanding of how early embryos establish totipotency and regulate the first lineage separation, and how the reprogramming process is regulated.
Funding
Financial support: Max Planck Society, NIH RO1 grant (CoPI with HS)
Selected publications
Wu G, Scholer HR. Lineage segregation in the totipotent embryo. Curr Top Dev Biol. 2016;117:301–317.
Tiemann U, Wu G, Marthaler AG, Scholer HR, Tapia N. Epigenetic aberrations are not specific to transcription factor-mediated reprogramming. Stem Cell Reports. 2016;6(1):35–43.
Marthaler AG, Adachi K, Tiemann U, Wu G, Sabour D, Velychko S, et al. Enhanced OCT4 transcriptional activity substitutes for exogenous SOX2 in cellular reprogramming. Sci Rep. 2016;6:19415.
Sugawa F, Arauzo-Bravo MJ, Yoon J, Kim KP, Aramaki S, Wu G, et al. Human primordial germ cell commitment in vitro associates with a unique PRDM14 expression profile. EMBO J. 2015;34(8):1009–1024.
Russell R, Ilg M, Lin Q, Wu G, Lechel A, Bergmann W, et al. A dynamic role of TBX3 in the pluripotency circuitry. Stem Cell Reports. 2015;5(6):1155–1170.
Wu G, Scholer HR. Role of Oct4 in the early embryo development. Cell Regen (Lond). 2014;3(1):7.
Tiemann U, Marthaler AG, Adachi K, Wu G, Fischedick GU, Arauzo-Bravo MJ, et al. Counteracting activities of OCT4 and KLF4 during reprogramming to pluripotency. Stem Cell Reports. 2014;2(3):351–365.
Kang E, Wu G, Ma H, Li Y, Tippner-Hedges R, Tachibana M, et al. Nuclear reprogramming by interphase cytoplasm of two-cell mouse embryos. Nature. 2014;509(7498):101–104.
Fischedick G, Wu G, Adachi K, Arauzo-Bravo MJ, Greber B, Radstaak M, et al. Nanog induces hyperplasia without initiating tumors. Stem Cell Res. 2014;13(2):300–315.
Wu G, Han D, Gong Y, Sebastiano V, Gentile L, Singhal N, et al. Establishment of totipotency does not depend on Oct4A. Nat Cell Biol. 2013;15(9):1089–1097.
Pijnappel WW, Esch D, Baltissen MP, Wu G, Mischerikow N, Bergsma AJ, et al. A central role for TFIID in the pluripotent transcription circuitry. Nature. 2013;495(7442):516–519.
Marthaler AG, Tiemann U, Arauzo-Bravo MJ, Wu G, Zaehres H, Hyun JK, et al. Reprogramming to pluripotency through a somatic stem cell intermediate. PLoS One. 2013;8(12):e85138.
Tapia N, Reinhardt P, Duemmler A, Wu G, Arauzo-Bravo MJ, Esch D, et al. Reprogramming to pluripotency is an ancient trait of vertebrate Oct4 and Pou2 proteins. Nat Commun. 2012;3:1279.
Ko K, Wu G, Arauzo-Bravo MJ, Kim J, Francine J, Greber B, et al. Autologous pluripotent stem cells generated from adult mouse testicular biopsy. Stem Cell Rev. 2012;8(2):435–444.
Hoing S, Rudhard Y, Reinhardt P, Glatza M, Stehling M, Wu G, et al. Discovery of inhibitors of microglial neurotoxicity acting through multiple mechanisms using a stem-cell-based phenotypic assay. Cell Stem Cell. 2012;11(5):620–632.
Fischedick G, Klein DC, Wu G, Esch D, Hoing S, Han DW, et al. Zfp296 is a novel, pluripotent-specific reprogramming factor. PLoS One. 2012;7(4):e34645.
Wu G, Scholer HR. Role of mouse maternal Cdx2: what’s the debate all about? Reprod Biomed Online. 2011.
Wu G, Liu N, Rittelmeyer I, Sharma AD, Sgodda M, Zaehres H, et al. Generation of healthy mice from gene-corrected disease-specific induced pluripotent stem cells. PLoS Biol. 2011;9(7):e1001099.
Wu G, Gentile L, Do JT, Cantz T, Sutter J, Psathaki K, et al. Efficient derivation of pluripotent stem cells from siRNA-mediated Cdx2-deficient mouse embryos. Stem Cells Dev. 2011;20(3):485–493.
Han DW, Greber B, Wu G, Tapia N, Arauzo-Bravo MJ, Ko K, et al. Direct reprogramming of fibroblasts into epiblast stem cells. Nat Cell Biol. 2011;13(1):66–71.
Wu G, Gentile L, Fuchikami T, Sutter J, Psathaki K, Esteves TC, et al. Initiation of trophectoderm lineage specification in mouse embryos is independent of Cdx2. Development. 2010;137(24):4159–4169.
Singhal N, Graumann J, Wu G, Arauzo-Bravo MJ, Han DW, Greber B, et al. Chromatin-remodeling components of the BAF complex facilitate reprogramming. Cell. 2010;141(6):943–955.
Sebastiano V, Dalvai M, Gentile L, Schubart K, Sutter J, Wu GM, et al. Oct1 regulates trophoblast development during early mouse embryogenesis. Development. 2010;137(21):3551–3560.
Greber B, Wu G, Bernemann C, Joo JY, Han DW, Ko K, et al. Conserved and divergent roles of FGF signaling in mouse epiblast stem cells and human embryonic stem cells. Cell Stem Cell. 2010;6(3):215–226.
Ko K, Tapia N, Wu G, Kim JB, Bravo MJ, Sasse P, et al. Induction of pluripotency in adult unipotent germline stem cells. Cell Stem Cell. 2009;5(1):87–96.
Kim JB, Sebastiano V, Wu G, Arauzo-Bravo MJ, Sasse P, Gentile L, et al. Oct4-induced pluripotency in adult neural stem cells. Cell. 2009;136(3):411–419.
Kim JB, Zaehres H, Wu G, Gentile L, Ko K, Sebastiano V, et al. Pluripotent stem cells induced from adult neural stem cells by reprogramming with two factors. Nature. 2008;454(7204):646–650.
Scholer HR, Wu G. Oocytes originating from skin? Nat Cell Biol. 2006;8(4):313–314.
Wu G, Hao L, Han Z, Gao S, Latham KE, de Villena FP, et al. Maternal transmission ratio distortion at the mouse Om locus results from meiotic drive at the second meiotic division. Genetics. 2005;170(1):327–334.