Nuclear architecture and epigenetic chromatin status in early embryos

(in collaboration with E.Wolf and V. Zakhartchenko, Chair for Molecular Animal Breeding and Biotechnology, Gene Center LMU)

 The major questions of this project can be summarized as follows:

1. What are the characteristic features of nuclear architecture and epigenetic chromatin modifications that are present in normal and in nuclear transfer (NT) embryos?

2. How does the nuclear architecture of somatic cells change upon transfer into enucleated oocytes?

3. Are there fundamental differences in the nuclear architecture between donor nuclei that exhibit a significantly different developmental potential?

The goal of this project is to advance our understanding on the epigenetic events that underlie the process of nuclear reprogramming with a special focus on the role of large scale chromatin arrangements. To achieve this aim we set out to systematically examine the nuclear architecture and the corresponding epigenetic chromatin modifications in donor cells with different developmental potential, in NT embryos reconstructed from these cells and in in vitro and in vivo produced embryos. These results yield insights into important aspects of chromatin architecture and modifications during early development as such and during reprogramming of transferred nuclei.

In terms of nuclear architecture, we intend to obtain a comprehensive view about stable and dynamic topological motives of functionally different nuclear compartments during early embryonic stages and throughout reprogramming of transferred nuclei. During the course of our project we attempt to increase our knowledge concerning aberrant epigenetic modifications affecting nuclear architecture and chromatin structure that impair faithful reprogramming of donor nuclei and hence impede normal embryonic development. The dynamics of nuclear architecture is further substantiated by major changes during postmitotic terminal cell differentiation. Recent breakthroughs of 3D fluorescence microscopy with resolution beyond the conventional Abbe limit in combination with 3D electron microscopy provide the potential to explore the topography of nuclear structure with unprecedented resolution and detail.

Relevant publications from our group:

Popken J (in preparation)

Popken J, Sterr M, Markaki Y, Cremer M, Beck A, Dahlhoff M, Habermann FA, Fezert P, Guengoer T, Reichenbach M, Wuensch A, Wolf E, Zakhartchenko V, Cremer T (2012) Studies of nuclear architecture in mammalian pre-implantation embryos and embryonic stem cells using super-resolution fluorescence microscopy. Reprod Fertil Dev 25:200

Cremer T, Zakhartchenko V (2011) Nuclear architecture in developmental biology and cell specialisation. Reprod Fertil Dev 23: 1–13

Brero A, Hao R, Schieker M, Wierer M, Wolf E, Cremer T, Zakhartchenko V (2009) Reprogramming of active and repressive histone modifications following nuclear transfer with rabbit mesenchymal stem cells and adult fibroblasts. Cloning Stem Cells 11:319-29

Koehler D, Zakhartchenko V, Ketterl N, Wolf E, Cremer T, Brero A (2010) FISH on 3D preserved bovine and murine preimplantation embryos. Methods Mol Biol, 659: 437-45.

Koehler D, Zakhartchenko V, Froenicke L, Stone G, Stanyon R, Wolf E, Cremer T, Brero A (2009). Changes of higher order chromatin arrangements during major genome activation in bovine preimplantation embryos. Exp. Cell Res. 315: 2053-2063.