Konstantinos Anastassiadis - Mechanisms that control the totipotency and differentiation of mouse ES cells

Previous and current research

We are interested in exploiting the mechanisms that control self- renewal and differentiation of mouse embryonic stem cells. These cells originate from the Inner Cell Mass (ICM) of the blastocyst and give rise to all tissues of the embryo including the germline. ES cells are a powerful experimental system to understand the mechanisms that underlie developmental processes.
In previous work we focused on factors that control the maintenance of the totipotent character. The transcription factor Oct-3/4 is expressed in the ICM, in the epiblast and only in germ cells later in development. Embryos with both alleles of the Oct-3/4 deleted die around implantation and blastocyst outgrowths do not sustain the ICM but differentiate into trophectoderm. On the other hand, overexpression of Oct-3/4 drives differentiation into primitive endoderm. Thus, the expression level of Oct-3/4 plays a critical role for the maintenance of ES cell totipotency.
Self-renewal and maintenance of totipotency is one side of a coin, differentiation is the other. Embryonic stem cells can differentiate into all 3 germ layers in culture. During differentiation the totipotent ES cells give rise to progenitor cells that in their turn give rise to terminally differentiated cells. The process of differentiation is guided by the various factors that are added to the culture media and is not yet well understood.
It is important to understand this process in order to guide and control it. For this reason we have developed (and continue to develop) various genetic experimental tools. We have modified the tetracycline-regulated system for a highly predictable application. For example ES cells carrying tetracycline controlled SV40 large T-Antigen have been made, differentiated into neurons and immortalized with tetracycline regulated T-Antigen expression. The differentiation status of the cells was investigated by immunostaining for neuronal specific markers, at various time points, both in induced cells and in cells where T-Antigen expression was switched off. Induced cells were positive for markers that characterize neural precursors and negative for markers that characterize post-mitotic neurons. Cells that the expression of T-Antigen was switched off, started expressing markers that characterize post-mitotic neurons. In other words, we have developed a system that enables conditional immortalization of cell populations that arise during ES cell differentiation. This technical advance opens a door to new mechanistic studies on gene expression hierarchies in differentiation.

Future prospects and goals

Differentiation of ES cells using lineage selection. The goal is to achieve a homogenous population of progenitors or differentiated cells.
Analyze the gene expression profile and the chromatin status of the conditionally immortalized progenitors.

Selected publications

Anastassiadis, K., J. Kim, N. Daigle, R. Sprengel, H.R. Schöler, A.F. Stewart (2002): A predictable ligand regulated expression strategy for stably integrated transgenes in mammalian cells in culture. Gene, 298: 159-172.

Voss, A.K., T. Thomas, P. Petrou, K. Anastassiadis, H. Schöler, P. Gruss (2000): Taube nuss is a novel gene essential for the survival of pluripotent cells of early mouse embryo. Development, 127(24): 5449-5461.

Pesce, M., K. Anastassiadis, H.R. Schöler (1999): Oct-4: Lessons of totipotency from embryonic stem cells. Cells Tissues Organs, 165: 144-152.

Nichols, J., B. Zevnik, K. Anastassiadis, H. Niwa, D. Klewe-Nebenius, I. Chambers, H. Schöler, A. Smith (1998): Formation of pluripotent stem cells in the mammalian embryo depends on the POU transcription factor Oct4. Cell, 95: 379-391.

Konstantinos Anastassiadis

1993: Dr. sc.agr., TU Berlin

1993-1995: Post Doctoral work at the TU Munich

1996-2001: Post Doctoral work at the EMBL Heidelberg

2002-2003: Post Doctoral work at the BIOTEC/TU Dresden

since 2004: Group leader in BIOTEC/TU Dresden