Stem Cells
Embryonic stem cells are the origin of all tissues in the mammalian body. Usually they are isolated from the "inner cell mass" of a 3-4 day old embryo, called the "blastocyst". They are pluripotent, which means they are undifferentialed and have the capability to develop into 200 different cell types. Another great advantage is that they can be cultured indefinitely and produce an unlimited amount of cells.
In contrast, adult stem cells are further developed than embryonic stem cells. They are multipotent, but no longer pluripotent. Adult Stem Cells have very important functions in the body, particularly the self-renewal and replacement of old or damaged cells and tissues. Some tissues, such as blood or intestinal tissues need millions of new cells every day. Other tissues, such as the highly specialised heart muscle cells or the neurons of the brain, do not have such self-renewal systems and are therefore not capable of repairing damages after e.g. a heart attack or stroke. Research on embryonic stem cells is a promising tool for future cell replacement therapies.
From the Zygote to Stem Cells In mammals, all cell types that form the adult animal are derived from embryonic stem (ES) cells of the inner cell-mass of the blastocyst. In mice, they can easily be isolated and after separation be cultivated for many passages. The ES-cell lines used in the FunGenES consortium have already existed for several years, just by cultivation without "destroying" one more single blastocyst. |
Self-renewal or differentiation
As long as ES cells are cultivated under suitable conditions they remain pluripotent and undifferentiated. The genetical, molecular and biochemical properties of these undifferentiated cells are explored in the FunGenES "self-renewal programme". Our current knowledge of the genetic mechanisms regulating pluripotency and differentiation of ES cells are limited to a few examples. For instance, leukaemia inhibiting factor LIF activates the transcription factor STAT-3 that is essential for maintenance of the undifferentiated state of murine ES cells, but genes targeted by STAT-3 are not well characterised. Similarly, although many of the conditions that facilitate lineage commitment and differentiation are known, we lack in-depth understanding of the underlying genetic programmes involved. Gene expression levels can be analysed, now that high throughput technologies are available. |
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Cultural dishes with ES cells |
Cultural dish with ES cells |
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Microscopy of ES cells |
ES cells under the Micros- |
Differentiation of ES cells
If we want to differentiate ES cells in vitro, specific protocols are needed. All FunGenES research groups use the so called "method of hanging drops", which was pioneered by FunGenES Partner Anna Wobus (IPK Gatersleben, Germany) around fifteen years ago. In that protocol we remove the lid of a culture dish and place drops containing around 100 undifferentiated ES cells onto it. We then turn the lid and wait for 3-4 days. Due to gravity the ES cells come into contact with each other and form a complex called "Embryoid Body (EB)". In these embryoid bodies, which are cultivated in suspension from day 5 to 7, differentiation processes take place. FunGenES' goal is to find out the genes involved in these differentiation processes, study their regulation and define their products.
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Embryoid Bodies |
The sequencing of the human and mouse genomes were first major steps towards understanding the secrets of differentiation processes. Knowledge of the complete genome, however, does not automatically provide understanding of organism formation. To understand pluripotency, we now need to document the subset of the genome that is used in the pluripotent state. Similarly we need to document the ways in which usage of the genome shifts from the pluripotent subset to other subsets that determine different cell types.
In the embryoid body, different cell types begin to develop without any modulation from outside. Comparable to patterning in the "gastrula stage" of an embryo, we can find cells of all three germ layers in the EB after around 5-7 days, i.e. ectoderm, mesoderm and endoderm. All tissues and cell types in the body result from these three layers.
FunGenES' research is organised into four projects with specific research focus:
Subproject (SP) 1 analyses the self-renewal of ES cells and their early commitment to the three germ layers ectoderm, mesoderm and endoderm.
Subproject (SP) 2 (Ectoderm) analyses the genes and signalling factors responsible for the differentiation of central and peripheral nerve cells, skin, adrenal, glands etc. and establishes neuronal and glial lineages for research purposes.
Subproject (SP) 3 (Mesoderm) analyses the genes and signalling factors responsible for the differentiation of heart cells, muscle, endothelium, blood, bone, cartilage etc. and establishes cardiac, endothelial, and adipocyte progenitor lineages for research purposes.
Subproject (SP) 4 (Endoderm) analyses the genes and signalling factors responsible for the differentiation of gut cells, liver, pancreas, respiratory system etc. and establishes hepatic and pancreatic progenitor lineages for research purposes.