VL2 - Alternatives to Animal Experiments Flashcards
Reprogramming of mature cells
Nobelprize in Physiology and Medicin (2012) - Shinya Yamanaka and Sir John Gurdon
–> Cellular reprogramming, specifically the discovery that mature cells can be reprogtrammed to become pluripotent stem cells (inducible pluripotent stem cells iPSCs)
Gurdon (1962):
-nucleus of mature, specialized cell could be reprogrammed to an undiffrentiated state. removed the nucleus of a fertilized egg cell from a frog and replaced it with the nucleus of a cell taken from a tadpole’s intestine.
–> Unfertilized Eggcell developed into a functional tadpole, the mature cell still contained the genetic information needed to form all types of cells.
Yamanaka (2006)
-development of induced pluripotent stemcells (iPSCs)
-identification of a set of transcription factors (TF) that, when introduced into adult diffrentiate cells, could reprogram these cells into a pluripotent state
Key TFs: Oct4, Sox2, Klf4, c-Myc
–> by inducing these TF into adult cells, typically skin cells, these cells could be transformed into pluripotent stem cells with similar characteristics to embyonic stem cells. These cells could diffrentiate into cell types of three germ layers in vitro. IPs cells can generate from adult fibroplasts.
Possible Treatment after myocardial infarction
Building organoids from iPSCs
Jürgen Knoblich (2013) demonstrated the generation of cerebral organoids from iPSCs. Organoids are 3d structures that mimic the organization and function of human brains.
Method:
- Genration of iPSCs (based on Yamanakas research)
- Diffrentiation into Neuronal Presecursor cells (NPCs). NPCs have the potential to give rise to various types found in the nervous system.
- Formation of 3D Aggregates. NPCs are cultered in a way that allows them to self-organize into 3d aggregates.
- Organoid Maturations. NPCs within 3D aggregates undergo further diffrentiation and organizition, recapitulating aspects of early human brain.
–> They used this to create a model for microcephaly, a disorder that has been difficult to recapitulate in mice.
–> genetic engineered cerebral organoids models brain tumor formation
Further interesting Experiments
- Mini-gut culture system (Hans Clevers)
- Organs on a chip (Lung and Heart)
Axis formation and germ layers
Cellular behaviors control the morphogenesis of tissue and organs
Name the axis of an embryo
Determination
Determination refers to a stable internal state of a cell that will not change even when transplanted into another environment
Fate
Fate indicates what a cell will normally develop into if not challenged with another environment (based on its position within the embryo)
Specification
A cell is specified when it develops into a particular fate even when kept in isolation
What is a competent cell?
A cell that is able to respond to an inducing signal is considered competent.
Compentence may be acquired during development by the expression of receptors or formation of gap junctions.
Signaling:
* diffusion
* direct contact
* gap junstions
What is the french flag model?
Cells can acquire an identity based on positional information. One mechanism by which this is achieved involves morphogens.
Morphogens diffuse over several cell diameters and induce different cell fates at different threshold concentrations.
Stem cell biology.
What is asymmetric distribution of cytoplasmic determinants?
The unequal segregation of cytoplasmic
determinants during mitosis into the two daughter
cells, can cause different fates.
Stemcells are able to renew themselves and generate of differentiated daughter cells.
