L7 Cloning and regenerative medicine Flashcards
What shows that terminal differentiation can be reversed?
Nuclear transfer
What is terminal differentiation?
Terminal differentiation refers to the final stage of cellular differentiation, where a cell becomes highly specialized in its function and often loses its ability to divide
What do cytoplasmic factors do?
They can control gene expression
What results in regeneration of cells?
Tissue loss can be sensed in some animals resulting in regeneration
How can human myosin be distinguished from mouse myosin?
Through inter species transfer which allows protein to be easily analysed.
How does interspecies transfer work?
- Mouse muscle cell and human liver cell is fused.
- This causes activation of human muscle cell gene expression.
- Where mouse and human muscle proteins are produced.
True or false: Gene expression in nuclei from terminally differentiated cells cannot be changed (under special circumstances).
False, Can be changed
Give me 2 examples of how nuclear transfer shows that “terminal differentiation” can be reversed
1) Human liver cell can fuse with mouse muscle cell which would activate human muscle gene expression creasing mouse and human muscle proteins
2) Plucking out iris of an organism can teams differentiate into lens cells to regenerate the missing tissue
What was the first animal to be cloned?
Frogs
How was frog cloning executed?
- This was fisrt done with tadpole gut cells in 1962, subsequently done with adult skin cells in 1975 because these were though to be more terminally differentiated.
- Nuclei can give rise to tadpoles but at a low rate.
What was the method used to clone frogs?
Somatic cell nuclear transfer.
Are the genetics of clones the same or different?
Clone cells are genetically identical
Give me an example that demonstrates totipotency
Several nuclei removed from blastula are far more successful in producing adult animals suggesting that younger cells are more stem- cell- like
Who discovered that mature cells can be reprogrammed to become pluripotent?
John B. Gurdon and Shinya Yamanaka
How was cloning of the first mammal executed?
- Mammary epithelial cells were extracted from the donor.
- An unfertilised egg was extracted from the host.
- Epithelial cells were cultured in low serum where cells exit the mitotic cycle into G0 phase.
- Chromosome is removed from the unfertilised egg.
- Fusion is induced by electric current.
- Embryo culture and transfer to foster mother.
What does regenerative medicine focus on using to improve health?
Regenerative medicine focuses on using in vitro technologies to improve health
How does in vitro regenerative medicine work?
Stem cells are converted into specific types of cells that needed for repair
These cells are either converted into scaffolds ( support 3 dimensional growth of cells) or directly released to the damaged tissue
How does in vivo regenerative medicine work ?
They use drugs or transgenes to transducers the neighbouring cells of the damaged tissue
What does transfect mean?
Transfect = introduce a modified gene into cells or an animal (to make a transgene)
What are the 3 different strategies to create insulin producing cells?
1) Somatic cell nuclear transfer - removal of nuclei from blastocyst and placed into ES cells tuskly produces insulin producing cells
2)Induced pluripotent - Trasnfection with OCT4, SOX2 and KLF4 to make iPS cells which eventually makes insulin producing cells
3) Transdifferentiation in vivo - Merge adult pancreas liver cells with Pdx1 to make insulin - producing glucose cells
What are iPS cells ?
They are induced pluripotent stem cells that are created by taking mature cells and “reprogramming” them back into a stem cell- like state
What are the positive of stem cell therapies based upon iPS cells?
- Corrects genetic defects
- Replaces simple tissue or single cell types
- Testing how your cells will respond to different pharmaceuticals
What are the limitations of stem cell therapies based upon iPS cells ?
- Transplantation could be difficult
- Organogenesis is very complex - tissue engineering scaffolds have had limited success
How was the innate power of cells to self-organise discovered?
- Wilson dissociated sponges by putting them through a fine sieve then watched as the cells reorganised into intact sponges.
- Adhesion molecules and cell signalling play roles in this process.
Henry Van Peters Wilson - 1907
How are organoids formed?
Organoids are formed by stem cells when cultures in special media.
What are organoids?
They are combined tissue which resemble an organ, the hope is that complex tissues or organs could be grown from organoids for study and regenerative medicine.
