Induced pluripotent stem cells Flashcards
What is the basic process of cell reprogramming into iPSCs?
- ectoptic expression of pluripotnecy factors leads to epigenetic changes such as histone modifications, DNA (de)methylation and miRNA expression changes
- drives some of the cells into a pluripotent state where the cell is no longer expressing its original factors but its own pluripotency factors
What are the 4 induced pluripotency factors also known as?
Yamanara factors
What are the 4 most important transcription factors in inducing plutipotent stem cells?
cmyc, sox2, oct3/4, klf4
What are the 3 questions sill not answered about the production of iPSCs?
- what are the mechanisms/underlying pathways behind the reprogramming?
- are iPSCs biologically the same as ESCs?
- why are such a small number (0.01%) of cells full reprogrammed?
How do the pluripotency factors likely work together?
- as a complex to alter gene expression and epigenetic code
- assumed to be this way as overexpression of all is required to induce pluripotency - combinational overexpression
Why is Nanog not essential in iPSCs despite being involved in the transormation to pluripotency.
exogenous Oct4 induces levels of endogenous Nanog to those sufficient for reprogramming
How do the 4 important transcription factors work to make iPSCs?
- cmyc makes somatic cells turn into immortalised cells with open chromatin
- klf4 can prevent apoptosis and sensecense
- together these could push the cell into tumour cells
- Oct3/4 changes cell fate from tumour cells to iPSCs and makes cells into nullipotent ESC-like cells
- the addition of Soz pushes these cells to iPSCs
What does c-myc do in stem cells?
immortalises them and opend up their chromatin - associated will proliferation
What does Oct3/4 do in stem cells?
involved in undifferentiated ESC self renewal. promotes pluripotency genes such as Nanog and Sox2 while inhibiting differentiation genes such as GATA6
What does Sox2 do in stem cells?
maintains pluripotency by preventing ESC differentiation. upregulates nanog and oct4. modulates signalling pathways such as B-catenin. inhibits differentiation genes
Describe the roles and mechanisms of Oct4 in iPSCs
works with Sox and nanog to repress genes linked to commitment and activate genes in pluripotency. can act on promoters or alter the epigenome or signalling pathways such as MAPK and B-catenin
- downregulated in gatrulation when cells are differentiating
- can be inhibited by retinoic acid
Name some potential applications of human iPSCs
-can be used in research to create models for the study of human disease and drug development
- can be used in treatment for regenerative medicine or tissue engineering
What are some disadvantages of using iPSCs over ESC?
- increased teratoma risk
- not as well studied
- can be abnrmalities following differentiation possibly due to increased divisions in culture before use leading to accumulation of genetic abnormalities in copy number, stability etc
What are the advantages of using iPSCs over ESC?
- fewer ethical considerations
- easier to collect
- can be autologous
What happens to iPSCs over time in culture?
their genetic differences to ESCs become less prominent - must be continued epigenetic changes occurring over time in culture
