3. Human Embryonic Stem Cells - Isolation, Regulation and Ethics Flashcards
What is a stem cell?
A single cell that can give rise to a progeny that differentiate into any of the specialized cells of embryonic or adult tissues. They are totipotent They can self renew
Are stem cells totipotent?
Yes
Are stem cells able to self renew?
Yes
What is symmetrical division?
When stem cells divide and give rise to identical daughter cells
What is asymmetrical division?
When stem cells differentiate into lineage-specific somatic (adult) cells
What is the primary biological property of a stem cell?
It can self renew
What are stem cell markers?
Stro-1
CD146
Alpha-smooth muscle actin
Oct 4 (Octamer- binding transcription factor 4)
What is genomic imprinting?
Allows constant rounds of proliferation without differentiation
Epigenetic system that determine monoallelic expression of a subset of genes according to parent of origin
What are the different types of stem cells?
Embryonic
Germinal
Nuclear Transfer Somatic Cell (NTSc)
Somatic progenitor cells / Adult Stem Cells
Induced pluripotent stem cells (iPS)
Where do embryonic stem cells originate?
Pre-implantation blastocyst
Can proliferate indefinitely
Where do germinal stem cells originate?
Early embryogenesis
Slightly restricted
Self renew
Removed from germ layer
What are Nuclear transfer Somatic Cells?
Reprogrammed adult somatic cells
Somatic cell nucleus transferred to oocyte
Stimulated
What are somatic progenitor cells / Adult stem cells?
Cells of a normal adult organ always replaced by progenitor cells or “transit - amplifying cells”
E.g. Bone marrow, MSCs etc
What are Induced pluripotent stem cells (iPS)?
Reprogrammed adult somatic cells
What are Embryoncal carcinoma cells?
Cells of teratocarcinomas derived from sponatneous gonadal tumours in 1970
What are Embryonic germ cells?
Isolated from pluripotent cells of preimplantation embryos or primordial germ cells
What are embryonic stem cells (hES)?
Derived from donated excess IVF embryos
Or
Pathogenetic activation of stem cells in inner cell mass
What are trohpoblast stem cells?
Isolated from trophectoderm cell linage
Restricted potential
From where are embryonic stem cells derived?
Inner cell mass of blastocyst (ICM)
They are pluripotent
What does pluripotent mean?
A cell is capable of differentiating into any cell/lineage (ecto, meso and endoderm)
What potency is the zygote?
Totipotent
Basically batman, can do anything
What does stemness mean?
Essential characteristic of stem cells that distinguishs it from other cells
Self renewel
Multilineage potential
What are stemness-related genes?
Genes acitvely involved in control of SC properties
Why are adult stem cells sorta shit?
Some stemness genes are lost
How were stemness genes first discovered?
Systematic transcipriptional profiling of mouse ESCs, compared to Neural SC and Haemopoetic SCs
What controls the stem cell state?
Small number of “core” transcriptional factors
What genes govern ESCs pluripotency?
Oct4
Sox2
Nanog
What does Oct4 do?
Functions as heterodimer with Sox2
What does Nanog do?
Promotes undifferentiated cell state
Co-occupies sites in genome with Oct4 and Sox2
What does reprogramming of a Somatic Cell by nueclear transfer etnail?
Adult Somatic Cells have their nucleus transferred to an oocyte
How was the sheep dolly made?
Via SCNT
Late 90s
What is the process for SCNT cloning?
- Cells from donor are grown
- Revmoval of DNA from egg
- Donor cell placed next to empty ovum, small current allows fusion
- Ovum is tricked, thinking its been fertilized
- Embryo implanted
What other examples of cloning have there been?
Rhesus monkey “Tetra”
Family of pigs
Mira the Goat
Copy cat
Snuppy, south Korea
Who discovered Induced Pluripotent Stem Cells?
Shinya Yamanaka (UofKJ)
John. B Gurdon
What are induced pluripotent stem cells (iPS)?
Reprogramming of fibroblasts into pluripotent ES-cell-like state
What transcription factors are “forced” in iPS and what are these factors called?
They are called Yamanaka or SKOM factors
Sox2
Klf4
Oct4
c-myc (transcriptional regulator)
What do you want to convert a fibroblast to in regards to iPSCs?
An intermediate epithelial cell via MET
How is EMT repressed in the reprogramming of iPSCs?
Stemness factors
Sox2/Oct4 - supress snail
**c-myc - **downregulates TGFB
Klf4 - induced expression of E-cadherin, decrease snail
Some ethical issues associated with ES research?
Creation of life for destruction
Concern over SCNT for cloning humans
Concern over exploitation of women for eggs
What body is stem cell research governed by in au?
NHMRC
National Health and Medical Research Council
What are the pros or potential useso of iPS?
Regenerative medicine
Cloning
Organi cloning
What are some of the safety concerns associated with iPS?
Potential formation of teratomas on transplantation
Tumorigenesis
Aberrant reprogramming
Immunorejection
