Exam 3 - Embryonic Stem Cells Flashcards
What are the defining characteristics of a stem cell? What do those characteristics mean?
- self-renewing - capable of dividing and renewing themselves for a long period
- unspecialized - do not have any tissue-specific structures that allow them to perform specialized functions
- can give rise to specialized cells - differentiation causes a cell’s DNA to acquire changes that restrict DNA expression in the cell and can be passed on through cell division
What is a totipotent stem cell? What are they capable of?
can develop into any cell in the body including the extraembryonic membranes
capable of producing an entire fertile adult organism
What stage of embryonic development are totipotent stem cells acquired from?
blastomere (a 2-8 cell, day 1-3 embryo)
What is a chimera?
a single organism composed of two or more genetically distinct cell lines that originated from different zygotes
Suppose a chimeric red/blue embryo was developed into a blastocyst and then separated into the inner cell mass and the trophectoderm. What color cells would be in the inner cell mass, trophectoderm, fetus, and placenta?
red and blue in all the parts
What are pluripotent stem cells? What are they capable of?
can develop into anything derived from the 3 germ layers (endoderm, mesoderm, and ectoderm) and the germ cells (eggs and sperm)
capable of forming the embryonic disc, amnion, yolk sac, but not the chorion (not the placenta)
What stage of embryonic development are pluripotent stem cells acquired from?
inner cell mass of a day 5 embryo
What tissues are derived from the endoderm, mesoderm, and ectoderm?
Endoderm - lining of respiratory tube (including lungs) and digestive tube (including liver, gall bladder & pancreas)
Mesoderm – skeleton, muscles, circulatory system, kidneys
Ectoderm – nervous system, outer layer of skin, hair, nails, tooth enamel
If you inject the inner cell mass of a red embryo into the empty trophectoderm of a blue embryo, you create a red blue chimera. What colors will compose the inner cell mass, trophectoderm, fetus, and placenta?
ICM: red
trophectoderm: blue
fetus: red
placenta: blue
If you inject cells from the inner cell mass of a red embryo into the trophectoderm of a blue embryo (which still contains its own ICM, you create a red blue chimera. What colors will compose the inner cell mass, trophectoderm, fetus, and placenta?
ICM: red and blue
trophectoderm: blue
fetus: red and blue
placenta: blue
What are multipotent/progenitor stem cells? What are they capable of?
adult stem cells
can become specialized cells but generally only in the tissue or organ in which it resides
can give rise to several kinds of cells, tissues, or structures, within a related lineage
If a genetic mutation occurred before Day 5, what cells would the mutation affect?
All cells, because those cells are totipotent
What is the “original” way to make embryonic pluripotent stem cells? When was this done for the first time?
- create embryo
- remove inner cell mass from the blastocyst
- culture the cells
1998 - first human embryonic stem cell line created
What are the tests to identify embryonic stem cells?
- grow and subculture for many months
- look for surface markers only found in undifferentiated cells
- examine the chromosomes, look for damage or changes in number
- determine if the cells can be grown after freezing, thawing, and re-plating
- demonstrate differentiation potential
What protein is found only in undifferentiated cells?
Oct4 - only in pluripotent undifferentiated stem cells
What are the methods of determining differentiation potential (name only)?
spontaneous differentiation, directed differentiation, teratoma formation, tetraploid complementation
What is spontaneous differentiation? Describe its use as a way to test embryonic stem cells.
Cells eventually clump together to form 3 dimensional aggregates called embroid bodies
this is not an efficient way to produce cultures of a specific cell type
What is directed differentiation? Describe its use as a way to test embryonic stem cells.
altering the surface of the cell culture dish (by changing chemical composition of the medium) or modifying the cells by inserting specific genes
embroid bodies can be guided down a particular pathway to become a certain type of cell
generates large numbers of a specific cell type
What is PAX6?
a marker for neuroepithelial cells
What is teratoma formation? Describe its use as a way to test embryonic stem cells.
can test the differentiation capacity of stem cells by injecting them into immuno-suppressed mice and inducing the formation of a teratoma in situ\
“gold standard” of pluripotency, demonstrates mixed cellular populations of all three embryonic germ layers
What is tetraploid complementation? Describe its use as a way to test embryonic stem cells.
basic process: form a zygote, fuse the 2 2n cells to form a 4n cell that wont function, inject the stem cells into the now empty blastocyst, see if the embryo produces a fertile adult
most rigorous test of pluripotency, creates a chimera where the embryonic stem cells become the fetus and the extra-embryonic lineage becomes the placenta
Describe the exact scheme of tetraploid complementation.
Get a fertilized zygote (2n)
Culture the zygote to the 2-cell stage (2 2n cells)
Use electrofusion to form a single 4n cell
4n cell mass stops functioning/dies/disappears but trophectoderm is fully functional
Inject the embryonic stem cells into the other embryo
ICM is derived from the ES cells, placenta is derived from the original “host” embryo
Surviving fetuses/adults are completely ES cell-derived and are fertile
What is regenerative medicine?
branch of medicine that develops methods to regrow, repair, or replace damaged or diseased cells, organs, and tissues
includes generation and use of therapeutic stem cells, tissue engineering, and production of artificial organs
What are some challenges of regenerative mediicne?
the stem cells must be made to…
- proliferate and generate enough tissue
- differentiate into desired cells
- be free of animal products
- survive in the recipient after the transplant
- integrate into the surrounding tissue after transplant
- function appropriately for the duration of a recipient’s life
- avoid harming the recipient in any way
