Crypt Stem Cells Article Background

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Author:
DesLee26
ID:
309897
Filename:
Crypt Stem Cells Article Background
Updated:
2015-10-20 13:14:49
Tags:
Genetics
Folders:
Zuzga
Description:
Test Two
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  1. What is tissue specific?
    it is a kind of cell specific because tissues have a lot of cells
  2. Embryonic stem cell?
    • has the fate to become anything 
    • --> the further along in differentiation you become, the more restricted they come
  3. Colon cancer derives from __
    epithelial cells, which go bad--> not other stuff
  4. Villi in the intestine do what?
    increase the surface area, which eventually increase the absorption
  5. How long do cells usually live in the intestine?
    • five days
    • cells are damaged by environment and accumulate DNA damage
  6. What are the dynamics involved with renewal?
    There are stem cells in the crypts, which divide slowly. Daughter cells rapidly divide and replace cells along the villus
  7. Explain stem cells in all of our tissues
    WE have stem cells in all of our tissues, maintained by adult stem cells. It is not that they can become anything, but things in their lineage
  8. Goblet cells
    mucus
  9. enteroendocrine cells
    hormonal and respond to signals
  10. Paneth cells
    hang out by the stem cells and maintain the environment that allows stem cells to survive
  11. absorptive cells
    involved in absorption
  12. What is the division of stem cells?
    asymmetric: one daughter cell differentiates and hte other remains a stem cell
  13. After division, what does the ES become?
    it becomes a transit amplifying cell, which replicates several more times before differentiating more and moving up
  14. Wnt signaling pathwa
    • directs cell proliferation
    • when cells emerge from the crypt, that's when they differentiate and do their job, eventually undergoing apoptosis

    Every 3-4 days, you have to replace your cells
  15. What can happen to TACs?
    • they can fail to stop dividing
    • failure of cells to stop dividing
    • or terminally differentiated cells can revert back to TACs
  16. In the crypts are?
    dozens of stem cells, which proliferate and become TACs and aeventually differentiate to become other cells

    --> it is like a conveyor belt
  17. What is differentiation?
    a cell makes a commitment to an ultimate lineage or fate
  18. How do you silence genes that will not be used?
    turn them into heterochromatin
  19. What happens as you commit to a pathway?
    you end up with a genome that has heterochromatin turning/ closing off vast portions of your genome and leaving only the stuff that can be transcribed and allow for the differentiation
  20. What does commitment rely on in liver cells?
    the Wnt Pathway
  21. Active wnt pathway?
    proliferation is on and differentiation is put off
  22. Inactive Wnt pathway?
    as cells emerge from the villus, they stop proliferating and begin differentiating
  23. Without Wnt signaling, what happens?
    complex of proteins, one being APC, binds beta-catenin in an APC complex. It is phosphorylated by GSK, leading to degadation of beta catenin
  24. Beta catenin
    • has other fates
    • also part of a complex of proteins in cell-cell junctions; any additional Beta-catenins bound by APC are degraded
  25. With Wnt signaling, what happens?
    A ligand, which binds a receptor--> active/ protein in APC complex is phosphorylated--> no longer able to bind Beta-catenin--> no degradation
  26. If beta-catenin is not degraded, what can happen?
    • it translocates into the nucleus where it finds transcription factors. 
    • TCF/LEF together turn on transcription for genes involved in proliferation (cell transits from G1 to S phase)
  27. Essentially, Beta catenin not being degraded allows what?
    allows accumulation and binding to TCF/LEF, which bind and allow expression of proliferative genes
  28. Explain outside of the crypts.
    outside of the crypts, there's no Wnt present (soluble factor). APC binds to Beta catenin, which is phosphorylated by GSK, and degraded
  29. The Wnt pathway regulates Beta catenin via __, without which Wnt can't regulate Beta-catenin.
    APC
  30. For sporadic colon cancer, what is the probable cause?
    loss of APC, causing Beta-catenin to not be degraded
  31. BMP
    bone morphogenic peptide

    inhibits production of Wnt, leading to APC not eing phosphorylated and thus not allowing beta catenin to bind
  32. A lot of Wnt present leads to __
    crypts everywhere
  33. There are inherited versions of colon cancer.
    • FAP--> One defective copy of APC
    • To get colon cancer indefinitely, both APC genes need to be knocked off

    polyps appear everyowhere
  34. Tumorigenesis
    is related to the processes of tissue renewal
  35. Enterocytes live for __
    three days
  36. Explain epithelial cell migration.
    From birth at the bottom of the crypt to the loss at the top of the villus; transit time is 3-6 days

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