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Chapter 23

Lecture 22 - Chapter 23 - Stem Cells - April 4.docx

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BIOL 2021
Patricia Lakin- Thomas

April 4, 2013 Lecture 23: Stem Cells Differentiation  Cell specialization o Terminal cell differentiation – final specialization o Usually stop dividing permanently – enter the G0 stage o Making different proteins (structural – ion channels and signals for gene regulatory proteins)  Classic nuclear transplantation experiment o **Egg reprogrammed** - skin nucleus acts as an embryonic nucleus o Different gene regulatory proteins – no DNA change Stem Cells  Not terminally differentiated  Can divide without limit  Daughter cells can remain stem cells or differentiate  Examples of stem cells in adult o Epidermal (epidermis of skin), intestinal (epithelium of gut), hemopoietic (blood)  Stem cells are rare and divide slowly o Only 1 in 10000 are stem cells Transit Amplifying Cells  Figure 23-8  Daughter of stem cells  Divide rapidly, but limited number of divisions, then differentiate  Advantages o Division rate increases rapidly (can rapidly repopulate) o Reduce the chances of mutations in stem cells Cancer Stem Cells  Figure 23-13  Cancer arises in normal stem cells or transit amplifying cells  Only stem cells last long enough – so Cancer stem cells maintain the tumor o Divide slowly but indefinitely  Cancer Transit Amplifying Cells o Make up most of the tumor – limited lifespan – divide quickly o After chemotherapy (which kills the amplifying cells) we need to kill the cancer stem cells in order to keep it from coming back Molecular Basis of Stem Cell State  What defines a stem cell at a molecular level? o We don’t know  Some stem cells are multipotent  Adult Stem Cells o Hematopoeitic stem cells  Blood cells formed  Terminally differentiated  Stem cells found in bone marrow  Fig 23-36  Fig 23-42 – shows multipotency in stem cells  Scheme of Hemopoeins  Few stem cells  committed  Pre-genitor cells = TAC  limited number of divisions  Stepwise commitments  Figure 23-41 (Mouse)  Proofs of Stem cells o Bone marrow transplant o Adult stem cells – 1 in 10000  Only need 5 stem cells to reconstitute blood o Use adult stem cells in therapy  Leukemia – destined for cancerous bone marrow che
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