BIOL 212 Lecture Notes - Lecture 34: Somatic Cell Nuclear Transfer, Hematopoietic Stem Cell, Stem-Cell Niche
18 May 2018
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Lecture 34 Notes
Different Cell Types
- Tissues comprised several different specialized cell types
- Different cells have to be produced in correct numbers and have to reside in appropriate spaces
Tissue Organization
- Cell comm: survival of cells requires continuous signals from neighbors
- Selective cell adhesion: homophilic cadherin interactions allow sorting out of cells in tissues
o Homophilic interactions b/t cell adhesion molecule can sort out cell populations
- Cell memory: stable patterns of gene expression, chromatin structure, DNA methylation
Cells Renewed
- Most cells in adults exit cell cycle and arrested in G0 stage
- Cells in most tissues continuously turned over
o Epidermis (skin, basal layer has stem cells) (lining of intestine)
- Differentiated cells replaced via proliferation and differentiation of stem cells
Stem Cell
- Renew themselves for long periods through cell division
- They are unspecialized but can give rise to more than one differentiated cell type
- Adult (somatic) stem cells
- Embryonic stem cells (ES cells)
- Induced pluripotent stem cells (iPS cells)
Adult Stem Cells
- Undifferentiated cells found among differentiated cells in tissues, most adult tissues continually renewed
and contain stem cells (skin, intestine, blood, etc)
- Usually scarce in mature organs
- Somatic stem cells are multipotent, give rise to a few cell types, but not all
- Somatic stem cells are specialized for maintaining particular type of tissue
- Limited proliferation potential
Blood
- Contains many different kinds of cells
- All blood cells derive from single precursor, hematopoietic stem cell (HSC)
Existence of Stem Cells
- Demonstrated in bone marrow transplantation experiments
- X-irradiation halts blood cell production, mouse would die if no further treatment given
- Inject bone marrow cells from healthy donor
- Mouse survives, injected stem cells colonize it hemopoietic tissues and generate a steady supply of new
blood cells
- 1 stem cell is sufficient to restore a complete hematopoietic system
“stemness”
- Combination of transcription factors, transmembrane receptors, cell cycle regulators and other proteins
that cooperate to keep a cell in a undifferentiated state
- Somewhat different sets of these factors and receptors characterize different kinds of somatic stem cells
- Signals can come from stem cell niche, help maintain hematopoietic stem cells
- Stem cell niche is microevironemnt that promotes stem cell maintenance, niche controls crucial choice
b/t self-renewal and differentiation
Wnt
- Inactive = no cell proliferation
- Active = cell proliferation
Therapies
- Cell-based therapies: may provide cure for Parkinson’s/Alzheimer’s diseases, spinal cord injury, stroke,
burns, heart disease, diabetes, osteoarthritis, rheumatoid arthritis : diseases associated w/loss of cells
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Tissues comprised several different specialized cell types. Different cells have to be produced in correct numbers and have to reside in appropriate spaces. Cell comm: survival of cells requires continuous signals from neighbors. Selective cell adhesion: homophilic cadherin interactions allow sorting out of cells in tissues: homophilic interactions b/t cell adhesion molecule can sort out cell populations. Cell memory: stable patterns of gene expression, chromatin structure, dna methylation. Most cells in adults exit cell cycle and arrested in g0 stage. Cells in most tissues continuously turned over: epidermis (skin, basal layer has stem cells) (lining of intestine) Differentiated cells replaced via proliferation and differentiation of stem cells. Renew themselves for long periods through cell division. They are unspecialized but can give rise to more than one differentiated cell type. Undifferentiated cells found among differentiated cells in tissues, most adult tissues continually renewed and contain stem cells (skin, intestine, blood, etc)
