Cell Identity & Behaviour

Cell Identity & Behaviour

1. STEM CELLS

   • Cell fate determination - cells release regulatory proteins (TFs) > determines which proteins they express > differentiation
     • Environmental influence
       • Adult stem cell niche
         • Microenvironment around them > support/signals regulating self-renewal/differentiation/migration/apoptosis
           • Neurons, blood vessels, soluble factors, niche cell interaction, ECM
   • Role of adult stem cell: maintain/repair the tissue in which FOUND
     • eg. Haematopoietic lineage (form blood cells but not heart/skin cell)
       • Bone Marrow
         • HAEMATOPOIETIC Stem Cell
           • MULTIPOTENT Stem Cell
             • Lymphoid Progenitor Cell
             • MYELOID Progenitor Cell
               • RBCs
               • Monocyte/Macrophage
               • Basophil
               • Eosinophil
               • Neutrophil

2. CELLULAR COMMUNICATIONS

   • AUTOcrine signals - act on same secreting cell
   • PARAcrine signals - diffuse locally, act on neighbouring cells
   • ENDOcrine - hormones in blood/body fluid to other cells
   • NEURAL signals - diffuse short distance BETW. neurons
   • Cell Junctions
     • Tight Junctions - seals neighbouring cells in epithelial sheet > prevent leakage of mol's
       • Blocks flow of fluid betw. cells
     • Desmosomes - strong adhesion betw. cells
       • Connects cells with filaments
     • Gap Junctions - contact cytoplasm of 2 cells > allows small sol ions/mol's through
       • Allows electric current
   • Cell <> Extracellular Matrix ECM
     • eg. Integrin (transmembrane protein) binds to Fibronectin (ECM protein) > signalling pathway in cell > nucleus

3. APOPTOSIS

   • Apoptosis = programmed physiological cell death - genes activated for death - cell dies NEATLY
   • vs Necrosis - external injury eg. hypoxia/toxins. Cell swells/bursts, spills contents > dangerous inflammatory response

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