Cell Communities Chapter 20 Key topics Structure & function of -- the extracellular matrix -- cell junctions Tissu

1. Cell Communities Chapter 20 Key topics Structure & function of -- the extracellular matrix -- cell junctions Tissue organization Properties of -- Stem cells -- Cancer cells Questions in this chapter you should be able to answer: Chapter 20: all Cell Communities

2. Extracellular Matrix – I • Plant cell wall • Composition • cellulose • hemicellulose • lignin • Organization • Middle lamella • 1O wall • 2O wall • Plasmadesmata Cell Communities

3. How are cellulose fibers synthesized and oriented? Cellulose organization Cellulose synthase -- pushed forward Microtubule tracts – constrain movement Cellulose fibers Microtubules Cell Communities

4. apical Animal tissue organization Epithelia Extracellular matrix -- Basal lamina -- Connective tissue Epithelia have polarity Tight junctions separate apical vs basal surfaces Cell Communities

5. What are the 1O components of the ECM? Collagens Proteoglycans Collagens structure (Glc - X - Y) function organization many types Gelatin Scurvy Vitamine-C prolyl-hydroxylase  hydrox-proline Fibroblasts Collagen Cell Communities

6. What are proteoglycans? Polysaccharide core (hyaluronate) + Protein linkers + GAG branches GAGs -- Repeating disaccharides -- cationic -- e.g., Chondroitin Functions hydroscopic swelling pressure influence cell migration Cell Communities

7. What creates Cell-Cell linkages? • Desmosomes – intermediate filaments • Adherin junctions – actin filamants • Cadherins family of proteins • -- cell-cell linkers ( • -- many types: C-, E-, P-, T- cadherins • -- “homophillic” binding • Classic newt embryo experiment • -- Townes and Holfreter (1955) Cadherins Cell Communities

8. Linkage to the ECM are also important Integrins – mediate linkages between cytoskeleton and ECM Hemidesmosomes – intermediate filaments Contact Adhesions – actin filaments linkages are ‘responsive’ Question 20-4 Why are these linkages more common in fibroblasts, and desmosomes and adherin junctions more common in epithelial cells? Cell Communities

9. How does tissue renewal occur? Cell division vs stem cells e.g., Liver vs skin What are the properties of stem cells? Self renewal Developmental commitment Precursor terminally differentiated Cell Communities

10. Somatic vs Embryonic Stem (ES) cells Somatic – tissue specific -- degrees of commitment -- multipotent vs unipotent ES – any developmental fate -- must follow developmental pathway -- else neoplasm Cell Communities

11. How do somatic stem cells renew skin? Skin structure Epidermal stem cells What stimulates Epidermal stem cell growth? -- EGF Cell Communities

12. How do somatic stem cells renew intestine? intestine structure Epithelial stem cells How is pattern of tissue regeneration different than for skin? Simple vs Stratified epithelium Cell Communities

13. Stem cell biotechnology Tissue repair -- CNS injury -- burns -- disease (macular degeneration) Genetic disorders / cancer -- cystic fibrosis -- hemophilia -- leukemia Organ replacement? Cell Communities ES-cells

14. Meningioma karyotype LOH - #17 Aneuploidy - #s 9, 7, and 20 Translocation/duplication - #s 2 and 6 Why do cells become cancerous? Mutated Tumor suppressor genes -- prevent DNA repair -- prevent cell from stopping cell division vs Oncogenes -- cause uncontrolled cell division Which type of mutation will lead to genetic instability? • Is it an oncogene, mutated TSG, or neither? • How many mutations needed to see effect? • A mutation that… • Constitutively activates Wnt receptor • Constitutively activates FRT-1 protein • Inactivates both β-Catenin genes • Inactivates both P53 genes • Constitutively activates P21 protein Cell Communities

15. What are the consequences of genetic instability? Loss of cell cycle control Accumulation of mutations Tumorigenicity  Carcinogenicity Cell Communities