Cell adhesion and junctional complexes

• What are the two types of extracellular matrix mentioned?

  Epithelium and Mesenchyme
• How are cells arranged in the epithelium compared to mesenchyme?


  Cells in epithelium are tightly packed, while in mesenchyme they are sparse
• What is the basement membrane also known as?


  Basal lamina
• What is the function of the basement membrane?


  It underlies epithelia and surrounds some non-epithelial cells
• What are the main components of the basement membrane?


  Collagen IV, Laminin, Nidogen, Perlecan
• What characterizes the fibrillar matrix?


  It is a 3D matrix composed of various fibers
• What are the main components of the fibrillar matrix?

  Collagen I, Fibronectin, Elastin, Proteoglycans
• What are the types of junctional complexes mentioned?

  Tight junction, Adherens junction, Desmosome, Gap junction, Hemidesmosome, Focal adhesion
• What is the function of tight junctions in epithelial cells?


  They turn epithelia into barriers
• What happens in a Claudin knockout mouse?


  Injection of purple dye spreads into upper layers, and pups lose weight due to water evaporation
• What do gap junctions do?


  They couple cells via permeable pores
• What is the approximate width of a hemidesmosome?


  ~100 nm wide
• What is the approximate height of a desmosome?


  ~500 nm high
• What role do intermediate filaments play in cells?


  They provide support against mechanical stress
• What condition is associated with mutations in intermediate filaments or desmosomal factors?


  Epidermolysis bullosa
• What is the role of adherens junctions?


  They are linked to the actin cytoskeleton
• How do focal adhesions function?


  They link the actin cytoskeleton to the ECM via integrins
• Who discovered the first cell adhesion molecule?


  Masatoshi Takeichi
• What are cadherins?


  Ca$^{2+}$-dependent adhesion molecules
• What is cancer metastasis linked to?


  Cell adhesion
• What are the main types of junctional complexes and their functions?

  • Tight junction: Forms barriers
  • Adherens junction: Links to actin cytoskeleton
  • Desmosome: Provides mechanical strength
  • Gap junction: Allows communication between cells
  • Hemidesmosome: Anchors cells to the ECM
  • Focal adhesion: Links actin cytoskeleton to ECM
• What are the main components of the extracellular matrix (ECM)?


  • Basement membrane: Collagen IV, Laminin, Nidogen, Perlecan
  • Fibrillar matrix: Collagen I, Fibronectin, Elastin, Proteoglycans
• What are the implications of cadherin function in cell adhesion?


  • Cadherins are essential for cell-cell adhesion
  • They require Ca$^{2+}$ for their function
  • Mutations can lead to diseases like epidermolysis bullosa
• What are the consequences of Claudin knockout in mice?


  • Loss of barrier function in epithelial cells
  • Increased water loss leading to weight loss
  • Dye spreads into upper layers of skin