ABIO303 - Cell Adhesion

What are cadherins?

- Calcium-dependent cell adhesion molecules that mediate homophilic interactions (bind the same type of cadherin on neighboring cells).

Why are cadherins important?

- They help maintain tissue structure and cell-cell adhesion in epithelial layers.

What connects cadherins to the cytoskeleton?

- Catenins, which link cadherins to actin filaments inside the cell.

What is the Differential Adhesion Hypothesis (DAH)?

- The idea that cells rearrange to minimize free energy (surface tension), forming stable structures with the most compatible adhesions.

How does adhesion relate to surface tension?

- Tissues with stronger adhesion behave like lower surface tension liquids, ending up inside weaker adhesive (higher surface tension) cells during sorting.

What determines final tissue position during sorting?

- The type and amount of cadherins expressed on each cell.

What is anoikis?

- A form of apoptosis triggered when cells lose adhesion to the extracellular matrix (ECM).

Why is anoikis important?

- It prevents detached cells from surviving and colonizing elsewhere — loss of anoikis resistance is linked to cancer metastasis.

What did classic dissociation-reaggregation experiments show?

- When embryonic cells are dissociated and then mixed, they reaggregate in a specific, reproducible order based on adhesion strength and cadherin type.

What does this demonstrate about cell behavior?

- That cell adhesion molecules drive tissue organization — it's an inherent property of cells, not dependent on external cues.

What is EMT?

- A process where epithelial cells lose adhesion and polarity and become migratory mesenchymal cells.

What molecular change marks EMT?

- Loss of E-cadherin expression, leading to weakened cell-cell adhesion.

What cytoskeletal changes occur during EMT?

- Actin reorganizes for motility, and cells gain a spindle-like, migratory shape.

Why is EMT important?

- It's essential for development, wound healing, and cancer metastasis.