Mbge 304 - Cell migration

Processes in which cell migration takes part in

•Tissue formation and patterning

•Immune surveillance and defense

•Tissue maintenance and renewal

•Tissue repair and remodeling

•Bone remodeling

•Cell positioning for function

•Disease progression when misregulated

cell migration is a mix of the which main 3 concepts?

cytoskeleton, adhesion, and signaling pathways.

key characteristics of ameoboid movement

•Cells have a rounded or irregular shape. •Movement is driven mainly by actin polymerization at the front and actomyosin contraction at the rear. •Adhesions are weak and transient, or largely absent.

•Cells can squeeze through confined spaces without degrading the extracellular matrix

Keratinocyte migration

•Keratinocytes migrate primarily during wound repair.

•Their movement closes the wound surface in a process called re-epithelialization.

•This restores the epidermal barrier, which is essential for preventing infection and water loss.

3 main steps of cell migration

1- protrusion

2- adhesion

3- contraction

Protrusion step

•Actin polymerizes at the plus ends at the leading edge.

•Branched actin networks push the plasma membrane forward, forming the lamellipodium. •This step defines the direction of migration.

Adhesion step

•Newly extended membrane forms integrin-based focal adhesions with the substratum.

•Actin filaments couple to adhesions, allowing force transmission.

•Adhesions provide traction, preventing backward slippage.

Contraction step

•Myosin II–driven contraction generates tension in the actin cortex.

•The cell body moves forward as the rear detaches.

•Unpolymerized actin is recycled toward the front.

Types of protrusive structures seen in cell migration

1- filopodia

2- lamellipodia

3- Invadopodia

Lamellipodia

•Broad, flat, sheet-like protrusions

•Built from a dense, branched actin network •Driven by Arp2/3-mediated actin polymerization •Form integrin-based adhesions to generate traction

•Main engine of persistent, directional cell migration

Key function: Force generation and forward movement

Found in kerationcytes and epithelial cells

Filopodia

•Thin, finger-like membrane protrusions •Composed of parallel bundles of actin filaments •Act as sensory and exploratory structures •Important for pathfinding and guidance, especially in neurons •Often precede or guide lamellipodial extension Key function: Direction sensing and environmental probing

Found in neurons and some fibroblasts