BIO 302 Study Guide - Midterm Guide: Basal Lamina, Ephrin, Somite
Developmental potential: What a cell group becomes if isolated from the embryo and placed
in culture. Potential of changes, gradually becoming narrower
Developmental fate: what a cell or group of cells actually becomes in the normal embryo.
Observed through observation / lineage-tracing procedures.
• Mesenchyme: Inhibit/embedded in extracellular matrix
o Cells inhabiting the spaces between the epithelial lining compromise the
mesenchyme.
o Nerve cells send out long projections through the matrix.
o
• Epithelium: line surfaces
o Closely adherent to each other (cell-cell junctions), rest on a basal lamina and
posses specialized junctions
o
• Extracellular Matrix:
o Collagen: most abundant protein ( signaling ligand or structural component of
the matrix)
o Fibronectin: glycoprotein heterodimer found in the basal lamina
▪ Possesses specific domains capable of interacting with many other
molecules in the matrix
▪ Signature amino acid sequence; RGD.
• Interacts between fibronectin and integrins
o Laminin is found between epithelium and mesenchyme.
▪ Composed of 3 different protein chains
• Integrins: membrane-associated molecules of the cell surface
o Link the extracellular matrix with the internal structures and signaling apparatus
of the cell.
o Tie cells to the matrix and to the cytoskeleton which allows the whole cell to hold
together.
Junctions
• Tight -seals neighboring cells together in an epithelial sheet to prevent leakage of
molecules between them
• Adherens- Joins an actin bundle in one cell to a similar bundle in a neighboring cell
• Desmosomes- Anchors the tough intermediate filaments in one cell to those in a
neighboring cell
• Gap - allows passage of small water-soluble ions and molecules between cells.
Cell Adhesion:
• Specific to different cell types- ex. Nerves + epidermis have different CAMs
• Dissociate cell types really do sort out and cells really do have mechanisms for sensing
other cells and expressing preferences for adhesion.
Cell motility:
• Neural Crest Cells: N.c cells only go through anterior part of the somite
o Ligand and receptor signaling system controls N.c cell migration
▪ Ligand: ephrin ; bound to cells
▪ Receptor: Eph ; RTK (receptor tyrosine kinase)
• Eph B3 is present on surface of NC cells and on cells on anterior
somite. Ephrin B1 is present on cells of the caudal somite, and NC
cells avoid this area/turn around.
• The ephrin-Eph system works by placing “ do not enter” sign.
• Axon Guidance:
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Document Summary
Developmental potential: what a cell group becomes if isolated from the embryo and placed in culture. Developmental fate: what a cell or group of cells actually becomes in the normal embryo. Interacts between fibronectin and integrins: laminin is found between epithelium and mesenchyme, composed of 3 different protein chains. Integrins: membrane-associated molecules of the cell surface: link the extracellular matrix with the internal structures and signaling apparatus of the cell. Tie cells to the matrix and to the cytoskeleton which allows the whole cell to hold together. Cell adhesion: specific to different cell types- ex. Nerves + epidermis have different cams: dissociate cell types really do sort out and cells really do have mechanisms for sensing other cells and expressing preferences for adhesion. Ephrin b1 is present on cells of the caudal somite, and nc cells avoid this area/turn around: the ephrin-eph system works by placing do not enter sign. Chemotaxis- attraction or repulsion by different chemical signals.
