BIOC 212 Lecture Notes - Lecture 26: Arginine, Small Molecule, Lysine
Cell Junctions & Cell Adhesion VI
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Cell Adhesion
• Short interactions between cells (transient)
• Example from early development
o Neural tube
o Some cells on top of neural tube start migrating out of the tube & proliferate
(green)
• Express certain cell adhesion molecules that guide their migration
• Migrate down neural tube along matrix proteins
• Eventually find their targets and bundle up
• Differentiate further into peripheral ganglia for example
o Require transient cell-cell adhesions using adhesions molecules (CAMs)
• Cell adhesion mechanisms when cells migrate over other cells or when they
assemble into tissues / repair mechanisms
• Precursor cells (ECM, other cells)
• Selective adhesions
• Progeny of the founder cell are retained in the epithelium by the basal lamina &
cell-cell adhesion mechanisms, including formation of intercellular junctions
o Mechanisms require cell motility, cell adhesion, chemotaxis &
chemorepulsion, pathway guidance, etc.
Changing Pattern of CAMs (Cadherins)
• Neural tube constricts and is pinched off
o Expression of different isoforms of cadherins
• E-Cadherin in ectoderm
• N-cadherin in neural tube
• Cadherin 6B at the junction
• Cells start growing and start expressing cadherin 7
o Organize and further differentiate
• Fine tuned expression pattern of different cadherins
• Changing patterns of CAMs during construction of the nervous system
• Cross-section of early chick embryos as neural tube detaches from ectoderm and
as the neural crest cells detach from the neural tube
• Immunofluorescence on top
• As pattern of gene expression change, different groups of cells aggregate from one
another according to the cadherins they express
Cell Dissociation Experiments
• Early in development (embryo) is very squishy and has little structural stability
between cells
• Embryonic tissue: easy dissociation of cells, using: