Flashcards in Devo Lect 8 + 9 - Cell connections Deck (16):
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Townes and Holtfreter experiment
separated cells with alkaline solution which spread out, placed in nutrients. Then they clumped together, moved about, then stop (stuck together)
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Cell adhesion molecules
Used in epithelial sheets, serve to condense mesenchyme; eg L-selectin on blastocyst; cadherins
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Cadherins
very common; homophilic (bind to same type); need Ca to bind; link to cytoskeleton (actin); usually cause contact inhibition. E (embryonic/ectodermal), P (placental), N (neural) types
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Cadherin knockout mice
E knockouts: cannot implant; N knockout: nervous system doesn’t develop much, aborted
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CAMs
Cell Adhesin Molecule; immunoglobulin-like domains, homophilic; N-CAM important in brain development; can work with cadherins; attraction or repulsion (low or high sialic acid - negative charge)
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Substrate adhesion molecules
bind cells to ECM (basal lamina); fibronectin: glycoprotein binds to integrins, allows cells to bind to it and move along
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Integrins
Bind fibronectin at RGD a.a. sequence, provide anchor; can also cause signal transduction as things bind to it
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Cell junctional molecules
Gap junctions; form at morula stage and in early heart;
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Cell adhesion in implantation
Blastocyst has L-selectin, E and P-cadherins so it can bind to endometrium wall; integrins on uterus and fibronectins on outside of blastocyst; serve to bind and signaling
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Cell crawling
Protrusion of leading edge; form focal contacts; retraction of trailing edge
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Cell motility components
contractile elements of cytoskeleton needed; lamellipodium: big front edge, more continuous; filopodia: small, spiky projections; focal contacts bind to substrates (ie. integrins); microfilaments (major) and microtubules
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Microfilaments in cell motility
Major contributor; Constantly forming and breaking down; high concentration along the front edge; actin experiments (blocking it)
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Haptotaxis
Guiding molecule is not freely diffusable, attached to something; ex: mesoderm cells follow fibronectin as they migrate inward
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Galvanotaxis
Changes in voltage which can alter cellular movement, align themselves. Important in wound healing. Skin and nerve cells respond to this
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Contact guidance
One cell moves and creates a path, another cell will follow
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