Devo Lect 8 + 9 - Cell connections

Question 2

Townes and Holtfreter experiment

Answer 2

separated cells with alkaline solution which spread out, placed in nutrients. Then they clumped together, moved about, then stop (stuck together)

Question 3

Cell adhesion molecules

Answer 3

Used in epithelial sheets, serve to condense mesenchyme; eg L-selectin on blastocyst; cadherins

Question 4

Cadherins

Answer 4

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

Question 5

Cadherin knockout mice

Answer 5

E knockouts: cannot implant; N knockout: nervous system doesn’t develop much, aborted

Question 6

CAMs

Answer 6

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)

Question 7

Substrate adhesion molecules

Answer 7

bind cells to ECM (basal lamina); fibronectin: glycoprotein binds to integrins, allows cells to bind to it and move along

Question 8

Integrins

Answer 8

Bind fibronectin at RGD a.a. sequence, provide anchor; can also cause signal transduction as things bind to it

Question 9

Cell junctional molecules

Answer 9

Gap junctions; form at morula stage and in early heart;

Question 10

Cell adhesion in implantation

Answer 10

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

Question 11

Cell crawling

Answer 11

Protrusion of leading edge; form focal contacts; retraction of trailing edge

Question 12

Cell motility components

Answer 12

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

Question 13

Microfilaments in cell motility

Answer 13

Major contributor; Constantly forming and breaking down; high concentration along the front edge; actin experiments (blocking it)

Question 14

Haptotaxis

Answer 14

Guiding molecule is not freely diffusable, attached to something; ex: mesoderm cells follow fibronectin as they migrate inward

Question 15

Galvanotaxis

Answer 15

Changes in voltage which can alter cellular movement, align themselves. Important in wound healing. Skin and nerve cells respond to this

Question 16

Contact guidance

Answer 16

One cell moves and creates a path, another cell will follow

Question 17

Contact inhibition

Answer 17

Movement is decreased after making contact with another. Most cells do this (not cancer cells)