Ch. 4 pt 1 Flashcards
all that you touch you change. all that you change changes you. the only lasting truth is change.
Octavia butler
in dealing with such a complex system as the embryo, it is futile t inquire whether a certain organ rudiment is determined and whether some feature of its surroundings , to the exclusion of others,
“determines” it. A score of different factors may be
involved, and their effects most intricately
interwoven. In order to resolve this tangle, we have
to inquire into the manner in which the system under
consideration reacts with other parts of the embryo
at successive stages of development and under as
great a variety of experimental conditions as it is
possible to impose
RG Harrison
_______: the construction of organized form
Morphogenesis
5 modern questions of morphogenesis:
1) how are separate tissues formed from populations of cells
2) how are organs constructed from tissues
3) how do organs form in their correct locations how do migrating cells find their correct destinations
4) how do cells and organs grow and coordinate their growth
5) how do structures achieve polarity
_______: form sheets and tubes and adhere to one another
epithelial cells
_______: typically migrate individually and will form extracellular matrixes of larger tissues
mesenchymal cells
What are the 3 behaviors that require cell-to-cell communication via cell surface?
1) differential cell adhesion
2) cell shape
3) cell signaling
What are the 3 very short signaling mechanisms?
1) autocrine signaling
2) juxtacrine signaling
3) Synaptic signaling
_______ signaling: a single cell produces both ligand and receptor
autocrine
_______ signaling: signals on the surface of one cell are bound by receptors on adjacent cells (contact-dependent)
juxtacrine
_______ signaling: across synaptic cleft, neural tissue specified
synaptic
_______ signaling: signals diffuse only a short distance from signaling cell to local “neighborhood” cell
paracrine
_______ signaling: hormone secreted into the bloodstream affect other parts of the body by stimulating responses in distant cells
endocrine
Endocrine signaling acts at _______ concentrations and has powerful effects on _______
low
gene expression
signaling molecules (_______) bind to receptors embeded in the cell membrane
ligands
_______: binding of a receptor to its ligand alters the receptors shape
conformational change
After signal transduction through conformational changes, phosphorylation, and cAMP/Ca2+, the signal culminates in _______ (fast) and _______ (slow)
pre-existing components
activating gene expression
What are the three ways that signals can alter the cell fast?
1) enzyme changes
2) biochemical changes
3) Cytoskeletal changes
Whats the difference between homophilic binding and heterophilic binding?
homophilic: same receptors
heterophilic: different receptors
_______ and _______ were responsible for the re-aggregation experiments
towns and holtfreter
In the re-aggregation experiments, cell types from different embryos were taken and then mixed. The results of this experiment showed that the cells what?
re-aggregated cells became spatially segregated by type
The results from the re-aggregation experiments were interpreted as _______
selective affinity
The automatic cellular sorting observed was attributed to each cell type’s _______ to the other types of cells
differential adhesion
Town and Holtfreter’s final conclusion suggested that these affinities can _______ during development, allowing relationships between cells/tissues/structures to change and be modified
change
Changes in cell surface adhesion molecules alter the _______ of the affinity between individual cells
strength
What 3 examples can change strength of cell adhesion:
1) changes in the _______ of receptors
2) changes in the _______ of receptors
3) changes in _______ of the cell
number
type
cell morphology
Cells will arrange themselves into the most ______ stable configuration
thermodynamically
- Changes in gene expression WILL result in changes in cell interactions
- Higher surface tension in center
_______ are the most common cell-surface adhesion molecule
cadherins
-homophilic
cadherins are ____-dependent homophilic binders
Ca2+
cadherins form ______ junctions with additional internal proteins (_______) that hold epithelial cells together
adherens
catenins (alpha beta gamma)
What are the 3 major functions of cadherins?
1) anchor cells together
2) assemble and link actin cytoskeleton
3) signaling function that can affect gene transcription
Cells with different cadherins _______ on another and form ______
repel
boundries
What are the 4 major types of cadherins?
E
P
N
R
E-cadherins are found in what cells?
embryonic cells
epithelial cells
P-cadherins are found in what cells?
placental cells
- connect embryo and uterus
N-cadherins are found in what cells?
neural tissues
R-cadherins are found in what cells?
retina formation
_______ lack the protein domain allowing attachment to the cytoskeleton through catenins. Helps keep similar migrating epithelial cells together.
protocadherins
Explain cadherins in neurulation
ectodermal cells express E-cadherin but those that become the neural tube lose it and express N-cadherin
Explain cadherins in uterine wall implantations
trophoblast cells of embryo express E and P-cadherins that allow it to stick to endometrium of uterus
- needs integrins and glycosyltransferases
The _______ is an insoluble non-cellular matrix of macromolecules between cells
extracellular matrix (ECM)
What are the 5 components of ECM?
1) collagen
2) proteoglycans
3) elastin
4) fibronectin
5) laminin
4,5 are glycoproteins
_______ creates a physical connection between the ECM and the cytoskeleton
integrins
Integrins bind to ____ sequences in ECM
RGD (Arg-Gly-Asp)
- fibronectin
- laminin
- vitronectin
- collegens
- these ecm have them
integrins connect to _______ through alpha actinin and talin
actin microfilaments
_______: Apoptosis due to loss of contact with ECM
anoikis
_______: when a polarized, adhered, stationary cell is transformed in an orderly way into an invasive and motile mesenchymal cell that can move to form new structures
epithelial to mesenchymal transition (EMT)
- ex) formation of neural crest cells, wound healing, metastatic tumors
Explain the process of epithelial to mesenchymal transition
1) paracrine signals from neighbors
2) Cadherins are down-regulated, and ECM is released
3) actin cytoskeleton rearranged for movement
4) cell secretes mesenchymal ECM molecules
4) cell released (basement membrane dissolved)
Integrins are _______ dependent and have those binding sites
Ca2+
