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Vertebrate development > Cell interactions + movements > Flashcards

Cell interactions + movements Flashcards

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1
Q

Morphogenesis

A

= generation of form

= origin and development of morphological characteristics

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2
Q

Cell adhesiveness

A

Animal cells adhere to one another + the ECM

- via interactions involving cell-surface proteins known as adhesion molecules

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3
Q

Cell shape changes

A

Cells can actively change shape by means of internal contractions + constrictions

  • caused by cytoskeletal rearrangements
  • crucial in development processes e.g. folding of cell sheet
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4
Q

Cell motility

A

Ability of cells to move as individuals or groups from 1 location to another

  • crucial to development
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5
Q

2 groups of embryonic cells

A

Epithelial cells
= sheet of cells joined to it’s neighbour by cell-cell adhesion

Mesenchymal cells
= scattered cells, embedded in loose ECM

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6
Q

3 germ layers

A

Ectoderm

Mesoderm

Endoderm

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7
Q

When do 3 germ layers form?

A

Gastrulation

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8
Q

Which germ layers are epithelial and mesenchymal cells found in?

A

Epithelial = all 3 germ layers

Mesenchymal = ectoderm + mesoderm

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9
Q

Epithelia

- composition

A

Cells organised into sheets or tubules

- attached to an underlying basement membrane

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10
Q

Mesenchyme

- composition

A

Scattered cells surrounded by loose ECM

Little/ no contact with adjacent cells

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11
Q

Mesenchyme

- role

A

Fills up much of the embryo

Later forms fibroblasts, adipose tissue, smooth muscle + skeletal muscle

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12
Q

Epithelia

- held together by..?

A

Cell junctions

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13
Q

Cell junctions

A

Specialised site on a cell at which it is attached to another cell

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14
Q

2 types of cell junction

A

Apical = cell-cell

Basal = cell-matrix

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15
Q

What polarity do epithelia have?

A

Apical-basal polarity

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16
Q

Apical interactions

- what do they both involve?

A

Cadherins

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17
Q

Apical interactions

- what are the 2 types?

A

Adherens junction

Desmosome

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18
Q

Adherens junction

- composition

A

Actin filaments

Cadherin

Alpha-catenin
Beta-catenin

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19
Q

Desmosome

- composition

A

Intermediate filaments

Cadherin

Plakoglobin
Desmoplakin

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20
Q

Basal interactions

- what do the both involve?

A

Integrins

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21
Q

Basal interactions

- what are the 2 types?

A

Focal adhesion

Hemidesmosome

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22
Q

Focal adhesion

- composition

A

Actin filaments

Integrin

Focal adhesion kinase

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23
Q

Hemidesmosome

A

Intermediate filaments

Integrin

Dystonin

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24
Q

Cadherins

- what are they?

A

Calcium-dependent transmembrane proteins

Protrude from cell

In presence of Ca2+
-> cadherins on adjacent cells stick together in zipper-like fashion

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25
Cadherins | - in adherens junctions
Cadherins linked to intracellular proteins called catenins -> catenins link to actin cytoskeleton
26
Cadherins | - in desmosomes
Cadherins linked to intracellular proteins called plakoglobin -> plakoglobin connected to intermediate filament proteins e.g. keratin
27
Adheren junctions + desmosomes | - where are they present?
Adheren junctions - many tissues Desmosomes - epithelia
28
Immunoglobin-like adhesion molecules
e.g. N-CAM = neural cell-adhesion molecule Some mediate homophilic binding Other = heterophilic - bind to integrins
29
Integrins | - what are they?
Proteins found in ECM Protrude from cell Bind to matrix proteins - e.g. collagen Have 2 subunits - alpha + beta
30
Integrins | - in focal adhesions
Focal Adhesion Kinase (FAK) links integrins to actin cytoskeleton
31
Integrins | - in heme-desmosomes
Dystonin links integrins to intermediate filaments
32
Apical junctions | - role
Mechanical links al cells within epithelial sheet
33
Basal junctions | - role
Allow integrins to transmit info about ECM to cell Signals can affect cell shape, motility, differentiation + metabolism
34
3 key cellular properties required for morphogenesis
Cell adhesiveness Cell shape change Cell motility
35
What happens when pieces of late ectoderm + endoderm from amphibian blastula are placed together?
Initially fuse to form smooth sphere -> then separate until only a narrow bridge of tissue connecting the 2 together is left
36
What happens when early ectoderm and mesoderm are placed together? Why is this?
(normally adhere to one another) Tissues don't separate - instead the 2 pieces of tissue remain in contact - > mesoderm envelops ectoderm They express complementary adhesion molecules so can interact with one another
37
How is cell adhesiveness involved in cell sorting?
Differential adhesiveness - due to differences in types + no.s of adhesion molecules on their surfaces Cadherins = cell-type specific Mix 2 cells expressing different cadherins or different amounts of same cadherin -> organise themselves into like
38
Changes in cell adhesiveness | - example
Ectoderm + mesoderm from amphibian blastulas are disaggregated into single cells when treated with alkaline solution When cells are mixed together -> sort out with mesoderm cells on outside
39
Changes in cell shape
Generated by constrictions + contractions of cytoskeleton
40
Cytoskeleton | - 3 principal types of protein polymers
Actin filaments Microtubules Intermediate filaments
41
Actin filaments + microtubules - features
Dynamic structures Polymerising + depolymerising according to the cell's requirements
42
Intermediate filaments
More stable Forms rope-like structures that: > transmit mechanical forces > spread mechanical stress > provide mechanical stability to cell
43
Cell shape | - what can actin filaments assemble with?
Myosin - into contractile structures = act as miniature muscles
44
Cell shape | - cleaving cell
Bundles of actin-myosin form a contractile ring - contraction of bundle pinches cell in 2
45
Cell shape | - apical constriction
Contraction of ring of actin myosin ring around apical end -> leads to apical constriction + elongation of cell (volume of cell doesn't;t charge)
46
Cell shape | - migrating cell
Embryonic cells move by migration - requires cell shape change Cells extend lamellipodium -> pushed outwards from cell by assembly of actin filaments Contraction of actin myosin assembly at front of cell draws cell forward
47
Cell motility
1. Cell makes several attachments to ECM 2. Actin rearrangements allow cell to send out lamellipodia at leading edge - > makes new attachments with substratum = cell is stretching + cytoskeleton is under tension 3. De-adhesion at rear end of cell releases tension 4. Whole cell moves forward
48
Which 2 factors does cell motility involve?
Changes in cell adhesiveness + cell shape
49
What kind of morphogenetic processes underlie diverse forms of embryos?
``` >Involution + invagination >Cavitation > Epithelial-to-mesenchymal transition > Convergent extension > Epiboly > Delamination + ingression ```
50
Involution + invagination | - generates?
Multi-layered structures from a simple epithelium | - can create hollow ball or tube
51
Involution + invagination | - process
Arise due to changes in cell shape caused by contraction of cytoskeletal filaments Localised contraction in actomyosin filaments in a few cells All cells are mechanically linked -> whole sheet drawn in at point of contraction
52
Involution | - example
Gastrulation in Xenopus Cells in marginal zone undergo apical constriction of cytoskeletal network -> elongate -> draws sheet in = involutes Caused by signalling molecules: >BMPs >Wnt
53
Cavitation | - what is it?
Formation of a hollow ball or tube
54
Cavitation - process - example
Occurs through fluid filling or apoptosis of cells in a solid mass e.g. blastocyst formation - vectorial transport of fluid creates a cavity = Blastocoele
55
Cavitation | - example
Mammalian blastocyst formation Blastocoele formed when sodium ions are actively pumped across basolateral surface of outer layer of trophectoderm cells Blastocoele inflates as water moves in via osmosis - prevented from escaping by tight junctions in apical regions -> hydrostatic pressure = gives blastocyst its spherical shape
56
EMT (epithelial-to-mesenchymal transition) and ingression | - what is it?
Conversion of an epithelium into a more loosely connected mass of mesenchyme OR into individual mesenchymal cells that can migrate
57
EMT and ingression | - what does it involve?
Dissolution of adherens junction between epithelial cells Migration of cells out of an epithelium
58
MET (mesenchymal-to-epithelial transition)
Results in polarisation of motile cells Establishes cell-cell contacts through formation of adherens junctions Creates an organised epithelium
59
Convergent extension | - what is it?
Sheet of cells changes shape due to active rearrangement of cells
60
Convergent extension | - process
Axes defined Cells become elongated in direction at 90 degrees to anterior-posterior direction Cells become aligned parallel to one another in direction perpendicular to direction of tissue extension Each end of bipolar cells from filopodia - allows them to exert traction of neighbouring cells
61
Epiboly
Expansion of sheet of cells to surround + enclose another population Cells spread + thin out Involves several changes: cell division, alteration in cell shape + intercalation of cells
62
Epiboly | - example
Gastrulation in fish Spreading + thinning of ectodermal sheet - expands over inner layers + eventually encloses them

Vertebrate development (12 decks)

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