Cell interactions and cell movements in development II

Question 1

How do epithelial sheets bend?

Answer 1

Actin cytoskeleton at one side contracts

Question 2

Example of invagination?

Answer 2

Eye development

Question 3

Invagination in eye development?

Answer 3

Ectoderm sits over optic vesicle
Signals from the ectoderm tell the optic vesicle to invaginate
Ectoderm then does the same
Ends up with the optic cup which pinches off to form the lens

Question 4

Example of involution?

Answer 4

Gastrulation

Question 5

Involution in gastrulation?

Answer 5

cells at the tip of an epithelial sheet pull the sheet inwards–> mesoderm migrates inwards

Question 6

What is cavitation?

Answer 6

Formation of a hollow ball or tube

Question 7

What is cavitation an alternative to?

Answer 7

Invagination

Question 8

Two ways that cavitation can occur?

Answer 8

Fluid filling or apoptosis of cells in a solid mass

Question 9

Example of cavitation?

Answer 9

Blastocyst formation

Question 10

Cavitation in blastocyst formation?

Answer 10

Active transport draws water in through the cells of the outer embryonic surface and into the extracellular space

Question 11

Importance of tight junctions in cavitation?

Answer 11

Keep the fluid inside

Question 12

What do trophectoderm cells express on the outside?

Answer 12

E-cadherin

Question 13

What is epithelial to mesenchymal transition (EMT)?

Answer 13

Migration of cells out of an epithelium

Question 14

What does EMT require?

Answer 14

A reduction in cell-cell adhesion in migrating cells

Question 15

Example of EMT?

Answer 15

Neural crest formtion

Question 16

EMT in neural crest formation?

Answer 16

Neural plate folds up on itself
Cells at the top of the neural tube migrate out
These can then go and give rise to diff structures

Question 17

Anteriormost cells of the neural crest destination?

Answer 17

Head structures–> cartilage and bone

Question 18

posteriormost cells of the neural crest destination?

Answer 18

cells in the adrenal gland, sensory neurons, pigment cells

Question 19

What is mesenchymal to epithelial transition (MET)?

Answer 19

Polarisation of motile cells
Establishes cell-cell contacts through formation of adherens junctions

Question 20

Example of MET?

Answer 20

Kidney tubule formation

Question 21

MET in kidney tubule formation?

Answer 21

All tubules in kidneys arise from MET
Ureteric bud signals to mesenchyme to move and get closer to one another

Question 22

What is convergent extension?

Answer 22

Change in shape due to rearrangement of cells

Question 23

What causes convergent extension?

Answer 23

Constriction of the epithelial sheet in same direction as cell movement and elongation of epithelial sheet at right angles to cell movement

Question 24

Example of convergent extension?

Answer 24

Neural tube formation

Question 25

Convergent extension in neural rube formation?

Answer 25

Convergent extension takes place to reduce the width of the epithelium that is being created, and make it longer along the anterior posterior axis

Question 26

What is epiboly?

Answer 26

Expansion of a sheet of cells to surround and enclose another population

Question 27

Example of epiboly?

Answer 27

FIsh gastrulation

Question 28

Epiboly in zebrafish gastrulation

Answer 28

ectoderm spreads out round the embryo to completely encompass it

Question 29

What is planar cell polarity?

Answer 29

Polarisation of cells in the same direction as the plane of the epithelium i.e. all actin in cells go to the same side

Question 30

What does planar cell polarity require?

Answer 30

Requires a long range signal to orient direction of polarisation

Question 31

Example of planar cell polarity?

Answer 31

cochlea

Question 32

Planar cell polarity in the cochlea?

Answer 32

Hair cells push their actin cytoskeleton up to give finger like protrusions to the top of the cell--> apical surface has the protrusions

Question 33

What is branching morphogenesis?

Answer 33

Morphogenetic behaviour characteristic of organogenesis

Question 34

Start of branching morphogenesis?

Answer 34

Originates with the formation of a bud that progressively increases the number of growing points to produce a branched structure

Question 35

Example of branching morphogenesis?

Answer 35

Lung development

Question 36

Planar bifurcation?

Answer 36

A single projection splits off in the same plane

Question 37

Orthagonal bifurcation?

Answer 37

Two splits who each split at right angles

Question 38

Domain branching?

Answer 38

single branch that has multiple branch points off of it