L7 - Regeneration

Question 1

Is regeneration linked to the complexity of an organism

Answer 1

No

Question 2

Thinking about the French flag model if there was the left hand portion removed what types of regeneration could occur

Answer 2

Morphallaxis

Epimorphosis

Question 3

What is morphallaxis

Answer 3

Little change in the number of cells

Cells present acquire new fates

Question 4

What is epimorphosis

Answer 4

Formation of a growth zone and proliferation occurs

Question 5

What mechanism of regenration is seen in Hydra

Answer 5

Mophallaxis

Question 6

Morphalaxis may also be known as

“regeneration without ______”

Answer 6

Growth

Question 7

Describe the basic organisation in hydra

Answer 7

Simple
Two germ layers (no mesoderm)
Simple mouth - hyposostome surrounded by tentacles and an elongated body column

Question 8

Describe growth in Hydra

Answer 8

Grows continuously meaning that cells must change their positional values

Question 9

During regeneration of the head how many gradients form - what are they

Answer 9

2 gradients

1) Positional value
2) Head inhibitor gradient

Question 10

What does the positional value determine

Answer 10

Head inducing ability

Resistance to the inhibitor

Question 11

Describe what is seen when head cells are transplated into the body
Why

Answer 11

Nothing is seen

Head inhibitory graidient is too high for head strucutres to develop

Question 12

Describe what is seen when head cells are transplanted into the upper body of a HEADLESS ORGANISM

Answer 12

Development of head structures as there is no source of head inhibitor

Question 13

Describe what happens when you transplant cells from the head region into the lower body (close to the basal disc)

Answer 13

Head inhibitor close to the basal disc is too low

Head strucutres are able to form

Question 14

How long does it take for a piece of region 1 to induce a secondary axis

How long does it take for a piece of region 5 to induce a secondary axis

Answer 14

6 hours

30 hours

Question 15

What signalling pathway is thouhgt to determine positional value

Answer 15

Wnt B-catenin

Question 16

How was it seen that Wnt signalling was thought to determine positional value

Answer 16

Inhibition of GSK3 leads to a build up of B-catenin in the nuc
All regions acquire characteristics of the head organiser

Question 17

What organism regenerated by epimorphosis

Answer 17

Urodele

Question 18

Regeneration depends on

Answer 18

The posiiton of the cut

E.g. distal cut only distal strucutres regenerated

Question 19

What is epimophosis

Answer 19

Regeneration by the growth of more tissue

Question 20

What is the first thing to occur following amputation

Answer 20

Migration of epidermal cells

REGENERATION IS DEPENDENT ON THIS HAPPENING!

Question 21

What happens to cells which are below the epithelum

Answer 21

Dedifferentiation forming a blastema

Question 22

Muscle cells are multinucleis what is required for them to revert to uninucleate

Answer 22

Thrombin CRUCIAL

Question 23

What is the blastema formed of

Answer 23

Dermis but can also be from dedifferentiated muscle and cartilage

Question 24

Is there much transdifferentiation during blastema fomration

Answer 24

NO everything remains true to type except

dermis can form cartilage (and vice versa)

Question 25

What are the (4) rules of regeneration

Answer 25

Limb regeneration always occurs distal to the wound
Regeneration occcurs appropriate to the positional value at the site of the cut
Not just a case of replacement of the missing parts
Morphogenic autonomy after transplant

Question 26

Describe what would be seen if the hand was amputated and the limb was inserted into the belly - vascualr connections est an humerus cut

Answer 26

Regeneration starts from the proximal and distal surfaces of the humerus
Both proximal and distal surfaces regeneerate distal structures

Question 27

How may proximal and distal blastema cells sort

Answer 27

Differential adhesion

Question 28

What signalling molecule has been shown to proximalise a blastema
How does this work

Answer 28

Retinoic acid

Resets the positional value to that of a more proximal value

Question 29

What is the mechanism for the proximalisation of the blastema through RA

Answer 29

Upregulation of meis homeobox genes of a GPI linked Prod1

Question 30

What is the requirement for innervation

Answer 30

Regeneration depends on the presence of a nerve - unless a nerve wasn;t present in the first place

Question 31

What is newt anterior gradient

Answer 31

A protein that can replace the nerve in supporting outgrowth

Question 32

The mechanism of insect appendage regeneration involves the sensing of ….

Answer 32

Disscontinuities in positional values - missing positional values are then fill in irrespective of the overall strucutre

Question 33

Describe what regeneration can be seen in mammals

Answer 33

Young children and mice can regenerate the tips of the digits

Question 34

Describe regeneration in the PNS

Answer 34

Axons are able to regrow (but not whole neurones)

Question 35

Describe regeneration in the CNS

Answer 35

Very little regenertion since the CNS is a non permissive enviro
Inhibitory myelin

Question 36

Describe mammalian heart regeneration

Answer 36

Cardiomyocytes are present but dont divide
Progenitors present but aren’t used
Scar/maladaptive hypertrophy

Question 37

Describe the ventricular regenerating in zebrafish

Answer 37

Not identical to emb dev in the head e.g. msxB and msxC
Regen dep on dediff muscle cells
Endocardium/epicardium involved
Neuregulin may be a signal from the epicardium