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Cellular Communications > Limb development > Flashcards

Limb development Flashcards

1
Q

What are the 3 axis ?

A

Anterior-posterior
distal-proximal
dorsal-ventral

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2
Q

What direction is anterior to posterior ?

A

up to down

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3
Q

What direction is distal to proximal?

A

left to right

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4
Q

What direction is dorsal to ventral?

A

front to back

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5
Q

Where is the origin of the initial growth?

A

flank of mesoderm

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6
Q

What signal is key in the initial growth?

A

FGF

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7
Q

What does FGF initiate?

A

Initiates signal transduction cascade to target genes.
TF of Tbx family
Outgrowth using Tbx induced by fibreglass growth factor

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8
Q

What does FGF stand for?

A

Fibroblast Growth factor

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9
Q

What is flank?

A

Side of body mesoderm

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10
Q

What is the AER ?

A

Apical Ectodermal Ridge

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11
Q

What does the AER express?

A

FGF genes and FGF proteins

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12
Q

What is the AER derived from?

A

ectoderm derived structures

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13
Q

What does FGF travel through?

A

Mesenchyme

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14
Q

What does FGF bind to?

A

FGF binds to receptor signals

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15
Q

What role does AER play in initiating growth? X4

A

Important signalling centre
maintains outgrowth
produces FGF
controls proximal to distal

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16
Q

Is the AER like a ‘seem’?

A

YES.

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17
Q

Does AER pattern or differentiate cells?

A

Pattern

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18
Q

In what zone can cells detect FGF?

A

Progressive zone

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19
Q

How is identity created in these cells?

A

time spent in progressive zone

might be counted by cell divisions

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20
Q

What axis is the initial growth on?

A

Proximal to distal

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21
Q

What two molecule signal opposing gradients?

A

FGF and RA

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22
Q

What kind of gradient does 2-signal model have?

A

opposing

antagonism between them

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23
Q

What happens to intermediate areas in 2-signal model?

A

may adopt intermediate fates

24
Q

What axis is FGF present?

A

AXIAL

25
Q

What axis is RA present?

A

Proximal

26
Q

What does FGF promote?

A

proliferation

27
Q

What does RA promote?

A

differentiation

28
Q

How does FGF inhibit RA?

A

Inhibits Raldh2, this will limit RA

29
Q

How does RA inhibit FGF?

A

inhibits Fgf8 transcription, promotes transcription degradation

30
Q

How do cells know what signal to follow? FGF or RA?

A

Depends on how close or how strong each signal is.

If a signal appears first it will dominate.

31
Q

How is patterning achieved across anterior to posterior axis?

A

ZPA (polarising region)

32
Q

What gene does ZPA have?

A

morphogen

33
Q

what specific signal is produced from ZPA?

A

Sonic Hedgehog signals

34
Q

What does a high concentration of sonic hedgehog signal induce at (proximal region)?

A

induce a pinky to form

35
Q

What digit number is a pinky?

A

5 (in humans)

36
Q

Does Posterior or Anterior have the highest concentration of sonic hedgehog signal?

A

Posterior

37
Q

can you create a ZPA on opposing anterior side?

A

YES= opposing gradients

38
Q

How does strength of opposing signal from ZPA effect duplication?

A

weak signal = very little mirror image duplication

39
Q

What is preaxial polydactyly?

A

Extra anterior digit due to loss of shh= loss of ZPA

40
Q

How is the mutant shh regulated ?

A

cis-regulation 1,000,000 bp away

41
Q

What patterns the dorso-ventral axis?

A

ectoderm

42
Q

What is a way to describe the mesenchyme?

A

meaty bit

43
Q

What patterns the mesenchyme?

A

ectoderm, compartmentalise to dorsal and ventral side

44
Q

What gene (TF) confers dorsal fate?

A

Lmx1b

45
Q

What ligand (extracellular signalling molecule) induces Lmx1b?

A

Wnt7a

46
Q

Where is Wnt7a produced?

A

ectoderm

47
Q

Where does Wnt7a diffuse to?

A

mesenchyme and induces expression of Lmx1b

48
Q

What receptor activation activities Transcription factor En1?

A

BMP

49
Q

What gene (TF) confers Ventral fate?

A

En1

50
Q

What does ligand does En1 repress?

A

Wnt7a and in turn represses Lmx1b

51
Q

Can both pathways ventral and dorsal pathways occurs at the same time?

A

No

52
Q

What ligand signals for cell death?

A

BMP

53
Q

What tissue determines cell death?

A

mesoderm

54
Q

What are HOX genes?

A

tell cell if they are going to be an arm, leg etc. Tell cells their location from anterior to posterior on entire embryo.

55
Q

What 3 molecules initiate the initial bud development?

A

Hox gene, Wnts and FGF in flank

56
Q

What 2 regions in turn help maintain each other?

A

apical ectodermal ridge and the polarising region (in limb bud)

Cellular Communications (7 decks)

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