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CSB331 > L20-21: Somatogenesis > Flashcards

L20-21: Somatogenesis Flashcards

1
Q

Which mesoderm do somites come from?

A

paraxial mesoderm

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2
Q

What direction do the the somite formation happen in?

A

anterior to posterior

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3
Q

What type of cells are somites before they become somites? and what process do they go through?

A

mesenchymal. MET

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4
Q

What is naggin?

A

BMP inhibitor. This is required specifically for somite development

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5
Q

Which transcription factor detects inhibition of BMP to promote somite development?

A

Pax3

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6
Q

Only the surface mesoderms turn into epithelial tissues. True or False?

A

True. It forms into a ball shape that are identical in size

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7
Q

Do somites form in a timely manner?

A

Yes. they form in a species specific time frame (90 min in chicken)

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8
Q

What are the five steps in somite formation

A
  1. periodicity
  2. cell boundaries
  3. epitheliailization
  4. specification
  5. differentiation
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9
Q

How do you prove that somite patterns are inherent in mesenchymal cells?

A

transplating border mesenchymal cells in non border regions cause new border formation.
Transplanting non-border cells in the same way doesnt produce any changes

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10
Q

Describe notch signalling

A
  1. Notch and delta binds
  2. Notch comformational change
  3. notch cytoplasmic domain cleaved by presenilin
  4. you
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11
Q

Describe notch signalling

A
  1. Notch and delta binds
  2. Notch comformational change
  3. notch cytoplasmic domain cleaved by presenilin
  4. cleaved notch part becomes a transcriptional factor
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12
Q

Is notch signalling essential for somite formation?

A

YES. or the poor mice get fked

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13
Q

How can we test for what happens if notch signalling didn’t happen through experimentation.

A

inactivate presenilin

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14
Q

What are some downstream effectors of notch?

A

Hes 1, Hes 7, Hairy 1, Lunatic frindge

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15
Q

How often are new somites created in chicks?

A

90 min

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16
Q

Which downstream effector of notch is seen oscillating in during somite formation every 90 min?

A

Hairy1, wnt

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17
Q

What are three other pathways that undergo oscilation during development of somites?

A

Dkk1 - extracellular signalling of wnt
Dact - intracellular signal transduction of wnt
Axin2 - inhibition of wnt

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18
Q

Axin2 and notch signalling. Which is dependent on the other?

A

Notch signalling is dependent on Axin2 (wnt) signalling as it precedes notch signalling in cycles

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19
Q

Describe the opposing gradient that occurs during each cycle.

A

Raldh2 -> RA

Fdf8 -> FGF

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20
Q

Describe the opposing gradient that occurs during each cycle.

A

Raldh2 -> RA > differentiation
Fdf8 -> FGF > suppress differentiation

anterior side with RA gradient
posterior side with FGF gradient
midline is the boundary

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21
Q

What is the middle of RA and FGF gradient called?

A

Determination front

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22
Q

Describe eph pathway involvement in somatogenesis

A

ephrin B2 in anterior cell bottom
eph A4 in posterior cell top

notch triggers this pathway

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23
Q

Are all muscles derived from somites?

A

No. Everything except head muscles

24
Q

What are the back muscles formed from? What are the signals required for this development?

A

Primaxial myotome.

shh from notochord, wnt from neural tube

25
Q

What are the limbs and body wall muscles formed from? What are the signals required for this development?

A

abaxial myotome

wnt from epidermis, other factors from lateral mesoderm

26
Q

What does shh contribute in?

A

primaxial myotome, sclerotome

27
Q

What are internal genes that are turned on in paraxial myotome, abaxial myotome and sclerotome?

A

myf5
myoD, pax3
Pax1

28
Q

describe wnt and hedgehog signalling

A

without wnt
- activate GSK3β complex > β catenin degraded > no transcription

with wnt
- no active GSK3β > β catenin removes groucho > transcription

29
Q

One day 2-3 which part goes through EMT? what does it form into?

A

Ventral medial cells (sclerotome) goes through EMT.

Turns into cartilage

30
Q

On which day of the embryo do we get myotome and sclerotome differentiation?

A

2-3 days

31
Q

Does myocyte elongation happen from only one side?

A

No from all 4 sides. can be seen with GFP for 48 hours.

32
Q

Does central myotome invade into primary myotome? are they differentiated before after? What do they express?

A

Yes. Can be seen with GFP. They are no differntiated. and they express Pax7

33
Q

Which parthway in primary myotome promotes EMT?

A

FGF > snail

34
Q

On which day is abaxial somatic bud and primaxial somatic lip formed?

A

late Day 4

35
Q

Which two pathways trigger central dermamyotome to EMT? and which way do they migrate aftewards?

A

wnt6, Neurotrophin-3. (from neural tube)

Up towards beneath epidermis

36
Q

Trigger for central dermamyotome comes through wnt6 and NT3 comes from where?

A

dorsal neural tube

37
Q

4 types of muscle cells

A
  1. Striated (in myoneural junction)
  2. Cadiac muscle fibres
  3. Myoepithelial cells (milk ducts, salivary glands)
  4. Smooth muscle cells on collagen
38
Q

How does limb and interlimb differ in abaxial EMT?

A

in interlimb, abaxial delamination produces limbs.

in interlimb, lateral dermamyotome migrates to underlying myotome.

39
Q

Explain pathways in limb budding

A 
From limb (FGF > HGF > c-met)
From abaxial myotome (Pax3 > MyoD)
40
Q

At limb target sites, does differentiation or proliferation happen first?

A

proliferation

41
Q

What are myotubes formed from?

A

multiple myoblasts joining together

42
Q

Does the number of myoblasts increase from birth to adulthood?

A

No.
They grow by fusing with single nucleated myoblasts (1st week)
Then grow my stretching with actin and myosin filaments

43
Q

cell fusion is referred to as?

A

syncytium

44
Q

What are the five steps in striated muscle cell formation. Along with signals needed in each step

A
  1. myotome cell (determination).
    bHLH > lineage specification with myoD, Myf5 > Myogenin and MRF4
  2. dividing myotoblasts
    FGF
  3. cell alignment (no more FGF)
    Fibronectin, integrins, cadherins
    myogenins > transcription of muscle specific genes
  4. myotube formation > maturation
    myoferlin & dysferlin
    muscle MMP
    IL-4 for myoblast fusion with myotube
45
Q

During myotube maturation, what is required? Which exact molecule is it needed by?

A

myoferlin with Ca2+

46
Q

What is the purpose of myostatin? What happens without it?

A 
inhibits myogenesis (proliferation to differentiation)
Without it, hyperplasia (more fibre), hypertropy (big muscle)
47
Q

myostatin is in which family of growth factor?

A

TGFβ

48
Q

Are myofibres surrounded by basal lamina? What is located in between these?

A

Yes. satellite cells

49
Q

What is another name of putative muscle stem cell?

A

satellite cell

50
Q

What are the functions of satellite cells?

A

self renewal, injury recovery, proliferation in response to stress/exercise

51
Q

Satellite cells are derived from which part of the somite?

A

central dermamyotome

52
Q

Satellite cells express what?

A

Pax3 and Pax7

53
Q

Satellite cells do not express what and why?

A

bHLH, myoD and myf5. Else it would differentiate all the time

54
Q

What is expressed in daughter satellite cell that divide?

A

Myf5 and myoD

55
Q

Which two structures are located on basal lamina to attach to actin filament?

A

integrin and dystroglycan

56
Q

What does RA promote or suppress? what is its gene?

A

promote cell differentiation. Raldh2

57
Q

What does FGF promote or suppress? What is its gene?

A

Suppresses cell differentiation. fgf8

CSB331 (10 decks)

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