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Advanced developmental biology > Lecture 7 - Muscle > Flashcards

Lecture 7 - Muscle Flashcards

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1
Q

what is a sarcoemere

A

the structural unit of a myofibril in a striated muscle

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2
Q

wgat us the smallest cellular unit of a muscle and it’s mportant property

A

myofibre

polynucleated

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3
Q

what do myofibres consist of

A

many myofibrils

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4
Q

how are somites patterned

A

siganals from adjacent tissues including notochord and lpm ectoderm etc
distinct code
distinct TF
give identity

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5
Q 
with the following signals what tissues release the signals
-WNts 
Shh
noggin
Bmp
A

Wnts = from the dorsal n.tube and epidermal ectoderm
Bmp4 lateral plate
Shh (and noggin) = notochord and floor plate of n.tubw

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6
Q

What do the signals define?
wnt
shh
bmp

A

wnt - induce Pax3 expr defines dermomyotome and supreses sclerotome form
shh- induce pax1 - sclerotome
bmp4 controls sim1 ecpr in the lateral/hypaxial

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7
Q

where do muscles form from

A

somites

competence at compartmentalisation

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8
Q

what the different TF combine to give identity to diff compartments of the somite

A 
dorsal 
Pax3/Pax7/En1 = epaxial muscles
pax3/pax7/sim1=hypaxial   = muscles
VEntral
sim1=hypaxial - sclerotome
pax1 - epaxial - sclerotome
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9
Q

what compartment are muscle precursors in somite

A

hypaxial - dorsal

bmp and wnt cooperate to specify

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10
Q

what is the dermomytome

A

pool of precursors cells of muscles

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11
Q

what is the sclerotome and how does it form

A

EMT (deepithalises) leaves behind dermomyotome and the myotome
gives rise to themcartilage and bone of the axial skeleton and ribs

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12
Q

what are the different sections of myotome

A

dorsomedial lip
dermomytome proper
early myotome
ventrolateral lip

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13
Q

descirbe propetries of the myotome

A

forms in rib musculature

first differnetiated muscle cell

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14
Q

what happens to Tf patterns from the tranistion form somites to dermomytome

A

are maintained
pax3/pax7 = muscle precursors
my15 - onset of differnetiation in myotome and lips

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15
Q

how is progenitor migration steered

A

signals from limb to receotive muscle precursors (which are in the ventrolateral lip )

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16
Q

what are the signals thta guide the cell migration and where are they expressed

A

siganl =SDF1 rec = CXCR4
expr where pax3 upreg - in limb region where limb will form
signal SF/HGF rec Cmet/hgf

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17
Q

what happens to the cells that get the singal and become migratory

A

emt (epithelial mesodermal transition)

18
Q

what is epithelial mesodermal tranisiton

A

cells give up epithelial identitiy and become migratory

19
Q

what tf define the expression of the signals SF/HGF

A

Fgf4/8 from the aer

20
Q

how do fgf4/8 from aer indirectly effect SDF1 signal

A

fgf impct on Lbx1 exor
lbx1 control cxcr4 expression
= why only cxcr4 in prospective limb

21
Q

what do teh Sf/cMEt mutants show

A

that with no rec there is no migration but the muscle precursor cells (lbx1 positive) accumulate in areas where is signal

22
Q

what do SDF-CXCR4 mutatns show

A

implant of sdf1 attract cxcr4 positive cells
- ectopic muscle
control implant no effect

23
Q

what the fucntional relationship between C-met and cxcr4

A

partially reduncant

strong ptype only when both taken out

24
Q

from studies in sebrafish what tf has been implicated in the formatino of multinucleate myotubes

A

kirrel

25
Q

what is the tf that define the myoblast (taking over from pax expr)

A

Myod
Myf5
Desmin

26
Q

what cells are likely to contribute to the induction of Myf5 expression

A

neural crest cells

27
Q

how are ncc cells thought to induce Myf5

A

neural crest cells express delta
=activate notch signalling
notch switches on myf5

28
Q

what transcription facotrs are key determinants of muslce differentiation

A 
myf5
mrf4
myoD
myogenin 
= all members of MDF/MRF family
29
Q

what is the expression patterns of the MDF/MRF family

A

=myf5/mrf4/myod expr in undiff cells
myod - in venrtal lip
mrf4 / myf5 strong expr in myotome weak in ventral lip
myogenin expr duirng differentiation high in both myotome and ventral lip

30
Q

what MRF fam member is suff and req for myogenic fate in culture

A

myod (ko and rescue)
when ko myod act myf5 but no other myogenic factors
- suggets myod the inductive signal

31
Q

what results show there is a high degree of interdepndence in teh myogenic factors

A

1)l myf5/mrf4 redundancy, early myogensis depends on
2) limb specific myogensis req myf5 and myod only
3)myotome-derived body musculature is more dependent on redundant functions of myf5 and mrf4
= redundsancy but have time and spatial expr imp

32
Q

what is mef2

A

master reg of muscle differntiation

downstream of the MDF/MRF

33
Q

what do mef2 mut show

A

early stages of precurso and specification -normal
specific differentiation -normal
functional differneitation doesnt occur
(mef2 act genes form myocyte fusion/anchor/innervation)

34
Q

what factors does mef2 activate

A

mbc

integrin

35
Q

what ptype for lof mbc and integrin

A

mbc -no fusion (mono - poly) but differentiate

integrin - fail to attach properly /not proper cell junction

36
Q

what mechnaism is used to maintain progenitors

A

asym div

37
Q

what is the role of notch in asym div

A

precursors expr notch -
beroe div switch on numb = decr notch
- allows MDF expr as norm notch singal via RBP-j inh mdf

38
Q

what is the pheontype of delta dbl mut mouse

rbpj mut

A

delta
precocious muscle differentiation and cessation of myogenesis
= using up of the muscle precursor pool
RBP-j
less undifferentiated myogenic cells at all stages of development

39
Q

what are satelite cells ?

A

muscle precursor cell remian undiff in adult

expr PAX7 and notch

40
Q

how was the regenerative power of satelite cells shown

A

conditional ko of in differnentiated uscle fibres causes hyperttrophy - satelite cells not effected get over induced to regerate muscle

41
Q

What strucutures does the sclerotome give rise to?

A

bones of the vertebra and ribs

42
Q

what structures does the dermomyotome give rise to

A

dermis and skeletal muscle

Advanced developmental biology (18 decks)

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