[LE 02] Gastrulation Flashcards

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1
Q

end goal of gastrulation

A

form the 3 germ layers

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2
Q

t or f: blastomere cell fate is already specified prior to gastrulation

A

t

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3
Q

difference between specification and determination

A

specification: cell fate is reversible
determination: cell fate is irreversible

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4
Q

what is “presumptive”

A

can’t say if specified or determined

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5
Q

cell movement which forms the dorsal lip of the blastopore

A

invagination

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6
Q

three cell movements involved in gastrulation

A
  • invagination
  • involution
  • epiboly
  • ingression
  • intercalation
  • convergent extension
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7
Q

what is the goal of epiboly?

A

to cover the cell

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8
Q

when will the yolk plug close during gastrulation?

A

when it is covered with ectoderm via epiboly

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9
Q

cell rearrangements that drive gastrulation

A
  • epiboly
  • vegetal rotation
  • bottle cell formation
  • tissue separation
  • cell migration
  • convergence and extension
  • convergent thickening
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10
Q

it is the rearrangement of cells which initiates invagination and involution

A

bottle cell formation

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11
Q

bottle cell formation forms via

A

apical constriction

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12
Q

t or f: apical constriction promotes tissue remodeling

A

t

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13
Q

what happens during apical constriction?

A

constriction of apical side, expansion of basal side

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14
Q

cell rearrangement wherein the cells go around the animal hemisphere

A

epiboly

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15
Q

cellular movement that is like EMT

A

ingression

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16
Q

what drives epiboly?

A

morphology change

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17
Q

cellular movement that is the specialized form of intercalation

A

convergent extension

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18
Q

t or f: direction does not matter in intercalation

A

f; intercalation is highly directional

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19
Q

where do bottle cells form?

A

at sites of invagination

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20
Q

bottle cells initiate what type of cell movement?

A

involution

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21
Q

these are the apically constricting cells

A

bottle cells

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22
Q

what happens during tissue separation in gastrulation?

A
  • there is a cycling between attachment and detachment
  • attachment triggers repulsion
  • there is reestablishment of contact when the cells are apart
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23
Q

t or f: during tissue separation, the mesoderm can invade the ectoderm

A

f; but it can still use the cells as a substrate for movement

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24
Q

explain the process of involution happening after bottle cell formation

A
  • apical constriction
  • outer marginal zone is pulled vegetally
  • mass of large vegetal cells is pulled directly inward
  • anterior mesoderm is pushed toward the animal pole
  • IMZ is rotated outward
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25
Q

what is the result of involution?

A

reorientation of the anterior marginal zone making it the leading movement into the blastocoel

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26
Q

how does ventral lip of the blastopore form?

A

forms from the progression of ectoderm surrounding the vegetal hemisphere

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27
Q

t or f: convergent extension occur during epiboly

A

t

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28
Q

cellular movement wherein the tissue elongates along one axis and narrows in one or both orthogonal axes

A

convergent extension

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29
Q

steps in the convergent extension of the dorsal mesoderm

A
  • several deep IMZ layers intercalate radially to form one, thin broad layer
  • IMZ extends vegetally because of the intercalation
  • deep cells reach the blastopore lip then involute
  • initiation of 2nd type of intercalation
  • intercalation causes convergent extension along the mediolateral axis
  • formation of a long, narrow band
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30
Q

why is there mediolateral intercalation in the convergent extension of the dorsal mesoderm?

A

to drive migrating mesoderm

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31
Q

effect of the continuous migration of the mesoderm to the animal pole

A

forms an endodermal roof of the archenteron

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32
Q

t or f: derivatives of bottle cells contribute to internal cell arrangements

A

t

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33
Q

processes present in the epiboly of the prospective ectoderm

A

cell division and intercalation

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34
Q

how does the cells of the prospective ectoderm migrate when it undergoes epiboly?

A

it uses fibronectin which assembles into fibrils

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35
Q

t or f: all cells in gastrulation move via convergent extension

A

f

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36
Q

steps in the epiboly of the prospective ectoderm

A
  • 3 rounds of cell division to increase the number of deep layers in the animal hemisphere
  • at the same time, complete integration of the numerous deep cells into one layer
  • superficial layer expands by cell division and flattening
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37
Q

t or f: epiboly of the prospective ectoderm involves convergent extension for cell movement

A

f; it uses fibronectin for migration

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38
Q

different Wnt-related signaling pathways

A
  • beta-catenin pathway
  • PCP/CE pathway
  • Ca2+ pathway
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39
Q

ligands in the beta-catenin pathway

A

Wnt1 and Wnt3a

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40
Q

ligands in the PCP/CE pathway

A

Wnt5a and Wnt11

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41
Q

ligands in the Ca2+ pathway

A

Wnt5a

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42
Q

process of the beta-catenin pathway

A
  • Wnt1 and Wnt3a bind
  • Dvl inhibits GSK-3beta, APC, and axin complex
  • beta-catenin is expressed
  • beta-catenin binds to Tcf/Lef
  • there is gene expression: cell proliferation and differentiation
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43
Q

end result of the beta-catenin pathway

A

gene expression: cell proliferation and differentiation

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44
Q

steps of the PCP/CE pathway

A
  • Wnt5a and Wnt11 binds
  • Dvl produces either RhoA or Rac
  • RhoA:Rho-kinase and Rac:JNK
  • act on cytoskeleton
  • cell polarity, cell migration
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45
Q

result of the PCP/CE pathway

A

cell polarity and migration

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46
Q

steps in the Ca2+ pathway

A
  • Wnt5a binds
  • Dvl induces production of Ca2+
  • Ca2+: CaMK or PKC
  • inhibits binding of beta-catenin to Tcf/Lef
  • cell migration, inhibition of beta-catenin pathway
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47
Q

draw the different wnt-related signaling pathways

A

gow

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48
Q

how is polarity established/regulated in cells?

A

thru the differential recruitment of protein complexes on opposite sides of the cell

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49
Q

protein that is responsible for the regulation of cell polarity

A

wnt gradient

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50
Q

how is polarity established by the complexes?

A

there is inhibition so that the complexes do not form on the same side

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51
Q

t or f: in regulation of polarity, the complexes inhibit extracellularly

A

f; bati sila extracellularly

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52
Q

proteins in polarity regulation that antagonize each other

A

Dgo and Dsh against Pk and vanguard

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53
Q

pathway regulated in the regulation of polarity

A

PCP pathway

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54
Q

pathway that regulates apical constriction during epithelial morphogenesis

A

PCP pathway

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55
Q

what triggers contraction in the process of apical constriction

A

myosin II

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56
Q

epithelial markers

A
  • E-cadherin
  • epithelial cell adhesion
  • occludins
  • claudins
  • alpha6 beta4 integrin
  • cytokeratins
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57
Q

mesenchymal markers

A
  • N-cadherin
  • Vimentin
  • Fibronectin
  • beta1 and beta3 integrins
  • MMPs
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58
Q

transcription factors in the maintenance of the epithelial state of cells

A
  • Crumbs
  • PATJ
  • LGL
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59
Q

t or f: fibrillogenesis can be in the folded state

A

t; if there is no need for long distance migration

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60
Q

mesenchymal marker which degrades ECM

A

MMPs

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61
Q

why do MMPs degrade the ECM?

A

it can be a barrier to cell movement

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62
Q

mesenchymal markers which are important for transient adhesions

A

beta1 and beta3 integrins

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63
Q

epithelial marker which is found in hemidesmosomes and keeps the cell attached to cell

A

alpha6 beta4 integrins

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64
Q

t or f: epithelial tissues does not have fibronectin

A

f; it does but there is difference in expression

65
Q

regulators of the EMT

A
  • ZEB family
  • SNAIL and/or SLUG
  • TWIST1
66
Q

what shall be done for epithelial to mesenchymal transition to happen?

A

inhibit the epithelial markers

67
Q

why does a blastocoel form?

A

it serves as a barrier to signals to prevent the cell into differentiating to mesoderm only; no ectoderm formation

68
Q

t or f: the vegetal hemisphere has inductive signals that induces the formation of the mesoderm

A

t

69
Q

it is the specification that induces the formation of the endoderm and mesoderm

A

bottom-up specification

70
Q

it is the endoderm specifying factor

A

nodal

71
Q

it induces the formation of mesoderm

A

eomes

72
Q

gradient established by cortical rotation across the blastula

A

beta-catenin

73
Q

t or f: dorsal side of the blastula is maintained because of beta-catenin

A

t

74
Q

is inhibited to maintain the dorsal side of the blastula

A

GSK-3

75
Q

t or f: GSK-3 is found in the ventral side of the blastula

A

t

76
Q

what degrades the beta-catenin at the ventral side of the blastula?

A

GSK-3

77
Q

t or f: beta-catenin is stable on the ventral side of the blastula

A

f; dorsal side

78
Q

t or f: the ventral side of the blastula is enriched with Dsh

A

f; dorsal side

79
Q

why is beta-catenin stable in the dorsal side of the blastula?

A

because Dsh inhibits GSK-3 which degrades beta-catenin thus it is abundant in the dorsal side

80
Q

it establishes a beta-catenin gradient across the blastula

A

cortical rotation

81
Q

it is a signal in the blastula which can diffuse upwards to induce the formation of mesoderm

A

Xnr

82
Q

t or f: Xnr is highest in the ventral side of the blastula

A

f; dorsal side

83
Q

t or f: beta-catenin and VegT and Vg1 exist at the same time in the blastula

A

t

84
Q

nodal expression is induced by what signal?

A

VegT

85
Q

t or f: the organizer center in the blastula has the highest Xnr expression

A

t

86
Q

t or f: the gradient of BMP4 and Xwnt in the blastula is not induced by Xnr

A

f

87
Q

signal that is blocked by the blastocoel

A

Xnr

88
Q

signals that induce the expression of Xnr

A

VegT, Vg1, and beta-catenin

89
Q

t or f: nodal can induce both eomes and VegT

A

t

90
Q

t or f: high concentrations of Xnr does not repress BMP4 and Xwnt in the blastula

A

f

91
Q

where are BMP4 and Xwnt-8 found in the blastula?

A

ventral mesoderm

92
Q

t or f: Xnr induces a gradient of BMP4 and Xwnt-8 in the blastula

A

t

93
Q

t or f: the gradient of Xnr is found in the mesoderm

A

f; endoderm

94
Q

t or f: factors in the vegetal hemisphere induces ectoderm and mesoderm specification

A

f; endoderm and mesoderm

95
Q

t or f: factors in the animal hemisphere induces ectoderm specification

A

t

96
Q

t or f: factors in the vegetal hemisphere induces the specification of ectoderm

A

f; animal hemisphere

97
Q

signals inhibited in the ectoderm area

A

nodal/ activin

98
Q

signals inhibited in the ventral side of the blastula

A

Wnt/ beta-catenin

99
Q

signals inhibited in the dorsal side of the blastula

A
  • axin
  • GSK3
  • GBP
  • beta-Trcp
100
Q

signals inhibited to maintain an endoderm area

A
  • norrin
  • coco
  • ectodermin
101
Q

it is the primary organizer in the blastula

A

spemann-mangolds organizer

102
Q

spemann-mangolds organizer induces the formation of what structures?

A

neural tube and mesoderm

103
Q

experiment that found out that a specific tissue is an organizer

A

transplant of the dorsal lip to another’s belly region and 2 notochords were developed thus two specimens developed

104
Q

t or f: the spemann-mangold organizer is found in the dorsal lip of the blastula

A

t

105
Q

this induces the spemann-mangolds organizer

A

nieuwkoop center

106
Q

t or f: NC forms even in regions without the overlap between beta-catenin and Vg1

A

f; forms only in the region with overlap

107
Q

organizer proteins

A

chordin, noggin, and goosecoid

108
Q

protein s that induce the expression of the organizer proteins in the blastula

A

siamois and twin

109
Q

what induces the signals that induce the expression of organizer proteins?

A

beta-catenin

110
Q

t or f: beta-catenin is enough to form the NC

A

f; needs Vg1 as well

111
Q

steps in the expression of the organizer proteins

A
  • beta-catenin binds to Tcf3 proteins
  • siamois and twin are expressed
  • siamois and twin plus Vg1-induced proteins induce the expression of organizer proteins
112
Q

t or f: without beta-catenin, the expression of the organizer proteins is still possible

A

f

113
Q

steps in the formation of the blastocoel in the chick embryo

A
  • blastodisc forms through cell division(?)
  • formation of the subgerminal cavity
  • epiblast thickens
  • hypoblast develops
114
Q

hypoblast islands form through what cell movement?

A

delamination

115
Q

hypoblast islands come from what layer?

A

epiblast

116
Q

hypoblast gives rise to what structure?

A

entire yolk sac

117
Q

how does the hypoblast layer form?

A
  • hypoblast islands form
  • secondary hypoblast cells from the area near koller’s sickle go anteriorly to join the primary hypoblast cells
118
Q

structure near the formation of the hypoblast cells

A

koller’s sickle

119
Q

t or f: hensen’s node is also responsible for cell migration

A

t

120
Q

steps in the formation of the primitive streak

A
  • posterior epiblast cells change shape and thicken
  • cells migrate, converging at the primitive streak which causes it to elongate
  • PS narrows and lengthens
  • primitive groove is formed
  • cells migrate inward into the gastrula through the primitive groove and hensen’s node
121
Q

t or f: cells migrating over the sides of the primitive groove form the mesoderm and ectoderm

A

f; mesoderm and endoderm

122
Q

it is the chick blastopore

A

primitive groove

123
Q

cells generated in hensen’s node and passing into the gastrula moves anteriorly to form what structures?

A

head structures and notochord

124
Q

t or f: the hypoblast is displaced by spreading endoderm

A

t

125
Q

these thickens and change shape to form the PS

A

posterior epiblast cells

126
Q

cell movement involved in cells moving into the PS

A

ingression

127
Q

t or f: cells move into the PS via involution

A

f; ingression

128
Q

t or f: the epiblast cells lose their epithelial character as they move into the PS

A

t

129
Q

transition involved in the movement of epiblast cells into the PS

A

EMT

130
Q

t or f: epiblast cells ingress into the PS in groups

A

f; they ingress one by one

131
Q

t or f: there is a basement membrane at the site of EMT in the PS

A

f

132
Q

mesenchyme cells become the endoderm via

A

MET

133
Q

t or f: humans also form the PS

A

t

134
Q

the trophoblast in humans become what structure?

A

chorion

135
Q

special epiblast structure formed during human gastrulation

A

polarized epiblast rosette

136
Q

in human gastrulation, the epiblast cells in contact with the overlying trophoblast gives rise to

A

amnion

137
Q

after the formation of the PS, this structure is the source of signals such as Shh

A

notochord

138
Q

the notochord elongates and extends toward what structure?

A

oropharyngeal membrane

139
Q

the left axis requires these active signals

A
  • nodal
  • pitx2
140
Q

it is a signal induced by Shh which is a positive regulator for nodal for the determination of the left axis

A

lefty1

141
Q

it is a signal blocked by nodal to activate Pitx2

A

snail or cSnR

142
Q

signal that inhibits nodal during the determination of the right axis

A

BMP

143
Q

the right axis activates this signal

A

activin

144
Q

signal blocked by activin in the right axis

A

Shh

145
Q

signal induced by BMP4 to block Pitx2

A

snail or cSnR

146
Q

t or f: if Shh is blocked, the left axis is determined

A

f; right axis

147
Q

t or f: in the absence of Pitx2, the right axis is determined

A

t

148
Q

t or f: if cSnR is active, left axis is determined

A

f

149
Q

signal that induces the expression of BMP4 in the right axis

A

activin

150
Q

roles of BMP4 in the determination of the right axis

A
  • blocks Shh
  • induces cSnR
151
Q

role of cSnR in the right axis determination

A

blocks Pitx2

152
Q

these regulate the anterior-posterior patterning in gastrulation

A

hox genes

153
Q

these are the anteriorizing genes

A
  • wnt
  • chordin and noggin
  • lefty
  • dickkopf
  • cerberus
154
Q

these are the posteriorizing genes in gastrulation

A
  • nodal
  • wnt
  • BMP
  • FGFs
  • RA
155
Q

anteriorizing gene that are BMP antagonists

A

chordin and noggin

156
Q

t or f: wnt is both an anteriorizing and posteriorizing gene

A

t

157
Q

mutant of this gene causes body pattern defects

A

homeotic complex C or hox genes

158
Q

t or f: hox genes are the same throughout the body region

A

f; they are unique

159
Q

t or f: hox genes are important for vertebra patterning

A

t