[LE 02] Gastrulation Flashcards
1
Q
end goal of gastrulation
A
form the 3 germ layers
2
Q
t or f: blastomere cell fate is already specified prior to gastrulation
A
t
3
Q
difference between specification and determination
A
specification: cell fate is reversible
determination: cell fate is irreversible
4
Q
what is “presumptive”
A
can’t say if specified or determined
5
Q
cell movement which forms the dorsal lip of the blastopore
A
invagination
6
Q
three cell movements involved in gastrulation
A
- invagination
- involution
- epiboly
- ingression
- intercalation
- convergent extension
7
Q
what is the goal of epiboly?
A
to cover the cell
8
Q
when will the yolk plug close during gastrulation?
A
when it is covered with ectoderm via epiboly
9
Q
cell rearrangements that drive gastrulation
A
- epiboly
- vegetal rotation
- bottle cell formation
- tissue separation
- cell migration
- convergence and extension
- convergent thickening
10
Q
it is the rearrangement of cells which initiates invagination and involution
A
bottle cell formation
11
Q
bottle cell formation forms via
A
apical constriction
12
Q
t or f: apical constriction promotes tissue remodeling
A
t
13
Q
what happens during apical constriction?
A
constriction of apical side, expansion of basal side
14
Q
cell rearrangement wherein the cells go around the animal hemisphere
A
epiboly
15
Q
cellular movement that is like EMT
A
ingression
16
Q
what drives epiboly?
A
morphology change
17
Q
cellular movement that is the specialized form of intercalation
A
convergent extension
18
Q
t or f: direction does not matter in intercalation
A
f; intercalation is highly directional
19
Q
where do bottle cells form?
A
at sites of invagination
20
Q
bottle cells initiate what type of cell movement?
A
involution
21
Q
these are the apically constricting cells
A
bottle cells
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
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
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
25
what is the result of involution?
reorientation of the anterior marginal zone making it the leading movement into the blastocoel
26
how does ventral lip of the blastopore form?
forms from the progression of ectoderm surrounding the vegetal hemisphere
27
t or f: convergent extension occur during epiboly
t
28
cellular movement wherein the tissue elongates along one axis and narrows in one or both orthogonal axes
convergent extension
29
steps in the convergent extension of the dorsal mesoderm
- 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
30
why is there mediolateral intercalation in the convergent extension of the dorsal mesoderm?
to drive migrating mesoderm
31
effect of the continuous migration of the mesoderm to the animal pole
forms an endodermal roof of the archenteron
32
t or f: derivatives of bottle cells contribute to internal cell arrangements
t
33
processes present in the epiboly of the prospective ectoderm
cell division and intercalation
34
how does the cells of the prospective ectoderm migrate when it undergoes epiboly?
it uses fibronectin which assembles into fibrils
35
t or f: all cells in gastrulation move via convergent extension
f
36
steps in the epiboly of the prospective ectoderm
- 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
37
t or f: epiboly of the prospective ectoderm involves convergent extension for cell movement
f; it uses fibronectin for migration
38
different Wnt-related signaling pathways
- beta-catenin pathway
- PCP/CE pathway
- Ca2+ pathway
39
ligands in the beta-catenin pathway
Wnt1 and Wnt3a
40
ligands in the PCP/CE pathway
Wnt5a and Wnt11
41
ligands in the Ca2+ pathway
Wnt5a
42
process of the beta-catenin pathway
- 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
43
end result of the beta-catenin pathway
gene expression: cell proliferation and differentiation
44
steps of the PCP/CE pathway
- Wnt5a and Wnt11 binds
- Dvl produces either RhoA or Rac
- RhoA:Rho-kinase and Rac:JNK
- act on cytoskeleton
- cell polarity, cell migration
45
result of the PCP/CE pathway
cell polarity and migration
46
steps in the Ca2+ pathway
- 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
47
draw the different wnt-related signaling pathways
gow
48
how is polarity established/regulated in cells?
thru the differential recruitment of protein complexes on opposite sides of the cell
49
protein that is responsible for the regulation of cell polarity
wnt gradient
50
how is polarity established by the complexes?
there is inhibition so that the complexes do not form on the same side
51
t or f: in regulation of polarity, the complexes inhibit extracellularly
f; bati sila extracellularly
52
proteins in polarity regulation that antagonize each other
Dgo and Dsh against Pk and vanguard
53
pathway regulated in the regulation of polarity
PCP pathway
54
pathway that regulates apical constriction during epithelial morphogenesis
PCP pathway
55
what triggers contraction in the process of apical constriction
myosin II
56
epithelial markers
- E-cadherin
- epithelial cell adhesion
- occludins
- claudins
- alpha6 beta4 integrin
- cytokeratins
57
mesenchymal markers
- N-cadherin
- Vimentin
- Fibronectin
- beta1 and beta3 integrins
- MMPs
58
transcription factors in the maintenance of the epithelial state of cells
- Crumbs
- PATJ
- LGL
59
t or f: fibrillogenesis can be in the folded state
t; if there is no need for long distance migration
60
mesenchymal marker which degrades ECM
MMPs
61
why do MMPs degrade the ECM?
it can be a barrier to cell movement
62
mesenchymal markers which are important for transient adhesions
beta1 and beta3 integrins
63
epithelial marker which is found in hemidesmosomes and keeps the cell attached to cell
alpha6 beta4 integrins
64
t or f: epithelial tissues does not have fibronectin
f; it does but there is difference in expression
65
regulators of the EMT
- ZEB family
- SNAIL and/or SLUG
- TWIST1
66
what shall be done for epithelial to mesenchymal transition to happen?
inhibit the epithelial markers
67
why does a blastocoel form?
it serves as a barrier to signals to prevent the cell into differentiating to mesoderm only; no ectoderm formation
68
t or f: the vegetal hemisphere has inductive signals that induces the formation of the mesoderm
t
69
it is the specification that induces the formation of the endoderm and mesoderm
bottom-up specification
70
it is the endoderm specifying factor
nodal
71
it induces the formation of mesoderm
eomes
72
gradient established by cortical rotation across the blastula
beta-catenin
73
t or f: dorsal side of the blastula is maintained because of beta-catenin
t
74
is inhibited to maintain the dorsal side of the blastula
GSK-3
75
t or f: GSK-3 is found in the ventral side of the blastula
t
76
what degrades the beta-catenin at the ventral side of the blastula?
GSK-3
77
t or f: beta-catenin is stable on the ventral side of the blastula
f; dorsal side
78
t or f: the ventral side of the blastula is enriched with Dsh
f; dorsal side
79
why is beta-catenin stable in the dorsal side of the blastula?
because Dsh inhibits GSK-3 which degrades beta-catenin thus it is abundant in the dorsal side
80
it establishes a beta-catenin gradient across the blastula
cortical rotation
81
it is a signal in the blastula which can diffuse upwards to induce the formation of mesoderm
Xnr
82
t or f: Xnr is highest in the ventral side of the blastula
f; dorsal side
83
t or f: beta-catenin and VegT and Vg1 exist at the same time in the blastula
t
84
nodal expression is induced by what signal?
VegT
85
t or f: the organizer center in the blastula has the highest Xnr expression
t
86
t or f: the gradient of BMP4 and Xwnt in the blastula is not induced by Xnr
f
87
signal that is blocked by the blastocoel
Xnr
88
signals that induce the expression of Xnr
VegT, Vg1, and beta-catenin
89
t or f: nodal can induce both eomes and VegT
t
90
t or f: high concentrations of Xnr does not repress BMP4 and Xwnt in the blastula
f
91
where are BMP4 and Xwnt-8 found in the blastula?
ventral mesoderm
92
t or f: Xnr induces a gradient of BMP4 and Xwnt-8 in the blastula
t
93
t or f: the gradient of Xnr is found in the mesoderm
f; endoderm
94
t or f: factors in the vegetal hemisphere induces ectoderm and mesoderm specification
f; endoderm and mesoderm
95
t or f: factors in the animal hemisphere induces ectoderm specification
t
96
t or f: factors in the vegetal hemisphere induces the specification of ectoderm
f; animal hemisphere
97
signals inhibited in the ectoderm area
nodal/ activin
98
signals inhibited in the ventral side of the blastula
Wnt/ beta-catenin
99
signals inhibited in the dorsal side of the blastula
- axin
- GSK3
- GBP
- beta-Trcp
100
signals inhibited to maintain an endoderm area
- norrin
- coco
- ectodermin
101
it is the primary organizer in the blastula
spemann-mangolds organizer
102
spemann-mangolds organizer induces the formation of what structures?
neural tube and mesoderm
103
experiment that found out that a specific tissue is an organizer
transplant of the dorsal lip to another's belly region and 2 notochords were developed thus two specimens developed
104
t or f: the spemann-mangold organizer is found in the dorsal lip of the blastula
t
105
this induces the spemann-mangolds organizer
nieuwkoop center
106
t or f: NC forms even in regions without the overlap between beta-catenin and Vg1
f; forms only in the region with overlap
107
organizer proteins
chordin, noggin, and goosecoid
108
protein s that induce the expression of the organizer proteins in the blastula
siamois and twin
109
what induces the signals that induce the expression of organizer proteins?
beta-catenin
110
t or f: beta-catenin is enough to form the NC
f; needs Vg1 as well
111
steps in the expression of the organizer proteins
- 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
t or f: without beta-catenin, the expression of the organizer proteins is still possible
f
113
steps in the formation of the blastocoel in the chick embryo
- blastodisc forms through cell division(?)
- formation of the subgerminal cavity
- epiblast thickens
- hypoblast develops
114
hypoblast islands form through what cell movement?
delamination
115
hypoblast islands come from what layer?
epiblast
116
hypoblast gives rise to what structure?
entire yolk sac
117
how does the hypoblast layer form?
- hypoblast islands form
- secondary hypoblast cells from the area near koller's sickle go anteriorly to join the primary hypoblast cells
118
structure near the formation of the hypoblast cells
koller's sickle
119
t or f: hensen's node is also responsible for cell migration
t
120
steps in the formation of the primitive streak
- 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
t or f: cells migrating over the sides of the primitive groove form the mesoderm and ectoderm
f; mesoderm and endoderm
122
it is the chick blastopore
primitive groove
123
cells generated in hensen's node and passing into the gastrula moves anteriorly to form what structures?
head structures and notochord
124
t or f: the hypoblast is displaced by spreading endoderm
t
125
these thickens and change shape to form the PS
posterior epiblast cells
126
cell movement involved in cells moving into the PS
ingression
127
t or f: cells move into the PS via involution
f; ingression
128
t or f: the epiblast cells lose their epithelial character as they move into the PS
t
129
transition involved in the movement of epiblast cells into the PS
EMT
130
t or f: epiblast cells ingress into the PS in groups
f; they ingress one by one
131
t or f: there is a basement membrane at the site of EMT in the PS
f
132
mesenchyme cells become the endoderm via
MET
133
t or f: humans also form the PS
t
134
the trophoblast in humans become what structure?
chorion
135
special epiblast structure formed during human gastrulation
polarized epiblast rosette
136
in human gastrulation, the epiblast cells in contact with the overlying trophoblast gives rise to
amnion
137
after the formation of the PS, this structure is the source of signals such as Shh
notochord
138
the notochord elongates and extends toward what structure?
oropharyngeal membrane
139
the left axis requires these active signals
- nodal
- pitx2
140
it is a signal induced by Shh which is a positive regulator for nodal for the determination of the left axis
lefty1
141
it is a signal blocked by nodal to activate Pitx2
snail or cSnR
142
signal that inhibits nodal during the determination of the right axis
BMP
143
the right axis activates this signal
activin
144
signal blocked by activin in the right axis
Shh
145
signal induced by BMP4 to block Pitx2
snail or cSnR
146
t or f: if Shh is blocked, the left axis is determined
f; right axis
147
t or f: in the absence of Pitx2, the right axis is determined
t
148
t or f: if cSnR is active, left axis is determined
f
149
signal that induces the expression of BMP4 in the right axis
activin
150
roles of BMP4 in the determination of the right axis
- blocks Shh
- induces cSnR
151
role of cSnR in the right axis determination
blocks Pitx2
152
these regulate the anterior-posterior patterning in gastrulation
hox genes
153
these are the anteriorizing genes
- wnt
- chordin and noggin
- lefty
- dickkopf
- cerberus
154
these are the posteriorizing genes in gastrulation
- nodal
- wnt
- BMP
- FGFs
- RA
155
anteriorizing gene that are BMP antagonists
chordin and noggin
156
t or f: wnt is both an anteriorizing and posteriorizing gene
t
157
mutant of this gene causes body pattern defects
homeotic complex C or hox genes
158
t or f: hox genes are the same throughout the body region
f; they are unique
159
t or f: hox genes are important for vertebra patterning
t
