[LE2] Lecture 7 Flashcards
(125 cards)
1
Q
- Chordates have ____________
- Vertebrates have __________
- Tetrapods have ________ limbs
- Amphibians are _________ because they don’t have an amnion in their egg
A
notochord
vertebra
jointed
amnions
2
Q
AMPHIBIANS AS EMBRYONIC MODEL:
large eggs, ______ development
A
rapid
3
Q
Amphibians such as Xenopus laevis and Rana pipiens were used frequently in ______________
A
early embryology
4
Q
Fell out of favor because they can’t do _________________. New techniques brought them back into favor.
A
genetic manipulations
5
Q
Interaction of surface glycoproteins or sperm and vitelline envelope and cell membrane in the egg
A
FERTILIZATION AT ANIMAL HEMISPHERE
6
Q
Remember that your frogs are ___________________ and there would be glycoproteins that would allow your sperm to bind
A
external fertilizers
7
Q
Sperm would only bind to the _____________ of the egg
A
animal pole
8
Q
Moving away the dorsal side 30° exposing the grey crescent. (rearrangement of egg cytoplasm)
A
Cortical rotation
9
Q
Fertilization can cause distinct changes in the arrangement of the egg cytoplasm. This is especially important and easily viewed in ____________ eggs
A
amphibian
10
Q
- Amphibian eggs have an animal pole and a vegetal pole
- __________ pole has dark pigment (more pigmented)
- Egg is ______________ around the A-P axis
A
animal
radially symmetrical
11
Q
Sperm can enter anywhere on the ________ pole
A
animal
12
Q
Point of entry would be opposite the ______________
A
grey crescent
13
Q
Once sperm enters, the darkly pigmented cortical (outer) cytoplasm _______________ relative to the clear inner cytoplasm. This exposes some of the more diffuse pigment granules in the animal pole, which appear grey - “grey crescent”
A
rotates (about 30°)
14
Q
Grey crescent is being _________ at first cleavage
A
bisected
15
Q
Reorganization of the ___________ and _________ rotation produce the gray crescent in frog eggs
A
cytoplasm, cortical
16
Q
The radial holoblastic cleavage is __________ because after third cleavage, the animal pole would divide faster than the yolk at the vegetal pole
A
unequal
17
Q
- (cleavage) Eventually would form the ____________ leading to blastula
- _________ prevents the interaction of immature cells
(you don’t want cells to interact with them yet
because you haven’t differentiated them yet)
A
blastocoel
18
Q
How is blastocoel created?
A
Sodium enters the cell and this creates the space
19
Q
An activity that usually describe what are the different locations of the germ layers
A
Fate mapping
20
Q
Blastopore starts at ______________
A
grey crescent
21
Q
Period where zygotic genes are being transcribed, cell cycle acquires gap phases, and blastomeres starts to become motile
A
THE MID-BLASTULA TRANSITION
22
Q
Promoters are ________________ allowing its transcription → play a pivotal role in regulating the timing of __________________
A
demethylated
gene expression
23
Q
Vegetal cells under VegT influence (maternal derived) becomes ___________ and secretes factors that induces cells above it to become mesoderm
A
endoderm
24
Q
[FUNCTION OF GASTRULATION]
- Bring inside the embryo those areas destined to form the ___________ organs
- Surround the embryo with cells capable of forming the _____________
- Place the ___________ cells in the proper positions between the ectoderm and endoderm
A
endoderm (inside)
ectoderm (surround)
mesodermal (between)
25
KEY MOVEMENTS DURING GASTRULATION:
1. Epiboly
2. Vegetal rotation
3. Invagination
4 Involution and Migration
5. Convergent extension
26
Ectoderm completely overline your entire embryo. It starts from the animal pole and will completely close the embryo.
a) Epiboly
b) Vegetal rotation
c) Invagination
d) Involution and Migration
e) Convergent extension
Epiboly
27
Superficial layer will remain the same but the deeper layer will intercalate with each other, which will drive the epiboly because of the thinner layer of cells
Radial intercalation
28
Endoderm would be moving together with the movement of your mesoderm. As it moves, it also brings the endoderm and is rotating internally
a) Epiboly
b) Vegetal rotation
c) Invagination
d) Involution and Migration
e) Convergent extension
VEGETAL ROTATION
29
- ____________ are the ones that invaginate initially creating the formation of where the cells would involute
- This would lead to having a dorsal and ventral __________ lip with the endoderm internalized
Bottle cells
blastopore
30
Dorsal moving to the bilateral lips, eventually forming the ventral lip
INVOLUTION AT THE BLASTOPORE LIP
31
Yolk plug would be the future site of ______
We are _________________ forms the anus first then the stomach/ mouth after
anus
deuterostomes
32
- Transcribe goosecoid gene
- Transcription factors that activate numerous genes for head formation
- Represses Wnt8
Prechordal plate cells
33
- Form the notochord (inducing and patterning the nervous system)
- Expresses tbxt (brachyury) gene
Chordamesoderm
34
- Transcribe hhexgene
- Encodes transcription factor for forming the head and heart
anterior endoderm cells
35
______________ lip cells- precordal plate → precursor of head mesoderm
dorsal blastopore
36
Space that prevents the ectoderm from binding into the underlying mesoderm
Cleft of Brachet
37
Collective cell migration occurs by following the leading cell that is ______________. It is only the ______________ that is able to move along the fibronectin
Lamellipodia
38
Allows that your mesoderm that is thick becomes thinner as it goes in and will eventually form your dorsal mesoderm
CONVERGENT EXTENSION OF THE DORSAL MESODERM
39
Mesodermal cells entering the ________________________ → gives rise to central dorsal mesoderm (notochord and somites)
dorsal blastoporal lips
40
Mesodermal cells entering the ______________________ → gives rise to mesodermal mantle (intermediate and ventral mesoderm) (heart, kidneys, bones, and other organs)
ventral and lateral blastoporal lips
41
Superficial cells of the __________________ zone (part of the vegetal area) → endoderm
involuting marginal
42
Remnant of the blastopore → ______
anus
43
Which germ layer?
epidermis and nerves
Ectoderm
44
Which germ layer?
bone, muscle, heart, blood, kidneys, etc.
Mesoderm
45
Which germ layer?
inner lining of the gut and associated organs
Endoderm
46
SPECIFICATION OF THE GERM LAYERS:
1. _______ encodes for Sox17 needed to activate genes to specify cells to become endoderm
VegT
47
SPECIFICATION OF THE GERM LAYERS:
2. ________ signals accumulation of pmad2 unpregulating eomersodermin and brachyury
Nodal
48
SPECIFICATION OF THE GERM LAYERS:
3. ________ and _________ activate zygotic VegT
eomes, smad 2
49
SPECIFICATION OF THE GERM LAYERS:
4. Animal cap receiving no signals and becomes the ___________
ectoderm
50
___________ would allow the involution at the start of gastrulation
B-catenin
51
What would happen if we tried to get a piece of the dorsal blastoporal lip and transplant it in an area with presumptive epidermis at the early stages of development?
We now have 2 invaginations and 2 involution that will occur forming and inducing secondary structures
52
In the early gastrula, you would notice that if your transferred presumptive neural ectoderm to a presumptive epidermis, it is still the ___________ that forms
epidermis
53
However, if you transplant a presumptive neural ectoderm to a presumptive epidermis, it will now form the _______________. There are already signals from the chordamesoderm.
neural plate
54
Interactions of the dorsal lip blastopore (organizer) and derivatives (notochord and head endomesoderm) cannot completely organize the _______________
whole embryo
55
[THE ORGANIZER ("SMO"): DISCOVERY OF HANS SPEMANN AND HILDE MANGOLD]
Experimental results:
- Induces the host's __________ tissues to change their fates to form a neural tube and dorsal mesodermal tissue
- Organizes host and donor tissues into a _____________ embryo with clear A-P and D-V axes
ventral
secondary
56
- They placed a ligature in 8-cell stage and confined the nucleus in one area
- At 16-cell stage, they allowed the migration of only one nucleus, but it still completed the embryo
- This means that a _________ contains the entire genome related to the formation of the embryo and we have all the maternal determinants still in that cell to allow the development of 2 embryos
nucleus
57
- If one blastomere does not contain a portion of the _______________, it will not form a normal embryo
- Conclusion: ____________ is essential for proper embryonic development
grey crescent
58
What is so special about the grey crescent?
- Fate maps show that these cells form the dorsal lip of the blastopore
- Dorsal lip cells initiate gastrulation
- These cels must be committed when the grey crescent forms
59
Scientists were able to try to look for different signaling molecules in the animal cap cells that lead to the ectoderm, the marginal for the mesoderm, and vegetal cells for the endoderm.
What leads to the formation of the organizer?
There is a Nieuwkoop center that has dorsal mesoderm-inducing signals, and this is what created the Nieuwkoop center which will be related to the formation of the organizer.
60
DORSAL SIGNAL 1: THE ______________ CENTER
NIEUWKOOP
61
The D1, D2, D3, D4 in the 16/32-cell embryo if placed near the animal cap.
○ D1 would form the ________________.
○ D3 would form the ________________.
○ D4 would form the _____________
○ The animal cap doesn't have any signals and this
will be your _________.
dorsal mesoderm
intermediate mesoderm
ventral mesoderm
ectoderm
62
Since the dorsal mesoderm is with the notochord
which will be related with the organizer, the Nieuwkoop Center is found to be in the ____
D1
63
Protein that accumulates in the dorsal portion of the egg after fertilization
DORSAL SIGNAL 2: B-CATENIN
64
2 known functions of B-Catenin
- Cell adhesion
- Nuclear transcription factor
in the WNT signaling pathway; leading to lesser WNT in the
dorsal side
65
The B-catenin was moved from the vegetal pole towards the _________ side during the cortical rotation.
dorsal
66
- B. B-catenin together with disheveled protein was moved toward the area of the _______________
- C. Cortical rotation
- D. It is now Dsh in your GBP protein together with WNT 11.
- E. GSK3 is not inhibited in the dorsal side because you don't have your Wnt, Dsh, & GBP. As such, your GSK3 ____________ your B-catenin leading to no B-catenin in the ventral side. B-catenin is stable in the dorsal side.
- F. B-catenin is located in the ____________ of your blastomere.
grey crescent
degrades
dorsal nucleus
67
_________ & ________ binds to enhance of several genes involved in organizer function
Siamois & Twin
68
Dorsal side of the embryo:
___________ & ________ → specifying dorsal mesoderm
Goosecoid & Xlim1
69
________, _________, ________, ________ → specifies neural ectoderm
Noggin, Chordin, Frzb, Cerberus
70
Ventral side of the embryo:
Combines with vegetal transcription factors → activates _____________ genes
endodermal
71
B-catenin would bind to ______ proteins which would then allow Siamois & Twin to be activated.
Tcf3
72
Siamois & Twin would then bind to the activating region together w/ Smad2, nodal-related proteins, Vg1, activin, etc, to allow organizer molecules or proteins to be _____________
transcribed
73
Without ____________, your Siamois & Twin will not be transcribed so there will be no protein formed.
B-catenin
74
B-catenin continues to accumulate in the _______ most vegetal cells
dorsal
75
However, aside from forming in the dorsal embryo, if Siamois & Twin would be on the _________ side, they would be activating endodermal genes to form your endoderm during the vegetal rotation.
ventral
76
Injection of B-catenin on the ventral side of the embryo induces a _________________
secondary axis
77
Depletion of B-catenin using anti-sense oligonucleotides results in the lack of ________ structures
Basically, B-catenin is needed for the formation of organizer
dorsal
78
DORSAL SIGNAL 3: SYNERGIZING WITH ____________ SIGNALS
VEGETAL
79
B-catenin & VegT, Vg1 are in the initial vegetal side. B-catenin leads to nodal-related proteins being expressed high in the dorsal side. Together with VegT & Vg1, it leads to _________. VegT & Vg1 with nodal-related proteins being low would be the _______________.
organizer
ventral mesoderm
80
_____ has a gradient that is higher in the dorsal side and lower in the ventral side. Further, mesodermal regions that don't have Xnr or little Xnr would have high levels of Bmps and Wnt8, which creates gradients such that high Xnr & low MP4 & Xwnt8 would become the organizer., then there would be a gradient which could be intermediate mesoderm, lateral mesoderm, etc.
Xnr
81
High levels of ________ and _________/________ transcription factor proteins work within the dorsal mesoderm cells and activates the genes giving rise to organizer properties
Smad2
Siamois/Twin
82
__________ pathway → activates genes encoding Siamois & Twin transcription factors
Wnt/ß-catenin
83
_________ pathway → activates expression of Nodal-related paracrine factors which activates Smad2 transcription factors
Vegetal
84
- ____________________ remains endodermal (dorsal most vegetal cells)
- __________ becomes the dorsal mesoderm and positions underneath the dorsal ectoderm
Nieuwkoop Center
Organizer
85
________________ → migration of organizer tissue and induces the forebrain and midbrain
1. Pharyngeal endoderm and head mesoderm (prechordal plate)
86
__________________ → induces hindbrain and trunk
2. Dorsal mesoderm (notochord)
87
____________________ → becomes chordaneural hinge that induces the tip of the tail
3. Dorsal blastopore lip
88
FUNCTIONS OF THE ORGANIZER
1. Self-differentiate into dorsal mesoderm (prechordal plate,chordamesoderm, etc.)
2. Dorsalize the surrounding mesoderm into paraxial (somite-forming) mesoderm
3. Dorsalize the ectoderm and induce the formation of the neural tube
4. Initiate the movements of gastrulation
89
- It is the __________ and _________ mesoderm that is induced to form and not the neural tissue
- Induced by _____________
epidermis and ventral mesoderm
bone morphogenetic proteins (BMPs)
90
Nervous system forms from regions that is protected from _________________ of BMPS
epidermal induction
91
Scientists were looking at the wrong pathway!
They thought we were inducing the neural tube. However, it is actually the ___________________ to form your neural tube. It is with BMPs being secreted that will induce the epithelium.
default ectoderm
92
IN SUMMARY
1. The default fate of the ____________ is to become neural tissue
2. Certain parts of the embryo induce the ectoderm to become epidermal tissue by ______________
3. The organizer tissue acts by secreting molecules that block BMPs, thereby protecting the ectoderm → becomes __________ tissue
1. ectoderm
2. secreting BMPs (primarily BMP4, and BMP2, BMP7, and AMP [anti-dorsalizing morphogenic protein])
3. neural
93
___________ (induced by Siamois & Twin) prevents transcription of bmp4 in the
dorsal region
Goosecoid
94
BMPs in
- Ectoderm _______ genes such as sox3, foxD4, and neurogenin involved in neural tissue
- Mesoderm activates differential mesodermal genes through ______________
repress
BMP4 gradients
95
All of the organizer molecules are needed to ensure that the neural tube will form at the right area which is dorsal to the __________.
organizer
96
_____ is not seen in the dorsalization of the mesoderm.
C: neural tube is forming greater
D: the entire ectoderm becomes neural ectoderm, & there is no dorsal ventral axis because the whole embryo is just your whole neural tissue.
Sox2
97
Bone morphogenetic proteins
- Induces ______________
skin ectoderm
98
BMP antagonists (noggin, chordin, follistatin)
- Specifies ________ ectoderm
neural
99
Decapentaplegic (Dpp) [BMP homologue]
- Induces the _____________
hypodermis (skin)
100
Short gastrulation (Sog) [Chordin homologue]
- Induces _____ & specifies the
__________ system
Dpp, neural
101
(a) If a roof archenteron is implanted in the early gastrula, this leads to a head with a __________; (b) area going caudal; (c) presumptive area; (d) caudal part
balancer
102
Endomesodermal tissues,
- Induces ____________________
anteriormost head structures
103
Blocks Wnts (low in head) and BMPs
Endomesodermal tissues
104
REGIONAL INDUCERS:
- Head inducers
- __________ > adhesive glands, eyes, nasals; Binds BMPs, nodals, Wnts
Cerberus
105
_______, __________ > blocks Wnt, for forebrain
Frzb, Dickkopf
106
______ → anterior neural tube with its brain and sensory placodes
IGFs
107
- Trunk inducers
- _________ → gradient for posterior neural tube
Xwnt8
108
Wnts are blocked in the anterior, while BMPs are blocked in the posterior. In the head, BMPs & Wnts are actually blocked. In the trunk & spinal cord, BMP is blocked. In the ____________, both are expressed such that this creates your Wnt-BMP signaling allowing your anterior or posterior signaling within the amphibian.
epidermis
109
binds Wnt in solution
Frzb
110
binds directly with Wt receptors
dickl = kopf
111
cleaves Wnt to render it
nonfunctional
Tiki
112
removes lipid moiety that keeps Wnt from forming
inactive dimers
notum
113
_______________ GROWTH FACTORS
- Allows anterior neural development
INSULIN-LIKE
114
[INSULIN-LIKE GROWTH FACTORS]
Required to induce the ________ and ________________
Prominent in the ___________ (RTK) signal transduction pathway
brain and sensory placodes
anterior kinase
115
- Interfere the _______ and _______
- ________ also play direct role in the induction and maintenance of genes important for mesodermal lineages & limb outgrowth
BMPs and WnT's
FGFs
116
Wt proteins (especially Wnt8) — _________________ molecules
posteriorizing
117
Wnt and B-catenin — highest in the _________ and absent in the __________
posterior, anterior
118
Wnt, FGF, and retinoic acid gradients function to determine boundaries of ____________
Hox genes
119
- Initial axes of Nodal-like TGF-B paracrine factors and B-catenin
- Induces the ______
D-V and A-P axes
120
- ____ Axis - BMP gradient high in ventral
- _____ Axis - Wnt gradient high in posterior
D-V
A-P
121
The crucial event in this axis formation is the expression of a _______ gene in the lateral plate mesoderm on the left side of the embryo
In Xenopus, this gene is _______
nodal
Xnr1 (Xenopus nodal-related 1)
122
- ____ seems to process Xnr1 into its active form predominantly on the left hand side of the embryo
- ____ → Xnr1 → activates pitx2
Vg1
123
______ persists on the embryo's left side as the head and gut develop, controlling their respective positions
Pitx2
124
Xenopus nodal-related 1 (Xnr1) - possibly encoded by Vg1 on the ______ only
Controlled by Pitx2 and Nodal and microtubules during the ________________
left
first cleavages
125
Mechanical mechanism → cilia formed at the dorsal blastopore lip drives _______________
Located at the posterior region of the embryo - perform a __________ rotation
leftward flow of Nodal
clockwise
