Term
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Definition
rotates relative to the inner cytoplasm
causes the *grey crescent* to form |
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Term
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Definition
MT driven
gives rise to dorsal lip blastopore
commit to invagination into the blastula
initiates gastulation
eventually forms the head endomesoderm and notochord
can differentiate cells during gastulation |
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Term
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Definition
cell cycle goes from biphasic to quint phasic
-blastopore ingresses into the embryo, causing a dorsal lip of the blastopore |
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Term
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Definition
| acts a barrier to prevent vegatal cells from interacting with animal cells prematurely(induction) |
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Term
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Definition
| found out that the vegatal cells release factors that tell the above cells (mesoderm) to become a specific thing |
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Term
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Definition
| splitting or migrating of one sheet into two sheets |
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Term
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Definition
the expansion of one cell sheet over other cells
Driven by Cell Division
and Intercalation
Animal cap expand
to cover the entire
embryo
• Mechanism includes:
– Increase in cell
division
– Integration of
cell deep layers
into one |
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Term
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Definition
| initiated on the future side of the dorsal side of the embryo-just below the grey crescent and across from the sperm entry |
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Term
| early cell movement during gastulation |
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Definition
| cells ingress, then invaginate to form a slit, |
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Term
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Definition
cells changing their shape forming a bottleneck appearence
line the acheneron |
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Term
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Definition
•In salamanders--bottle cells appear to have an active role in the early movements of
gastrulation
•Dorsal marginal zone cells (which would normally give rise to the dorsal lip of the
blastopore) were excised and placed on inner prospective endoderm tissue
Bottle cells sank below the surface of the inner endoderm
Bottle cells created a depression reminiscent of the early blastopore
Bottle cells ability to invaginate into the deep endoderm is an innate property of the
dorsal marginal zone cells |
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Term
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Definition
bottle cells bring the marginal cells in by involution
-cells migrate along the basal surface of the bastocoel roof
- |
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Term
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Definition
| removal stops archenteron formation |
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Term
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Definition
– Involves filopodial extensions
of involuted mesodermal cells
that contact one another
– Requires fibronectin |
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Term
| Differential Cell Cohesion |
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Definition
– Requires adhesion molecules
that include paraxial
protocadherin (somite-forming
mesoderm) and axial
protocadherin (notochord)
• A dominant negative form of
axial protocadherin (secreted
and not membrane bound
form) prevents convergent
extension |
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Term
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Definition
– Increase observed cell/tissues
undergoing convergent
extension
• Regulate contraction of actin
filaments |
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Term
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Definition
oocyte has animal vegetal polarity
A-V provides information about which cells will form which germ layer |
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Term
| vegetal cells(2 functions) |
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Definition
differentiate into endoderm
induce cells above them to become mesoderm |
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Term
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Definition
| dorsal is opposite sperm entry |
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Term
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Definition
| movement on invoulting tissue(head mesoderm)during gastulation |
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Term
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Definition
| process forming dorsal-ventral and anterior-posterior |
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Term
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Definition
dorsal blastopore lip
-primary embryonic induction
-Induce ventral tissues to
change fate to form neural
tube and dorsal
mesoderm (somites)
-Organize through initial
inductive events the
embryos anterior-posterior
and dorsa-ventral axes |
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Term
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Definition
ligation experiment
conclusion from experiment: early amphibian muclei were indentical
each cell was capable of developing a complete organism |
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Term
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Definition
| fate depends on their location in the embryo(cells are uncommitted) |
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Term
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Definition
| their fate was already determined(epidermal and neural) |
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Term
| primary embryonic induction |
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Definition
Numerous inductions during
embryonic development—
key induction dorsal lip cells
induce dorsal axis and
neural tube |
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Term
| induction forms the organizer |
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Definition
recieves signals from the endoderm(the organizer does)
-dorsal most vegetal cells can induce the organizer |
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Term
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Definition
dorsal most vegetal cells
induce animal cells to be come dorsal mesoderm |
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Term
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Definition
Transplantation and Recombination
Experiments (1986)—Demonstrated the existence of the
Nieuwkoop Center |
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Term
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Definition
Β-Catenin is localized
on Dorsal side
•Duel Function:
Transcription factor and
transmembrane protein
•Location:Prior to fertilization-- Β-Catenin
located throughout oocyte
Shortly after fertilization--Β-Catenin
accumulates dorsal region during
early cleavage |
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Term
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Definition
Nieuwkoop Center secretes TGF-
Β Family paracrine factors of which
induces expression of Smad2/4
– Vg1 belongs to TGF-Β family
– Other TGF-Β Family include activin, and
Derriere |
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Term
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Definition
Activation of Organizer by binding of transcription
factors Smad2/4 and Siamois |
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Term
|
Definition
a DNA binding protein
-activated by Nieuwkoop center
activates the migration properties (involution and
convergent extension) of the dorsal blastopore lip
cells
– autonomously determines the dorsal mesodermal
fates of those cells expressing it
– enables the goosecoid-expressing cells to recruit
neighboring cells into the dorsal axis. |
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Term
|
Definition
Β-catenin acts synergistically with VegT and Vg1 to activate transcription of
Xnr (Nodal family)
Vg1 and Xnr = TGF-B Family |
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Term
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Definition
To initiate the movements of gastrulation
• To become dorsal mesoderm
• To dorsalize the surrounding mesoderm into
lateral mesoderm (when it would otherwise form
ventral mesoderm)
• To dorsalize the ectoderm into neural ectoderm
• To cause the neural plate (the induced neural
ectoderm) to become the neural tube
Inhibits Epidermal Inducer,
Thus Neural Tissue is Formed |
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Term
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Definition
Induction of Neural
Ectoderm and Dorsal Mesoderm
• Ectoderm is induced to become epidermal
tissue by binding Bone Morphogeneic
Proteins (BMPs; ex BMP4)
– BMPs are powerful ventralizing factors
• Form dorsalateral muscle, ventral mesenchyme
(blood), ventral lateral plate (kidney), and
epidermal ectoderm (skin)
• Three major BMP inhibitors include
Noggin, Chordin, Follistatin
– Promotes Dorsal Endoderm and Neural
Ectoderm to form |
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Term
| Organizer and Anterior-Posterior Axis and strucure |
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Definition
In Xenopus (and other vertebrates), the formation of the anteriorposterior axis follows the formation of the dorsal-ventral axis.
• Once the dorsal portion of the embryo is established, the movement
of the involuting mesoderm establishes the anterior-posterior axis
• The mesoderm that migrates first through the dorsal blastopore lip
gives rise to the anterior structures
take place at the dorsal blastopore lip |
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Term
| Regional specific induction |
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Definition
•Cells of the organizer to enter the embryo first induce the formation of
brain and head
•Cells entering from the dorsal lip of later-stage embryos induce the
cells to become spinal cord and tail |
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Term
Organizer Function and A-P Axis
Specification in Xenopus |
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Definition
A. Head and Brain Formation:
– Wnt and BMP inhibitors (1
and 2) in the anterior of the
organizer (pharyngeal
mesendoderm) allow the
induction of head structures
by blocking BMP 4 and
XWnt8
• B. Neural Ectoderm and
Trunk Inducer: (1)
– BMP inhibitors from
organizer tissue block the
formation of epidermis
whereas Wnt induces neural
tissue to form
• C. Caudal Inducer: (3)
– Gradient of caudalizing
factors (eFGF, retinoic acid,
and/or Wnt3a) specify
regions of neural tube
through expression of Hox
genes |
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Term
| Left-Right Axis Formation |
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Definition
Two separate molecular mechanisms used to form L-R axis
– Regulated by two factors: paracrine Nodal (Xnr1) and transcription factor Pitx2
• Nodal gene (Xnr1) only expressed on the lateral plate mesoderm on left side of embryo
– Cilia may also play a role in establishing L-R axis
• Cells in organizer have cilia that beat clockwise flow of fluid—possible sweeping Xnr1
predominately to the left and thus activating Pitx2
– Pitx2—controls position of heart and gut |
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