Gastrulation Flashcards
What are the characteristics of a common vertebrate body plan?
notochord
hollow dorsal neural tube with distinct brain vesicles
somites (extend to the tail)
pharyngeal arches
similar expression pattern of developmental genes
What is derived from ectoderm?
epidermis
CNS (also partially PNS)
sensory organs
melanocytes
What is derived from mesoderm?
muscles bones kidneys gonads adrenal glands heart blood
What is derived from endoderm?
digestive tract liver pancreas pharynx thymus thyroid gland
Gastrulation morphogenetic movements are evolutionary conserved. What is emboly?
meso- and endodermal cells become internalized
Gastrulation morphogenetic movements are evolutionary conserved. What is epiboly?
germ layers are spread and thinned
Gastrulation morphogenetic movements are evolutionary conserved. What is convergence?
germ layers are narrowed dorsoventrally
Gastrulation morphogenetic movements are evolutionary conserved. What is extension?
germ layers are elongated along AP axis
When does the gastrulation start in xenopus?
when cell in the region of the grey crescent move inward –> dorsal blastopore lip formation
What happens after DBL formation in xenopus?
cells of the animal pole spread out push surface cells toward and across the dorsal lip (epiboly) cells move into the interior of the embryo form endo- and mesoderm archenteron cavity (future digestive tract) becomes bigger, blastocoel dissapears blastopore lip forms a circle (cells moving to the interior all around; yolk plug visible in the middle)
What is the equivalent of DBL in zebrafish?
shield around the yolk
Which cells drive convergence and extension of the embryo?
mesenchymal
What is the difference between radial and mediolateral intercalation?
radial: several LAYERS intercalate along the radius of the embryo –> form fewer layers, but greater area
mediolateral: several ROWS intercalate along the mediolateral axis –> form longer and narrower array
What is the equivalent of DBL in mammals?
primitive streak
and
Hensen’s node at the anterior end
What happens during gastrulation in chick embryos?
- primary hypoblast cells delaminate individually (form island cells beneath the epiblast)
- secondary hypoblast cells (derived from deep yolky cells at posterior margin) migrate beneath the epiblast
- come Koller’s sickle
- incorporate island cells and push them anteriorly
- secondary hypoblast forms beneath the epiblast
= 2-layered blastoderm with blastocoel between them - as hypoblast moves towards A pole, epiblast cells collect at the region anterior to Koller’s sickle -> thickening -> PRIMITIVE STREAK with Hensen’s node at the A end
What controls cellular movements during gastrulation?
movements coordinated with cell fate specification
for gastrulation movements, position of distinct identities along the axes is required
–> created by Wnt PLANAR CELL POLARITY PATHWAY (PCP)
Which signals specify the mesoderm and endoderm during gastrulation?
Nodal paracrine signaling:
- Nodal in the vegetal pole
In xenopus: what is the role of Wnt signaling in the embryo?
Dorsal enrichment of Dsh and GBP, accumulation of B-catenin -> Siamois and Twin proteins -> transcription of organizer genes
Wnt &
B-catenin;
Nodal &
TGF-B role?
DV patterning
mesoderm induction
What is the difference between conditional (regulative) development and autonomous development?
Conditional: early gastrula - fate of the transplant depends on the location in the host embryo (EXCEPT: DBL)
Autonomous: late gastrula - the fate of the transplant is already determined and develops as in the donor embryo
