Early Invertebrate Development Flashcards
What is autonomous cell fate specification?
A cellular response that can be attributed to a cellular of molecular mechanism occurring within that same cell.
What is non-autonomous cell fate specification?
A cellular response that occurs due to the influence of another cell or external factor.
What is meant by a “double-negative gate”?
A repressor which acts on a repressor, causing activation.
What is the purpose of the Notch signalling pathway?
To promote proliferative signalling during neurogenesis. Regulator of embryonic development.
How is nuclear beta-catenin linked to the endomesoderm?
More nuclear beta-catenin = more endomesoderm. Less nuclear beta-catenin = less endomesoderm.
What signalling steps follow the activation of Pmar1 by beta-catenin?
Pmar1 represses HesC, stopping repression of Tbr, Delta, Ets, and Dri (double-negative gate).
What developmental process is allowed to proceed upon inactivation of HesC?
Skeletogenic diffferentiation by Tbr, Ets, and Dri. Delta activated to stimulate the Notch signalling pathway.
What is ChIP? (3 steps)
Chromatin immunoprecipitation.
- Crosslink DNA/protein
- Fragment DNA
- Precipitate DNA of interest with protein-specific antibody
What 3 phases describe gastrulation?
- Mesenchymal cells migrate from endoderm to blastoceal
- Vegetal plate “invaginates” the blastoceal (=primitive gut)
- Secondary mesenchyme delaminates and enters blastoceal
What is meant by “induction”?
The non-autonomous effect of one cell on other cells during development.
In the Wnt signalling pathway, what occurs in the absence of Wnt?
Ubiquitin-mediated proteosome degradation.
What main feature differentiates gastrulation in deuterostomes from gastrulation in protostomes?
Deuterostomes: gastrulation begins at anus
Protostomes: gastrulation begins at mouth
What is the “imaginal rudiment” in a pluteus?
The very early sea urchin. A pentagonal structure which is nurtured within the pluteus until it matures, becoming an adult sea urchin.
What is the “archenteron”?
A primitive gut structure produced by invagination during the sea urchin blastula stage.
During sea urchin gastrulation, which cells are responsible for inducing endoderm formation? What do these cells become later in development?
The micromeres become the mesoderm in the sea urchin blastula, but are able to induce endoderm formation.
What differentiates a cell which is specified from one which is determined?
Specification: fate is established but can still be influenced by outside factors
Determination: fate of the cell is fixed and unchangeable
What element and molecule are crucial for cell adhesion and release?
Cadherin mediates cell-cell adhesion, calcium disrupts.
In the sea urchin embryo, what cells are fated to become ectoderm? What about endoderm and mesoderm?
Ectoderm: an1 and an2
Endoderm: veg1 and veg2
Mesoderm: large/small micromeres
What tissues are derived from the ectoderm?
Epidermis, CNS, neural crest.
What tissues are derived from the mesoderm?
Notochord, bone, blood, muscle, kidney tubules.
What tissues are derived from the endoderm?
Digestive tract, thyroid, Respiratory tract, germ cells.
What is the purpose of cyclin? When is it active?
Linked to mitosis, required for chromatin condensation and spindle formation.
How does radial cleavage differ from displaced radial cleavage?
Identical except in displaced radial cleavage the first horizontal cleavage is not equidistant from the poles.
How are cellular processes initiated and regulated in the early embryo given that transcription is not active?
Mainly through phosphorylation, also proteolytic cleavage.
How can cyclin allow for faster cell division during early development?
By bypassing G1 and G2 phases of cell division.
At what stage of the cell cycle do mammalian eggs get arrested prior to fertilization?
Second metaphase.
What is Silver-Russell syndrome? What might cause this?
Intra-uterine and postnatal growth restriction, facial dysmorphism, dwarfism. Likely results from the loss of DNA methylation regulating IGF2 and H19.
What 2 important regions are imprinted by DNA methylation in human sperm?
The regions which code for the expression of IGF2 and H19.
What requires imprinting by methylation to be fully functional? (4 things)
- Cell proliferation
- Embryonic/extraembryonic development
- Fitness
- Behaviour
Are male and female pronuclei equivalent? Why? Why not?
No, mammalian pronuclei are non-equivalent because they each have some of the necessary imprinting (DNA methylation) for development but not all.
