Developmental biology 4 Flashcards
(22 cards)
What key event begins sea urchin gastrulation?
An epithelial to mesenchymal transition (EMT).
Where does gastrulation begin in Drosophila?
On the ventral side, starting with an EMT.
What are defining characteristics of epithelial cells?
Polarized cell sheet
specialized junctions
basal lamina attachment
expression of cytokeratin.
What are defining characteristics of mesenchymal cells?
Secrete ECM
Are flattened
Can be motile (such as fibroblasts)
Unique feature of mesenchymal cells is that they express the protein Vimentin
What are somites and where do they form?
Balls of mesodermal epithelial cells that form on either side of the neural tube and become the segmented vertebral column
Which part of the somite forms back muscles?
The epithelial half that retains e-cadherin expression.
The somites form from separation of the __________ from the anterior to posterior direction. Newer somites will be the more __________ ones.
mesoderm, posterior
Which part of the somite forms ribs and cartilage?
The half that undergoes EMT and loses e-cadherin expression.
What are the steps in EMT induction?
Apical constriction, downregulation of cell-cell adhesion, and upregulation of ECM adhesion.
What do primary mesenchymal cells in sea urchins do to invade?
Detach from the hyaline layer and express proteases to degrade ECM and basal lamina.
What are the two approaches to studying EMT signals?
Genetic models (drosophila) and in vitro culture systems (induce EMT with growth factors)
Which transcription factors regulate EMT in Drosophila?
Twist (activates mesenchymal genes such as ECM adhesion molecules) and Snail (represses epithelial genes such as e-cadherin).
What maternal product regulates Drosophila EMT transcription factors?
Dorsal protein, forming a gradient which is most concentrated on the ventral side.
What change is observed in vitro when EMT is induced with growth factors?
Downregulation of desmosomes, adherens junctions, cytokeratin; upregulation of motility, vimentin.
How does EMT relate to cancer?
Cancer cells undergo EMT during metastasis; blocking EMT could prevent invasion/spread.
How can EMT inhibitors be tested in the lab?
By inducing EMT and observing whether treated cells resist spreading and remain compact.
What do MET events do in kidney development?
Convert mesenchyme to epithelium to form collecting ducts, nephrons, and other kidney structures.
What does the ureteric bud become after MET?
the future collecting duct
What does the metanephrogenic mesenchyme become after MET?
Nephrons, Bowman’s capsules, and podocytes.
What happens between nephron and collecting duct epithelium as development progresses?
The basement membrane breaks down to allow tubule integration.
What was shown when FGF was used on metanephric mesenchyme in vitro?
Tubules formed even without the ureteric bud, suggesting FGF induces MET.
The metanephrogenic mesenchyme and the ureteric bud are both _____________ tissues and ___________ induce each other to undergo the MET.
mesenchymal, reciprocally
