Lecture 5 - Cell Differentiation and Neural Induction V Flashcards
the role of beta catenin
accumulates in the region that gives rise to endoderm (ventral to dorsal lip) induces nearby cells give rise to mesoderm; maternally deposited
overexpression of beta catenin
affect prenatal brain development
proneural genes
essential for the development of the NS in drosophila (achaete, scute, sog, dpp)
AS-C
transcriptional factor, expression is first step to becoming neural cells
sog
insect homologue of chordin
dpp
insect homologue of BMP
delamination
one cell detaches from the sheet of neighboring cells
neuroblast
a cell that will divide to produce neural cells
how a neuroblast is chosen
- AS-C is expressed, intensifies in only one of the rosette (center)
- neighbors expression of AS-C diminishes
- the cell with highest AS-C level delaminates to become a neuroblast
- neighbors stop expressing and become epidermal cells (ventral skin)
competition for neuroblast
after delaminated cell is killed, another will delaminate > shows communication
notch
encodes notch protein, membrane-bound receptor that binds to delta
mutations in notch
overabundance of neuroblasts
Enhancer of split
promotes expression of AS-C
AS-C promotes expression of…
delta
binding of delta to notch
causes intracellular portion of notch to detach and bind to enhancer of split, forming a heterodimer (TF) to inhibit AS-C expression
without AS-C
delta is not expressed; cells next to delta expressing cell will not express it themselves
DSH
accumulation of beta catenin on dorsal side; inhibits GSK-3 (which inhibits beta catenin) > GSK degrades beta catenin, DSH inhibits GSK
lateral inhibition in insect ectodermal cells
- rosette expresses AS-C, promoting expression of notch and delta
- each cell inhibits neighbors by expressing delta, activating notch in the neighbor to suppress proneural genes
- one cell is still expressing proneural genes and delta (neuroblast)
why the neuroblast tends to come from the center
position > center of mesodermal signaling for proneural expression; got more signal and made more delta
