Lecture 5 - Cell Differentiation and Neural Induction V

Question 1

the role of beta catenin

Answer 1

accumulates in the region that gives rise to endoderm (ventral to dorsal lip) induces nearby cells give rise to mesoderm; maternally deposited

Question 2

overexpression of beta catenin

Answer 2

affect prenatal brain development

Question 3

proneural genes

Answer 3

essential for the development of the NS in drosophila (achaete, scute, sog, dpp)

Question 4

AS-C

Answer 4

transcriptional factor, expression is first step to becoming neural cells

Question 5

sog

Answer 5

insect homologue of chordin

Question 6

dpp

Answer 6

insect homologue of BMP

Question 7

delamination

Answer 7

one cell detaches from the sheet of neighboring cells

Question 8

neuroblast

Answer 8

a cell that will divide to produce neural cells

Question 9

how a neuroblast is chosen

Answer 9

1. AS-C is expressed, intensifies in only one of the rosette (center)
2. neighbors expression of AS-C diminishes
3. the cell with highest AS-C level delaminates to become a neuroblast
4. neighbors stop expressing and become epidermal cells (ventral skin)

Question 10

competition for neuroblast

Answer 10

after delaminated cell is killed, another will delaminate > shows communication

Question 11

notch

Answer 11

encodes notch protein, membrane-bound receptor that binds to delta

Question 12

mutations in notch

Answer 12

overabundance of neuroblasts

Question 13

Enhancer of split

Answer 13

promotes expression of AS-C

Question 14

AS-C promotes expression of…

Answer 14

delta

Question 15

binding of delta to notch

Answer 15

causes intracellular portion of notch to detach and bind to enhancer of split, forming a heterodimer (TF) to inhibit AS-C expression

Question 16

without AS-C

Answer 16

delta is not expressed; cells next to delta expressing cell will not express it themselves

Question 17

DSH

Answer 17

accumulation of beta catenin on dorsal side; inhibits GSK-3 (which inhibits beta catenin) > GSK degrades beta catenin, DSH inhibits GSK

Question 18

lateral inhibition in insect ectodermal cells

Answer 18

1. rosette expresses AS-C, promoting expression of notch and delta
2. each cell inhibits neighbors by expressing delta, activating notch in the neighbor to suppress proneural genes
3. one cell is still expressing proneural genes and delta (neuroblast)

Question 19

why the neuroblast tends to come from the center

Answer 19

position > center of mesodermal signaling for proneural expression; got more signal and made more delta