Drosophila Wing development

Question 1

What is the developmental origin of wings?

Answer 1

wing imaginal disc

Question 2

At which stage of development is wing primordium singled out from epidermis? What is this based on (which genes)?

Answer 2

at the end of segmentation (so still early embryogenesis)

depends on positional blueprint = AP and DV information
-> wing where vestigal and scalloped are expressed
= at the intersection of decapentaplegic and wingless
= determined by Hox gene expression in T2 and T3

Question 3

Vestigal and distal-less are both needed in wing development. What’s the difference between them?

Answer 3

distal-less specifies appendage, but it could also be a leg, antenae…
vestigal specifies the wing

Question 4

There is no cell migration during development in the fly. How are the structures formed?

Answer 4

directionality of mitoses

local cell rearrangement

Question 5

Which marker is used to visualize which cells contained mutations in the genome (talking about wing mosaic models by Antonio Garcia-Bellido)?

Answer 5

usually, one cell = one hair
after inducing chromosomal breaks and rearrangement of the chromosomes:
one cell = 3 hairs

Question 6

What is the Minute technique and what did it reveal in wing development?

Answer 6

Minute mutation affects the rate of division
= get cells that divide faster
= mutated 3 haired cell will have big clones and will be easier to visualize

in wing: some M+ clones followed straight lines down the middle of the wing
- some cells never seemed to cross the invisible line dividing the wing in A and P compartment, even though there was no morphological difference between them
= cells create compartments

Question 7

Which transcription factor is only found in posterior wing compartment? How do we know that it is important in P and not A?

Answer 7

engrailed

WT + engrailed KO in A = wt phenotype
WT + engrailed KO in P = cells cross the boundary and acquire A identity

Question 8

Wing can be divided in 4 compartments: anterior dorsal, anterior ventral, posterior dorsal and posterior ventral. Which selector genes determine their identity?

Answer 8

engrailed = posterior
apterous = dorsal

Question 9

Why is establishing the boundaries important, what are the consequences of that?

Answer 9

e.g. AP boundary: starts expressing dpp, which creates a gradient -> different domains