figure 23.14 homologous pathways specifying neural ectoderm in protostomes (drosophila) and...
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Figure 23.14 Homologous Pathways Specifying Neural Ectoderm in Protostomes (Drosophila) and Deuterostomes (Xenopus) D/V
Gastrulation - Drosophila
:// . . / / /http www flybase org data images Ani/mation
AND Course Site (Movies)
I. RTK pathway Sets follicle cell D/V state
II. Proteolytic cascade Sets embryos’ cell D/V state
III. Toll/Cactus/Doral Sets nuclear D/V state
IV. Dorsal TF thresholds Diff. pathway per D/V address
4 STAGES OF ESTABLISHING DORSAL/VENTRAL – 4 SEQUENTIAL PATHWAYS +
STAGE PATHWAY PATHWAY OUTCOME
I. RTK pathway Sets follicle cell D/V state
II. Proteolytic cascade Sets embryos’ cell D/V state
III. Toll/Cactus/Doral Sets nuclear D/V state
IV. Dorsal TF thresholds Diff. pathway per D/V address
4 STAGES OF ESTABLISHING DORSAL/VENTRAL – 4 SEQUENTIAL PATHWAYS +
STAGE PATHWAY PATHWAY OUTCOME
Lateral inhibition in neurectoderm to specify neruogenesis: Notch mediated
All Rhomboid expressing cells express Notch, then undergo a stochastic process for ¼ cells to become neuronal
Key factor for Dorsal identities inDrosophila
Key factor for D-V identities inVertebrates
TGF-Beta family
Figure 23.14 Homologous Pathways Specifying Neural Ectoderm in Protostomes (Drosophila) and Deuterostomes (Xenopus) D/V
Bicoid mRNA 1. Bicoid RNA ‘caught’ at the ‘entrance’
2. Unanchored Bicoid RNA returned to the anterior side by dynein on MTs
Gap genes are turned on in broad stripes by maternal genes, each other. ALL TFs.
Hunchback
Gt
Kr
kn
hb (later)
Gap genes are turned on in broad stripes by maternal genes, each other
Pair rule genes are turned on in 7 stripes each, harder to conceptualize
Each stripe has its own enhancer, responding to a different combinatorial of Gap and Maternal proteins
Gap genes are turned on in broad stripes by maternal genes, each other
Pair rule genes are all Trascription Factors too – turn on Segment Polarity gene expression
The embryoNow has twoAdjacent organizersWhich release a
Morphogen
From syncitium withGradient of 1 (or 2)Morphogens, to seriesOf segments, each
With 2 morphogens
Figure 6.16 Scanning Electron Micrograph of a Compound Eye in Drosophila
Eye disc patterning controlled by ‘reuse’ of the pathways seen in general axis specification