Date post: | 19-Dec-2015 |
Category: |
Documents |
View: | 237 times |
Download: | 1 times |
D
V
High [Dorsal]
Low [Dorsal]
No Dorsal
Graded Dorsal Concentration
Created by Mother
Hierarchy of Gene Action in D/V Patterning
Mesoderm Genes
Neuroectoderm Genes
Non-neural Genes
D/V Genes Basic Tissue Types
Controlled by Embryo
= Mesoderm = Non-Neural Ectoderm= Neuroectoderm
Epidermal GenesDpp Neuronal Genes
AS-C
Rho Ventral Epidermal Genes
Neural Genes
Twist Mesodermal GenesSnail Neural Genes
Brk, Sog Dorsal Genes
D A
Dorsal Region Cell
Inside
Outside
OnOff
RepressorFrom Mother
N
Nucleus
Regulatory Region
Coding Region
Nucleus
Dorsal or Lateral Region Cell
Inside
Outside
DppReceptor
Sog
Signal Relay
OnOff
Non-neural genes(e.g. dpp)
OnOff
Neural genes(e.g. AS-C)
dpp mRNA
No Dorsal
Dpp Protein
Dpp versus Sog Function
Mesodermal Genes
Neuronal Genes
= Mesoderm = Non-Neural Ectoderm= Neuroectoderm
Dpp
Sog
dpp- versus sog- Mutants
X Neuronal GenesEpidermal Genes
Mesodermal Genes
Neuronal Genes
= Mesoderm = Non-Neural Ectoderm= Neuroectoderm
Dpp
Sog
sog- Mutant
X
Neuronal GenesEpidermal Genes
Mesodermal Genes
= Mesoderm = Non-Neural Ectoderm= Neuroectoderm
Dpp Neuronal GenesEpidermal Genes
sog- Mutant
The Default State of Ectoderm is Neural
N o n -n e u r a l
E c t o d e r m
N e u r o e c t o d e r m
( D e f a u l t S t a t e )
SogBlocks Dpp Autoactivation
Permits Neurogenesis
NeurogenesisDpp
Autoactivates
Skin
Subdivision of the Ectoderm intoNeural Versus Non-neural Regions
Sog diffuses and patterns the dorsal region
The Players
Dpp: A signal that promotes dorsal fates
Sog: A secreted inhibitor of Dpp
Tolloid = Tld: A protease that cleaves and destroys Sog
Sog Creates a BMP activity gradient dorsally
Sog Dpp
V D
Relative DppActivity
[Sog]
1) A dorsal Sog gradient is created by a ventral source and a dorsal sink for Sog.
2) A reciprocal Dpp activity gradient forms.
= Mesoderm = Non-Neural Ectoderm= Neuroectoderm
High
Low
None
[Dorsal]
High
Low
None
DppNon-neural genes
Neural genes
Dorsal
Subdivision of the Neuroectoderm
Neuronal genes
Msh
Ind
Vnd
Drosophila Neuroectoderm
Mouse Neural Tube
Sonic Hh
BMPsMsx Nkx2.2Gsh
Dorsal
Dpp
indmsh
vnd
dpp
Patterning the Neuroectoderm in Flies and Mice
Reciprocal Patterning of the Ectoderm by Sog and Dpp
Sog Dpp
V D
[Sog]
1) A Sog gradient creates an inverse Dpp activity gradient dorsally -> Non-neural Ectoderm vs Amnioserosa.
2) A Dpp activity gradient forms within the neuroectoderm -> Three rows of neuroblasts.
[Dpp]
Relative BMPActivity
mshindvndNeuroectoderm Non-neural
EctodermA.S.race