Drosophila dorsal ventral axis detemination
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Drosophila dorsal/ventral axis detemination. How are different tissue types specified at distinct positions on the embryonic dorsal-ventral axis?. Cell fate specification at the blastoderm stage. amnio-serosa. dorsal. dorsal ectoderm. neuro-ectoderm. mesoderm. ventral. fate map.

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Drosophila dorsal/ventral axis detemination

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Drosophila dorsal ventral axis detemination

Drosophila dorsal/ventral axis detemination

How are different tissue types specified at distinct positions on the embryonic dorsal-ventral axis?


Drosophila dorsal ventral axis detemination

Cell fate specification at the blastoderm stage

amnio-serosa

dorsal

dorsal ectoderm

neuro-ectoderm

mesoderm

ventral

fate map

mesoderm formation


Drosophila dorsal ventral axis detemination

Dorsal-Ventral fate map


Drosophila dorsal ventral axis detemination

Genes identified in a famous screen for Drosophila mutants with embryo patterning defects

Torpedo

Gurken


Drosophila dorsal ventral axis detemination

Localized maternal mRNA sets up anterior and posterior poles


Gurken protein specifies the anterior posterior axis of the drosophila embryo during oogenesis

Gurken protein specifies the Anterior-Posterior axis of the Drosophila embryo during oogenesis

(Similar to EGF)


Gurken also signals dorsal pole formation during oogenesis

migration of nucleus

10A

8

1-6

-

+

-

gurken expression in the oocyte

gurken expression in the oocyte

Gurken also signals dorsal pole formation during oogenesis

oocyte nucleus

D

D

10A

1-6

7

8

+

-

A

P

-

V

anterior

posterior

V

follicle cells

microtubules


Drosophila dorsal ventral axis detemination

Expression of the Gurken Message and Protein Between the Oocyte Nucleus and the Dorsal Anterior Cell Membrane


Gurken signaling inhibits production of an extracellular signal sp tzle by follicle cells

Gurken signaling inhibits production of an extracellular signal (Spätzle) by follicle cells

follicle cells

Torpedo = EGF receptor

(in follicle cells)

Gurken = Epidermal Growth Factor (EGF)

Oocyte

pipe

expression

X

Ventral follicle cell

Pipe (Golgi?)

X

Wind (ER?)

X

Nucleus

modified from van Eeden & St.Johnston


Drosophila dorsal ventral axis detemination

Maternal effect mutations in dorso-ventral patterning

Somatic (follicle cells)

ndl, pipe, wbl

gd, snk, ea - serine proteases

Spätzle spz - ligand

Germline (nurse cells)

nudel, pipe, wbl

dorsal RNA

Toll protein

Spätzle protein

Dorsal protein

Toll

Tl - membrane receptor

tube - cytoplasmic protein

pelle - ser/thr protein kinase

Dorsal protein

amnio serosa

cact - cytoplasmic inhibitor of Dorsal nuclear translocation

cactus

dorsal ectoderm

neuro-ectoderm

dorsal

dl - transcription factor (morphogen)

mesoderm

Dl

nuclear protein


Drosophila dorsal ventral axis detemination

dorsal and cactus mutants (maternal germline effect)

dorsal

dorsal mutant

cactus mutant

Wild type

ventral

A8

T1

A7

dorsalized

ventralized

T2

T3

A1

A2

A6

A3

A4

A5


Translocation of dorsal protein into ventral nuclei but not lateral or dorsal nuclei

Translocation of Dorsal protein into ventral nuclei but not lateral or dorsal nuclei

Wild type toll mutant cactus mutant


Generation of dorsal ventral polarity in drosophila

Generation of Dorsal-Ventral Polarity in Drosophila


Generation of dorsal ventral polarity in drosophila1

Generation of Dorsal-Ventral Polarity in Drosophila


Drosophila dorsal ventral axis detemination

The Toll pathway in dorso-ventral pattern formation

Inject wild-type cytoplasm

into toll mutant eggs

toll mutant

ventral

dorsalized

local

rescue

dorsal ectoderm

Wild type

dorsal

neuro-ectoderm

(denticle belts)

mesoderm

polarity reversal


Drosophila dorsal ventral axis detemination

Conserved pathway for regulating nuclear transport of transcription factors in Drosophila and mammals


Drosophila dorsal ventral axis detemination

Cells with highest nuclear Dorsal levels become mesoderm


Drosophila dorsal ventral axis detemination

Zygotically expressed genes


Drosophila dorsal ventral axis detemination

Action of Dorsal protein in ventral cells


Drosophila dorsal ventral axis detemination

Action of Dorsal protein in ventral cells

High affinity for promoter,

Not much Dorsal needed to activate


Drosophila dorsal ventral axis detemination

Action of Dorsal protein in ventral cells

Lower affinity for promoter,

More Dorsal needed to activate


Drosophila dorsal ventral axis detemination

Zygotically expressed genes


Drosophila dorsal ventral axis detemination

Action of Dorsal protein in ventral cells

Snail repression of rhomboid creates domains with distinct gene expression patterns


Drosophila dorsal ventral axis detemination

Dorso-ventral pattern formation: summary

nudel, pipe, windbeutel

dorsal RNA

Toll protein

Spätzle protein

Dorsal protein

Dorsal protein

dpp

twist

oocyte nucleus dorsal

> repression of ventral fate

in dorsal follicle cells

ventral production of ligand

> activation of Toll receptor

> graded nuclear uptake

of Dorsal morphogen

> regulation of zygotic

target gene expression

> cell fates along DV axis


Drosophila dorsal ventral axis detemination

Use of a similar regulatory system to pattern insects and vertebrates


Drosophila dorsal ventral axis detemination

Patterns ectoderm in Drosophila

Patterns mesoderm in vertebrates


Gastrulation in drosophila

Gastrulation in Drosophila


Schematic representation of gastrulation in drosophila

Schematic representation of gastrulation in Drosophila


Drosophila dorsal ventral axis detemination

Anterior-posterior patterning in Drosophila


Drosophila dorsal ventral axis detemination

3 head

The fly body plan: each segment has a unique identity

and produces distinctive

structures

3 thorax

8 abdomen


Drosophila dorsal ventral axis detemination

Mutations affecting the antero-posterior axis

3 independent maternal systems: anterior, posterior, terminal

fate map

larva

triple mutants

active

active

systems

systems

APT

---

wild-type

single mutants

double mutants

-PT

-P-

anterior

bicoid

A-T

--T

posterior

oskar

AP-

A--

terminal

torso

additive phenotypes


Drosophila dorsal ventral axis detemination

Maternal effect mutations


Drosophila dorsal ventral axis detemination

Zygotic effect mutations


Drosophila dorsal ventral axis detemination

bicoid mutant phenotype

Embryo from wild-type mother

Embryo from bicoid mother


Drosophila dorsal ventral axis detemination

Anterior: bicoid is required for head and thorax

bicoid mutant

Wild type

blastoderm fate map

head

abdomen

+ thorax

abdomen


Drosophila dorsal ventral axis detemination

Bicoid mRNA localization in embryo

(tethered to microtubules)


Nuclei divide without cell division in drosophila to produce a syncytial blastoderm embryo

Nuclei divide without cell division in Drosophila to produce a syncytial blastoderm embryo

Fig. 9.1


Drosophila dorsal ventral axis detemination

Bicoid protein gradient in syncytial blastoderm embryo

- diffuses after translation from localized mRNA

- protein unstable


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