SLIDE 1
Modified from Satoh et al, 2003
Ciona intestinalis developmental program: Maternal factors establish three domains of gene expression
- Gata.a AD
- β-catenin VD
- Zic-r.a PVD
16-cell stage Posterior vegetal domain
Innsbruck, 18/06/2020 Ciona intestinalis developmental program: - - PowerPoint PPT Presentation
Innsbruck, 18/06/2020 Ciona intestinalis developmental program: - - PowerPoint PPT Presentation
Innsbruck, 18/06/2020 Ciona intestinalis developmental program: Maternal factors establish three domains of gene expression Gata.a AD -catenin VD Zic-r.a PVD Modified from Satoh et al, 2003 Posterior vegetal domain
SLIDE 2
SLIDE 3
Ciona intestinalis: simple and conserved lineage and body plan
Fujii et al. 2008
- AD epidermal and neural cells
- VD mesendodermal tissues and the
nerve cord
- PVD Muscles and mesenchymal
- Invariant cells division
- Sequenced and compact genome
- Primitive chordate body plan
Marletàz et al, 2003
SLIDE 4
Maternal factors crosstalk to initiate the zygotic genetic program
AD VD AD VD
SLIDE 5
Open Questions
- How β-catenin and Zic-r.a cooperate to activate Tbx6.b specifically in
the PVD?
- Why Tbx6.b is not activated in the anterior vegetal cells by β-catenin?
- how β-catenin represses Gata.a activity in the VD?
β-catenin MO CO Tbx6.b CO
SLIDE 6
Fgf Enhancer activity: Tcf sites are essential for specific expression in VD
CO β-catenin MO
In situ hybridization
SLIDE 7
Tbx6.b Enhancer activity: Tcf sites are required for expression in PVD
CO β-catenin MO Zic-r.a MO In situ hybridization
SLIDE 8
Fgf vs Tbx6.b Enhancer expression: additional repressive elements?
Fgf Tbx6.b VD PVD
?
SLIDE 9
Efna.d Enhancer activity: GATA sites are necessary for expression in AD
CO
CO β-catenin MO Gata.a MO In situ hybridization
SLIDE 10
β-catenin, Tcf and Gata.a interact to create different gene expression patterns in AD and VD
- Efna.d regulatory
region doesn’t bind Tcf/ β-catenin complex
- How β-catenin suppress
the activity in VD?
Hypothesis: β-catenin might prevent Gata.a from binding to its target sites?
- Gata.a specific binding was not disrupted by co-incubation
with either Tcf7 or β-catenin
- Co-incubation with both Tcf7 and β-catenin reduced Gata.a
binding In the VD of normal embryos, β-catenin and Tcf7 interact with Gata.a and suppress the binding activity of Gata.a.
ß-catenin Tcf7
GATA
X
Gata.a
SLIDE 11
Discussion
- β-catenin and Tcf7 activate gene expression in the VD. This complex may
interferes with Gata.a binding to GATA sites reducing target genes expression in the VD
- Genes specifically expressed in the PVD posses elements that prevent
activation of these genes by β-catenin and Tcf7.
- Zic-r.a can function in regulatory regions to overcome the repressive
activity indirectly through Tcf.
- Insertion of repressor elements in reporter constructs usually expressed
independently of Zic-r.a, evoked Zic-r.a-dependent expression in the PVD.
SLIDE 12
Conclusion
Three maternal factors coordinate to establish three distinct expression domains. Negative regulatory mechanisms of the animal fate in the vegetal hemisphere and those of the posterior vegetal fate in the anterior vegetal hemisphere are important.
Present analysis
- Tcf repress GATA sites independently of β-catenin?
- GATA site signature influence repression?
- incomplete Tcf site masks GATA sites?
Tcf7
GATA
X
Gata.a
aGATAAAGTATCt
SLIDE 13