1. Dickkopf-1 regulates gastrulation movements by coordinated modulation of Wnt/  -catenin and Wnt/PCP activities, through interaction with the Dally-like homolog Knypek 2007, Genes & Dev Luca Caneparo

2. Roles of Dkk1 in Gastrulation During gastrulation, anterior territories (neural plate) keep their identities by moving away from posteriorizing signals or inhibiting them (Wilson S.W et al, 2004, Dev Biol) Among the most studied posteriorizing signals are the Wnt molecules (Erter et al, 2001, Development) Fight against Wnt! (sFRP, WIF, Cerberus and Dkk)

3. Roles of Dkk1 in Gastrulation (continue) In frog and fish, Dkk1 overexpression is able to anteriorize neural tissue (Kazanskaya et al, 2000, Development) The genetic knockout of the mouse dkk1 leads to the formation of headless (Mukhopadhyay et al, 2001, Dev cell) embryos due to lack of maintenance of anterior neural identity during gastrulation But, mechanism by Dkk1 is yet to be unraveled

4. Gastrulation movement in zebrafish

5. Dkk1 is “Head inducer” The morphant embryos show a severe reduction of forebrain territories

6. Dkk1 is important in rostal population of axial mesendoderm Dkk1 antibody injected Xenopus embryo, gsc and shh (anterior endoderm marker) in prechordal plate are down-regulated (Kazanskaya et al, 2001, Development) In the mouse dkk1/noggin double mutants, Hesx1 expression is down-regulated in the presumptive prechordal plate (del Barco et al, 2003, Genes & Development) Absence of Dkk1 give the same effect in zebra fish?

7. Axial mesendoderm marker Dkk1 regulates gastrulation movement dorsal - Significant reduction of gsc in dkk MO - Position of the rostal-most limit of the axial mesendoderm is different Acceleration of Axial mesendoderm movement?

8. Dkk1 Dkk1 MO accelerates gastrulation movement

9. - The number of internalized cell/min - The AP length of the clone - Distance of the rostal-most cell from the posterior margin Dkk1 MO accelerates gastrulation movement

10. How does Dkk1 reduce gastrulation movement? Two hypothesis Dkk1 Canonical Wnt signaling block Interact with LRP5/6Interact with X ? Gastrulation defect

11. Influence of Dkk1 on gastrulation is Wnt/  -catenin independent Clones are more dispersed Don’t rescue the phenotype in Dkk1 MO

12. Knypek is a Dally-like heparan sulfate proteoglycan (Dally) In embryo lacking Knypek, mediolateral intercalations are impaired (Topczewski et al, 2001, Dev cell) kny mutations exacerbate the CE defect of slb/Wnt11 mutants in a dose-dependent manner (Lin F. et al, 2005, J cell biol) And, Kny enhances Wnt11 signaling in overexpression experiments Kny is a positive modulator of non-canonical Wnt signaling If Dkk1 interacts with Kny ?

13. Dkk1 interacts with Knypek and it regulates propagation of Dkk1 Synergistic effect Interact with Kny Require Kny for its propagation Kny-/-Kny-/- + Dkk1Wt+Dkk1 Propagation is necessary for dkk1 function

14. Dkk1 promotes Wnt / PCP pathway activin activin+Wnt8activin+Dkk1 C&E defect

15. Dkk1 may act as a switch between the  -catenin and PCP pathway Phenocopy Dkk1 MO

16. Dkk1 Canonical Wnt signaling block Interact with LRP5/6Interact with knypek Fine-tuned Gastrulation Summary Dkk1 propagation ? Internalization Wnt/PCP activation

17. Possible model