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Organizer restriction through modulation of Bozozok stability by the E3 ubiquitin ligase Lnx-like

Nature Cell Biology volume 11, pages 11211127 (2009) | Download Citation



The organizer anchors the primary embryonic axis, and balance between dorsal (organizer) and ventral domains is fundamental to body patterning. LNX (ligand of Numb protein-X) is a RING finger and four PDZ domain-containing E3 ubiquitin ligase1,2. LNX serves as a binding platform and may have a role in cell fate determination, but its in vivo functions are unknown1,2,3,4,5. Here we show that Lnx-l (Lnx-like) functions as a critical regulator of dorso-ventral axis formation in zebrafish. Depletion of Lnx-l using specific antisense morpholinos (MOs) caused strong embryonic dorsalization. We identified Bozozok (Boz, also known as Dharma or Nieuwkoid) as a binding partner and substrate of Lnx-l. Boz is a homeodomain-containing transcriptional repressor induced by canonical Wnt signalling that is critical for dorsal organizer formation6,7,8,9,10,11,12. Lnx-l induced K48-linked polyubiquitylation of Boz, leading to its proteasomal degradation in human 293T cells and in zebrafish embryos. Dorsalization induced by Boz overexpression was suppressed by raising the level of Lnx-l, but Lnx-l failed to counteract dorsalization caused by mutant Boz lacking a critical motif for Lnx-l binding. Furthermore, dorsalization induced by depletion of Lnx-l was alleviated by attenuation of Boz expression. We conclude that Lnx-l modulates Boz activity to prevent the invasion of ventral regions of the embryo by organizer tissue. These studies introduce a ubiquitin ligase, Lnx-l, as a balancing modulator of axial patterning in the zebrafish embryo.

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  1. 1.

    et al. The mammalian numb phosphotyrosine-binding domain. Characterization of binding specificity and identification of a novel PDZ domain-containing numb binding protein, LNX. J. Biol. Chem. 273, 9179–9187 (1998).

  2. 2.

    et al. LNX functions as a RING type E3 ubiquitin ligase that targets the cell fate determinant Numb for ubiquitin-dependent degradation. EMBO J. 21, 93–102 (2002).

  3. 3.

    et al. The Coxsackievirus and adenovirus receptor (CAR) forms a complex with the PDZ domain-containing protein ligand-of-numb protein-X (LNX). J. Biol. Chem. 278, 7439–7444 (2003).

  4. 4.

    et al. Ligand-of-Numb protein X is an endocytic scaffold for junctional adhesion molecule 4. Oncogene 25, 5071–5084 (2006).

  5. 5.

    , & The Lnx family proteins function as molecular scaffolds for Numb family proteins. Mol. Cell Neurosci. 18, 525–540 (2001).

  6. 6.

    & The nieuwkoid gene characterizes and mediates a Nieuwkoop-center-like activity in the zebrafish. Curr. Biol. 8, 1199–1206 (1998).

  7. 7.

    et al. A novel homeobox gene, dharma, can induce the organizer in a non-cell-autonomous manner. Genes Dev. 12, 2345–2353 (1998).

  8. 8.

    et al. The zebrafish bozozok locus encodes Dharma, a homeodomain protein essential for induction of gastrula organizer and dorsoanterior embryonic structures. Development 126, 1427–1438 (1999).

  9. 9.

    et al. Cooperative roles of Bozozok/Dharma and Nodal-related proteins in the formation of the dorsal organizer in zebrafish. Mech. Dev. 91, 293–303 (2000).

  10. 10.

    & The role of the homeodomain protein Bozozok in zebrafish axis formation. Int. J. Dev. Biol. 45, 299–310 (2001).

  11. 11.

    et al. Regulation of dharma/bozozok by the Wnt pathway. Dev. Biol. 231, 397–409 (2001).

  12. 12.

    , , , & Direct binding of Lef1 to sites in the boz promoter may mediate pre-midblastula-transition activation of boz expression. Dev. Dyn. 228, 424–432 (2003).

  13. 13.

    et al. Establishment of the dorso-ventral axis in Xenopus embryos is presaged by early asymmetries in β-catenin that are modulated by the Wnt signaling pathway. J. Cell Biol. 136, 1123–1136 (1997).

  14. 14.

    et al. Establishment of the Dorsal–Ventral Axis in Xenopus Embryos Coincides with the Dorsal Enrichment of Dishevelled That Is Dependent on Cortical Rotation. J. Cell Biol. 146, 427–437 (1999).

  15. 15.

    et al. Siah-1 mediates a novel β-catenin degradation pathway linking p53 to the adenomatous polyposis coli protein. Mol. Cell 7, 927–936 (2001).

  16. 16.

    & Regulated proteolysis of Xom mediates dorsoventral pattern formation during early Xenopus development. Dev. Cell 3, 557–568 (2002).

  17. 17.

    , , , & A SMAD ubiquitin ligase targets the BMP pathway and affects embryonic pattern formation. Nature 400, 687–693 (1999).

  18. 18.

    , , & The DSmurf ubiquitin-protein ligase restricts BMP signaling spatially and temporally during Drosophila embryogenesis. Dev. Cell 1, 567–578 (2001).

  19. 19.

    , , , & c-Src is a PDZ interaction partner and substrate of the E3 ubiquitin ligase Ligand-of-Numb protein X1. FEBS Lett. 581, 5131–5136 (2007).

  20. 20.

    et al. bozozok directly represses bmp2b transcription and mediates the earliest dorsoventral asymmetry of bmp2b expression in zebrafish. Development 130, 3639–3649 (2003).

  21. 21.

    , & Modification of proteins by ubiquitin and ubiquitin-like proteins. Annu. Rev. Cell Dev. Biol. 22, 159–180 (2006).

  22. 22.

    & How the ubiquitin-proteasome system controls transcription. Nature Rev. Mol. Cell Biol. 4, 192–201 (2003).

  23. 23.

    & Polyubiquitin chains: polymeric protein signals. Curr. Opin. Chem. Biol. 8, 610–616 (2004).

  24. 24.

    , , & The homeobox gene bozozok promotes anterior neuroectoderm formation in zebrafish through negative regulation of BMP2/4 and Wnt pathways. Development 127, 2333–2345 (2000).

  25. 25.

    , , & Patterning the early zebrafish by the opposing actions of bozozok and vox/vent. Dev. Biol. 224, 275–285 (2000).

  26. 26.

    , , & Antagonistic role of vega1 and bozozok/dharma homeobox genes in organizer formation. Proc. Natl. Acad. Sci. USA 97, 12121–12126 (2000).

  27. 27.

    , , & Functional interaction of vega2 and goosecoid homeobox genes in zebrafish. Genesis 28, 58–67 (2000).

  28. 28.

    et al. Head and trunk in zebrafish arise via coinhibition of BMP signaling by bozozok and chordino. Genes Dev. 14, 3087–3092 (2000).

  29. 29.

    , , , , & A novel repressor-type homeobox gene, ved, is involved in dharma/bozozok-mediated dorsal organizer formation in zebrafish. Mech. Dev. 118, 125–138 (2002).

  30. 30.

    , , & bozozok and squint act in parallel to specify dorsal mesoderm and anterior neuroectoderm in zebrafish. Development 127, 2583–2592 (2000).

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We thank M. Rath and J. Gonzales for help with fish maintenance, and S.-Y. Choi for helpful comments. This work was supported by the Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institutes of Health.

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  1. Laboratory of Molecular Genetics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892–2425, USA.

    • Hyunju Ro
    •  & Igor B. Dawid


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H.R. designed, carried out and interpreted experiments and wrote the paper. I.B.D. designed and interpreted experiments and wrote the paper.

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The authors declare no competing financial interests.

Corresponding author

Correspondence to Igor B. Dawid.

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