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Gene Review

smad5  -  SMAD family member 5

Danio rerio

Synonyms: MAD homolog 5, Mothers against DPP homolog 5, Mothers against decapentaplegic homolog 5, Protein somitabun, SBN, ...
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High impact information on smad5

  • The phenotype of laf mutants and alk8 morphants can be rescued by injected mRNA encoding Alk8 or the Bmp-regulated transcription factor Smad5, but not by mRNA encoding Bmp2b or Bmp7 [1].
  • Double mutant analyses and RNA injection experiments show that sbn and bmp2b interact and that sbn acts downstream of Bmp2b signaling to mediate Bmp2b autoregulation during early dorsoventral (D-V) pattern formation [2].
  • However, in somitabun(-) (sbn(-)) embryos, which probably retain higher residual Bmp activity, it is the sensory neurons and not the interneurons that are expanded [3].
  • The weakest phenotype is a reduction in the ventral tail fin, observed as a dominant phenotype of swirl, piggytail, and somitabun and a recessive phenotype of mini fin, lost-a-fin and some piggytail alleles [4].
  • Mutations in the piggytail gene display an unusual dominance that depends on both a maternal and zygotic heterozygous genotype, while somitabun is a fully penetrant dominant maternal-effect mutation [4].

Biological context of smad5

  • Taking advantage of the maternal effect of a zebrafish smad5 null mutation (Mm169), we investigate the effect of early signaling by members of the bone morphogenetic proteins (Bmps) on eye field patterning and optic vesicle morphogenesis [5].
  • However, it requires Bmp signal transduction through Alk8 and Smad5 to negatively regulate Ca(2+)/Cadherin-dependent cell-cell adhesiveness [6].

Anatomical context of smad5

  • We observe a loss in neural crest progenitors in swirl/bmp2b mutant embryos, while somitabun mutants display an opposite, dramatic expansion of the prospective neural crest [7].
  • Examination of dorsally and ventrally restricted markers during gastrulation reveals a successive reduction and reciprocal expansion in nonneural and neural ectoderm, respectively, in snailhouse, somitabun, and swirl mutant embryos, with swirl/bmp2b mutants exhibiting almost no nonneural ectoderm [7].
  • In the strong phenotypes, displayed hy homozygous embryos of snailhouse, swirl and somitabun, the somites circle around the embryo and the midbrain region is expanded laterally [4].
  • Early expression of foxc1a in the paraxial mesoderm is modified in chordino, swirl, somitabun, and spadetail mutants [8].

Other interactions of smad5

  • Injection studies and mutant analyses suggest that the ventral smad1 expression is positively regulated by Bmp2b, but not by Bmp4 signaling, whereas smad5 expression is independent of Bmp2b [9].
  • They do not respond to injected bmp2b mRNA, indicating that Smad5 is absolutely essential for ventral development and Bmp2/7 signaling [10].
  • Embryos lacking maternal Smad5 function (Mm169(-/-) embryos) are even more strongly dorsalized thanbmp2b or bmp7 null mutants [10].
  • We have previously shown that the maternal effect dorsalization of zebrafish embryos from sbn(dtc24) heterozygous mothers is caused by a dominant negative mutation in Smad5, a transducer of ventralizing signaling by the bone morphogenetic proteins Bmp2b and Bmp7 [10].
  • Morpholino phenocopies of the swirl, snailhouse, somitabun, minifin, silberblick, and pipetail mutations [11].


  1. The type I serine/threonine kinase receptor Alk8/Lost-a-fin is required for Bmp2b/7 signal transduction during dorsoventral patterning of the zebrafish embryo. Bauer, H., Lele, Z., Rauch, G.J., Geisler, R., Hammerschmidt, M. Development (2001) [Pubmed]
  2. The smad5 mutation somitabun blocks Bmp2b signaling during early dorsoventral patterning of the zebrafish embryo. Hild, M., Dick, A., Rauch, G.J., Meier, A., Bouwmeester, T., Haffter, P., Hammerschmidt, M. Development (1999) [Pubmed]
  3. Bmp activity establishes a gradient of positional information throughout the entire neural plate. Barth, K.A., Kishimoto, Y., Rohr, K.B., Seydler, C., Schulte-Merker, S., Wilson, S.W. Development (1999) [Pubmed]
  4. Genes establishing dorsoventral pattern formation in the zebrafish embryo: the ventral specifying genes. Mullins, M.C., Hammerschmidt, M., Kane, D.A., Odenthal, J., Brand, M., van Eeden, F.J., Furutani-Seiki, M., Granato, M., Haffter, P., Heisenberg, C.P., Jiang, Y.J., Kelsh, R.N., Nüsslein-Volhard, C. Development (1996) [Pubmed]
  5. Loss of maternal Smad5 in zebrafish embryos affects patterning and morphogenesis of optic primordia. Hammerschmidt, M., Kramer, C., Nowak, M., Herzog, W., Wittbrodt, J. Dev. Dyn. (2003) [Pubmed]
  6. The bmp gradient of the zebrafish gastrula guides migrating lateral cells by regulating cell-cell adhesion. von der Hardt, S., Bakkers, J., Inbal, A., Carvalho, L., Solnica-Krezel, L., Heisenberg, C.P., Hammerschmidt, M. Curr. Biol. (2007) [Pubmed]
  7. Ventral and lateral regions of the zebrafish gastrula, including the neural crest progenitors, are established by a bmp2b/swirl pathway of genes. Nguyen, V.H., Schmid, B., Trout, J., Connors, S.A., Ekker, M., Mullins, M.C. Dev. Biol. (1998) [Pubmed]
  8. Sequence and expression of zebrafish foxc1a and foxc1b, encoding conserved forkhead/winged helix transcription factors. Topczewska, J.M., Topczewski, J., Solnica-Krezel, L., Hogan, B.L. Mech. Dev. (2001) [Pubmed]
  9. Smad1 and Smad5 have distinct roles during dorsoventral patterning of the zebrafish embryo. Dick, A., Meier, A., Hammerschmidt, M. Dev. Dyn. (1999) [Pubmed]
  10. Maternally supplied Smad5 is required for ventral specification in zebrafish embryos prior to zygotic Bmp signaling. Kramer, C., Mayr, T., Nowak, M., Schumacher, J., Runke, G., Bauer, H., Wagner, D.S., Schmid, B., Imai, Y., Talbot, W.S., Mullins, M.C., Hammerschmidt, M. Dev. Biol. (2002) [Pubmed]
  11. Morpholino phenocopies of the swirl, snailhouse, somitabun, minifin, silberblick, and pipetail mutations. Lele, Z., Bakkers, J., Hammerschmidt, M. Genesis (2001) [Pubmed]
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