The role of maternal Activin-like signals in zebrafish embryos.
Maternal Activin-like proteins, a subgroup of the TGF-beta superfamily, play a key role in establishing the body axes in many vertebrates, but their role in teleosts is unclear. At least two maternal Activin-like proteins are expressed in zebrafish, including the Vg1 orthologue, zDVR-1, and the nodal-related gene, Squint. Our analysis of embryos lacking both maternal and zygotic squint function revealed that maternal squint is required in some genetic backgrounds for the formation of dorsal and anterior tissues. Conditional inactivation of the ALK4, 5 and 7 receptors by SB-505124 treatment during the cleavage stages ruled out a role for maternal Squint, zDVR-1, or other Activin-like ligands before the mid-blastula transition, when the dorsal axis is established. Furthermore, we show that maternal Squint and zDVR-1 are not required during the cleavage stages to induce zygotic nodal-related gene expression. nodal-related gene expression decreases when receptor inhibition continues past the mid-blastula transition, resulting in a progressive loss of mesoderm and endoderm. We conclude that maternally expressed Activin-like signals do not act before the mid-blastula transition in zebrafish, but do have a variably penetrant role in the later stages of axis formation. This contrasts with the early role for these signals during Xenopus development.
Hagos
Engda G
EG
Department of Cellular Biology, The University of Georgia, Athens, GA 30602, USA.
Fan
Xiang
X
Dougan
Scott T
ST
D029404:Activin Receptors / Q000235:genetics / Q000378:metabolism; D030201:Activin Receptors, Type I; D028341:Activins / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D052117:Benzodioxoles / Q000494:pharmacology; D019521:Body Patterning; D004707:Endoderm / Q000196:embryology / Q000378:metabolism; D007093:Imidazoles / Q000494:pharmacology; D008648:Mesoderm / Q000196:embryology / Q000378:metabolism; D009154:Mutation; D055456:Nodal Signaling Ligands; D011725:Pyridines / Q000494:pharmacology; D018125:Receptors, Transforming Growth Factor beta / Q000037:antagonists & inhibitors / Q000378:metabolism; D015398:Signal Transduction; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D015027:Zebrafish / Q000196:embryology / Q000378:metabolism*; D029961:Zebrafish Proteins / Q000235:genetics / Q000378:metabolism*
C519132:2-(5-benzo(1,3)dioxol-5-yl-2-tert-butyl-3H-imidazol-4-yl)-6-methylpyridine hydrochloride; D052117:Benzodioxoles; C079678:Gdf3 protein, zebrafish; D007093:Imidazoles; D055456:Nodal Signaling Ligands; D011725:Pyridines; D018125:Receptors, Transforming Growth Factor beta; D016212:Transforming Growth Factor beta; D029961:Zebrafish Proteins; C485171:ndr1 protein, zebrafish; D028341:Activins; D029404:Activin Receptors; D030201:Activin Receptors, Type I; C512426:acvr1ba protein, zebrafish