Bone morphogenetic protein heterodimers assemble heteromeric type I receptor complexes to pattern the dorsoventral axis.
Patterning the embryonic dorsoventral axis of both vertebrates and invertebrates requires signalling through bone morphogenetic proteins (BMPs). Although a well-studied process, the identity of the physiologically relevant BMP signalling complex in the Drosophila melanogaster embryo is controversial, is generally inferred from cell culture studies and has not been investigated in vertebrates. Here, we demonstrate that dorsoventral patterning in zebrafish, Danio rerio, requires two classes of non-redundant type I BMP receptors, Alk3/6 and Alk8 (activin-like kinases 3/6 and 8). We show, under physiological conditions in the embryo, that these two type I receptor classes form a complex in a manner that depends on Bmp2 and Bmp7. We found that both Bmp2-7 heterodimers, as well as Bmp2 and Bmp7 homodimers, form in the embryo. However, only recombinant ligand heterodimers can activate BMP signalling in the early embryo, whereas a combination of Bmp2 and Bmp7 homodimers cannot. We propose that only heterodimers, signalling through two distinct classes of type I receptor, possess sufficient receptor affinity in an environment of extracellular antagonists to elicit the signalling response required for dorsoventral patterning.
Little
Shawn C
SC
Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, 1211 BRBII/III, 421 Curie Boulevard., Philadelphia, PA 19104-6058, USA.
Mullins
Mary C
MC
D029404:Activin Receptors / Q000378:metabolism; D030201:Activin Receptors, Type I / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D019521:Body Patterning / Q000502:physiology*; D055396:Bone Morphogenetic Protein 2 / Q000235:genetics / Q000378:metabolism; D055419:Bone Morphogenetic Protein 7 / Q000235:genetics / Q000378:metabolism; D052005:Bone Morphogenetic Protein Receptors, Type I / Q000235:genetics / Q000378:metabolism*; D019485:Bone Morphogenetic Proteins / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000002:abnormalities / Q000378:metabolism; D008954:Models, Biological; D016376:Oligonucleotides, Antisense / Q000235:genetics; D010766:Phosphorylation; D011485:Protein Binding / Q000502:physiology; D012333:RNA, Messenger / Q000037:antagonists & inhibitors / Q000235:genetics; D015398:Signal Transduction / Q000502:physiology*; D051898:Smad1 Protein / Q000378:metabolism; D051902:Smad5 Protein / Q000378:metabolism; D015027:Zebrafish / Q000196:embryology*; D029961:Zebrafish Proteins / Q000235:genetics / Q000378:metabolism*
D055396:Bone Morphogenetic Protein 2; D055419:Bone Morphogenetic Protein 7; D019485:Bone Morphogenetic Proteins; D016376:Oligonucleotides, Antisense; D012333:RNA, Messenger; D051898:Smad1 Protein; D051902:Smad5 Protein; D029961:Zebrafish Proteins; C405936:bmp2b protein, zebrafish; C525826:bmp7a protein, zebrafish; C497801:smad5 protein, zebrafish; D029404:Activin Receptors; D030201:Activin Receptors, Type I; D052005:Bone Morphogenetic Protein Receptors, Type I; C512426:acvr1ba protein, zebrafish; C424203:acvr1l protein, zebrafish