The novel Smad-interacting protein Smicl regulates Chordin expression in the Xenopus embryo.
In this paper, we investigate the function of Smicl, a zinc-finger Smad-interacting protein that is expressed maternally in the Xenopus embryo. Inhibition of Smicl function by means of antisense morpholino oligonucleotides causes the specific downregulation of Chordin, a dorsally expressed gene encoding a secreted BMP inhibitor that is involved in mesodermal patterning and neural induction. Chordin is activated by Nodal-related signalling in an indirect manner, and we show here that Smicl is involved in a two-step process that is necessary for this activation. In the first, Smad3 (but not Smad2) activates expression of Xlim1 in a direct fashion. In the second, a complex containing Smicl and the newly induced Xlim1 induces expression of Chordin. As well as revealing the function of Smicl in the early embryo, our work yields important new insight in the regulation of Chordin and identifies functional differences between the activities of Smad2 and Smad3 in the Xenopus embryo.
Collart
Clara
C
Department of Developmental Biology (VIB-07 Institute for Biotechnology (VIB), and Laboratory of Molecular Biology (Celgen), University of Leuven, B-3000 Leuven, Belgium.
Verschueren
Kristin
K
Rana
Amer
A
Smith
James C
JC
Huylebroeck
Danny
D
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D003001:Cloning, Molecular; D004625:Embryo, Nonmammalian / Q000196:embryology / Q000378:metabolism; D005775:Gastrula / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D006023:Glycoproteins / Q000235:genetics / Q000378:metabolism*; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D020407:Internet; D060850:LIM-Homeodomain Proteins; D051379:Mice; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics; D015398:Signal Transduction; D051785:Smad Proteins / Q000378:metabolism; D014157:Transcription Factors; D014981:Xenopus / Q000196:embryology* / Q000235:genetics / Q000378:metabolism*; D029867:Xenopus Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism
D006023:Glycoproteins; D018398:Homeodomain Proteins; D036341:Intercellular Signaling Peptides and Proteins; D060850:LIM-Homeodomain Proteins; C543964:Lhx1 protein, Xenopus; D012333:RNA, Messenger; C093133:SIA1 protein, Xenopus; D051785:Smad Proteins; D014157:Transcription Factors; D029867:Xenopus Proteins; C506006:ZC3H3 protein, Xenopus; D051176:beta Catenin; C054234:chordin