Role of the LIM class homeodomain protein Xlim-1 in neural and muscle induction by the Spemann organizer in Xenopus.
Like all known LIM class homeobox genes, Xlim-1 encodes a protein with two tandemly repeated cysteine-rich LIM domains upstream of the homeodomain. In Xenopus laevis, Xlim-1 is specifically expressed in the Spemann organizer, whose major functions include neural induction and dorsalization of ventral mesoderm. From RNA injection experiments we conclude here that: (1) the LIM domains behave as negative regulatory domains; (2) LIM domain mutants of Xlim-1 elicited neural differentiation in animal explants; (3) mutant, and to a lesser extent wild-type, Xlim-1 enhanced muscle formation after coinjection with Xbra; (4) both of these activities are mediated by extracellular signals as seen in combined explant experiments; (5) Xlim-1 mutants activated goosecoid (gsc) expression in animal explants, but not expression of noggin or follistatin; (6) mutant Xlim-1 elicited formation of partial secondary axes, and cooperated with gsc in notochord formation. Thus Xlim-1 has latent activities, implicating it in organizer functions.
Taira
M
M
Laboratory of Molecular Genetics, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892.
Otani
H
H
Saint-Jeannet
J P
JP
Dawid
I B
IB
D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins; D002454:Cell Differentiation / Q000235:genetics / Q000502:physiology; D046508:Culture Techniques; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D004627:Embryonic Induction; D005326:Fetal Proteins / Q000235:genetics / Q000502:physiology; D038681:Follistatin; D006023:Glycoproteins / Q000096:biosynthesis; D051956:Goosecoid Protein; D018398:Homeodomain Proteins; D060850:LIM-Homeodomain Proteins; D008969:Molecular Sequence Data; D009132:Muscles / Q000196:embryology*; D009154:Mutation; D009420:Nervous System / Q000196:embryology*; D009672:Notochord / Q000196:embryology; D014176:Protein Biosynthesis; D011506:Proteins; D012333:RNA, Messenger / Q000235:genetics; D012097:Repressor Proteins; D015398:Signal Transduction; D020825:T-Box Domain Proteins; D014157:Transcription Factors; D029867:Xenopus Proteins; D014982:Xenopus laevis; D000098908:Brachyury Protein; D000099176:Noggin Protein
D002352:Carrier Proteins; D017931:DNA Primers; D004268:DNA-Binding Proteins; D005326:Fetal Proteins; D038681:Follistatin; D006023:Glycoproteins; D051956:Goosecoid Protein; D018398:Homeodomain Proteins; D060850:LIM-Homeodomain Proteins; D011506:Proteins; D012333:RNA, Messenger; D012097:Repressor Proteins; D020825:T-Box Domain Proteins; D014157:Transcription Factors; D029867:Xenopus Proteins; D000098908:Brachyury Protein; D000099176:Noggin Protein; C543964:Lhx1 protein, Xenopus