Molecular identification of spadetail: regulation of zebrafish trunk and tail mesoderm formation by T-box genes.
Inhibition of fibroblast growth factor (FGF) signaling prevents trunk and tail formation in Xenopus and zebrafish embryos. While the T-box transcription factor Brachyury (called No Tail in zebrafish) is a key mediator of FGF signaling in the notochord and tail, the pathways activated by FGF in non-notochordal trunk mesoderm have been uncertain. Previous studies have shown that the spadetail gene is required for non-notochordal trunk mesoderm formation; spadetail mutant embryos have major trunk mesoderm deficiencies, but relatively normal tail and notochord development. We demonstrate here that spadetail encodes a T-box transcription factor with homologues in Xenopus and chick. Spadetail is likely to be a key mediator of FGF signaling in trunk non-notochordal mesoderm, since spadetail expression is regulated by FGF signaling. Trunk and tail development are therefore dependent upon the complementary actions of two T-box genes, spadetail and no tail. We show that the regulatory hierarchy among spadetail, no tail and a third T-box gene, tbx6, are substantially different during trunk and tail mesoderm formation, and propose a genetic model that accounts for the regional phenotypes of spadetail and no tail mutants.
Griffin
K J
KJ
Department of Biochemistry, Box 357350, University of Washington, Seattle, Washington 98195-7350, USA.
Amacher
S L
SL
Kimmel
C B
CB
Kimelman
D
D
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D017931:DNA Primers / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology; D005326:Fetal Proteins; D005346:Fibroblast Growth Factors / Q000502:physiology; D018507:Gene Expression Regulation, Developmental; D017403:In Situ Hybridization; D008648:Mesoderm / Q000166:cytology / Q000502:physiology; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009154:Mutation; D010641:Phenotype; D016133:Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D020825:T-Box Domain Proteins; D013623:Tail / Q000196:embryology; D014157:Transcription Factors / Q000235:genetics* / Q000502:physiology; D014714:Vertebrates / Q000196:embryology / Q000235:genetics; D015027:Zebrafish / Q000196:embryology* / Q000235:genetics* / Q000502:physiology; D029961:Zebrafish Proteins; D000098908:Brachyury Protein
D017931:DNA Primers; D004268:DNA-Binding Proteins; D005326:Fetal Proteins; D005346:Fibroblast Growth Factors; D020825:T-Box Domain Proteins; D014157:Transcription Factors; D029961:Zebrafish Proteins; D000098908:Brachyury Protein; C112539:tbx16 protein, zebrafish