HNF1(beta) is required for mesoderm induction in the Xenopus embryo.
XHNF1(&bgr;) is a homeobox-containing gene initially expressed at the blastula stage in the vegetal part of the Xenopus embryo. We investigated its early role by functional ablation, through mRNA injection of an XHNF1(beta)/engrailed repressor fusion construct (XHNF1(beta)/EngR). Dorsal injections of XHNF1(beta)/EngR mRNA abolish dorsal mesoderm formation, leading to axial deficiencies; ventral injections disrupt ventral mesoderm formation without affecting axial development. XHNF1(beta)/EngR phenotypic effects specifically depend on the DNA-binding activity of its homeodomain and are fully rescued by coinjection of XHNF1(beta) mRNA. Vegetal injection of XHNF1(beta)/EngR mRNA blocks the mesoderm-inducing ability of vegetal explants. Both B-Vg1 and VegT maternal determinants trigger XHNF1(beta) expression in animal caps. XHNF1(beta)/EngR mRNA blocks B-Vg1-mediated, but not by eFGF-mediated, mesoderm induction in animals caps. However, wild-type XHNF1(beta) mRNA does not trigger Xbra expression in animal caps. We conclude that XHNF1(beta) function is essential, though not sufficient, for mesoderm induction in the Xenopus embryo.
Vignali
R
R
Dipartimento di Fisiologia e Biochimica, Laboratori di Biologia Cellulare e dello Sviluppo, Università di Pisa, Via G. Carducci 13, Italy. rvignali@dfb.unipi.it.
Poggi
L
L
Madeddu
F
F
Barsacchi
G
G
D000818:Animals; D001483:Base Sequence; D019521:Body Patterning / Q000187:drug effects / Q000235:genetics; D017931:DNA Primers / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics*; D004627:Embryonic Induction / Q000187:drug effects / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D005801:Genes, Homeobox; D051539:Hepatocyte Nuclear Factor 1-beta; D017403:In Situ Hybridization; D008648:Mesoderm / Q000166:cytology* / Q000378:metabolism; D008845:Microinjections; D010641:Phenotype; D012333:RNA, Messenger / Q000008:administration & dosage / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics*; D016212:Transforming Growth Factor beta / Q000235:genetics; D014981:Xenopus / Q000196:embryology* / Q000235:genetics* / Q000378:metabolism; D029867:Xenopus Proteins
D017931:DNA Primers; D004268:DNA-Binding Proteins; C000627649:Hnf1b protein, Xenopus; D012333:RNA, Messenger; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D029867:Xenopus Proteins; D051539:Hepatocyte Nuclear Factor 1-beta