The snail repressor establishes a muscle/notochord boundary in the Ciona embryo.

Abstract	Previous studies have identified a minimal 434 bp enhancer from the promoter region of the Ciona Brachyury gene (Ci-Bra), which is sufficient to direct a notochord-specific pattern of gene expression. Here we present evidence that a Ciona homolog of snail (Ci-sna) encodes a repressor of the Ci-Bra enhancer in the tail muscles. DNA-binding assays identified four Ci-Sna-binding sites in the Ci-Bra enhancer, and mutations in these sites cause otherwise normal Ci-Bra/lacZ transgenes to be misexpressed in ectopic tissues, particularly the tail muscles. Selective misexpression of Ci-sna using a heterologous promoter results in the repression of Ci-Bra/lacZ transgenes in the notochord. Moreover, the conversion of the Ci-Sna repressor into an activator results in the ectopic induction of Ci-Bra/lacZ transgenes in the muscles, and also causes an intermixing of notochord and muscle cells during tail morphogenesis. These results suggest that Ci-Sna functions as a boundary repressor, which subdivides the mesoderm into separate notochord and tail muscle lineages.
Authors	S Fujiwara, J C Corbo, M Levine
Journal	Development (Cambridge, England) (Development) Vol. 125 Issue 13 Pg. 2511-20 (Jul 1998) ISSN: 0950-1991 [Print] England
PMID	9609834 (Publication Type: Journal Article, Research Support, U.S. Gov't, Non-P.H.S.)
Chemical References	DNA-Binding Proteins Recombinant Fusion Proteins Repressor Proteins Snail Family Transcription Factors Transcription Factors
Topics	Animals Animals, Genetically Modified Base Sequence Body Patterning Ciona intestinalis (embryology, genetics) DNA-Binding Proteins (biosynthesis, genetics) Embryo, Nonmammalian (physiology) Embryonic Induction Gene Expression Regulation, Developmental In Situ Hybridization Molecular Sequence Data Muscles (embryology) Mutagenesis, Site-Directed Notochord (physiology) Recombinant Fusion Proteins (biosynthesis) Repressor Proteins (biosynthesis) Restriction Mapping Snail Family Transcription Factors Transcription Factors

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