Regulation of notochord-specific expression of Ci-Bra downstream genes in Ciona intestinalis embryos.
Brachyury, a T-box transcription factor, is expressed in ascidian embryos exclusively in primordial notochord cells and plays a pivotal role in differentiation of notochord cells. Previously, we identified approximately 450 genes downstream of Ciona intestinalis Brachyury (Ci-Bra), and characterized the expression profiles of 45 of these in differentiating notochord cells. In this study, we looked for cisregulatory sequences in minimal enhancers of 20 Ci-Bra downstream genes by electroporating region within approximately 3 kb upstream of each gene fused with lacZ. Eight of the 20 reporters were expressed in notochord cells. The minimal enchancer for each of these eight genes was narrowed to a region approximately 0.5-1.0-kb long. We also explored the genome-wide and coordinate regulation of 43 Ci-Bra-downstream genes. When we determined their chromosomal localization, it became evident that they are not clustered in a given region of the genome, but rather distributed evenly over 13 of the 14 pairs of chromosomes, suggesting that gene clustering does not contribute to coordinate control of the Ci-Bra downstream gene expression. Our results might provide Insights Into the molecular mechanisms underlying notochord formation in chordates.
Department of Developmental Biology, National Institute for Basic Biology, Okazaki, Aichi 445-8585, Japan. taka@nibb.ac.jp
Hiroki
H
Takahashi
Kohji
K
Hotta
Chiyo
C
Takagi
Naoto
N
Ueno
Nori
N
Satoh
Eiichi
E
Shoguchi
D000818:Animals; D002938:Ciona intestinalis / Q000196:embryology*; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D016678:Genome; D009672:Notochord / Q000378:metabolism*