Interplay of negative and positive signals controls endoderm-specific expression of the ascidian Cititf1 gene promoter

Cititf1 is an early and specific marker of endoderm development in Ciona intestinalis [Ristoratore, F., et al. (1999) Development 126, 5149]. Here, we examine Cititf1 transcriptional regulation focusing in particular on its endodermal restricted expression. Through the analysis of Ciona embryos, electroporated with different portions of Cititf1 5'-flanking region fused to lacZ, we characterized a minimal 300-bp cis-regulatory sequence able to closely reproduce the spatial and temporal expression pattern of the endogenous gene. This enhancer contains at least three distinct regulatory regions, two of which are responsible for activation of transcription in the endoderm and in the mesenchyme, respectively, while the third is a negative control element that represses mesenchyme transcription. We have further defined the sequences responsible for transcriptional activation in the endoderm by clustered point mutations and DNA-binding assays. (C) 2003 Elsevier Inc. All rights reserved.