SpMyb functions as an intramodular repressor to regulate spatial expression of CyIIIa in sea urchin embryos.

The CyIIIa actin gene of Strongylocentrotus purpuratus is transcribed exclusively in the embryonic aboral ectoderm, under the control of 2.3 kb cis-regulatory domain that contains a proximal module that controls expression in early embryogenesis, and a middle module that controls expression in later embryogenesis. Previous studies demonstrated that the SpRunt-1 target site within the middle module is required for the sharp increase in CyIIIa transcription which accompanies differentiation of the aboral ectoderm, and that a negative regulatory region near the SpRunt-1 target site is required to prevent ectopic transcription in the oral ectoderm and skeletogenic mesenchyme.

Green Fluorescent Protein in the sea urchin: new experimental approaches to transcriptional regulatory analysis in embryos and larvae.

The use of Green Fluorescent Protein (GFP) as a reporter for expression transgenes opens the way to several new experimental strategies for the study of gene regulation in sea urchin development. A GFP coding sequence was associated with three different previously studied cis-regulatory systems, viz those of the SM50 gene, expressed in skeletogenic mesenchyme, the CyIIa gene, expressed in archenteron, skeletogenic and secondary mesenchyme, and the Endo16 gene, expressed in vegetal plate, archenteron and midgut. We demonstrate that the sensitivity with which expression can be detected is equal to or greater than that of whole-mount in situ hybridization applied to detection of CAT mRNA synthesized under the control of the same cis-regulatory systems.

Developmental expression of synthetic cis-regulatory systems composed of spatial control elements from two different genes.

Synthetic cis-regulatory systems consisting of positively and negatively acting cis-regulatory modules of the Endo16 gene were combined with the lineage-specific regulatory element of the SM50 gene associated with a reporter and injected into eggs of sea urchins. We show here that synthetic cis-regulatory systems consisting of the positive Endo16 regulatory elements linked with the SM50 regulatory element are expressed spatially exactly as the sum of the individual endodermal and skeletogenic expression patterns. In combination, both lineage-specific positive regulatory elements function autonomously.

Modular cis-regulatory organization of developmentally expressed genes: two genes transcribed territorially in the sea urchin embryo, and additional examples.

The cis-regulatory systems that control developmental expression of two sea urchin genes have been subjected to detailed functional analysis. Both systems are modular in organization: specific, separable fragments of the cis-regulatory DNA each containing multiple transcription factor target sites execute particular regulatory subfunctions when associated with reporter genes and introduced into the embryo. The studies summarized here were carried out on the CyIIIa gene, expressed in the embryonic aboral ectoderm and on the Endo16 gene, expressed in the embryonic vegetal plate, archenteron, and then midgut.

SpRunt-1, a new member of the runt domain family of transcription factors, is a positive regulator of the aboral ectoderm-specific CyIIIA gene in sea urchin embryos.

In this paper we present a structural and functional characterization of a new sea urchin embryo transcription factor, SpRunt-1. This factor was isolated by means of its specific interaction with a cis-regulatory target site of the CyIIIa gene. Here we show that this target site, the P7I site, is required for normal embryonic activation of CyIIIa x CAT reporter gene constructs.