DEVELOPMENTAL EXPRESSION OF SYNTHETIC CIS-REGULATORY SYSTEMS COMPOSEDOF SPATIAL CONTROL ELEMENTS FROM 2 DIFFERENT GENES

Synthetic cis-regulatory systems consisting of positively and negative ly acting cis-regulatory modules of the Endo16 gene were combined with the lineage-specific regulatory element of the SM50 gene associated w ith a reporter and injected into eggs of sea urchins. We show here tha t synthetic cis-regulatory systems consisting of the positive Endo16 r egulatory elements linked with the SM50 regulatory element are express ed spatially exactly as the sum of the individual endodermal and skele togenic expression patterns. In combination, both lineage-specific pos itive regulatory elements function autonomously. However, addition of the Endo16 regulatory module that represses ectopic skeletogenic expre ssion of Endo16 receptor constructs does not affect expression driven by the SM50 regulatory elements in the same skeletogenic cells. The re pression function of this element is thus dedicated to control of the positive spatial output of the Endo16 regulatory system.