IRVINE, Steven Q; University of Rhode Island: Genomic regulation of the Dll-A/B gene cluster in Ciona intestinalis.

The ascidian Ciona intestinalis has a compact genome, including an apparent homolog of the Dlx clusters in vertebrates. The Dll-A/B cluster in C. intestinalis is much smaller than its vertebrate counterparts, and in combination with the ability in ascidians to introduce transgenes by electroporation, forms a good model system for the study of the common genomic motif of clustered developmental genes. We have made a 20 kilobase construct with a reporter gene inserted in an exon of Dll-B, which includes the entire gene cluster along with upstream regions. This transgene faithfully reproduces much of the endogenous spatial and temporal pattern of expression for Dll-B. Comparison with reporter constructs which include less flanking DNA, and/or a reporter gene inserted in Dll-A, suggest that interactions between cis-regulatory elements and both of the cluster’s promoters are in part responsible for the specificity of the endogenous expression pattern.