Analysis of cis-regulatory elements controlling spatio-temporal expression of T-brain gene in sea urchin, Hemicentrotus pulcherrimus.

In sea urchin development, micromere descendants play important roles in skeletogenesis and induction of gastrulation. We previously reported that the T-brain homolog of sea urchin Hemicentrotus pulcherrimus, HpTb expresses specifically in micromere descendants and is required for induction of gastrulation and skeletogenesis. Thus, HpTb is thought to play important roles in the function of micromere-lineage cells. To identify cis-regulatory regions responsible for spatio-temporal gene expression of HpTb, we isolated approximately 7kb genomic region of HpTb gene and showed that GFP expression driven by this region exhibits the spatio-temporal pattern corresponding substantially to that of endogenous HpTb expression. Deletion of interspecifically conserved C2 and C4 regions resulted in an increase of ectopic expression. Mutations in Hairy family and Snail family consensus sequences in C1 and C2 regions also increased ectopic expression. Furthermore, we demonstrated that C4 region functions as enhancer, and that three Ets family consensus sequences are involved in this activity but not in spatial regulation. Therefore, we concluded that expression of HpTb gene is regulated by multiple cis-regulatory elements.