ChIP-seq provides a genome-wide view of the binding sites of Alx1, a pivotal transcription factor in a gene regulatory network that controls skeletogenesis in sea urchins and other echinoderms. Overall design: Three independent cultures of S. purpuratus were collected and processed at the mesenchyme blastula stage (24 hpf). For each culture, ChIP was performed using a-Sp-Alx1 and normal rabbit IgG (Sigma-Aldrich, Cat. No. 12370) was used for mock IP.