Cleavage and morphogenesis of Ciona embryos was blocked by treatment with cytochalasin B prior to gastrulation. Drug treated embryos and DMSO treated controls were harvested at stage 19.5 (after control embryos had undergone neurulation and were completing notochord intercalation). Only 55 genes showed a significant difference in expression between the two treatments. Overall design: Dechorionated embryos were treated with 10 uM cytochalasinB or with DMSO alone as a control. Drug was added at 3.75 hpf at 21.5C (64 cell stage). For each of the replicates, 400 experimental and 400 control embryos were harvested at stage 19.5 (7.5hpf) for RNA purification. Triple biological replicates of purified RNA were analyzed by RNAseq and transcript enrichment was calculated using the Cufflinks software suite