Fig. 4

Deletions and mutations reveal sites important for regulatory activity. E5 chick retinae were electroporated with full length (a) ECR65 or (b) ECR9 driving TdT along truncated or mutated versions of the enhancers and CAG::IRFP as a co-electroporation control. Retinae were cultured for 18–22 h before dissociation and analysis by flow cytometry. Labelled blocks in (a) and (b) represent the enhancer constructs labelled along the Y-axis. Grey blocks in (c) and (d) denote putative TF binding sites. Deleted versions of enhancers were oriented in the expression vector such that the truncated end is farther from the TATA box. Percent of enhancer activity was calculated as a ratio between the total GFP(+) cells and the total TdT(+) cells and scaled to the activity of the full-length enhancer. Error bars represent 95% confidence interval. See Methods section for statistical tests