Transcriptional analysis of fluorescence-activated sorted Mesp-GFP-labeled B7.5 founder trunk ventral cell lineage cells from Ciona intestinalis

The Ciona heart progenitor lineage (TVC, trunk ventral cells) is first specified by Fibroblast Growth Factor/Map Kinase (FGF/MapK) activation of the transcription factor Ets1/2 (Ets). For this analysis, B7.5 lineage cells were labeled with the Mesp-GFP reporter. In the first experiment, we targeted a dominant-negative form of the sole Ciona FGF receptor (FGFRdn) to the B7.5 lineage using the Mesp enhancer (Mesp-FGFRdn). In the second experiment, we targeted a dominant repressor form of Ets1/2 to the B7.5 lineage using the Mesp enhancer (Mesp-EtsWRPW). This construct is designed to repress Ets1/2 target gene transcription and has previously been shown to abolish TVC induction. We employed whole-genome microarray analysis of sorted B7.5 lineage cells to identify primary FGF:MapK:Ets1/2 target genes.