Genome-wide strategies reveal downstream target genes of Npas4l associated with cardiovascular development in zebrafish [ATAC-Seq]

The development of a vascular network is essential to nourish tissues and sustain organ function throughout life. Endothelial cells (ECs) are the building blocks of blood vessels, yet our understanding of EC specification in vertebrates remains incomplete. cloche/npas4l mutants have broadly been used as an avascular model in zebrafish, but little is known about the molecular mechanism of action of Npas4l. Here, to identify the direct and indirect target genes of this transcription factor, we combined complementary genome-wide approaches, including transcriptome analyses and chromatin immunoprecipitation (ChIP). The cross-analysis of these datasets indicate that Npas4l functions as a master regulator by directly inducing a wave of transcription factor genes crucial for hematoendothelial specification in vertebrates, including etv2, tal1, and lmo2. We identified additional target genes acting downstream of npas4l and investigated the function of a subset of them using CRISPR/Cas9 technology. Phenotypic characterization of tspan18b mutants reveals a novel role for tspan18b in developmental angiogenesis, confirming the reliability of the datasets generated. Collectively, these data represent a useful resource for future studies aimed to investigate novel genes with a potential role in vascular development and EC fate determination in vertebrates. ATAC-seq examination of wild type and npas4lbns297/bns297 zebrafish embryos.