ATACseq of kdrl-GFP+ endothelial cells in 28hpf zebrafish embryos

The goal of this study is to analyse the open chromatin regions via ATACseq in zebrafish embryonic endothelial cells at 26-27hpf using Tg(Kdrl:GFP) transgenic zebrafish embryos. 40000-50000 cells were FAC-sorted directly into 100 µl of 1x HBSS/10 mM HEPES/0.25% BSA buffer for Tagmentation (as described by Buenrostro et al. (2013), Nat. Methods 10, 1213-1218), but with 1.5 µl Tn5 transposase (Illumina) in a 50 µl reaction volume. DNA was purified using the QIAquick PCR purification kit (Qiagen). Fragments were amplified for 16 cycles. Overall design: Genomic control DNA was isolated from 30.000 cells using the DNeasy Blood & Tissue kit (Qiagen) and eluted with EB buffer. Tagmentation was performed as described. Fragments were amplified for 9 cycles. Sequencing was performed on a NextSeq machine. Sequenced reads were checked for base qualities, trimmed where 20% of the bases were below quality score 20, and filtered to exclude adapters using Trimmomatic (Version 0.32).