Developmental features of DNA methylation during activation of the embryonic zebrafish genome

Zygotic genome activation (ZGA) occurs at the mid-blastula transition (MBT) in zebrafish and is a period of chromatin remodeling. Genome-scale gametic demethylation and remethylation occurs after fertilization, during blastula stages, but how ZGA relates to promoter DNA methylation states is unknown. Using methylated DNA immunoprecipitation coupled to high-density microarray hybridization (MeDIP-ChIP), we characterize genome-wide promoter DNA methylation dynamics before, during and after ZGA onset, in relation changes in post-translational histone modification and gene expression (Series GSE22830). A Kolmogorov-Smirnov (KS) test was applied with P <= 0.01 to identify methylation peaks. MeDIP-chip experiments were performed on24 hpf zebrafish embryos and sperm. Samples were lysed and proteins digested by proteinase k treatment. DNA was extracted with phenol-chloroform-isoamylalcohol and ethanol precipitation. The DNA was RNAse treated and sonicated to fragment lengths between 300-1000 bp. From each stage, duplicate immuneoprecipitations were performed using anti-5-methylcytosine antibody (10 ng/µl; Mab-006-100; Diagenode) coupled to Dynabeads M-280 sheep anti-mouse IgG (Invitrogen). MeDIP and input DNA (150 ng each) were amplified (WGA-2; Sigma-Aldrich), cleaned up, eluted and processed for array hybridization. MeDIP and input DNA were labeled and co-hybridized onto the Nimbegen promoter arrays. The array covers 15 kb of upstream regulatory sequence and 5 kb downstream of the TSS of all zebrafish genes. A Kolmogorov-Smirnov (KS) test was applied with P <= 0.01 to identify methylation peaks.