Fig. 1.

Age-dependent DNA hypomethylation in the zebrafish genome. a The genomic DNA of zebrafish sperm, 2-day post fertilization embryos (d2), and muscle of 3-, 12-, and 30-month-old fish (3 m, 12 m, and 30 m, respectively) were digested with each of the three methylation-sensitive restriction enzymes indicated and were run on an agarose gel. HpyCH4IV digestion clearly showed age-dependent hypomethylation. MspI, an isoschizomer of HpaII, is a methylation-insensitive enzyme. b Genomic DNAs of sperm, embryos (h; hours post fertilization), and adult muscle of the indicated ages were digested with HpyCH4IV. Hypomethylation was recognizable as early as d2 and became evident at d6 (larval stage). A high molecular weight DNA band was seen until 9 months (lanes 2 ~ 11, white arrowhead). No discernible difference in the smearing pattern was observed after 12 months (lanes 12 ~ 14). c Liver DNA from four individuals of 1- and 30-month-old zebrafish were digested and electrophoresed as in b. d Genomic DNA isolated from various tissues of an aged zebrafish (30-month-old) was digested with HpyCH4IV and run on an agarose gel. The molecular marker of DNA loaded on the first lane of each gel was a 1-kb ladder. The 100-bp DNA ladder was also loaded on the last lane in b