Ueda T, Yamazaki K, Suzuki R, Fujimoto H, Sasaki H, Sakaki Y, Higashinakagawa T
Laboratory of Mammalian Developmental Biology, Mitsubishi Kasei Institute of Life Sciences, Tokyo, Japan.
Development. 1992 Dec;116(4):831-9. doi: 10.1242/dev.116.4.831.
The methylation status of a mouse metallothionein-I/human transthyretin fusion gene was studied during gametogenesis in transgenic mice. In the adult tissues of this mouse line, the promoter region of the transgene on chromosome 11 is methylated when it is maternally inherited and undermethylated when it is paternally inherited. Germ cells from various developmental stages of gametogenesis were isolated, and their DNAs were assayed using methylation-sensitive restriction endonucleases and the polymerase chain reaction. Only low to nonexistent levels of transgene methylation were detected in germ cells from 14.5-day-old male and female fetuses irrespective of the parental origin of the transgene. This undermethylated state persisted in oocytes from newborn females as well as in testicular spermatogenic cells and sperm. By contrast, the transgene promoter was completely methylated in fully grown oocytes arrested at the first meiotic prophase. The endogenous metallothionein-I gene promoter, located on a different chromosome, remained undermethylated at all stages examined, consistent with previous findings reported for a typical CpG island. Taken together, the results suggest that parental-specific adult patterns of transgene methylation are established during gametogenesis.
在转基因小鼠的配子发生过程中，研究了小鼠金属硫蛋白-I/人转甲状腺素蛋白融合基因的甲基化状态。在该小鼠品系的成年组织中，11号染色体上转基因的启动子区域在母系遗传时发生甲基化，而在父系遗传时发生低甲基化。分离了配子发生不同发育阶段的生殖细胞，并使用甲基化敏感的限制性内切酶和聚合酶链反应对其DNA进行检测。无论转基因的亲本来源如何，在14.5天龄的雄性和雌性胎儿的生殖细胞中，仅检测到低水平至不存在的转基因甲基化。这种低甲基化状态在新生雌性的卵母细胞以及睾丸生精细胞和精子中持续存在。相比之下，在第一次减数分裂前期停滞的完全成熟的卵母细胞中，转基因启动子完全甲基化。位于不同染色体上的内源性金属硫蛋白-I基因启动子在所有检测阶段均保持低甲基化，这与先前报道的典型CpG岛的研究结果一致。综上所述，结果表明在配子发生过程中建立了转基因甲基化的亲本特异性成年模式。
