Kiessling A A, Markoulaki S
Department of Surgery, Beth Israel Deaconess Medical Center, Boston, Massachusetts 02115, USA.
Mol Reprod Dev. 2000 Jun;56(2 Suppl):271-4. doi: 10.1002/(SICI)1098-2795(200006)56:2+<271::AID-MRD12>3.0.CO;2-N.
The mechanism of incorporation of foreign DNA into newly fertilized eggs is poorly understood. It is not known with certainty if S phase DNA replication is required or if integration could occur at other times of the cell cycle that involve DNA strand breaks, such as chromatin rearrangements. We have investigated DNA strand breaks in mouse eggs and zygotes with a sensitive terminal uridine nucleotide end labeling (TUNEL) assay. Greater than 90% of all polar bodies and metaphase II chromosomes in freshly ovulated mouse eggs are TUNEL-assay positive. Approximately one-third of zygotes assayed 6 hr after fertilization contain at least one TUNEL assay positive pro-nucleus and/or decondensing sperm head. These results indicate that early embryonic DNA contains multiple transient DNA breaks that could play a role in the incorporation of foreign DNA.
外源DNA整合到新受精卵子中的机制目前尚不清楚。S期DNA复制是否是必需的，或者整合是否能在细胞周期的其他涉及DNA链断裂的时期（如染色质重排）发生，目前还不确定。我们用灵敏的末端尿苷酸末端标记（TUNEL）试验研究了小鼠卵子和受精卵中的DNA链断裂情况。刚排卵的小鼠卵子中，超过90%的极体和中期II染色体的TUNEL试验呈阳性。受精后6小时检测的受精卵中，约三分之一至少含有一个TUNEL试验呈阳性的原核和/或正在解聚的精子头部。这些结果表明，早期胚胎DNA含有多个短暂的DNA断裂，可能在外源DNA整合中发挥作用。
