Ku70 and non-homologous end joining protect testicular cells from DNA damage
Ku70 and non-homologous end joining protect testicular cells from DNA damage
复制标题
DOI：
10.1242/jcs.122788
复制
发表时间：
2013-07-15
影响因子：
4
通讯作者：
Scherthan, Harry
中科院分区：
文献类型：
--
作者：
Ahmed, Emad A.;Sfeir, Agnel;Scherthan, Harry
精子发生是一个复杂的过程，产生单倍体生殖细胞或孢子，并进行减数分裂，这是同源染色体分离所需的两次特殊细胞分裂的连续过程。在第一次减数分裂的前期，同源重组（HR）在端粒移动的情况下修复Spo 11依赖的DNA双链断裂（DSB），以允许在减数分裂I分裂时染色体配对和分离。与HR相反，非同源末端连接（NHEJ），在G1细胞周期阶段期间的主要DSB修复机制，在早期减数分裂前期下调。在体细胞哺乳动物端粒，NHEJ因子Ku 70/80抑制HR，就像shelterin复合物的Rap 1组分一样。在这里，我们研究Ku 70和Rap 1的作用，在减数分裂端粒重新分配和基因组保护精子发生的单和双基因敲除小鼠。Ku 70（-/-）小鼠显示睾丸尺寸减小和精子发生受损，而在Ku 70（-/-）和Ku 70（-/-）Rap 1（Delta/Delta）敲除精母细胞中正常发生减数分裂端粒动力学和染色体束形成。中期前细线期频率升高与Ku缺陷型B精原细胞和分化的支持细胞DNA损伤显著增加相关。Ku 70（-/-）双线期精母细胞中γ H2 AX灶水平显著升高，表明DSB亚组的DNA修复进展受损。这可能解释了Ku 70缺陷的第十二阶段睾丸小管中存在的减数分裂中期凋亡升高，表明纺锤体组装检查点激活。总之，我们的数据表明Ku 70对于修复睾丸体细胞和晚期精母细胞中的DSB是重要的，从而确保精子发生的保真度。
Spermatogenesis is a complex process that generates haploid germ cells or spores and implements meiosis, a succession of two special cell divisions that are required for homologous chromosome segregation. During prophase to the first meiotic division, homologous recombination (HR) repairs Spo11-dependent DNA double-strand breaks (DSBs) in the presence of telomere movements to allow for chromosome pairing and segregation at the meiosis I division. In contrast to HR, non-homologous end joining (NHEJ), the major DSB repair mechanism during the G1 cell cycle phase, is downregulated during early meiotic prophase. At somatic mammalian telomeres, the NHEJ factor Ku70/80 inhibits HR, as does the Rap1 component of the shelterin complex. Here, we investigated the role of Ku70 and Rap1 in meiotic telomere redistribution and genome protection in spermatogenesis by studying single and double knockout mice. Ku70(-/-) mice display reduced testis size and compromised spermatogenesis, whereas meiotic telomere dynamics and chromosomal bouquet formation occurred normally in Ku70(-/-) and Ku70(-/-) Rap1(Delta/Delta) knockout spermatocytes. Elevated mid-preleptotene frequencies were associated with significantly increased DNA damage in Ku-deficient B spermatogonia, and in differentiated Sertoli cells. Significantly elevated levels of gamma H2AX foci in Ku70(-/-) diplotene spermatocytes suggest compromised progression of DNA repair at a subset of DSBs. This might explain the elevated meiotic metaphase apoptosis that is present in Ku70-deficient stage XII testis tubules, indicating spindle assembly checkpoint activation. In summary, our data indicate that Ku70 is important for repairing DSBs in somatic cells and in late spermatocytes of the testis, thereby assuring the fidelity of spermatogenesis.