Juan H-C, Lin Y, Chen H-R, Fann M-J
Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei, Taiwan, Republic of China.
Brain Research Center, National Yang-Ming University, Taipei, Taiwan, Republic of China.
Cell Death Differ. 2016 Jun;23(6):1038-48. doi: 10.1038/cdd.2015.157. Epub 2015 Dec 11.
The maintenance of genomic integrity during early embryonic development is important in order to ensure the proper development of the embryo. Studies from cultured cells have demonstrated that cyclin-dependent kinase 12 (Cdk12) is a multifunctional protein that maintains genomic stability and the pluripotency of embryonic stem cells. Perturbation of its functions is also known to be associated with pathogenesis and drug resistance in human cancers. However, the biological significance of Cdk12 in vivo is unclear. Here we bred mice that are deficient in Cdk12 and demonstrated that Cdk12 depletion leads to embryonic lethality shortly after implantation. We also used an in vitro culture system of blastocysts to examine the molecular mechanisms associated with the embryonic lethality of Cdk12-deficient embryos. Cdk12(-/-) blastocysts fail to undergo outgrowth of the inner cell mass because of an increase in the apoptosis of these cells. Spontaneous DNA damage was revealed by an increase in 53BP1 foci among cells cultured from Cdk12(-/-) embryos. Furthermore, the expression levels of various DNA damage response genes, namely Atr, Brca1, Fanci and Fancd2, are reduced in Cdk12(-/-) embryos. These findings indicate that Cdk12 is important for the correct expression of some DNA damage response genes and indirectly has an influence on the efficiency of DNA repair. Our report also highlights that DNA breaks occurring during DNA replication are frequent in mouse embryonic cells and repair of such damage is critical to the successful development of mouse embryos.
在早期胚胎发育过程中维持基因组完整性对于确保胚胎的正常发育至关重要。来自培养细胞的研究表明，细胞周期蛋白依赖性激酶12（Cdk12）是一种多功能蛋白，可维持基因组稳定性和胚胎干细胞的多能性。其功能的紊乱也已知与人类癌症的发病机制和耐药性有关。然而，Cdk12在体内的生物学意义尚不清楚。在这里，我们培育了缺乏Cdk12的小鼠，并证明Cdk12的缺失会导致植入后不久胚胎致死。我们还使用了囊胚的体外培养系统来研究与Cdk12缺陷胚胎的胚胎致死相关的分子机制。由于这些细胞的凋亡增加，Cdk12（-/-）囊胚未能经历内细胞团的生长。从Cdk12（-/-）胚胎培养的细胞中53BP1病灶的增加揭示了自发DNA损伤。此外，各种DNA损伤反应基因，即Atr、Brca1、Fanci和Fancd2在Cdk12（-/-）胚胎中的表达水平降低。这些发现表明，Cdk12对于某些DNA损伤反应基因的正确表达很重要，并间接影响DNA修复的效率。我们的报告还强调，在小鼠胚胎细胞中，DNA复制过程中发生的DNA断裂很频繁，修复这种损伤对于小鼠胚胎的成功发育至关重要。
