Hiendleder Stefan
Department of Animal Science, The University of Adelaide, Roseworthy Campus, Roseworthy, South Australia 5371, Australia.
Adv Exp Med Biol. 2007;591:103-16. doi: 10.1007/978-0-387-37754-4_8.
Mitochondrial biogenesis and function is under dual genetic control and requires extensive interaction between biparentally inherited nuclear genes and maternally inherited mitochondrial genes. Standard SCNT procedures deprive an oocytes' mitochondrial DNA (mtDNA) of the corresponding maternal nuclear DNA and require it to interact with an entirely foreign nucleus that is again interacting with foreign somatic mitochondria. As a result, most SCNT embryos, -fetuses, and -offspring carry somatic cell mtDNA in addition to recipient oocyte mtDNA, a condition termed heteroplasmy. It is thus evident that somatic cell mtDNA can escape the selective mechanism that targets and eliminates intraspecific sperm mitochondria in the fertilized oocyte to maintain homoplasmy. However, the factors responsible for the large intra- and interindividual differences in heteroplasmy level remain elusive. Furthermore, heteroplasmy is probably confounded with mtDNA recombination. Considering the essential roles of mitochondria in cellular metabolism, cell signalling, and programmed cell death, future experiments will need to assess the true extent and impact of unorthodox mtDNA transmission on various aspects of SCNT success.
线粒体生物发生和功能受双重遗传控制，需要双亲遗传的核基因与母系遗传的线粒体基因之间广泛相互作用。标准的体细胞核移植程序使卵母细胞的线粒体DNA（mtDNA）失去相应的母系核DNA，并要求其与一个完全外来的细胞核相互作用，而这个细胞核又与外来的体细胞线粒体相互作用。结果，大多数体细胞核移植胚胎、胎儿和后代除了携带受体卵母细胞mtDNA外，还携带体细胞mtDNA，这种情况称为异质性。因此很明显，体细胞mtDNA可以逃避在受精卵中靶向并消除种内精子线粒体以维持同质性的选择机制。然而，导致异质性水平在个体内和个体间存在巨大差异的因素仍然难以捉摸。此外，异质性可能与mtDNA重组混淆。考虑到线粒体在细胞代谢、细胞信号传导和程序性细胞死亡中的重要作用，未来的实验需要评估非正统mtDNA传递对体细胞核移植成功的各个方面的真实程度和影响。
