Cummins J M, Wakayama T, Yanagimachi R
School of Veterinary Studies, Murdoch University, Western Australia.
Zygote. 1998 Aug;6(3):213-22. doi: 10.1017/s0967199498000148.
Mouse round spermatids labelled with MitoTracker were microinjected into Sr(2+)-activated mouse oocytes. The labelled mitochondria were tracked up to the morula/blastocyst stage using fluorescence microscopy. The overall incidence of embryos with labelled mitochondria fell from 80% in the 1-cell zygote to 25% in 2-cell, 9% in 4-cell and approximately 1% in 8-cell or later stages. Thus it appears that almost all round spermatid mitochondria finally disappear from embryos during the 4-cell to 8-cell transition, as happens for mature spermatozoa (Cummins et al. Zygote 1997, 5:301-8). The spermatid mitochondria remained tightly bound together during this process. In contrast, labelled primary spermatocyte and cumulus mitochondria dispersed rapidly throughout the oocyte cytoplasm within 3 h. We hypothesise that spermatid mitochondria may be bound together by cytoskeletal elements produced in the early haploid spermatid. These elements, together with terminal differentiation of the sperm mitochondria, may be central to the processes by which the embryo 'recognises' the sperm mitochondria and inhibits inheritance of paternal mitochondrial DNA. These results suggest that round spermatid injection for infertile men will not pose a significant risk to offspring by transmitting abnormal mitochondrial genomes.
将用MitoTracker标记的小鼠圆形精子细胞显微注射到经Sr(2+)激活的小鼠卵母细胞中。使用荧光显微镜追踪标记的线粒体直至桑椹胚/囊胚阶段。带有标记线粒体的胚胎的总体发生率从1细胞合子阶段的80%下降到2细胞阶段的25%、4细胞阶段的9%以及8细胞或更后期阶段的约1%。因此，似乎几乎所有圆形精子细胞的线粒体最终在4细胞到8细胞转变过程中从胚胎中消失，就像成熟精子的情况一样（Cummins等人，《合子》，1997年，5:301 - 8）。在此过程中，精子细胞的线粒体保持紧密结合在一起。相比之下，标记的初级精母细胞和卵丘线粒体在3小时内迅速分散到整个卵母细胞细胞质中。我们推测，精子细胞的线粒体可能由早期单倍体精子细胞产生的细胞骨架成分结合在一起。这些成分，连同精子线粒体的终末分化，可能是胚胎“识别”精子线粒体并抑制父系线粒体DNA遗传过程的核心。这些结果表明，对于不育男性进行圆形精子细胞注射不会因传递异常线粒体基因组而对后代构成重大风险。
