Analyzes of genes responsible for aging and the pathogenesis of diabetes by isolation of transgenic mice with pathogenic mtDNA mutation

我们发现，用抗肿瘤双嵌入剂ditercalinium处理，在我们测试的所有小鼠细胞系中完全排除mtDNA是非常有效的。由此产生的小鼠无mtDNA（rho^0）细胞系通过rho^0细胞与小鼠脑突触体（代表从神经细胞分离的突触末梢）融合，成功地用于捕获活神经细胞的mtDNA进入分裂的培养细胞。具有神经元mtDNA的胞质杂交体克隆获得了所有恢复的线粒体翻译活性，无论mtDNA是来自年轻小鼠还是老年小鼠，这表明至少线粒体基因组中的缺陷不涉及在老年小鼠脑中观察到的与年龄相关的线粒体功能障碍。此外，我们可以捕获非常少量的常见的5823 bp缺失突变体mtDNA（DELTAmtDNA^<5823>），其可以通过PCR在胞质杂交体克隆中检测到。由于在细胞质杂交体的长期培养过程中，大规模缺失的突变mtDNA的数量预计会增加，这些细胞应该可以用于建立含有缺失突变mtDNA的小鼠。虽然我们不能实现本项目的主要目的，但我们成功分离rho^0小鼠细胞将引导我们分离mtDNA敲除小鼠。

We found that treatment with ditercalinium, an antitumor bis-intercalating agent, was extremely effective for completely excluding mtDNA in all the mouse cell lines we tested. The resulting mouse mtDNA-less (rho^0) cell lines were succesafully used for trapping mtDNA of living nerve cells into dividing cultured cells by fusion of the rho^0 cells with mouse brain synaptosomes, which represent synaptic endings isolated from nerve cells. The cybrid clones with neuronal mtDNA obtained all restored mitochondrial translation activity similarly irrespective of whether the mtDNA was derived from young or aged mice, suggesting that at least defects in mitochondrial genomes are not involved in the age-associated mitochondrial dysfunction observed in the brain of aged mice. Furthermore, we could trap a very small amount of a common 5823 bp-deletion mutant mtDNA (DELTAmtDNA^<5823>) that was detectable by PCR in the cybrid clones. As the amount of mutant mtDNA with large-scale deletions was expected to increase during prolonged cultivation of the cybrids, these cells should be available for establishment of mice containing the deletion mutant mtDNA.Although we could not accomplish the main purpose of this project, our sucesss for isolation of rho^0 mouse cells would lead us to the isolation of mtDNA knockout mice.