Selection of a mtDNA sequence variant in hepatocytes of heteroplasmic mice is not due to differences in respiratory chain function or efficiency of replication
Selection of a mtDNA sequence variant in hepatocytes of heteroplasmic mice is not due to differences in respiratory chain function or efficiency of replication
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DOI：
10.1093/hmg/10.22.2469
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发表时间：
2001-10-15
影响因子：
3.5
通讯作者：
Shoubridge, EA
中科院分区：
文献类型：
--
作者：
Battersby, BJ;Shoubridge, EA
我们以前已经构建了两个近交系（NZB/BinJ和BALB/c）的异质性小鼠品系，以研究mtDNA序列变异的分离机制。几种组织中mtDNA的分离行为分析表明，NZB基因型总是选择在肝/肾和BALB基因型在血液/脾。在有丝分裂后的组织中分离不显著。在这里，我们已经调查了这种新的模式mtDNA分离在离体肝细胞，以确定选择的机制。呼吸链功能的极谱测量结果表明，在BALB核背景下，含有0或91- 97%NZB mtDNA的线粒体之间没有差异。在分离的肝细胞中的mtDNA的单细胞PCR分析表明，大多数肝细胞最终固定NZB基因型。选择率是恒定的，随着时间的推移和独立的初始基因型频率。基于9.4天的mtDNA复制率，NZB mtDNA比BALB mtDNA具有类似于14%的选择性优势;然而，用BrdU进行的体内脉冲标记表明，这不是基于复制效率。令人惊讶的是，当体外培养肝细胞时，大多数独立的集落选择BALB mtDNA，即使它们在最初接种时几乎固定为NZB mtDNA基因型。这些数据表明，这些小鼠肝脏中NZB mtDNA的选择不是基于细胞或细胞器水平上的呼吸链功能，或者简单的复制优势，而是基于与mtDNA维持有关的因素。
We have previously constructed lines of heteroplasmic mice from two inbred strains (NZB/BinJ and BALB/c) to investigate the mechanisms of segregation of mtDNA sequence variants. Analysis of the segregation behaviour of mtDNA in several tissues showed that the NZB genotype was invariably selected in liver/kidney and the BALB genotype in blood/spleen. Segregation was not significant in post-mitotic tissues. Here we have investigated this novel pattern of mtDNA segregation in isolated hepatocytes to determine the mechanism of selection. Polarographic measurements of respiratory chain function showed no difference between mitochondria containing either 0 or 91-97% NZB mtDNAs on a BALB nuclear background. Single-cell PCR analysis of mtDNA in isolated hepatocytes demonstrated that most hepatocytes eventually fix the NZB genotype. The rate of selection was constant with time and independent of the initial genotype frequency. Based on a mtDNA replication rate of 9.4 days, NZB mtDNA has an similar to 14% selective advantage over BALB mtDNA; however, in vivo pulse labelling with BrdU demonstrated that this was not based on efficiency of replication. Surprisingly, when hepatocytes were cultured in vitro, the majority of independent colonies selected BALB mtDNA, even if they were nearly fixed for the NZB mtDNA genotype when initially plated. These data suggest that selection for NZB mtDNA in the liver of these mice is not based on respiratory chain function at the cellular or organellar level, or a simple replicative advantage, but on a factor(s) involved with mtDNA maintenance.