[31]Construction of heteroplasmic mice containing two mitochondrial DNA genotypes by micromanipulation of single-cell embryos

This chapter discusses the construction of heteroplasmic mice containing two mitochondrial DNA genotypes by micromanipulation of single-cell embryos. Mitochondrial DNA heteroplasmy can be artificially created in mice by using a combination of methods developed for altering the nuclear genotype of mouse embryos. Although difficult, the procedures are feasible for any laboratory experienced in transgenic mouse production. Artificial heteroplasmic mice differ from naturally occurring heteroplasmic animals in having multiple sequence differences in their mitochondrial DNA (mtDNA) genomes, making it easy to distinguish the rate of segregation from mutation. Studies with these animals suggest that several unexpected events can occur during mtDNA segregation and selection in mammals. Heteroplasmy appears important in the creation of normal variation within the mtDNA of a mammalian species and for the phenotypic variation seen in individuals with mixtures of normal and defective mtDNA genotypes. To examine the segregation rate of mtDNA genomes in mammals, there is a development of techniques to produce mice containing two genetically distinct, functional mitochondria within individual cells of the animals. The methods may also be useful for creating mice containing in vitro modified mtDNA.