Xenomitochondrial embryonic stem cells and mice: modeling human mitochondrial biology and disease

Abstract

The characterization of mitochondrial diseases has proceeded rapidly since the first descriptions of mitochondrial DNA (mtDNA)-linked disease mutations appeared in the late 1980s. To elucidate mechanisms of a variety of mitochondrial disorders and disease, both in vitro and in vivo modeling systems have been exploited. To produce these models, numerous approaches have been undertaken due to the difficulty associated with targeted mutagenesis and directed modification of the mitochondrial genome. Currently available models of mitochondrial disease are discussed in this paper, including our xenomitochondrial mice. In this model, mitochondria from one donor species are transferred to another. By doing so, cells and animals were generated with varying levels of heteroplasmy (or homoplasmy) for the introduced mitochondrial genomes. This caused graded variations in electron transport chain (ETC) dysfunction which were dependent upon the evolutionary divergence between donor and recipient. The protocol in generating these models involved the utilization of rhodamine-6G (R6G) to remove or eliminate endogenous mtDNA from the recipient cells. This paper will highlight the process and the implications of R6G treatment of mouse embryonic stem (ES) cells to create transmitochondrial cybrids. We summarize the history and mechanism of action of R6G as well as the future prospects for xenomitochondrial models toward increasing our understanding of mitochondrial biology and the dynamic interplay in signaling between mitochondria and the nucleus.