Cytoplasmic hybrid (cybrid) cell lines as a practical model for mitochondriopathies

Abstract

Cytoplasmic hybrid (cybrid) cell lines can incorporate human subject mitochondria and perpetuate its mitochondrial DNA (mtDNA)-encoded components. Since the nuclear background of different cybrid lines can be kept constant, this technique allows investigators to study the influence of mtDNA on cell function. Prior use of cybrids has elucidated the contribution of mtDNA to a variety of biochemical parameters, including electron transport chain activities, bioenergetic fluxes, and free radical production. While the interpretation of data generated from cybrid cell lines has technical limitations, cybrids have contributed valuable insight into the relationship between mtDNA and phenotype alterations. This review discusses the creation of the cybrid technique and subsequent data obtained from cybrid applications.

Keywords: Cybrid; Mitochondria; Mitochondrial DNA; Rho zero.

Graphical abstract

Fig. 1

The mitochondrial genome. This figure depicts the circular mitochondrial genome. Structural genes are shown in yellow. rRNA genes are shown in blue, while tRNA genes are shown in black. The regulatory region, D-loop, is shown in red. CO = cytochrome oxidase, ND = NADH dehydrogenase.

Fig. 2

Cybrid generation techniques. Cybrids are produced by combining cytoplasm from nucleated cells with non-nucleated cells or cytoplasts. The nucleated cell can be unaltered, or could have undergone depletion of endogenous mtDNA before cytoplasmic mixing. In either case, the goal is to populate the nucleated cell with mtDNA from the non-nucleated cell.

Fig. 3

Applications of the cybrid model. Cybrids can be used to (A) evaluate heteroplasmy-threshold corrections. It is unknown whether heteroplasmic mtDNA changes are found at the cellular level or the level of each mitochondrion. Such that, a single mitochondria could contain both wild-type and mutated mtDNA, or a cell could contain a population of mitochondria which have wild-type mtDNA and a population of mitochondria which have mutant mtDNA. Beyond that, a particular cell could contain all wild-type mtDNA, while a separate cell contains all mutant mtDNA. (B) Test mtDNA–nuclear DNA compatibility and (C) screen for mtDNA-determined functional differences between cell lines containing mtDNA from different sources.