Mitochondrial DNA haplotypes define gene expression patterns in pluripotent and differentiating embryonic stem cells

Mitochondrial DNA haplotypes are associated with various phenotypes, such as altered susceptibility to disease, environmental adaptations and ageing. Accumulating evidence suggests that mitochondrial DNA is essential for cell differentiation and the cell phenotype. However, the effects of different mitochondrial DNA haplotypes on differentiation and development remain to be determined. Using embryonic stem cell lines possessing the same Mus musculus chromosomes but harboring one of Mus musculus, Mus spretus or Mus terricolor mitochondrial DNA haplotypes, we have determined the effects of different mitochondrial DNA haplotypes on chromosomal gene expression, differentiation and mitochondrial metabolism. In undifferentiated and differentiating embryonic stem cells, we observed mitochondrial DNA haplotype-specific expression of genes involved in pluripotency, differentiation, mitochondrial energy metabolism and DNA methylation. These mitochondrial DNA haplotypes also influenced the potential of embryonic stem cells to produce spontaneously beating cardiomyocytes. The differences in gene expression patterns and cardiomyocyte production were independent of ATP content, oxygen consumption and respiratory capacity, which until now have been considered to be the primary roles of mitochondrial DNA. Differentiation of embryonic stem cells harboring the different mitochondrial DNA haplotypes in a 3D environment significantly increased chromosomal gene expression for all haplotypes during differentiation. However, haplotype-specific differences in gene expression patterns were maintained in this environment. Taken together, these results provide significant insight into the phenotypic consequences of mitochondrial DNA haplotypes and demonstrate their influence on differentiation and development. We propose that mitochondrial DNA haplotypes play a pivotal role in the process of differentiation and mediate the fate of the cell.