Aberrant Nucleo-cytoplasmic Cross-Talk Results in Donor Cell mtDNA Persistence in Cloned Embryos

Abstract

Mitochondrial DNA is an extranuclear genome normally maternally inherited through the oocyte. However, the use of nuclear transfer can result in both donor cell and recipient oocyte mitochondrial DNA persisting through to blastocyst and being transmitted to the offspring. The degree of donor mitochondrial DNA transmission appears to be random and currently no evidence exists to explain this phenomenon. To determine whether this is a dilution factor or directly related to the transcriptional status of the donor cell in respect of mitochondrial DNA transcription factors, we have generated sheep nuclear transfer embryos using donor cells: (1) possessing their full mitochondrial DNA complement, (2) those partially depleted, and (3) those depleted but containing residual levels. For each donor type, donor mitochondrial DNA persisted in some blastocysts. It is evident from the donor cells used that nuclearencoded mitochondrial DNA transcription and replication factors persist even after mitochondrial DNA depletion, as do transcripts for some of the mitochondrial-encoded genes. These cells are therefore still programmed to drive mitochondrial DNA replication and transcription. In nuclear transfer-derived embryos, we have observed the persistence of these nuclear-encoded mitochondrial DNA transcription and replication factors but not in those embryos generated through in vitro fertilization. Consequently, nucleo-mitochondrial interaction following nuclear transfer is out of sequence as the onset of mitochondrial replication is a postimplantation event.

The Senescence-Related Mitochondrial/Oxidative Stress Pathway is Repressed in Human Induced Pluripotent Stem Cells

“…Induction of nuclear factors involved in the biogenesis of mitochondria has been described in response to mtDNA depletion [46]. Accordingly, mtDNA content in undifferentiated iPSCs appeared significantly decreased in comparison to somatic cells (Fig.…”

Segregation of Naturally Occurring Mitochondrial DNA Variants in a Mini-Pig Model

“…However, the reduction in mtDNA copy number that takes place during preimplantation development in larger mammals, due to there being no expression of the key mtDNA replication factors (Lloyd et al 2006;Bowles et al 2007;Spikings et al 2007), and persists in the inner cell mass (Spikings et al 2007) and up to gastrulation, most likely filters the levels of variants persisting in the offspring. This process is aided by the shedding of mtDNA during preimplantation development (Stigliani et al 2014).…”

Modulation of mitochondrial biogenesis and bioenergetic metabolism upon in vitro and in vivo differentiation of human ES and iPS cells

“…This may represent a nuclear response to decreased content of mitochondrial DNA (mtDNA) (Lloyd et al, 2006), which was found reduced in undifferentiated human ES and iPS cells (Armstrong et al 2010;Prigione et al, 2010). Indeed, cells depleted of mtDNA have been shown to induce the expression of mitochondrial biogenesis factors (Holmuhamedov et al, 2003) and POLG expression was upregulated in cells harboring large deletions of mtDNA (Alemi et al, 2007).…”

“…However, the same genes have been found up-regulated upon differentiation of human mesenchymal stem cells (Chen et al, 2008) and mouse ES cells (Facucho-Oliveira et al, 2007). The most likely explanation of these conflicting results may be that the nuclear response is depending on the mtDNA content (Mercy et al, 2005;Lloyd et al, 2006) which may vary within different cell types or different time points. Interestingly, within teratoma samples, some genes involved in both mitochondrial biogenesis and bioenergetic metabolism were up-regulated compared to undifferentiated cells, suggesting a different mitochondrial response during in vitro and in vivo spontaneous differentiation of human pluripotent cells, possibly due to the tumorigenic nature of teratomas.…”