Cell Lineage Specific Mitochondrial Resilience During Mammalian Organogenesis

Mitochondrial activity differs markedly between organs, but it is not known how and when this arises. Here we show that cell lineage specific expression profiles involving essential mitochondrial genes emerge at an early stage in mouse development, including tissue-specific isoforms present before organ formation. However, the nuclear transcriptional signatures were not independent of organelle function. Genetically disrupting intra-mitochondrial protein synthesis with two different mtDNA mutations induced cell lineage specific compensatory responses, including molecular pathways not previously implicated in organellar maintenance. We saw down regulation of genes whose expression is known to exacerbate the effects of exogenous mitochondrial toxins, indicating a transcriptional adaptation to mitochondrial dysfunction during embryonic development. The compensatory pathways were both tissue and mutation specific, and under the control of specific transcription factors which promote organelle resilience. These are likely to contribute to the tissue specificity which characterizes human mitochondrial diseases, and are potential targets for organ-directed treatments. Overall design: Heteroplasmic immortalized MEFs carrying the m.5024C>T mutation were cultured under standard laboratory conditions. Five high heteroplasmy populations and five low heteroplasmy populations were selected as biological replicates. 1x107 cells per MEF line were harvested following trypsinisation and total RNA was extracted. Following QC to confirm RNA integrity, libraries were constructed using polyA capture and pooled for sequencing. 50bp paired-end read sequencing was performed using one lane of an Illumina NovaSeq6000 SP flowcell.