Ancestry affects the transcription of small mitochondrial RNAs in human lymphocytes

Mitochondrial mutations have been linked to changes in phenotypes such as fertility or longevity, however, these changes have been often inconsistent across populations for unknown reasons. A hypothesis that could explain this inconsistency is that some still uncharacterized mitochondrial products are mediating the phenotypic changes across populations. It has been hypothesized that one such product could be the small RNAs encoded in the mitochondrial genome, thus this work will provide new evidence for their existence and function. By using data from the 1000 genome project and knowledge from previously characterized nuclear small RNAs, this study found that 10 small RNAs encoded in tRNA fragments are consistently expressed in 450 individuals from five different populations. Furthermore, this study demonstrated that the expression of some small mitochondrial RNAs is different in individuals of African ancestry, similar to what was observed before in nuclear and mitochondria mRNAs. Lastly, we investigate the causes behind these differences in expression, showing that at least one of the mt-tRFs might be regulated by TRMT10B. The analyses presented in this work further support the small mitochondrial RNAs as functional molecules, and their population-specific expression supports the hypothesis that they act as a mediator between the nucleus and mitochondria differently across populations.