Mitochondrial tRNA-derived fragments as candidate metastasis-modifying RNA

Area of Science:

• Genetics
• Molecular Biology
• Epigenetics

Background:

• Mitochondrial DNA (mtDNA) polymorphisms are known to influence complex phenotypes, but the mechanisms are not fully understood.
• Previous studies using Mitochondrial-Nuclear eXchange (MNX) mice demonstrated that mtDNA single nucleotide polymorphisms (SNP) can modify metastasis and cardiovascular disease independently of metabolic changes.
• A specific mtDNA SNP in the mitochondrial tRNA-Arginine (mt-tRNAArg (UCG), mt-TR) gene was found to correlate with these phenotypes, suggesting a role for non-protein-coding regions.

Purpose of the Study:

• To identify and characterize novel tRNA-derived fragments (tRFs) originating from the mt-TR gene.
• To investigate the differential expression of these tRFs in relation to mtDNA SNP, tissue type, and sex.
• To explore the potential role of these SNP-dependent tRFs as modifiers of complex phenotypes, particularly metastasis.

Main Methods:

• Northern blotting was employed to detect and analyze tRFs generated from mt-TR.
• Small RNA sequencing was performed on untreated RNA, followed by specific RNA processing (demethylation and terminal restoration) to enable tRF detection.
• Bioinformatic analysis, including exact matching to the mitochondrial genome and normalization to the parental molecule, was used to identify putative tRF sequences and cleavage sites.

Main Results:

• Distinct tRFs were identified and shown to be differentially expressed based on mtDNA SNP, between lung and liver tissues, and between sexes.
• Standard small RNA sequencing failed to detect these tRFs in high abundance, but specific processing enabled their identification, consistent with Northern blot findings.
• Putative tRF sequences with shared cleavage sites were identified, linked to mtDNA SNP and correlated with metastasis, suggesting a functional role.

Conclusions:

• Novel tRNA-derived fragments (tRFs) generated from the mitochondrial tRNA-Arginine (mt-TR) gene have been identified and characterized.
• These tRFs exhibit differential expression patterns influenced by mtDNA SNP, tissue, and sex, and their detection requires specific RNA processing.
• The findings suggest that these SNP-dependent tRFs may function as metastasis modifiers, expanding the known functional output of the mitochondrial genome in phenotype modification.