tRNA fragment biomarkers of Neurological Disease: Challenges and Opportunities

Transfer RNAs play a crucial role in protein translation where they bring amino acids to the ribosome to be incorporated into nascent polypeptide chains. During stress conditions tRNAs can be cleaved to generate tRNA-derived fragments. Several ribonucleases have been identified that cleave tRNA, however mutations in the stress-induced ribonuclease Angiogenin have been identified in a range of neurological disorders including Amyotrophic Lateral Sclerosis, Parkinson’s Disease, and Alzheimer’s Disease, suggesting that tRNA cleavage may be dysregulated in neurological disease. tRNA fragments have been detected in biofluids indicating they may be of use as biomarkers for neurological diseases. There is considerable variability in the methods used to quantify tRFs from size selection, adapter ligation, removal of RNA modifications, and sequence analysis approaches which can make it difficult to reconcile multiple studies. Here we review the biology of transfer RNAs and the biogenesis of tRNA-derived fragments, with a focus on the methods used to identify and quantify tRNA fragments and how different methodological approaches can influence tRNA fragment detection. We provide an overview of current literature on the identification of tRNA fragments in neurological disease models and patient samples, with a focus on circulating tRNA fragments as potential biomarkers of neurological diseases.