Diagnostic marker development of tRNA-derived fragments in cerebrospinal fluid and blood serum

The development of non-invasive diagnostic methods is crucial in early disease detection and thus better treatment options. Small RNAs have been identified as good candidates for such diagnostic markers due to their small size, which allows ease of transport from live cells. Correlating small RNAs in bodily fluid with those in tissue cells of interest may even shed light on disease mechanisms and the development of therapeutic targets. tRNA-derived RNA fragments (tRFs), a family of recently discovered small non-coding RNAs (sncRNAs), have been found to be significantly changed in various disease states, including Alzheimer's disease (AD), the most common type of dementia. Previously, tRFs have been found to be significantly enhanced in human AD hippocampus tissues. However, whether tRFs change in body fluids is unknown. In this study, we planned to identify baselines for potential usage of tRFs as biomarkers in cerebrospinal fluid and blood serum for future development of AD biomarkers. Towards this goal, we used T4 polynucleotide kinase-RNA-seq, a modified next-generation sequencing technique, to identify detectable tRFs in human cerebrospinal fluid (CSF) and serum samples. Interestingly, we found an abundance of tRFs in both CSF and serum samples in comparison to microRNAs, well-known small RNAs (about 3-10 times higher in read counts). This clearly indicates the significant potential of tRFs as non-invasive biomarkers in CSF and serum. Overall design: We obtained CSF samples through the National Institutes of Health (NIH) NeuroBioBank (https://neurobiobank.nih.gov/). Serum samples were requested and obtained from the Texas Alzheimer's Research and Care Consortium (TARCC).