Potential Misidentification of Natural Isomers and Mass-Analogs of Modified Nucleosides by Liquid Chromatography-Triple Quadrupole Mass Spectrometry

Exploring urinary modified nucleosides as biomarkers for diabetic retinopathy: Development and validation of a ultra performance liquid chromatography-tandem mass spectrometry method

The dynamic modification of RNA plays a crucial role in biological regulation and is strongly linked to human disease development and progression. Notably, modified nucleosides in urine have shown promising potential as early diagnostic biomarkers for various conditions. In this study, we developed and validated a rapid, sensitive, and accurate UPLC-MS/MS method for quantifying eight types of modified nucleosides (N1-methyladenosine (m1A), N6-methyladenosine (m6A), 5-methyluridine (m5U), 5-taurinomethyl-2-thiouridine (τm5s2U), 5-methylcytidine (m5C), 2'-O-methylcytidine (Cm), N1-methylguanosine (m1G), and N7-methylguanosine (m7G) in human urine. Using the method, we measured the urinary concentrations of m1A, m6A, m5U, τm5s2U, m5C, Cm, m1G, and m7G in a total of 21 control individuals and 23 patients diagnosed with diabetic retinopathy (DR). Cm levels showed promise as a diagnostic marker for diabetic retinopathy (DR), with a significant value (P < 0.01) and an AUC of 0.735. Other modified nucleosides also exhibited significant differences within specific subpopulations. As non-proliferative diabetic retinopathy (NPDR) signifies the latent early stage of diabetic retinopathy, we developed a multivariate linear model that integrates patients' sex, age, height, and urinary concentration of modified nucleosides which aims to predict and differentiate between healthy individuals, NPDR patients, and proliferative diabetic retinopathy (PDR) patients. Encouragingly, the model achieved satisfactory accuracy rates: healthy (81%), NPDR (75%), and PDR (80%). Our findings provide valuable insights into the development of an early, cost-effective, and noninvasive diagnostic approach for diabetic retinopathy.

A Preliminary Survey of Transfer RNA Modifications and Modifying Enzymes of the Tropical Plant Cocos nucifera L

The coconut (Cocos nucifera L.) is a commercial crop widely distributed among coastal tropical regions. It provides millions of farmers with food, fuel, cosmetics, folk medicine, and building materials. Among these, oil and palm sugar are representative extracts. However, this unique living species of Cocos has only been preliminarily studied at molecular levels. Benefiting from the genomic sequence data published in 2017 and 2021, we investigated the transfer RNA (tRNA) modifications and modifying enzymes of the coconut in this survey. An extraction method for the tRNA pool from coconut flesh was built. In total, 33 species of modified nucleosides and 66 homologous genes of modifying enzymes were confirmed using a nucleoside analysis using high-performance liquid chromatography combined with high-resolution mass spectrometry (HPLC-HRMS) and homologous protein sequence alignment. The positions of tRNA modifications, including pseudouridines, were preliminarily mapped using a oligonucleotide analysis, and the features of their modifying enzymes were summarized. Interestingly, we found that the gene encoding the modifying enzyme of 2'-O-ribosyladenosine at the 64th position of tRNA (Ar(p)64) was uniquely overexpressed under high-salinity stress. In contrast, most other tRNA-modifying enzymes were downregulated with mining transcriptomic sequencing data. According to previous physiological studies of Ar(p)64, the coconut appears to enhance the quality control of the translation process when subjected to high-salinity stress. We hope this survey can help advance research on tRNA modification and scientific studies of the coconut, as well as thinking of the safety and nutritional value of naturally modified nucleosides.