Main research lines


GO TO: publications & grants

What we do:

Our goal is to develop new analytical methods for the detection / quantitation of macromolecules such as RNA and proteins in human clinical samples. Our focus is placed on extracellular vesicles and extracellular RNAs (exRNAs) because of their potential as early disease biomarkers in minimally-invasive liquid biopsies. We are also interested in understanding the biology of extracellular RNAs and their role in intercellular communication. 


Novel separation and quantitation methods of exRNAs

Accurate measurementes of RNA molecules inside and outside cells is essential to understand RNA secretion mechanisms and exRNA function. However, this has proven challenging because exRNA usually contain many post transcriptionally-modified bases and their extracellular half life is also highly variable. We are trying to develop new sequencing and RT-qPCR techniques which overcome many of these hurdles in order to get more reliable snapshots of the extracellular RNAome. 


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Selected publications:


Nicked tRNAs are stable reservoirs of tRNA halves in cells and biofluids.Costa B, Li Calzi M, Castellano M, Blanco V, Cuevasanta E, Litvan I, Ivanov P, Witwer K, Cayota A, Tosar J.P.* (2023) P.N.A.S. 120(4) e2216330120Comment in: Staying together after the breakup: tRNA halves in extracellular fluids

Exomeres and Supermeres: monolithic or diverse?Tosar JP*, Cayota A, Witwer K. (2022). J. Extracell. Biol. 1(6):e45. 
Die hard: resilient RNAs in the blood.Tosar JP* (2021). Nat Rev Mol Cell Biol  22(6): 373.
Revisiting Extracellular RNA Release, Processing, and Function. Tosar JP*, Witwer KW, Cayota A (2021) Trends Biochem Sci. 46(6): 438-445.
Circulating SNORD57 rather than piR-54265 is a promising biomarker for colorectal cancer: common pitfalls in the study of somatic piRNAs in cancer.Tosar JP*, García-Silva MR, Cayota A (2021) RNA 27(4): 403-410. 
RI-SEC-seq: Comprehensive Profiling of Nonvesicular Extracellular RNAs with Different Stabilities.Tosar JP*, Gámbaro F, Castellano M, Cayota A (2021). Bio-protocol 11(4): e3918. 
Fragmentation of extracellular ribosomes and tRNAs shapes the extracellular RNAome Tosar JP*, Segovia M, Gámbaro F, Akiyama Y, Fagúndez P, Olivera A, Costa B, Possi T, Hill M, Ivanov P, Cayota A*.Nucleic Acids Res. 2020 48(22): 12874-12888.
Extracellular tRNAs and tRNA-derived fragments.Tosar JP*, Cayota A*.RNA Biol. 2020 Feb 19:1-19. doi: 10.1080/15476286.2020.1729584.
Stable tRNA halves can be sorted into extracellular vesicles and delivered to recipient cells in a concentration-dependent manner.Gámbaro F, Li Calzi M, Fagúndez P, Costa B, Greif G, Mallick E, Lyons S, Ivanov P, Witwer K, Cayota A*, Tosar JP.*RNA Biol. 2019 Dec 29:1-15. doi: 10.1080/15476286.2019.1708548
Plant microRNAs in human sera are likely contaminants.Fromm B, Kang W, Rovira C, Cayota A, Witwer K*, Friedländer MR*, Tosar JP*.J Nutr Biochem. 2019 Mar;65:139-140.
Dimerization confers increased stability to nucleases in 5' halves from glycine and glutamic acid tRNAs.Tosar JP*, Gámbaro F, Darré L, Pantano S, Westhof E, Cayota A*.Nucleic Acids Res. 2018 Sep 28;46(17):9081-9093.
Non-coding RNA fragments account for the majority of annotated piRNAs expressed in somatic non-gonadal tissues.Tosar JP*, Rovira C, Cayota A*.Commun Biol. 2018 Jan 22;1:2.
Detection and Analysis of Non-vesicular Extracellular RNA.Tosar JP*, Cayota A*.Methods Mol Biol. 2018;1740:125-137.
Ribonucleic artefacts: are some extracellular RNA discoveries driven by cell culture medium components?Tosar JP, Cayota A, Eitan E, Halushka MK, Witwer KW*.J Extracell Vesicles. 2017 Jan 12;6(1):1272832.  
Assessment of small RNA sorting into different extracellular fractions revealed by high-throughput sequencing of breast cell lines.Tosar JP, Gámbaro F, Sanguinetti J, Bonilla B, Witwer KW, Cayota A*.Nucleic Acids Res. 2015 Jun 23;43(11):5601-16. 
Mining of public sequencing databases supports a non-dietary origin for putative foreign miRNAs: underestimated effects of contamination in NGS.Tosar JP, Rovira C, Naya H, Cayota A*.RNA. 2014 Jun;20(6):754-7.

Research grants:


2023–2027: Diagnostic and therapeutic applications of extracellular RNA. PI: Juan Pablo Tosar. Co-PI: Alfonso Cayota. CSIC Research Grups. Universidad de la República, Uruguay.2019 - 2023: Separation methods for exRNA carriers: extracellular vesicles, lipoprotein particles, and protein aggregates. PI: Kenneth Witwer. Role: Key Personnel. NIH Extracellular RNA Communication Consortium. National Institutes of Health, USA.
2022-2024: Extracellular RNA decoding by innate immune sensors. PI: Juan Pablo Tosar. National Agency for Research and Innovation (ANII), Uruguay. (FCE_1_2021_1_166344)
2021-2023: Extracellular RNA biogenesis  and role in intercellular communication. PI: Juan Pablo Tosar. CSIC, Universidad de la República, Uruguay.
2019-2021: Release of RNAs from the translation machinery as a stress-response mechanism. PI: Juan Pablo Tosar. National Agency for Research and Innovation (ANII), Uruguay. (FCE_3_2018_1_148745)


Biosensors for the determination of extracellular vesicles & exRNA

The analysis of extracellular vesicles (EVs) and exRNA demands costly equipment and laborious procedures which require trained personnel and dedicated infrastructure. Our group is working in the development of semi-automatic point-of-care (POC) devices capable of measuring these analytes in real time and with low costs. Availability of devices like these will push liquid biopsy-based diagnosis to the next level. We are currently working on electrochemical biosensors and colorimetric assays based on gold nanoparticles. 


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Selected publications:


Systematic process evaluation of the conjugation of proteins to gold nanoparticlesFagúndez P, Botasini S, Tosar JP, Méndez E (2021). Heliyon 7 (6): e07392. 
Electrochemical Detection of dsDNA-Specific Antibodies.Fagúndez P, Brañas G, Laíz J, Tosar JP*.Methods Mol Biol. 2020;2063:73-83.
An electrochemical biosensor for rapid detection of anti-dsDNA antibodies in absolute scale.Fagúndez P, Brañas G, Cairoli E, Laíz J, Tosar JP*.Analyst. 2018 Aug 6;143(16):3874-3882.
Electrochemical Sandwich Immunosensor for Determination of Exosomes Based on Surface Marker-Mediated Signal Amplification.Doldán X, Fagúndez P, Cayota A, Laíz J, Tosar JP*.Anal Chem. 2016 Nov 1;88(21):10466-10473.

Research grants:


2017-2019: Biosensors for descentralized detection of exosomes and Dengue virus. PI: Juan Pablo Tosar. CSIC, Universidad de la República, Uruguay.