Decay of Piwi-Interacting RNAs in Human Cells Is Primarily Mediated by 5' to 3' Exoribonucleases

A novel piwi-interacting RNA associates with type 2-high asthma phenotypes

BACKGROUND

Piwi-interacting RNAs (piRNAs), comprising the largest noncoding RNA group, regulate transcriptional processes. Whether piRNAs are associated with type 2 (T2)-high asthma is unknown.

OBJECTIVE

We sought to investigate the association between piRNAs and T2-high asthma in childhood asthma.

METHODS

We sequenced plasma samples from 462 subjects in the Childhood Asthma Management Program (CAMP) as the discovery cohort and 1165 subjects in the Genetics of Asthma in Costa Rica Study (GACRS) as a replication cohort. Sequencing reads were filtered first, and piRNA reads were annotated and normalized. Linear regression was used for the association analysis of piRNAs and peripheral blood eosinophil count, total serum IgE level, and long-term asthma exacerbation in children with asthma. Mediation analysis was performed to investigate the effect direction. We then ascertained if the circulating piRNAs were present in asthmatic airway epithelial cells in a Gene Expression Omnibus (GEO; www.ncbi.nlm.nih.gov/geo) public data set.

RESULTS

Fifteen piRNAs were significantly associated with eosinophil count in CAMP (P ≤ .05), and 3 were successfully replicated in GACRS. Eleven piRNAs were associated with total IgE in CAMP, and one of these was replicated in GACRS. All 22 significant piRNAs were identified in epithelial cells in vitro, and 6 of these were differentially expressed between subjects with asthma and healthy controls. Fourteen piRNAs were associated with long-term asthma exacerbation, and effect of piRNAs on long-term asthma exacerbation are mediated through eosinophil count and serum IgE level.

CONCLUSION

piRNAs are associated with peripheral blood eosinophils and total serum IgE in childhood asthma and may play important roles in T2-high asthma.

Insights in piRNA targeting rules

PIWI-interacting RNAs (piRNAs) play an important role in the defense against transposons in the germline and stem cells of animals. To what extent other transcripts are also regulated by piRNAs is an ongoing topic of debate. The amount of sequence complementarity between piRNA and target that is required for effective downregulation of the targeted transcript is guiding in this discussion. Over the years, various methods have been applied to infer targeting requirements from the collections of piRNAs and potential target transcripts, and recent structural studies of the PIWI proteins have provided an additional perspective. In this review, I summarize the findings from these studies and propose a set of requirements that can be used to predict targets to the best of our current abilities. This article is categorized under: Regulatory RNAs/RNAi/Riboswitches > Regulatory RNAs RNA Interactions with Proteins and Other Molecules > Protein-RNA Interactions: Functional Implications RNA-Based Catalysis > RNA-Mediated Cleavage.

PIWI-RNAs Small Noncoding RNAs with Smart Functions: Potential Theranostic Applications in Cancer

P-element-induced wimpy testis (PIWI)-interacting RNAs (piRNAs) are a new class of small noncoding RNAs (ncRNAs) that bind components of the PIWI protein family. piRNAs are specifically expressed in different human tissues and regulate important signaling pathways. Aberrant expressions of piRNAs and PIWI proteins have been associated with tumorigenesis and cancer progression. Recent studies reported that piRNAs are contained in extracellular vesicles (EVs), nanosized lipid particles, with key roles in cell-cell communication. EVs contain several bioactive molecules, such as proteins, lipids, and nucleic acids, including emerging ncRNAs. EVs are one of the components of liquid biopsy (LB) a non-invasive method for detecting specific molecular biomarkers in liquid samples. LB could become a crucial tool for cancer diagnosis with piRNAs as biomarkers in a precision oncology approach. This review summarizes the current findings on the roles of piRNAs in different cancer types, focusing on potential theranostic applications of piRNAs contained in EVs (EV-piRNAs). Their roles as non-invasive diagnostic and prognostic biomarkers and as new therapeutic options have been also discussed.

PiRNA Obtained through Liquid Biopsy as a Possible Cancer Biomarker

In recent years PIWI-interacting RNAs (piRNAs) have gained the interest of scientists, mainly because of their possible implications in cancer. Many kinds of research showed how their expression can be linked to malignant diseases. However, most of them evaluated the expression of piRNAs in tumor tissues. It was shown how these non-coding RNAs can interfere with many signaling pathways involved in the regulation of proliferation or apoptosis. A comparison of piRNA expression in tumor tissue and adjacent healthy tissues has demonstrated they can be used as biomarkers. However, this way of obtaining samples has a significant drawback, which is the invasiveness of such a procedure. Liquid biopsy is an alternative for acquiring biological material with little to no harm to a patient. Several different piRNAs in various types of cancer were shown to be expressed in bodily fluids such as blood or urine. Furthermore, their expression significantly differed between cancer patients and healthy individuals. Hence, this review aimed to assess the possible use of liquid biopsy for cancer diagnosis with piRNAs as biomarkers.