One locus, several functional RNAs-emerging roles of the mechanisms responsible for the sequence variability of microRNAs

With the development of modern molecular genetics, the original "one gene-one enzyme" hypothesis has been outdated. For protein coding genes, the discovery of alternative splicing and RNA editing provided the biochemical background for the RNA repertoire of a single locus, which also serves as an important pillar for the enormous protein variability of the genomes. Non-protein coding RNA genes were also revealed to produce several RNA species with distinct functions. The loci of microRNAs (miRNAs), encoding for small endogenous regulatory RNAs, were also found to produce a population of small RNAs, rather than a single defined product. This review aims to present the mechanisms contributing to the astonishing variability of miRNAs revealed by the new sequencing technologies. One important source is the careful balance of arm selection, producing sequentially different 5p- or 3p-miRNAs from the same pre-miRNA, thereby broadening the number of regulated target RNAs and the phenotypic response. In addition, the formation of 5', 3' and polymorphic isomiRs, with variable end and internal sequences also leads to a higher number of targeted sequences, and increases the regulatory output. These miRNA maturation processes, together with other known mechanisms such as RNA editing, further increase the potential outcome of this small RNA pathway. By discussing the subtle mechanisms behind the sequence diversity of miRNAs, this review intends to reveal this engaging aspect of the inherited "RNA world", how it contributes to the almost infinite molecular variability among living organisms, and how this variability can be exploited to treat human diseases.

Overview of host miRNA properties and their association with epigenetics, long non-coding RNAs, and Xeno-infectious factors

MicroRNA-derived structures play impressive roles in various biological processes. So dysregulation of miRNAs can lead to different human diseases. Recent studies have extended our comprehension of the control of miRNA function and features. Here, we overview some remarkable miRNA properties that have potential implications for the miRNA functions, including different variants of a miRNA called isomiRs, miRNA arm selection/arm switching, and the effect of these factors on miRNA target selection. Besides, we review some aspects of miRNA interactions such as the interaction between epigenetics and miRNA (different miRNAs and their related processing enzymes are epigenetically regulated by multiple DNA methylation enzymes. moreover, DNA methylation could be controlled by diverse mechanisms related to miRNAs), direct and indirect crosstalk between miRNA and lnc (Long Non-Coding) RNAs as a further approach to conduct intercellular regulation called "competing endogenous RNA" (ceRNA) that is involved in the pathogenesis of different diseases, and the interaction of miRNA activities and some Xeno-infectious (virus/bacteria/parasite) factors, which result in modulation of the pathogenesis of infections. This review provides some related studies to a better understanding of miRNA involvement mechanisms and overcoming the complexity of related diseases that may be applicable and useful to prognostic, diagnostic, therapeutic purposes and personalized medicine in the future.

[Causes of catheter removal and complications depending on the insertion side of peripherally inserted central venous catheter in patients with hematologic disorders]

Central venous catheter (CVC) insertion is an essential medical procedure in patients with hematologic disorders. Recently, the use of peripherally inserted central venous catheters (PICCs) for CVC insertion has been increasing. However, the suitable arm for PICC insertion has not been fully discussed. This study retrospectively examined catheter-related complications on the insertion side of PICC in patients with hematologic disorders. Total 809 PICCs were inserted in 316 patients with hematologic disorders. The insertion side was the right upper arm for 515 PICCs and the left upper arm for 294 PICCs. In a direct comparison between the insertion side groups, there was no obvious difference in the basic demographic characteristics of the patients except the age at the time of insertion. Moreover, there was no significant difference in the reasons for PICC removal, and the incidence of catheter-related bloodstream infection was similar and low in both the study groups. During the selection of the insertion side for PICC, it may be possible to consider the side that seems more suitable for insertion by confirming the vessels in both upper arms with ultrasonography, and, if the conditions are equivalent, to consider the side where the patient wishes to insert the PICC.