Current Status of Regulatory Non-Coding RNAs Research in the Tritryp

Abstract

Trypanosomatids are protozoan parasites that cause devastating vector-borne human diseases. Gene expression regulation of these organisms depends on post-transcriptional control in responding to diverse environments while going through multiple developmental stages of their complex life cycles. In this scenario, non-coding RNAs (ncRNAs) are excellent candidates for a very efficient, quick, and economic strategy to regulate gene expression. The advent of high throughput RNA sequencing technologies show the presence and deregulation of small RNA fragments derived from canonical ncRNAs. This review seeks to depict the ncRNA landscape in trypanosomatids, focusing on the small RNA fragments derived from functional RNA molecules observed in RNA sequencing studies. Small RNA fragments derived from canonical ncRNAs (tsRNAs, snsRNAs, sdRNAs, and sdrRNAs) were identified in trypanosomatids. Some of these RNAs display changes in their levels associated with different environments and developmental stages, demanding further studies to determine their functional characterization and potential roles. Nevertheless, a comprehensive and detailed ncRNA annotation for most trypanosomatid genomes is still needed, allowing better and more extensive comparative and functional studies.

Keywords: Trypanosoma; leishmania; ncRNA; non-coding RNA; siRNA; snRNA; snoRNA; tRNA; tritryp; trypanosomatids.

Figure 1

Outlook of the non-coding genomic annotations available in TriTrypDB. All Leishmania spp. and Trypanosoma spp. genomic data was obtained from TritrypDB (Release 56) for protein-coding genes (A) and non-protein-coding genes (B). The inset plot presents the distribution of the number of genes annotated for all genomes grouped by reference and non-reference strains. For the main ncRNAs biotypes (tRNAs, snoRNAs, snRNAs, and rRNAs) the number of features annotated is presented in bar plots (C) for all genomes with a least 1 ncRNA annotation. Arrows point out species with large numbers of genome strains sequenced.

Figure 2

Overview of the ncRNAs and their derived sncRNAs products identified in trypanosomatids. The sncRNAs represented were found in at least one trypanosomatids, either intracellular and/or in EVs (Extracellular vesicles). snsRNA, sdRNA, tsRNA, sdrRNA are the small RNAs derived from snRNA, snoRNA, tRNA and rRNA, respectively. Specific features or observations are commented on with the text. Created with BioRender.com (accessed on 13 May 2022).

Figure 3

Regulatory non-canonical ncRNAs with experimentally demonstrated roles reported in trypanosomatids. The illustrations represent the structure, processing and proposed mechanisms of action of the four ncRNAs reported so far [28,30,37,57]. Created with BioRender.com (accessed on 13 May 2022).