Abstract
The role of microRNAs (miRNAs) as a post-transcriptional gene regulator has been elucidated in a broad range of organisms including domestic animals. Characterization of miRNAs in normal tissues is an important step to investigate the functions of miRNAs in various physiological and pathological conditions. Using Illumina Next Generation Sequencing (NGS) technology, we identified a total of 292 known and 329 novel miRNAs in normal horse tissues including skeletal muscle, colon and liver. Distinct sets of miRNAs were differentially expressed in a tissue-specific manner. The miRNA genes were distributed across all the chromosomes except chromosomes 29 and 31 in the horse reference genome. In some chromosomes, multiple miRNAs were clustered and considered to be polycistronic transcript. A base composition analysis showed that equine miRNAs had a higher frequency of A+U than G+C. Furthermore, U tended to be more frequent at the 5′ end of miRNA sequences. This is the first experimental study that identifies and characterizes the global miRNA expression profile in normal horse tissues. The present study enriches the horse miRNA database and provides useful information for further research dissecting biological functions of miRNAs in horse.
Highlights
MicroRNAs play a crucial role in various physiological and pathological conditions in a broad range of organisms from viruses to animals [1,2]
After eliminating 39 adapter null, 59 adapter contaminants, insert null, smaller than 18 nucleotides and poly A sequences, more than 94% of clean reads in all tissue samples were subjected to further analyses using bioinformatic tools (Table S1)
We identified 292 known and 329 novel miRNAs in normal equine tissues by using Next Generation Sequencing (NGS) technology
Summary
MicroRNAs (miRNAs) play a crucial role in various physiological and pathological conditions in a broad range of organisms from viruses to animals [1,2]. The short non-coding RNAs regulate the expression of thousands of genes by partial or complementary binding to target mRNAs, resulting in translational inhibition and/or degradation of the target mRNAs [3,4,5]. The mature miRNAs are generated from serial stepwise processing [6]. The enzyme Drosha cleaves the single stranded primary miRNA transcripts(pri-miRNAs) to produce a precursor stem-loop secondary structure(pre-miRNAs) [7]. The pre-miRNAs are cleaved by the enzyme Dicer to produce mature miRNA duplexes [8]. One of the two strands acts as a regulatory RNA associated with RNA-induced silencing complex (RISC) [9]
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