Non-coding RNA profiling by high throughput sequencing
Summary
MicroRNAs (miRNA) are short single-stranded RNA molecules that regulate gene expression post-transcriptionally by binding to complementary sequences in the 3' untranslated region (3' UTR) of target mRNAs. MiRNAs participate in the regulation of myogenesis, and identification of the complete set of miRNAs expressed in muscles is likely to significantly increase our understanding of muscle growth and development. To determine the identity and abundance of miRNA in porcine skeletal muscle, we applied a deep sequencing approach. This allowed us to identify the sequences and relative expression levels of 212 annotated miRNA genes, thereby providing a thorough account of the miRNA transcriptome in porcine muscle tissue. The expression levels displayed a very large range, as reflected by the number of sequence reads, which varied from single counts for rare miRNAs to several million reads for the most abundant miRNAs. Moreover, we identified numerous examples of mature miRNAs that were derived from opposite sides of the same predicted precursor stem-loop structures, and also observed length and sequence heterogeneity at the 5' and 3' ends. Furthermore, KEGG pathway analysis suggested that highly expressed miRNAs are involved in skeletal muscle development and regeneration, signal transduction, cell-cell and cell-extracellular matrix communication and neural development and function.
Overall design
Examination of small RNA profiles in 7 isolates of porcine muscle
The raw sequences were trimmed to 30 nucleotides, and it was set as a requirement that any sequence must appear at least three times and be present in at least two of the seven libraries. All identical reads within a library were grouped and converted into unique sequences. Reads containing Ns or long tracks (¡Ý8) of As were removed and the sequences were trimmed for adaptor-sequences. To annotate the unique sequences, a Decypher Tera-BLASTN Search was performed against a database of mature miRNAs obtained from miRBase (release 12.0). Hits with a match of 16 or more nucleotides to a miRNA from the database were gathered, and the count of each miRNA was normalized to the total number of sequence reads per lane. The outcome of this procedure can be seen in the Aarhus_University_GBI_FC208D2AAXX_blast_mirbase table below.
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