Abstract
BackgroundRecent completion of swine genome may simplify the production of swine as a large biomedical model. Here we studied sequence and location of known swine miRNA genes, key regulators of protein-coding genes at the level of RNA, and compared them to human and mouse data to prioritize future molecular studies.ResultsDistribution of miRNA genes in pig genome shows no particular relation to different genomic features including protein coding genes - proportions of miRNA genes in intergenic regions, introns and exons roughly agree with the size of these regions in the pig genome. Our analyses indicate that host genes harbouring intragenic miRNAs are longer from other protein-coding genes, however, no important GO enrichment was found. Swine mature miRNAs show high sequence similarity to their human and mouse orthologues. Location of miRNA genes relative to protein-coding genes is also similar among studied species, however, there are differences in the precise position in particular intergenic regions and within particular hosts. The most prominent difference between pig and human miRNAs is a large group of pig-specific sequences (53% of swine miRNAs). We found no evidence that this group of evolutionary new pig miRNAs is different from old miRNAs genes with respect to genomic location except that they are less likely to be clustered.ConclusionsThere are differences in precise location of orthologues miRNA genes in particular intergenic regions and within particular hosts, and their meaning for coexpression with protein-coding genes deserves experimental studies. Functional studies of a large group of pig-specific sequences in future may reveal limits of the pig as a model organism to study human gene expression.Electronic supplementary materialThe online version of this article (doi:10.1186/s12863-015-0166-3) contains supplementary material, which is available to authorized users.
Highlights
Recent completion of swine genome may simplify the production of swine as a large biomedical model
We examined whether the number of intragenic miRNA genes are proportional to the total relative size of protein-coding genes in genome (% of total represented bp: pig 25%, human 39%, mouse 25%)
Within the group of the 463 pig-specific miRNA genes we identified 16 genes represented in the expression study, whereas the remaining group was represented by 96 miRNA
Summary
Recent completion of swine genome may simplify the production of swine as a large biomedical model. We studied sequence and location of known swine miRNA genes, key regulators of protein-coding genes at the level of RNA, and compared them to human and mouse data to prioritize future molecular studies. MiRNAs are different from other classes of interfering RNA with its biogenesis, which was intensively investigated in human and mouse [1]. They are cut out from hairpin pre-miRNA (~70 nt) by enzyme Dicer in cytoplasm. Pre-miRNA is excised in nucleus from pri-miRNA - long transcript of miRNA gene - by enzyme Drosha. An individual pri-miRNA sequence may code multiple copies of pre-miRNA [2]
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