Broadening the miRNA catalogue in livestock species: A contribution to the functional annotation of animal genomes.

MicroRNAs play a crucial role in the regulation of gene expression. Their action is crucial in many biological processes and functions, such as cell development
and differentiation, and in response to disease. Moreover, it has been shown that polymorphisms in miRNAs can be linked to diseases and complex traits. An improved annotation of miRNAs in domestic animals is therefore required to acquire a comprehensive understanding of their impact on livestock traits. There are a large number of published studies with public data sets across most of livestock species and covering a wide range of tissues. However there have been few resources to capitalize on these data to better understand these features, distribution and biogenesis in these genomes. Therefore, a working group was established for the development of analysis pipelines and methods of data analysis of small-RNA-seq data in the framework of COST-Action FAANG-Europe. A total of 846 quality ap- proved small-RNA-seq data sets available from public repositories for 6 livestock species (Gallus gallus, Sus scrofa, Equus caballus, Ovis aries, Capra hircus and Bos taurus) were used to quantify miRNA expression in different tissues as well as to identify putative novel miRNA candidates. Our analyses has identified across the 6 species a total of 1,404 novel pre-miRNAs, with a larger impact for Bos taurus and Sus scrofa, in which these represent an increase of 50% for these species in comparison with miRBase v22. We will use these to perform large-scale analysis of miRNA function and biogenesis. These analyses will include global expression comparison, co-expression of miRNA clusters. Additionally we will report for the first time in these tissues a global analysis of miRNA epi-transcriptomic modifications and access their prevalence across species and tissues. We believe these findings will further contribute to the understanding of the functional genome of the studied species. AJA is supported by a post-doctoral fellowship within IMAGE H2020 project (REF 677353–2). This abstract is based upon the work from COST Action FAANG-Europe (CA15112) supported by COST (European Cooperation in Science and technology) and co-funded by FCT grant UID/CVT/00276/2013.