Mapping and expression studies of the mir17-92 cluster on pig chromosome 11

We have identified the first porcine microRNA (miRNA) cluster (the mir17-92 cluster) and localized it to the q-arm of pig Chromosome 11. The miRNA cluster was found by sequence similarity search with human miRNA sequences against the pig genomic data generated within the Sino-Danish pig genome project. The resulting data contained three complete and two incomplete miRNA precursors of seven miRNAs from the human mir17-92 cluster. Because there is a 100% sequence identity between the four pig miRNAs and the corresponding human miRNAs, the sequences of three unavailable pig miRNAs were derived from the human data. The expression profiles of seven studied miRNAs were analyzed by hybridization to Northern blots containing five porcine tissues: cerebellum, cortex, hippocampus, kidney, and liver. In order to determine the localization of the mir17-92 cluster in the pig genome, we mapped it by PCR in the porcine somatic cell hybrid (SCH) panel and in the INRA-University of Minnesota (INRA-UMN) porcine radiation hybrid (IMpRH) panel. The PCR results enabled us to localize this cluster to the q-arm of pig Chromosome 11 and map it in relation to two microsatellites. Our study presents the first expression analyses of miRNAs in pig and adds information for further functional studies in this species.