Tissue distribution of selected microRNA in Atlantic salmon

Abstract

microRNAs (miRNAs) are small non‐coding RNAs that regulate numerous fundamental biological functions. So far miRNAs have only been identified in few commercially important fish species. Similarly to messenger RNA (mRNA) expression analysis, miRNA qPCR analysis requires thoroughly investigated endogenous controls. In this paper, we have in a pilot study investigated miRNAs in Atlantic salmon (liver, heart, brain, kidney, spleen, intestine, gill, white, and red muscle) by qPCR analysis. The expression of seven putative endogenous control genes (ssa‐let‐7a, ssa‐miR‐16a, ssa‐miR‐16b, ssa‐miR‐194a, ssa‐miR‐22a, ssa‐miR22b, and ssa‐miR‐27c) was examined with regard to their tissue distribution and use as endogenous controls microRNA expression studies. The candidates for endogenous controls were selected as they had been reported by others to be evenly expressed among tissues. The most suitable endogenous control was miR‐27c in this study. Further the expression of ssa‐miR 26b, ssa‐miR‐92a‐1, ssa‐miR‐122, ssa‐miR‐722, ssa‐miR‐21‐1, and ssa‐miR‐143‐1 were investigated and tissue specific expression of all miRNAs except ssa‐miR194a were found. The expression of sss‐miR‐122 and ssa‐miR‐722 were specific for liver, ssa‐miR‐26b mostly expressed in brain and ssa‐miR143‐1 mostly expressed in gill and kidney. This study has provided information of endogenous control genes and has also identified tissue specific expression of miRNAs in Atlantic salmon. Further investigation of endogenous control genes target genes in response to treatment would increase the knowledge of the role of miRNAs in Atlantic salmon.