Evaluation of the microRNA transcriptome in feline whole blood

Abstract Circulating microRNAs (miRNAs) are potential biomarkers for numerous diseases. Characterization of the whole blood (WB) miRNA-transcriptome (miRNome) in cats is lacking, which limits the potential use of miRNAs as biomarkers for i.e. feline heart disease. The aims of the present study were to identify and evaluate circulating miRNAs in feline WB by high-throughput sequencing of the total miRNome in WB from twelve cats, representing domestic mixed breed (DOM) and Norwegian Forest (NFO) cats with or without preclinical hypertrophic cardiomyopathy (HCM). A total of 459 mature miRNAs were identified in feline WB, of which 40 were identified as potential novel miRNAs for cat. A majority, 85.3%, of the miRNAs showed sequence similarity with human miRNAs. An effect of breed was found, with up to thirteen miRNAs being differentially expressed between breeds. One miRNA, miR-204-5p, was potentially associated with preclinical HCM in NFO cats, but needs to be confirmed in a larger and sex-unbiased cohort. Most of the identified miRNAs in feline WB can be associated with regulation of haematopoietic cells. In conclusion, miRNome-sequencing can identify hundreds of circulating miRNAs in feline WB and breed should be considered when evaluating the miRNome in feline WB, especially in cohorts including preclinical patients.