Identification and analysis of new miRNAs and isomirs and their targets in cows exposed to mastitis

Bovine mastitis is an inflammation disease of the mammary gland that impose considerable costs to the dairy industry. Regulatory mechanisms of this disease is complex and controlled by various gene regulatory elements and more studies are needed to better understand this disease. In the present study aimed to better understand of regulatory elements involved in mastitis, milk samples of two groups of healthy and infected cows during time series of 0, 12, 24, 36 and 48 hours after contamination were collected. The miRNA-seq data obtained from the milk samples and using the advanced bioinformatics, novel miRNAs, their targets and probability functions, isomirs and novel miRNAs* were identified. The results led to the identification of 92 novel miRNA including 26 miRNAs with homologous and 66 miRNAs without homologous genes in other species. Investigation of the functional groups of predicted targets genes, confirmed the roles of new miRNAs in response to internal and external stimulations, apoptosis and production of immunoglobulin. Furthermore, 135 novel miRNAs were identified. Also, 493 novel isomeric sibling miRNAs (isomers) were discovered that immune related functions of these isomirs were demonstrated in some species like human and mouse. Identification of miRNAs target genes with associated functions in mastitis, including safety, apoptosis and inflammation, can indicated the possible regulatory roles of the identified miRNAs in mastitis.