MicroRNAs (miRNAs) are small single-stranded non-coding RNAs that have an important regulatory function in animal growth and developmental processes. However, the differential expression of miRNA and the role of these miRNAs in heat-stressed Holstein cows are still unknown. In this study, the profile of differentially expressed miRNAs and the target genes analysis in the serum of heat-stressed and normal Holstein cows were investigated by a Solexa deep-sequencing approach and bioinformatics. The data identified 52 differentially expressed miRNAs in 486 known miRNAs which were changed significantly between heat-stressed and normal Holstein cows (fold change >2, P < 0.001). Target genes analysis showed that at least 7 miRNAs (miR-19a, miR-19b, miR-146a, miR-30a-5p, miR-345-3p, miR-199a-3p, and miR-1246) were involved in the response to stress, oxidative stress, development of the immune system, and immune response among the identified 52 differentially expressed miRNAs. Five miRNAs (miR-27b, miR-181a, miR-181b, miR-26a, and miR-146b) were involved in stress and immune responses and the expression of five miRNAs was striking (P < 0.001). In addition, RT-qPCR and deep-sequencing methods showed that 8 miRNAs among the 12 selected miRNAs (miR-19a, miR-19b, miR-27b, miR-30a-5p, miR-181a, miR-181b, miR-345-3p, and miR-1246) were highly expressed in the serum of heat-stressed Holstein cows. GO and KEGG pathway analysis showed that these differentially expressed miRNAs were involved in a pathway that may differentially regulate the expression of stress response and immune response genes. Our study provides an overview of miRNAs expression profile and the interaction between miRNAs and their target genes, which will lead to further understanding of the important roles of miRNAs in heat-stressed Holstein cows.

MicroRNA (miRNA) is endogenous non-coding RNA that has been proposed to play an important role in the formation of body fat. However, the differential expression of miRNA and the role of these miRNAs in bovine intramuscular and subcutaneous fat tissue are still unknown. In this study, the profile of differentially expressed miRNA and the target gene analysis in intramuscular adipose and subcutaneous adipose of adult beef cattle were investigated by microarray and bioinformatics. The data identified 88 differentially expressed miRNAs in 213 miRNAs which were detected on the microarray, and 30 miRNAs among these 88 miRNAs were changed significantly between intramuscular and subcutaneous fat (fold change >1, P < 0.001). miR-143, miR-145, miR-26a, miR-2373-5p and miR-23b-3p were highly expressed in intramuscular fat, whilst miR-26a, miR-2373-5p, miR-2325c, miR-3613 and miR-2361 showed highest abundance in subcutaneous fat. Bioinformatics of KEGG pathway analysis and GO term enrichment suggested that these differentially expressed miRNAs involved in different pathways and target genes may regulate differently the fat deposition. Taken together, our study provides the first evidence for better understanding the differential expression and mechanisms of miRNA in bovine fat deposition, and provides thinking to improve the quality of beef by reducing subcutaneous fat and increasing intramuscular fat of beef cattle.