Novel and known miRNAs in zebu (Tharparkar) and crossbred (Karan-Fries) cattle under heat stress.

MicroRNAs (miRNAs) are small single-stranded non-coding RNAs that act as the master regulator of animal growth and development. RNA-RNA interaction is an important mechanism of gene regulation during biotic and abiotic stress. Heat stress (HS) is one of the most important abiotic factors which affect the growth, milk yield and reproductive health of the dairy animals. In the present investigation, we identified 387 known and 77 novel miRNAs from Tharparkar (TH) and Karan Fries (KF) cattle under HS condition. Family distribution analysis showed the identified miRNAs belong to more than 15 different families in which miR-2284 was the most abundant. We identified 42,350 targets for the known miRNAs reported in cattle. Pathway analysis of the identified targets showed most of the target genes were involved in cancer, mitogen-activated protein kinase (MAPK) signaling, calcium signaling, Ras signaling, and cAMP signaling pathways. Differential gene expression showed more than 344 miRNAs changed their expression significantly between control and HS condition. Heat map was generated for the top 20 most up and downregulated miRNAs. Ten miRNAs were validated using qRT-PCR to be heat responsive, based on read count value and differential gene expression. These novel miRNAs are new addition to the miRNA database of cattle. This study provides an overview of miRNA profile and their interaction with the target genes which leads to further understanding in deciphering the thermotolerance mechanism in cattle.