Identification of effective signaling pathways in cow's milk production using micro-RNA data

Information from RNAs, because they are the link between genotype and phenotype, helps to understand the biological aspects of physiological pathways. MicroRNAs are molecules with 22 nucleotides in length and single strand which can specifically affect the function and expression of genes, hence many studies have been done on the role of these molecules in various biological processes, such as milk production. The milk production trait is one of the most important traits in the dairy cattle industry. This trait is a polygenic trait in farm animals and controlled by a large number of genes and each gene may be involved in various biological pathways and mutually any biological pathway can include a large number of genes. These relationships form the complex network which indicates the association of a large number of biological pathways with lots of genes. Signal molecules that can act as morphogens control the pattern of the gene network of tissue structure throughout the lifespan of the growing embryo stage to the adult organism. The morphogens depend on the amount of secretion and the destination of secretion source can produce different cellular responses. Therefore, the aim of the present study was to investigate target genes of differentially expressed microRNAs in bovine mammary tissue to identify a number of biological pathways involved in the milk production process.

In order to identify and investigate the biological pathways involved in milk production, microRNA sequenced data were used which were extracted from ArrayExpress database with E-GEOD-61227 access number. In present study, all stages of standardization of data, differences between expression of microRNA and significance determination were performed by GEO2R software. The criteria for the selection of microRNA in this study were corrected P-value

The results of this study showed that there are 23 microRNAs with different expressions that affect many genes. These genes are involved in the signaling pathways of TGF-β, WNT, MAPK, mTOR, PI3k-Akt, insulin, estrogen and prolactin. Most of these signaling pathways are involved in cell growth and proliferation, mammary gland development, and epithelial cell activity. Since these identified pathways are associated with milk production, the genes identified in these signaling pathways can be used to improve milk production trait.

MAPK1, MAPK8, FASLG and PTEN genes are activate in most biological pathways and they are associated with various genes, accordingly these genes are the major genes in the process of milk production.