The Role of miRNA in Differentiation, Cell Proliferation, and Pathogenesis of Poultry Diseases

To date, several noncoding RNAs are known that play a prominent role in the processes of transcription, translation, and structural conformation of RNA. By binding miRNA to 3'-untranslated regions, mRNA regulates gene expression in animals through inhibition of translation initiation, elongation, and other mechanisms. There is evidence for the differential expression of miRNA that regulates transcription with the inclusion of several stages of myoblast proliferation, differentiation, and apoptosis. These molecules play a significant role in cell differentiation, proliferation, apoptosis, and tumorigenesis. Some miRNAs are known to target 100–200 genes. Polymorphisms of miRNA genes, especially in the competent regions of the genome, can be biomarkers for phenotypic traits important for breeding birds. The findings confirm the key role of miRNA in controlling the metabolic switch that occurs between the embryo development and the chick hatching. Differentially expressed miRNAs and their possible target genes are involved in egg production functions. The available miRNA data complement our understanding of the molecular genetic control underlying abdominal fat accumulation and myogenesis in chickens. Hundreds of differentially expressed miRNAs from individuals differing in body weight were found. A new understanding into the functions of miRNA during chicken gonads’ rapid development is being formed. Hundreds of miRNAs expressed by hypothalamic genes and involved in the initial phase of rapid gonad growth have been identified. There is increasingly clear evidence that miRNA play a major role in regulating the innate immune response and are important effectors in complex host–pathogen interaction networks for salmonellosis, Marek’s disease, carcinogenic, and other diseases. Many of the miRNAs are associated with cell proliferation, apoptosis, and tumorigenesis. Bacterial pathogens are able to modulate the expression of the host miRNAs and affect the regulation of miRNAs and the outcome of infection. Several miRNAs are induced by TLR activation in innate immune cells and target the 3′-untranslated regions of the mRNA encoding the components of the TLR signaling system. Modern genome-editing tools suggest an artificial increase in the diversity of miRNAs and an increased use of miRNAs for directional action. Structure determination of RNA, RNA–RNA, RNA–DNA, and ribonucleoprotein complexes is becoming a rapidly developing area requiring the development of new technologies.