microRNA as an Important Mediator in the Regulation of Male Reproduction: Current State of the Problem.

During all periods of male ontogenesis, physiological processes responsible for the correct functioning of reproductive organs and spermatogenesis are under the influence of various factors (neuro-humoral, genetic, and paratypical). Recently, the attention of researchers has increasingly turned to the study of epigenetic factors. In scientific publications, one can increasingly find references to the direct role of microRNAs, small non-coding RNAs involved in post-transcriptional regulation of gene expression, in the processes of development and functioning of reproductive organs. Although the role of microRNAs in the reproduction of mammals, including humans, has been intensively studied, this area of knowledge in birds remains under-researched and limited to single experiments. This is likely due to the unique features of embryogenesis and the structure of the avian reproductive system. This review summarizes the current state of knowledge on the role of microRNAs in avian reproduction. Insight into the molecular basis of spermatogenesis in is provided. Data on the functions and mechanisms by which microRNAs influence the processes of growth, development, and formation of rooster germ cells that determine the necessary morphofunctional qualitative characteristics of mature spermatozoa are summarized. Particular attention is paid to miRNA biogenesis as an important step affecting the success of spermatogenesis, as well as the role of miRNAs in avian sex differentiation during early embryogenesis. The modern literature sources systematized in this review, revealing the questions about the role of miRNAs in the reproductive function of birds, create a theoretical basis and define new perspectives and directions for further research in this field.