MicroRNAs are small non-coding RNAs that regulate genes expression. Huge interest in studying their role in reproduction has exploded in recent years. An international collaboration, led by dr. Rolando Pasquariello under the supervision of prof. Fulvio Gandolfi and prof. Tiziana Brevini, identified specific microRNAs that play a key role in determining bovine oocyte quality. In previous studies the same group had shown that ovaries with a limited number of follicles provide poor quality oocytes. The new results obtained thanks to a ‘next generation sequencing’ approach, unveiled the presence of microRNAs expressed in the follicular fluid and in the oocytes of low fertility cows. In addition, the new research demonstrated that the expression of microRNAs is altered in poor quality oocytes and this compromises the pathways controlling follicular growth and acquisition of oocyte developmental competence. The mechanisms mainly affected are those related to the accumulation of messenger RNAs in the ooplasm and the function of the mitochondria; both known to influence oocyte quality. The impact of the research is considerable for managing the reproductive efficiency of the cows, as it allows the identification of “problem animals” without having to wait for a given animal to become a repeat breeder.
In the picture: staining of mitochondria of an oocyte obtained from high and low antral follicle count ovaries: From the right to the left: oocyte (a); active (orange, b) and inactive (green, c) mitochondria, DNA staining (blue, d).
Pasquariello R, Manzoni EFM, Fiandanese N, Viglino A, Pocar P, Brevini TAL, Williams JL, Gandolfi F. Implications of miRNA expression pattern in bovine oocytes and follicular fluids for developmental competence. Theriogenology. 2020 Mar 15;145:77-85 [doi: 10.1016/j.theriogenology.2020.01.027].