Currently the spermatozoa is no longer known only as a cell that delivers the male genetic material to the oocyte, since it provides fundamental factors for fertilization and embryonic development. We can include microRNAs (miRNAs) as one of these factors. MiRNAs are small RNAs that do not encode proteins but modulate gene expression and are present in spermatozoa. It is known that these molecules are important in biological processes, including embryonic development. In bovine, there is a great oscillation on in vitro production of embryos (IVP) when using different bulls, constituting groups of animals with high and low in vitro fertility. Sperm miRNAs may influence embryonic development and therefore may be correlated to high and low fertility. The aim of this work will be to identify and correlate miRNAs expressed in semen samples of bulls with high and low IVP fertility, starting with the analysis of the differential miRNAs gene expression in semen samples from commercially used bulls with known high and low IVP fertility rates. Later, we aim to verify if these differentially expressed miRNAs interfere in embryonic development through the use of mimics or inhibitors in zygotes produced in vitro, using semen samples of bulls with proven high or low IVP fertility. We expect to identify miRNA molecules that could be modulated to allow an increase in the production of embryos from bulls with high genetic merit and great commercial interest, however with low fertility in IVP.
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