Caracterização e investigação das bases moleculares de fenótipos associados à produção in vitro de embriões em raças leiteiras taurinas e zebuínas

Abstract

In the last years the in vitro production of embryos became a technique of great importance in the reproduction of cattle. In the dairy cattle, it has been widely used with spotlight for the Gyr and Holstein breeds. Among other features, this two breeds exhibit differences related to reproductive physiology and reflects on the potential of production of embryos in the system in vitro. Knowing the importance of both breed for the Brazilian herd, it is critical to understand the physiological basis of these differences and search tools to evaluate the quality and viability of oocytes and embryos. The aim of this study was to characterize the phenotype "donor" based on embryo production and evaluate some genes as potential markers for production in these breeds. To do this initially, data from in vitro production of embryos from a commercial laboratory were analyzed. Subsequently, the molecular characterization and evaluation of the relative expression of candidate genes was performed in samples of granulosa cells from culture of animals with different profiles of production embryos using the Real-time PCR. A higher production of total and viable oocyte-cumulus complexes (COC) was observed in donor Gyr. Likewise, animals Gyr had a higher conversion rate and higher total production of embryos, independent of breed of sire used for fertilization. However, in the two breeds there was no difference in the production of COC between animals with different conversion rates COC / embryo. There was no differences in the expression of genes (BAX, INHA, IGFIR, LHR, STAR) between animals with high or low production of embryos, as well as between breeds. However, the PRDX1 gene was overexpressed in donor Holstein characterized as high production of embryos. These datas confirm the higher production of COC in Gyr breed animals when compared to Holstein cows, as well as the highest total production of embryos in vitro system, but suggest that the two breeds efficiency in the production of embryos is not determined by the total production of COC. The assessment of gene expression of granulosa cells obtained from cultures for in vitro production of embryos did not allow the characterization of potential markers for predicting embryo production of donors.