Perfil do RNA-seq de oócitos bovinos de acordo com as fases do ciclo ovariano

Abstract

Knowledge from studies supported by hormonal analyses and the use of B-mode ultrasound on reproductive physiology and folliculogenesis has enabled the development of biotechnologies applied to reproduction. In bovine females, oocyte quality and competence are essentially dependent on the follicular state. When considering the differences in the quality of oocytes recovered by follicular aspiration and in the rates of blastocysts produced in vitro, one can observe the influence of differences in follicular growth patterns (number of follicular waves), in the number of antral follicles recruited, as well as in the stage of the estrous cycle. Currently, improvements in equipment and data processing have increased the popularity and volume of studies of 'omics' technologies, which allow the analysis of hundreds or thousands of compounds simultaneously. Thus, the importance of integrating molecular research to broaden the understanding of the mechanisms that act on the female gamete in the ovarian cycle will contribute with information necessary for the advancement of reproductive biotechnologies. The aim of this study was to describe the RNA-Seq profile in bovine oocytes at different phases of the ovarian cycle. Transcriptomic analysis by RNA-Seq was performed in the four phases of the ovarian cycle corresponded to experimental groups: P1, P2, P3 and P4. The ovarian cycle was classified based on the corpus luteum, follicular developmental and divergence (≥ 6mm). For each experimental group, transcriptomics was performed in three replicates, with 10 oocytes/replicate (n = 120). Data were analyzed using CLC Genomics Workbench (QIAGEN). The results showed the existence of a distinction in gene expression between the phases, based on the absence of shared genes among the six contrasts, which indicates alterations in oocyte metabolism. The comparison between phase 4 and phase 1 [P4 vs. P1] resulted in the highest number of differentially expressed genes (DEGs), with 934 genes, clearly marking the final process of oocyte maturation. The lowest number of DEGs observed occurred between phases 2 and 1 [P2 vs. P1], with only one single gene out of a total of 9 genes. The study allowed the identification of 2,129 DEGs present in the different phases of the ovarian cycle, outlining a transcription profile of the different phases and expanding knowledge about gene expression in oocytes.