MiRNA expression profile in relation to oocyte developmental competence

The objective of this study was to identify the expression profile of miRNAs in porcine oocytes derived from follicles of different sizes using RNA high throughput sequencing technology. Oocytes were aspirated from large (3-6 mm) or small (<2 mm) ovarian follicles and tested for developmental competence and chromatin configurations. Small RNA libraries were constructed from both groups and then sequenced on an Illumina NextSeq500. Oocytes from large follicles showed higher developmental competence and different chromatin configuration compared to small oocyte group. In total, 167 and 162 known miRNAs were detected in large and small oocyte groups, respectively with 153 miRNAs were commonly expressed in both groups. In addition, 155 predicted novel miRNAs were detected and quantified. MiR-205, miR-16, miR-148a-3p, miR-125b, and let-7 family were among the top 10 highly abundantly expressed miRNAs in both oocyte groups. Further analysis showed that 8 miRNAs were differentially expressed (DE) between both groups (>2 fold change) with 4 up- and 4 down-regulated miRNAs in large compared to small oocyte group. Target gene prediction followed by KEGG pathway analysis revealed 46 pathways that were enriched with miRNA-target genes. Oocyte meiosis pathway and signaling pathways including FoxO, PI3K-Akt, TGFβ, and cAMP were predictably targeted by DE miRNAs. These results give more insights into the potential role of miRNAs in controlling oocyte developmental competence. Six small RNA libraries were constructed from two oocytes groups (From large and small follicles, 3 biological replicates each) and then sequenced on an Illumina NextSeq500