Transcriptome analyses reveal transcriptional profiles of horse oocytes before and after in vitro maturation

Oocyte in vitro maturation is necessary for the study and application of animal-assisted reproduction technology in animal reproduction and breeding. The comprehensive transcriptional profile of equine oocyte maturated in vitro has not been fully mined yet, which makes many key transcriptional events still unidentified. Here, Smart-seq2 was performed to analyse the gene expression pattern and the underlying regulatory mechanism of horse germinal vesicle (GV) and in vitro metaphase II (MII) oocytes. The results showed that 6402 genes (2640 up-regulated and 3762 down-regulated in MII samples compared to GV) and 4021 lncRNA transcripts (1210 up-regulated and 2811 down-regulated in MII samples compared to GV) were differentially expressed in GV and MII oocytes. Further, GO and KEGG analysis found that differentially expressed mRNAs and lncRNAs were mainly enriched in the pathways related to energy and lipid metabolism. In addition, LGALS3 was found a key gene in mediating the regulation of oocyte meiosis recovery and fertilization ability. This study provides novel knowledge about gene expression and energy metabolism during equine oocyte maturation and a reference for the further study and application of assisted reproductive technology in horse reproduction and breeding.