Abstract
Season clearly influences oocyte competence in buffalo (Bubalus bubalis); however, changes in the oocyte molecular status in relation to season are poorly understood. This study characterizes the microRNA (miRNA) and transcriptomic profiles of oocytes (OOs) and corresponding follicular cells (FCs) from buffalo ovaries collected in the breeding (BS) and non-breeding (NBS) seasons. In the BS, cleavage and blastocyst rates are significantly higher compared to NBS. Thirteen miRNAs and two mRNAs showed differential expression (DE) in FCs between BS and NBS. DE-miRNAs target gene analysis uncovered pathways associated with transforming growth factor β (TGFβ) and circadian clock photoperiod. Oocytes cluster in function of season for their miRNA content, showing 13 DE-miRNAs between BS and NBS. Between the two seasons, 22 differentially expressed genes were also observed. Gene Ontology (GO) analysis of miRNA target genes and differentially expressed genes (DEGs) in OOs highlights pathways related to triglyceride and sterol biosynthesis and storage. Co-expression analysis of miRNAs and mRNAs revealed a positive correlation between miR-296-3p and genes related to metabolism and hormone regulation. In conclusion, season significantly affects female fertility in buffalo and impacts on oocyte transcriptomic of genes related to folliculogenesis and acquisition of oocyte competence.
Highlights
Water buffalo (Bubalus bubalis) is an important livestock resource for both developing and developed countries
The present study aims to investigate the causes of the decreased oocyte competence during the non-breeding season (NBS) in buffalo
The reduced oocyte developmental competence recorded during the NBS in buffalo is associated with changes in miRNA and mRNA content in OOs and corresponding follicular cells (FCs)
Summary
Water buffalo (Bubalus bubalis) is an important livestock resource for both developing and developed countries. The embryonic mortality is due to inadequate luteal growth and function, resulting in reduced progesterone secretion[5] This has a negative impact on embryo growth, associated with alterations in transcriptomic and proteomic profiles of the embryos and chorioamnios/caruncles[6,7], which impair embryo attachment to the uterine endometrium. Changes in transcriptome and miRNA expression in relation to season were further investigated in sheep, another short-day breeder, where oocyte competence was observed to decline during the NBS, as indicated by impaired in vitro embryo development[16]. In this study we investigated, for the first time, if reproductive failure in the NBS is associated to changes in gene expression affecting oocyte developmental competence in buffalo. To evaluate seasonal effects on oocyte competence, the miRNA and transcriptomic profiles of oocytes and corresponding follicular cells were characterized from abattoir-derived ovaries collected in the BS and NBS
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