Abstract
This study aimed to investigate the miRNA expression patterns in granulosa cells of subordinate (SF) and dominant follicle (DF) during the early luteal phase of the bovine estrous cycle. For this, miRNA enriched total RNA isolated from granulosa cells of SF and DF obtained from heifers slaughtered at day 3 and day 7 of the estrous cycle was used for miRNAs deep sequencing. The results revealed that including 17 candidate novel miRNAs, several known miRNAs (n = 291–318) were detected in SF and DF at days 3 and 7 of the estrous cycle of which 244 miRNAs were common to all follicle groups. The let-7 families, bta-miR-10b, bta-miR-26a, bta-miR-99b and bta-miR-27b were among abundantly expressed miRNAs in both SF and DF at both days of the estrous cycle. Further analysis revealed that the expression patterns of 16 miRNAs including bta-miR-449a, bta-miR-449c and bta-miR-222 were differentially expressed between the granulosa cells of SF and DF at day 3 of the estrous cycle. However, at day 7 of the estrous cycle, 108 miRNAs including bta-miR-409a, bta-miR-383 and bta-miR-184 were differentially expressed between the two groups of granulosa cell revealing the presence of distinct miRNA expression profile changes between the two follicular stages at day 7 than day 3 of the estrous cycle. In addition, unlike the SF, marked temporal miRNA expression dynamics was observed in DF groups between day 3 and 7 of the estrous cycle. Target gene prediction and pathway analysis revealed that major signaling associated with follicular development including Wnt signaling, TGF-beta signaling, oocyte meiosis and GnRH signaling were affected by differentially expressed miRNAs. Thus, this study highlights the miRNA expression patterns of granulosa cells in subordinate and dominant follicles that could be associated with follicular recruitment, selection and dominance during the early luteal phase of the bovine estrous cycle.
Highlights
Follicular development is the result of complex hormonal and biochemical synergies that could be activated or switched off within the follicular environment in a spatiotemporal manner
To understand the miRNAs enrichment and degradation during the luteal phase of the bovine estrous cycle, twelve miRNA libraries were prepared from granulosa cells of subordinate (SF) and dominant (DF) at day 3 and day 7 of the estrous cycle using Illumina HiSeq 2000 and sequence reads with maximum 50 base-pair length were obtained
Sequence alignment of filtered reads indicated that 59.5% and 64.2% of the sequence reads in subordinated follicle (SF) and dominant follicle (DF), respectively at day 3 of the estrous cycle and 59.8% and 67.7% of the total filtered reads in SF and DF, respectively at day 7 of the estrous cycle were aligned to the bovine reference genome (Figure 1A)
Summary
Follicular development is the result of complex hormonal and biochemical synergies that could be activated or switched off within the follicular environment in a spatiotemporal manner. The primary follicle in turn undergoes a continual differentiation and development of the granulosa cells and accompanied by enlargement of the oocyte volume which may gradually become Graafian follicle [3]. This programmed and complex transit of the primordial follicle into large sized antral follicle is mainly initiated by morphological transformation and functional differentiation of the granulosa cells. When the follicles start to develop from state of resting pool, the oocytes continue to grow and the granulosa cells proliferate until the stage of preantral follicle [4]. The fate of follicular growth and development is believed to be mainly determined by the growth and development of the granulosa cells [8]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
