Abstract
Early studies have provided a wealth of information on the functions of microRNAs (miRNAs). However, less is known regarding their functions in the hypothalamus involved in sheep reproduction. To explore the potential roles of hypothalamic messenger RNAs (mRNAs) and miRNAs in sheep without FecB mutation, in total, 172 and 235 differentially expressed genes (DEGs) and 42 and 79 differentially expressed miRNAs (DE miRNAs) were identified in polytocous sheep in the follicular phase versus monotocous sheep in the follicular phase (PF vs. MF) and polytocous sheep in the luteal phase versus monotocous sheep in the luteal phase (PL vs. ML), respectively, using RNA sequencing. We also identified several key mRNAs (e.g., POMC, GNRH1, PRL, GH, TRH, and TTR) and mRNA–miRNAs pairs (e.g., TRH co-regulated by oar-miR-379-5p, oar-miR-30b, oar-miR-152, oar-miR-495-3p, oar-miR-143, oar-miR-106b, oar-miR-218a, oar-miR-148a, and PRL regulated by oar-miR-432) through functional enrichment analysis, and the identified mRNAs and miRNAs may function, conceivably, by influencing gonadotropin-releasing hormone (GnRH) activities and nerve cell survival associated with reproductive hormone release via direct and indirect ways. This study represents an integral analysis between mRNAs and miRNAs in sheep hypothalamus and provides a valuable resource for elucidating sheep prolificacy.
Highlights
Reproduction, one of the major factors significantly affecting the sheep industry, is a complicated but important physiological process
Regarding the expression level of messenger RNAs (mRNAs), our results showed that the fragments per kilobase per million mapped reads (FPKM) of those genes obtained from RNA sequencing (RNA-seq) at 500, constituted about 0.5% (Supplementary Table 3), which suggested that the data obtained from the hypothalamus via RNA-seq were relatively reasonable
The results indicated that both mRNAs and miRNAs in sheep hypothalamus displayed expression patterns similar to the sequencing results (Figure 7), demonstrating the reliability of the data generated from RNA-seq
Summary
Reproduction, one of the major factors significantly affecting the sheep industry, is a complicated but important physiological process. Sheep with one copy of the FecB mutation can experience significant increase in litter size, by 0.67, while this increase is about 1.5 when there are two mutated copies (Liu et al, 2014). This mutation was detected in diverse sheep species, such as Booroola Merino sheep (Mulsant et al, 2001) (Australia), Garole sheep (Polley et al, 2010) (India), Hu sheep (Davis et al, 2006) (China), and Small Tail Han sheep (STH sheep; China) (Davis et al, 2006). The fact is that there are STH sheep with FecB++ and which show a polytocous phenomenon (Davis et al, 2006), and how this mechanism was established remains largely unclear
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