Abstract
Simple SummaryThe present study searched for the presence and abundance of porcine spermatozoa small RNA sequences (microRNAs) that have the potential to alter gene expression patterns. Four different sperm sources were compared: spermatozoa from three different sections of the ejaculate and from the caudal epididymis, also classed as spermatozoa from higher (HF) or lower (LF) fertility boars. Sperm miRNAs were compared using high-output small RNA sequencing. We identified five sperm miRNAs not previously reported in pigs. Differences in abundance of four miRNAs known to affect the expression of genes with key roles in fertility were related to boar fertility. These miRNAs could be used as fertility markers in artificial insemination programs.MicroRNAs (miRNAs) are short non-coding RNAs (20–25 nucleotides in length) capable of regulating gene expression by binding -fully or partially- to the 3’-UTR of target messenger RNA (mRNA). To date, several studies have investigated the role of sperm miRNAs in spermatogenesis and their remaining presence toward fertilization and early embryo development. However, little is known about the miRNA cargo in the different sperm sources and their possible implications in boar fertility. Here, we characterized the differential abundance of miRNAs in spermatozoa from the terminal segment of the epididymis and three different fractions of the pig ejaculate (sperm-peak, sperm-rich, and post-sperm rich) comparing breeding boars with higher (HF) and lower (LF) fertility after artificial insemination (AI) using high-output small RNA sequencing. We identified five sperm miRNAs that, to our knowledge, have not been previously reported in pigs (mir-10386, mir-10390, mir-6516, mir-9788-1, and mir-9788-2). Additionally, four miRNAs (mir-1285, mir-92a, mir-34c, mir-30), were differentially expressed among spermatozoa sourced from ejaculate fractions and the cauda epididymis, and also different abundance was found between HF and LF groups in mir-182, mir-1285, mir-191, and mir-96. These miRNAs target genes with key roles in fertility, sperm survival, immune tolerance, or cell cycle regulation, among others. Linking the current findings with the expression of specific sperm proteins would help predict fertility in future AI-sires.
Highlights
The expression of more than 60% of all genes is estimated to be under the regulation of non-coding small RNAs [1]
Studies of miRNAs in spermatozoa searched for their role in spermatogenesis and their remaining presence toward fertilization and early embryo development, attempting to disclose if their presence or absence in mature spermatozoa might be related to abnormal development and functioning [11,12] and/or fertility modulation, as found in the murine species where the transfer of sperm miRNAs into the oocyte after fertilization was associated with differential early embryo development [3,13–16]
We report deep sequencing of miRNAs from spermatozoa collected from three fractions of the ejaculate of mature breeding boars
Summary
The expression of more than 60% of all genes is estimated to be under the regulation of non-coding small RNAs (ncsRNAs) [1]. Studies of miRNAs in spermatozoa searched for their role in spermatogenesis and their remaining presence toward fertilization and early embryo development, attempting to disclose if their presence or absence in mature spermatozoa might be related to abnormal development and functioning [11,12] and/or fertility modulation, as found in the murine species where the transfer of sperm miRNAs into the oocyte after fertilization was associated with differential early embryo development [3,13–16]. We report deep sequencing of miRNAs from spermatozoa collected from three fractions of the ejaculate (ejaculated spermatozoa exposed to different secretions of the accessory sexual glands, namely SPF, rest of SRF and post-SRF) of mature breeding boars.
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