Sperm-Specific MicroRNAs - Their Role and Function

Abstract

The sperm cell is highly specialised, with the sole purpose to fertilize an oocyte. Sperm assumes a simplistic structure, consisting of a head, which is mostly void of cytoplasm, a nucleus packed with DNA tightly wound around protamines; a midpiece housing the mitochondria necessary to fuel its locomotion, and a tail or principle piece that whips in motion to move the sperm towards the oocyte. However, despite the lack of cytoplasmic space, increasing studies in sperm biology have revealed that the sperm cell contains a myriad of molecular constituents that may play a role post-fertilization, influencing the oocyte and embryo development (figure 1). One such group of molecules are the small non-coding RNAs, which include the microRNAs (miRNAs). microRNAs miRNAs are small non-coding single-strand RNA molecules with sizes ranging from 17-26 nucleotides. The first miRNA to be discovered was lin-4 in the nematode, Caenorhabditis elegans. Lin-4 was detected with conserved complementary site on lin-14 and subsequently affected the larvae developmental timing by targeting mRNA and inhibiting its function [1]. Since then, miRNAs have emerged to play key roles in many biological functions through binding to 3'UTR (Untranslated Region) of specific mRNAs leading to either mRNA degradation or protein translation inhibition [2]. These miRNAs are involved in regulating cell functions including gene expression during development, differentiation, cell proliferation and apoptosis [3,4].In addition to having an influence in normal biological and developmental processes, miRNAs have been found to be involved in many pathogenic processes including Cardiovascular Diseases (CVD), cancer, inflammatory or autoimmune diseases, metabolic disorders and neurodegenerative disorders [5]. miRNA biogenesis miRNAs are encoded in the genome and transcribed by RNA polymerase II to form long primary miRNA transcripts (pri-miRNAs) that contain a cap structure at the 5' end and are poly-adenylated at the 3' end.The primary miRNAs are subsequently processed in the nucleus by Drosha to form shorter stem loop structures called pre curser-miRNAs or pre-miRNA (figure 2).These pre-miRNAs are then HSOA Journal of Genetics & Genomic Sciences Mini ReviewAbstract microRNAs (miRNAs) are small non-coding single-stranded molecules (containing about 22 nucleotides) that are widely found in many organisms, as varied as micro-organisms, plants, invertebrates and vertebrates. These miRNAs function in RNA silencing and post-transcriptional regulation of gene expression. miRNAs have been found to be involved in a number of biological and pathological processes, including sperm biology and infertility. This review will describe and discuss the role of miRNAs in terms of their role in sperm function, male infertility and gene regulation. a) The fertilising sperm introduces more than the paternal genome, the oocyte-activating factor (PLCζ), proteins from post-acrosomal, and perinuclear thecal proteins and centrioles; b) Sperm also contain a complex population of RNA, ...

Micro-RNAs differentially expressed in comparative analysis of sperm samples with high and low efficiency in the in vitro production of bovine (Bos Taurus) embryos

“…The determination of miRNA profiles has become relevant for the understanding of the regulation mechanisms of the different biological processes, including fertility in males, and that bulls with low fertility present larger populations of miRNAs when compared to those of high fertility (RAUBER, 2013). The profiles of certain miRNAs may make them possible fertility markers (MILLER;OSTERMEIER, 2006;AL-GAZI;CARROLL, 2015).…”