Spermatozoal RNAs: What about their functions?

Abstract

The profound architectural changes that transform spermatids into spermatozoa result in a high degree of DNA packaging within the sperm head. However, the mature sperm chromatin that harbors imprinted genes exhibits a dual nucleoprotamine/nucleohistone structure with DNase-sensitive regions, which could be implicated in the establishment of efficient epigenetic information in the developing embryo. Despite its apparent transcriptionally inert state, the sperm nucleus contains diverse RNA populations, mRNAs, antisense and miRNAs, that have been transcribed throughout spermatogenesis. There is also an endogenous reverse transcriptase that may be activated under certain circumstances. It is now commonly accepted that sperm can deliver some RNAs to the ovocyte at fertilization. This review presents potential links between male-specific genomic imprinting, chromatin organization, and the presence of diverse RNA populations within the sperm nucleus and discusses the functional significance of these RNAs in the spermatozoon itself and in the early embryo following fertilization. Some recent data are provided, supporting the view that analyzing the profile of spermatozoal RNAs could be useful for assessment of male fertility.

Sperm-borne microRNA-34c is required for the first cleavage division in mouse

“…Phospholipase Cζ and postacrosomal sheath WW domain-binding protein of the sperm initiate calcium signaling crucial to oocyte activation (1) and promote meiotic resumption and pronuclear formation (2). Mammalian sperm contain an array of RNAs including mRNA and microRNA (miRNA) (3). Some of these RNAs are delivered to the oocyte during fertilization (4).…”

Smoking induces differential miRNA expression in human spermatozoa: A potential transgenerational epigenetic concern?

“…[29][30][31] While extrapolation to humans remains speculative, human spermatozoa are known to contain a range of RNA molecules, including microRNAs. [32][33][34][35] Furthermore, smokers have been shown to exhibit altered spermatozoal mRNA profiles compared with non-smokers, and miRNA changes have been observed in the placenta of human smokers vs. non-smokers. 36,37 It is therefore possible that cigarette smoke could also induce changes in the miRNA profiles of human spermatozoa, leading to altered phenotypes that could be transmitted to future generations through the male germ line.…”

Markers for Sperm Freezability and Relevance of Transcriptome Studies in Semen Cryopreservation: A Review

“…Even though microarray techniques, coupled with either quantitative real-time qPCR or qRT-PCR, have revealed limited features of the transcriptome and global paterns of gene expression in spermatozoa, these techniques have revealed that sperm transcripts afecting diferent metabolic pathways are related to semen fertility [48,49,[51][52][53][54]. A study based on the evaluation of sperm capacitation status provides evidence, indicating that the sperm-derived RNAs can be translated de novo using mitochondrial-type ribosomes, and at least 26 such sperm-translated proteins are known to be required during capacitation, sperm-egg interactions, and fertilization [11,54].…”

“…Recent technological advances have conirmed that the spermatozoon carries epigenetic factors that constitute their epigenome, such as proper packaging of the chromatin with protamines, modiications of histones, and a large population of messenger ribonucleic acid (mRNA) and microRNA (miRNA) transcripts [11][12][13]. The diversity of the RNA constellation in the seminal plasma (SP) and spermatozoa has been used as a patern for the genomic analysis of semen quality characteristics, particularly for the estimation of the fertility potential of spermatozoa [12][13][14][15][16][17].…”