RNA dynamics of fertile and infertile spermatozoa

Abstract

The presence of a complex population of mRNAs in human mature spermatozoa is well documented; among them, transcripts of aromatase and ERs (oestrogen receptors) have been described but their significance is not clear. Therefore, to clarify the role of this complex population of mRNAs in human ejaculated sperm, we have isolated on discontinuous density gradients two main fractions from the same sample: high- and low-motile spermatozoa. The levels of different transcripts coding for molecules involved in nuclear condensation [Prm-1 (protamine 1) and Prm-2], capacitation [eNOS (endothelial nitric oxide synthase), nNOS (neuronal nitric oxide synthase), c-myc], motility and sperm survival (aromatase) have been assessed using semi-quantitative RT (reverse transcriptase)-PCR. The viability of sperm as well as the percentage of apoptosis were identical in high- and low-motile fractions. No significant change in the c-myc/Prm-2 ratio between the two populations of spermatozoa was observed. Conversely the amount of Prm-1 mRNA was significantly higher in low-motile than in high-motile fraction; in most of the high-motile sperm samples analysed, eNOS and nNOS transcripts were undetectable, whereas they were observed in low-motile sperm. Moreover, a partial or complete disappearance of c-myc transcripts was observed after capacitation. As to the aromatase expression, a significant decrease in the amount of transcripts in immotile sperm fraction was recorded in all samples studied. To conclude, analysing mRNA profiles in humans could be helpful either as a diagnostic tool to evaluate male fertility, since they reflect spermatogenesis gene expression, and/or a prognosis value for fertilization, since these RNAs are delivered to oocytes.

Stallion Sperm Transcriptome Comprises Functionally Coherent Coding and Regulatory RNAs as Revealed by Microarray Analysis and RNA-seq

“…Therefore, early claims about the presence of RNA in mouse [3], bull [4], rat and human sperm [5] were met with skepticism. However, research over the past decade has provided compelling evidence that mature mammalian sperm contain complex populations of RNAs [1], [2], [6], [7], [8], [9]. These include over 3,000 mRNAs [6], [8], and a heterogeneous population of small and long non-coding RNAs [8], [10], [11], [12], [13], [14], though typically sperm are depleted of intact ribosomal RNAs [6].…”

Evaluation of the effectiveness of semen storage and sperm purification methods for spermatozoa transcript profiling

“…Over the past decade, several groups have independently provided compelling evidence that the transcriptionally and translationally inert mature spermatozoon contain a complex population of RNAs [Carreau et al 2007; Dadoune 2009; Fischer et al 2012; Galeraud-Denis et al 2007; Hamatani 2012; Krawetz 2005; Ostermeier et al 2002; Ostermeier et al 2005a; Ostermeier et al 2005b; Pessot et al 1989]. The functions of the majority of sperm RNAs remain enigmatic although their use in early embryonic development has been proposed [Krawetz 2005].…”

“…The functions of the majority of sperm RNAs remain enigmatic although their use in early embryonic development has been proposed [Krawetz 2005]. Many approaches (microarrays, RNA-Seq, RT-PCR) have been applied to identify the potential functions of transcripts retained in sperm [Card et al 2013; Carreau, et al 2007; Jodar et al 2012; Lima-Souza et al 2012; Platts et al 2007; Yang et al 2009]. Success using these technologies is dependent on the quality of the RNA obtained.…”

Estrogens and male reproduction: a new concept

“…These observations of decreased sperm motility in men with aromatase deficiency, together with our data showing a significant decrease of aromatase in immotile human spermatozoa, could suggest that aromatase is involved in the acquisition of sperm motility. In mouse as well as in man it has been shown that estrogens are positively involved in sperm capacitation and acrosome reaction (54). The existence of ERs on the sperm membrane (55) and in the mitochondria (52) is likely to be relevant for a role of estrogens in male gamete motility.…”

“…As also suggested by Ostermeier et al (56), the genetic fingerprint of fertile men could include the analysis of mRNA profiles and thus aromatase and ERs may be helpful. Nevertheless, it is clear that further studies are necessary to elucidate the real impact of estrogen on human male reproduction, although it is obvious that several steps are involved (54). Even if numerous estrogentargeted genes remain to be defined, there is now a body of evidence in favor of a positive role for estrogens in male reproduction via genomic and rapid membrane effects (for a review, see Ref.…”