Male Infertility and Genomics: Fertile men carried a complete set of the sperm RNA elements; however, most of the infertile men did not
Reporter: Aviva Lev-Ari, PhD, RN
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Abstract
Semen parameters are typically used to diagnose male infertility and specify clinical interventions. In idiopathic infertile couples, an unknown male factor could be the cause of infertility even when the semen parameters are normal. Next-generation sequencing of spermatozoal RNAs can provide an objective measure of the paternal contribution and may help guide the care of these couples. We assessed spermatozoal RNAs from 96 couples presenting with idiopathic infertility and identified the final reproductive outcome and sperm RNA elements (SREs) reflective of fecundity status. The absence of required SREs reduced the probability of achieving live birth by timed intercourse or intrauterine insemination from 73 to 27%. However, the absence of these same SREs does not appear to be critical when using assisted reproductive technologies such as in vitro fertilization with or without intracytoplasmic sperm injection. About 30% of the idiopathic infertile couples presented an incomplete set of required SREs, suggesting a male component as the cause of their infertility. Conversely, analysis of couples that failed to achieve a live birth despite presenting with a complete set of SREs suggested that a female factor may have been involved, and this was confirmed by their diagnosis. The data in this study suggest that SRE analysis has the potential to predict the individual success rate of different fertility treatments and reduce the time to achieve live birth.
SOURCE
http://stm.sciencemag.org/content/7/295/295re6
The authors said that nine of the 648 SREs corresponded to intergenic regions, while 12 corresponded to sperm-specific intronic elements, and 42 were within 24 different non-coding RNAs, “all of which are likely regulatory.” They added that most of the SREs, 585, were within exonic regions of 262 different genes. Of those genes, 40 percent were “ontologically classified as associated with spermatogenesis, sperm physiology, fertility, and early embryogenesis before implantation.”
They noted that approximately 13 percent of all couples of reproductive age have problems of infertility, and while physical examination of men can reveal lowered sperm count, shape, or motility, in some cases there’s no apparent cause of infertility. RNA sequencing could help resolve those unknown cases.
The scientists found that fertile men carried a complete set of the sperm RNA elements; however, most of the infertile men did not. Men whose sperm lacked the full transcriptional profile were less successful at impregnating their partner. Men with the whole package of required SREs were able to achieve live births without the aid of reproductive assistance in 22 of 30 cases, but men with at least one missing required SRE were only able to do so in 3 of 11 cases.
The authors acknowledged that their biomarkers need validation in a larger, prospective, blinded, controlled study, which would “clarify which are essential for diagnosis and may contribute to the birth of a healthy child.” But they noted the decreasing cost of NGS and said RNA sequencing could produce a clinical benefit.
RNA sequencing could help identify the most effective fertility treatments for couples struggling to conceive. In the study, 14 men with at least one critical SRE absent from their sperm RNA profile attempted to conceive with their partner using assisted reproductive technologies such as in vitro fertilization. Of those, 11 were successful.
The authors noted that women are more likely to bear the burden of extensive evaluation in the case of failure and that non-invasive RNA sequencing of sperm might reduce risks associated with that evaluation. “This may permit an informed choice of a treatment paradigm that would help the female partner avoid undergoing invasive procedures such as egg collection,” the authors wrote.
SOURCE
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