Researchers confirmed that sperm accumulate mutations over the years, increasing the risk of transmitting diseases to offspring. All products featured on WIRED are independently selected by our editors. However, we may receive compensation from retailers and/or from purchases of products through these links. Human semen not only accumulates genetic mutations with age; as the percentage of sperm carrying potentially serious mutations increases, so does the risk of developing diseases in offspring. This is according to a new study by researchers at the Sanger Institute and King's College London.

The embryos weren't used to try to establish a pregnancy, but the researchers behind the technique say it could one day be used to address infertility. In a controversial step that raises the possibility of a new kind of infertility treatment, scientists report that they have produced functional human eggs in the lab that were able to be fertilized with sperm. The proof-of-concept study, published today in the journal Nature Communications, involves using human skin cells to generate eggs, some of which were capable of producing early-stage embryos. None of the embryos were used to try to establish a pregnancy, and it's unlikely that they would have developed much further in the womb. Yet the authors, from Oregon Health and Science University, say the technique could one day be used as an alternative to in vitro fertilization, or IVF.

Breakthroughs, discoveries, and DIY tips sent every weekday. Egg-freezing boomed in the last decade, with a 400 percent increase since 2012. Now, research about sperm degradation and its impact on family-building is driving a generation of health-conscious men to consider their own fertility preservation. Whether men of the past were left out or checked-out of the fertility conversation depends on who you ask. But old beliefs about the lifelong assurance of fatherhood are out and men are taking control of their reproductive futures with the help of mail-in sperm testing and freezing.

Although the terms are often confused or used interchangeably, sperm and semen are not the same thing. Semen is the fluid that comes out of the penis, while sperm are the microscopic cells within the semen. Sperm cells are specialized for the task of fertilizing an egg. Semen analysis is considered essential for diagnosis of male infertility, but is not readily available at medical institutions other than those specializing in infertility treatment. 'Fertility specialists take it for granted that the first step in diagnosing male infertility is to perform a semen analysis,' Professor Kobayashi added.

Okay, I know what you're probably thinking. We've been hearing about the use of tiny robots in medicine for years, maybe even decades. Where are my medical microbots already? They're coming, says Brad Nelson, who works in robotics at ETH Zürich. And they could be a game changer for a number of serious diseases.

Scientists have discovered that the way sperms swim defies Newton's law of motion, which states there is an equal and opposite reaction Researchers at Kyoto University found the sperms' flagella, or tail, propels the agents forward by changing their shape to interact with the fluid. Sperms do so in a non-reciprocal way, which violates Newton's third law because they do not elicit an equal and opposite reaction from their surroundings. The flagellum's elasticity also suggests that there should be no movement at all, but instead, sperms whip their tails without releasing much energy into their surroundings. Researchers at Kyoto University found the sperms' flagella, or tail, propels the agents forward by changing their shape to interact with the fluid The team used human sperm cells and algae for the research because both have flagella that help them propel through the liquid, New Scientist reports. Men's bulging waistlines are blamed for the worrying trend and'everywhere chemicals' in the environment.

An artificial intelligence that can scan sperm to work out which are healthiest has been developed by scientists. Even in men who eat well and exercise regularly, barely one in ten sperm are healthy -- and in some men the ratio falls below four percent. At the Oma Clinic in California, however, scientists have developed a'sperm health test' algorithm that scans swimmers for their shape and how they move to pick out the best ones for fertilizing an egg from the crowd. They hope that it will boost success rates with invitro fertilization (IVF) and lower costs, meaning couples will need fewer rounds of the treatment. To develop the algorithm, the scientists began by extracting a subset of sperm from each sample -- which contained up to 20,000 swimmers.

One in four couples in developing countries is impacted by infertility. About 48.5 million couples experience infertility worldwide. Today, infertility is rapidly becoming an epidemic. In vitro fertilization (IVF) is a technique that helps people facing fertility problems have a baby. Despite IVF's potential, the outcomes are unpredictable. To make matters worse, access to fertility care is abysmal.

More than 300 million people worldwide suffer from some form of infertility. Many are opting for parenthood at a later stage in life – in their thirties and forties – when the quality of their gametes (the egg and sperm) is no longer at their biological prime. Recent studies also show that we are simply not as fertile as our grandparents. According to Shanna Shaw, an environmental and reproductive epidemiologist at the Icahn School of Medicine, and author of the book Count Down, the average men's sperm concentration – that is, the number of sperm per millilitre of semen – has decreased by more than 50 per cent in the past four decades, with the blame placed on factors such as environmental pollution and unhealthy lifestyles. Increasingly, couples have been forced to resort to assisted reproductive techniques such as in vitro fertilisation, commonly known as IVF. According to the US Centers for Disease Control and Prevention, about nine million babies have been born using IVF since the first such case in 1978.

Physiological functions of the microtubule cytoskeleton are expected to be regulated by a variety of posttranslational tubulin modifications. For instance, tubulin glycylation is almost exclusively found in cilia and flagella, but its role in the function of these organelles remains unclear. Gadadhar et al. now demonstrate in mice that glycylation, although nonessential for the formation of cilia and flagella, coordinates the beat waveform of sperm flagella. This activity is a prerequisite for progressive sperm swimming and thus for male fertility. At the ultrastructural level, lack of glycylation perturbed the distribution of axonemal dynein conformations, which may explain the observed defects in flagellar beat. Science , this issue p. [eabd4914][1] ### INTRODUCTION Microtubules are key components of the eukaryotic cytoskeleton. Although they are involved in a wide variety of functions, microtubules are structurally highly similar across most cell types and organisms. It was suggested that a “tubulin code,” formed by combinations of tubulin posttranslational modifications, adapts individual microtubules to specific functions within living cells. However, clear-cut functional and mechanistic data verifying this concept are still scarce. Glycylation is among the least explored posttranslational modifications of tubulin and has, so far, exclusively been found on microtubules of cilia and flagella from a variety of species. Previous work has suggested that glycylation might be essential for cilia and flagella, but mechanistic insight remains lacking. ### RATIONALE Two enzymes from the tubulin-tyrosine ligase-like (TTLL) family, TTLL3 and TTLL8, are essential to initiate glycylation of tubulin in mammals. To entirely abolish glycylation at the organism level and to determine its physiological function, we generated a double-knockout mouse lacking both glycylating enzymes ( Ttll3−/−Ttll8−/− ). Inactivation of these two enzymes led to a lack of glycylation in all analyzed cilia and flagella. This allowed us to investigate the role of glycylation in the function of these organelles. ### RESULTS Despite the absence of glycylation in Ttll3−/−Ttll8−/− mice, no gross defects were observed at the organism and tissue levels. Motile ependymal cilia in brain ventricles as well as motile cilia in the respiratory tract were present and appeared normal. Sperm flagella were also assembled normally, and sperm were able to swim. However, in vitro fertility assays showed that male Ttll3−/−Ttll8−/− mice were subfertile. Computer-assisted sperm analyses revealed motility defects of Ttll3−/−Ttll8−/− sperm. Further analyses showed that lack of glycylation leads to perturbed flagellar beat patterns, causing Ttll3−/−Ttll8−/− sperm to swim predominantly along circular paths. This is highly unusual for mammalian sperm and interferes with their ability to reach the oocyte for fertilization. To determine the molecular mechanisms underlying this aberrant flagellar beat, we used cryo–electron tomography. The three-dimensional structure of the 96-nm repeat of the Ttll3−/−Ttll8−/− sperm axoneme showed no aberrations in its overall assembly. By contrast, the structure of both outer and inner dynein arms (ODAs and IDAs) was perturbed in Ttll3−/−Ttll8−/− flagella. Classification analysis showed that the incidence and distribution of pre-powerstroke and post-powerstroke conformations of ODAs and IDAs were altered in Ttll3−/−Ttll8−/− sperm. These ultrastructural findings indicate that glycylation is required to efficiently control the dynein powerstroke cycle, which is essential for the generation of a physiological flagellar beat. ### CONCLUSION Our work shows that tubulin glycylation regulates the beat of mammalian flagella by modulating axonemal dynein motor activity. Lack of glycylation leads to perturbed sperm motility and male subfertility in mice. Considering that human sperm are more susceptible than mouse sperm to deficiencies in sperm motility, our findings imply that a perturbation of tubulin glycylation could underlie some forms of male infertility in humans. ![Figure][2] Tubulin glycylation controls sperm motility. ( A ) Microtubules in sperm flagella are rich in tubulin posttranslational modifications. Mice deficient for the glycylating enzymes TTLL3 and TTLL8 lack glycylation. ( B ) Mammalian sperm swim in linear paths. In the absence of glycylation, abnormal, mostly circular swimming patterns are observed, which impede progressive swimming. ( C ) Absence of glycylation leads to perturbed distribution of axonemal dynein conformations in Ttll3−/−Ttll8−/− flagella, which impedes normal flagellar beating. Posttranslational modifications of the microtubule cytoskeleton have emerged as key regulators of cellular functions, and their perturbations have been linked to a growing number of human pathologies. Tubulin glycylation modifies microtubules specifically in cilia and flagella, but its functional and mechanistic roles remain unclear. In this study, we generated a mouse model entirely lacking tubulin glycylation. Male mice were subfertile owing to aberrant beat patterns of their sperm flagella, which impeded the straight swimming of sperm cells. Using cryo–electron tomography, we showed that lack of glycylation caused abnormal conformations of the dynein arms within sperm axonemes, providing the structural basis for the observed dysfunction. Our findings reveal the importance of microtubule glycylation for controlled flagellar beating, directional sperm swimming, and male fertility. [1]: /lookup/doi/10.1126/science.abd4914 [2]: pending:yes