CP110 and CEP135 Localize Near the Proximal Centriolar Remnants of Mice Spermatozoa.

Centrioles form centrosomes that organize microtubules, assist in cell structure, and nucleate cilia that provide motility and sensation. Within the sperm, the centrosome consists of two centrioles (proximal and distal centriole) and a pericentriolar material known as the striated column and capitulum. The distal centriole nucleates the flagellum. Mice spermatozoa, unlike other mammal spermatozoa (e.g., human and bovine), have no ultra-structurally recognizable centrioles, but their neck has the centriolar proteins POC1B and FAM161A, suggesting mice spermatozoa have remnant centrioles. Here, we examine whether other centriolar proteins, CP110 and CEP135, found in the human and bovine spermatozoa centrioles are also found in the mouse spermatozoa neck. CP110 is a tip protein controlling ciliogenesis, and CEP135 is a centriole-specific structural protein in the centriole base of canonical centrioles found in most cell types. Here, we report that CP110 and CEP135 were both located in the mice spermatozoa neck around the proximal centriolar remnants labeled by POC1B, increasing the number of centriolar proteins found in the mice spermatozoa neck, further supporting the hypothesis that a remnant proximal centriole is present in mice.

The evolution of centriole degradation in mouse sperm.

Centrioles are subcellular organelles found at the cilia base with an evolutionarily conserved structure and a shock absorber-like function. In sperm, centrioles are found at the flagellum base and are essential for embryo development in basal animals. Yet, sperm centrioles have evolved diverse forms, sometimes acting like a transmission system, as in cattle, and sometimes becoming dispensable, as in house mice. How the essential sperm centriole evolved to become dispensable in some organisms is unclear. Here, we test the hypothesis that this transition occurred through a cascade of evolutionary changes to the proteins, structure, and function of sperm centrioles and was possibly driven by sperm competition. We found that the final steps in this cascade are associated with a change in the primary structure of the centriolar inner scaffold protein FAM161A in rodents. This information provides the first insight into the molecular mechanisms and adaptive evolution underlying a major evolutionary transition within the internal structure of the mammalian sperm neck.

Artificial Intelligence in Andrology: From Semen Analysis to Image Diagnostics.

Artificial intelligence (AI) in medicine has gained a lot of momentum in the last decades and has been applied to various fields of medicine. Advances in computer science, medical informatics, robotics, and the need for personalized medicine have facilitated the role of AI in modern healthcare. Similarly, as in other fields, AI applications, such as machine learning, artificial neural networks, and deep learning, have shown great potential in andrology and reproductive medicine. AI-based tools are poised to become valuable assets with abilities to support and aid in diagnosing and treating male infertility, and in improving the accuracy of patient care. These automated, AI-based predictions may offer consistency and efficiency in terms of time and cost in infertility research and clinical management. In andrology and reproductive medicine, AI has been used for objective sperm, oocyte, and embryo selection, prediction of surgical outcomes, cost-effective assessment, development of robotic surgery, and clinical decision-making systems. In the future, better integration and implementation of AI into medicine will undoubtedly lead to pioneering evidence-based breakthroughs and the reshaping of andrology and reproductive medicine.

Abnormal centriolar biomarker ratios correlate with unexplained bull artificial insemination subfertility: a pilot study.

The mechanisms underlying male infertility are poorly understood. Most mammalian spermatozoa have two centrioles: the typical barrel-shaped proximal centriole (PC) and the atypical fan-like distal centriole (DC) connected to the axoneme (Ax). These structures are essential for fertility. However, the relationship between centriole quality and subfertility (reduced fertility) is not well established. Here, we tested the hypothesis that assessing sperm centriole quality can identify cattle subfertility. By comparing sperm from 25 fertile and 6 subfertile bulls, all with normal semen analyses, we found that unexplained subfertility and lower sire conception rates (pregnancy rate from artificial insemination in cattle) correlate with abnormal centriolar biomarker distribution. Fluorescence-based Ratiometric Analysis of Sperm Centrioles (FRAC) found only four fertile bulls (4/25, 16%) had positive FRAC tests (having one or more mean FRAC ratios outside of the distribution range in a group's high-quality sperm population), whereas all of the subfertile bulls (6/6, 100%) had positive FRAC tests (P = 0.00008). The most sensitive biomarker was acetylated tubulin, which had a novel labeling pattern between the DC and Ax. These data suggest that FRAC and acetylated tubulin labeling can identify bull subfertility that remains undetected by current methods and may provide insight into a novel mechanism of subfertility.

CP110 and CEP135 localize near the proximal and distal centrioles of cattle and human spermatozoa.

Centrosomes play an important role in the microtubule organization of a cell. The sperm's specialized centrosome consists of the canonical barrel-shaped proximal centriole, the funnel-shaped distal centriole, and the pericentriolar material known as striated columns (or segmented columns). Here, we examined the localization of the centriole proteins CEP135 and CP110 in cattle and human spermatozoa. In canonical centrioles, CP110 is a centriole tip protein that controls cilia formation, while CEP135 is a structural protein essential for constructing the centriole. In contrast, we found antibodies recognizing CEP135 and CP110 label near the proximal and distal centrioles at the expected location of the striated columns and capitulum in cattle and humans in an antibody and species-specific way. These findings provide a pathway to understanding the unique functions of spermatozoan centrosome.

Revisiting the mystery of centrioles at the beginning of mammalian embryogenesis.

The prevailing assumption has been that the human spermatozoon provides only one centriole to the zygote: the proximal centriole, with a canonical, cylinder-like shape. This overly simplistic view has come under challenge since discovering that the human spermatozoon provides a second, atypical centriole to the zygote. The study of human zygotes is challenging for ethical reasons, and bovine zygotes provide an important model due to a similarity in centrosome embryonic inherence and function. Detailed ultrastructural analyses by Uzbekov and colleagues identify the persistence of atypical centrioles in bovine early embryos, raising questions about the original single-centriole model. Whether the parental origin of nascent atypical centrioles or their wide structural diversity and deviation from the canonical centriolar form in blastomeres constitutes sufficient evidence to warrant a reconsideration of the single-centriole model is discussed herein. Because previous human studies identified only one canonical centriole in the zygote, atypical centrioles are likely present in the early human embryo; therefore, it is time to rethink the role of paternal centrioles in human development.

IgG antibodies label the spermatozoan centriole of Drosophila melanogaster.

Centrioles are microtubule-based, barrel-shaped, subcellular organelles with evolutionarily conserved composition, structure, and function. Yet, in sperm cells, centrioles are remodeled, gaining species-specific composition and structure. The sperm centrioles of Drosophila melanogaster undergo dramatic remodeling, during which most known centriolar proteins are lost. Here, we find that IgG antibodies unexpectedly label Drosophila melanogaster spermatozoan centrioles . This labeling offers a simple method for marking the spermatozoan centriole, though it may interfere with testing new anti-centriolar antibodies using immunofluorescence.

Centrosome Formation in the Bovine Early Embryo.

Centrosome formation during early development in mice and rats occurs due to the appearance of centrioles de novo. In contrast, in humans and other non-rodent mammals, centrioles are thought to be derived from spermatozoa. Ultrastructural study of zygotes and early embryos of cattle at full series of ultrathin sections show that the proximal centriole of the spermatozoon disappears by the end of the first cleavage division. Centrioles appear in two to four cell embryos in fertilized oocytes and in parthenogenetic embryos. Centriole formation includes the appearance of atypical centrioles with randomly arranged triplets and centrioles with microtubule triplets of various lengths. After the third cleavage, four centriolar cylinders appear for the first time in the blastomeres while each embryo still has two atypical centrioles. Our results showed that the mechanisms of centriole formation in different groups of mammals are universal, differing only in the stage of development in which they occur.

The Renaissance of Male Infertility Management in the Golden Age of Andrology.

Infertility affects nearly 186 million people worldwide and the male partner is the cause in about half of the cases. Meta-regression data indicate an unexplained decline in sperm concentration and total sperm count over the last four decades, with an increasing prevalence of male infertility. This suggests an urgent need to implement further basic and clinical research in Andrology. Andrology developed as a branch of urology, gynecology, endocrinology, and, dermatology. The first scientific journal devoted to andrological sciences was founded in 1969. Since then, despite great advancements, andrology has encountered several obstacles in its growth. In fact, for cultural reasons, the male partner has often been neglected in the diagnostic and therapeutic workup of the infertile couple. Furthermore, the development of assisted reproductive techniques (ART) has driven a strong impression that this biotechnology can overcome all forms of infertility, with a common belief that having a spermatozoon from a male partner (a sort of sperm donor) is all that is needed to achieve pregnancy. However, clinical practice has shown that the quality of the male gamete is important for a successful ART outcome. Furthermore, the safety of ART has been questioned because of the high prevalence of comorbidities in the offspring of ART conceptions compared to spontaneous conceptions. These issues have paved the way for more research and a greater understanding of the mechanisms of spermatogenesis and male infertility. Consequently, numerous discoveries have been made in the field of andrology, ranging from genetics to several "omics" technologies, oxidative stress and sperm DNA fragmentation, the sixth edition of the WHO manual, artificial intelligence, management of azoospermia, fertility in cancers survivors, artificial testis, 3D printing, gene engineering, stem cells therapy for spermatogenesis, and reconstructive microsurgery and seminal microbiome. Nevertheless, as many cases of male infertility remain idiopathic, further studies are required to improve the clinical management of infertile males. A multidisciplinary strategy involving both clinicians and scientists in basic, translational, and clinical research is the core principle that will allow andrology to overcome its limits and reach further goals. This state-of-the-art article aims to present a historical review of andrology, and, particularly, male infertility, from its "Middle Ages" to its "Renaissance", a golden age of andrology.

The Centrosome: Conclusions and Perspectives.

The centrosome consists of two centrioles surrounded by pericentriolar material [...].

Tubulin posttranslational modifications modify the atypical spermatozoon centriole.

Sperm cells are transcriptionally and translationally silent. Therefore, they may use one of the remaining mechanisms to respond to stimuli in their environment, the post-translational modification of their proteins. Here we examined three post-translational modifications, acetylation, glutamylation, and glycylation of the protein tubulin in human and cattle sperm. Tubulin is the monomer that makes up microtubules, and microtubules constitute the core component of both the sperm centrioles and the axoneme. We found that the sperm of both species were labeled by antibodies against acetylated tubulin and glutamylated tubulin.

Sperm centriole assessment identifies male factor infertility in couples with unexplained infertility - a pilot study.

Unexplained infertility affects about one-third of infertile couples and is defined as the failure to identify the cause of infertility despite extensive evaluation of the male and female partners. Therefore, there is a need for a multiparametric approach to study sperm function. Recently, we developed a Fluorescence-Based Ratiometric Analysis of Sperm Centrioles (FRAC) assay to determine sperm centriole quality. Here, we perform a pilot study of sperm from 10 fertile men and 10 men in couples with unexplained infertility, using three centriolar biomarkers measured at three sperm locations from two sperm fractions, representing high and low sperm quality. We found that FRAC can identify men from couples with unexplained infertility as the likely source of infertility. Higher quality fractions from 10 fertile individuals were the reference population. All 180 studied FRAC values in the 10 fertile individuals fell within the reference population range. Eleven of the 180 studied FRAC values in the 10 infertile patients were outliers beyond the 95% confidence intervals (P = 0.0008). Three men with unexplained infertility had outlier FRAC values in their higher quality sperm fraction, while four had outlier FRAC values in their lower quality sperm fraction (3/10 and 4/10, P = 0.060 and P = 0.025, respectively), suggesting that these four individuals are infertile due, in part, to centriolar defects. We propose that a larger scale study should be performed to determine the ability of FRAC to identify male factor infertility and its potential contribution to sperm multiparametric analysis.

The Centriole's Role in Miscarriages.

Centrioles are subcellular organelles essential for normal cell function and development; they form the cell's centrosome (a major cytoplasmic microtubule organization center) and cilium (a sensory and motile hair-like cellular extension). Centrioles with evolutionarily conserved characteristics are found in most animal cell types but are absent in egg cells and exhibit unexpectedly high structural, compositional, and functional diversity in sperm cells. As a result, the centriole's precise role in fertility and early embryo development is unclear. The centrioles are found in the spermatozoan neck, a strategic location connecting two central functional units: the tail, which propels the sperm to the egg and the head, which holds the paternal genetic material. The spermatozoan neck is an ideal site for evolutionary innovation as it can control tail movement pre-fertilization and the male pronucleus' behavior post-fertilization. We propose that human, bovine, and most other mammals-which exhibit ancestral centriole-dependent reproduction and two spermatozoan centrioles, where one canonical centriole is maintained, and one atypical centriole is formed-adapted extensive species-specific centriolar features. As a result, these centrioles have a high post-fertilization malfunction rate, resulting in aneuploidy, and miscarriages. In contrast, house mice evolved centriole-independent reproduction, losing the spermatozoan centrioles and overcoming a mechanism that causes miscarriages.

Atypical Centriolar Composition Correlates with Internal Fertilization in Fish.

The sperm competition theory, as proposed by Geoff Parker, predicts that sperm evolve through a cascade of changes. As an example, internal fertilization is followed by sperm morphology diversification. However, little is known about the evolution of internal sperm structures. The centriole has an ancient and evolutionarily conserved canonical structure with signature 9-fold, radially symmetric microtubules that form the cell's centrosomes, cilia, and flagella. Most animal spermatozoa have two centrioles, one of which forms the spermatozoan flagellum. Both are delivered to the egg and constitute the embryo's first two centrosomes. The spermatozoa of mammals and insects only have one recognizable centriole with a canonical structure. A second sperm centriole with an atypical structure was recently reported in both animal groups and which, prior to this, eluded discovery by standard techniques and criteria. Because the ancestors of both mammals and insects reproduced by internal fertilization, we hypothesized that the transition from two centrioles with canonical composition in ancestral sperm to an atypical centriolar composition characterized by only one canonical centriole evolved preferentially after internal fertilization. We examined fish because of the diversity of species available to test this hypothesis−as some species reproduce via internal and others via external fertilization−and because their spermatozoan ultrastructure has been extensively studied. Our literature search reports on 277 fish species. Species reported with atypical centriolar composition are specifically enriched among internal fertilizers compared to external fertilizers (7/34, 20.6% versus 2/243, 0.80%; p < 0.00001, odds ratio = 32.4) and represent phylogenetically unrelated fish. Atypical centrioles are present in the internal fertilizers of the subfamily Poeciliinae. Therefore, internally fertilizing fish preferentially and independently evolved spermatozoa with atypical centriolar composition multiple times, agreeing with Parker's cascade theory.

On the Origin and Evolution of Sperm Cells.

Sperm cells have intrigued biologists since they were first observed nearly 350 years ago by Antonie van Leeuwenhoek and Johan Ham [...].

A dynamic basal complex modulates mammalian sperm movement.

Reproductive success depends on efficient sperm movement driven by axonemal dynein-mediated microtubule sliding. Models predict sliding at the base of the tail - the centriole - but such sliding has never been observed. Centrioles are ancient organelles with a conserved architecture; their rigidity is thought to restrict microtubule sliding. Here, we show that, in mammalian sperm, the atypical distal centriole (DC) and its surrounding atypical pericentriolar matrix form a dynamic basal complex (DBC) that facilitates a cascade of internal sliding deformations, coupling tail beating with asymmetric head kinking. During asymmetric tail beating, the DC's right side and its surroundings slide ~300 nm rostrally relative to the left side. The deformation throughout the DBC is transmitted to the head-tail junction; thus, the head tilts to the left, generating a kinking motion. These findings suggest that the DBC evolved as a dynamic linker coupling sperm head and tail into a single self-coordinated system.

Fluorescence-Based Ratiometric Analysis of Sperm Centrioles (FRAC) Finds Patient Age and Sperm Morphology Are Associated With Centriole Quality.

A large proportion of infertility and miscarriage causes are unknown. One potential cause is a defective sperm centriole, a subcellular structure essential for sperm motility and embryonic development. Yet, the extent to which centriolar maladies contribute to male infertility is unknown due to the lack of a convenient way to assess centriole quality. We developed a robust, location-based, ratiometric assay to overcome this roadblock, the Fluorescence-based Ratiometric Assessment of Centrioles (FRAC). We performed a case series study with semen samples from 33 patients, separated using differential gradient centrifugation into higher-grade (pellet) and lower-grade (interface) sperm fractions. Using a reference population of higher-grade sperm from infertile men with morphologically standard sperm, we found that 79% of higher-grade sperm of infertile men with substandard sperm morphology have suboptimal centrioles (P = 0.0005). Moreover, tubulin labeling of the sperm distal centriole correlates negatively with age (P = 0.004, R = -0.66). These findings suggest that FRAC is a sensitive method and that patient age and sperm morphology are associated with centriole quality.