The Experts below are selected from a list of 915 Experts worldwide ranked by ideXlab platform
Laura Cecilia Giojalas - One of the best experts on this subject based on the ideXlab platform.
-
Molecular Mechanism for Human Sperm Chemotaxis Mediated by Progesterone
PloS one, 2009Co-Authors: Maria E. Teves, Héctor Alejandro Guidobaldi, Diego Rafael Uñates, Raúl Sánchez, Werner Miska, Stephen J. Publicover, Aduen Andres Morales Garcia, Laura Cecilia GiojalasAbstract:Sperm Chemotaxis is a chemical guiding mechanism that may orient Spermatozoa to the egg surface. A picomolar concentration gradient of Progesterone (P), the main steroidal component secreted by the cumulus cells that surround the egg, attracts human Spermatozoa. In order to elucidate the molecular mechanism of Sperm Chemotaxis mediated by P, we combine the application of different strategies: pharmacological inhibition of signaling molecules, measurements of the concentrations of second messengers and activation of the chemotactic signaling. Our data implicate a number of classic signal transduction pathways in the response and provide a model for the sequence of events, where the tmAC-cAMP-PKA pathway is activated first, followed by protein tyrosine phosphorylation (equatorial band and flagellum) and calcium mobilization (through IP3R and SOC channels), whereas the sGC-cGMP-PKG cascade, is activated later. These events lead to Sperm orientation towards the source of the chemoattractant. The finding proposes a molecular mechanism which contributes to the understanding of the signal transduction pathway that takes place in a physiological process as Chemotaxis.
-
Human Sperm Chemotaxis depends on critical levels of reactive oxygen species
Fertility and sterility, 2008Co-Authors: Raúl Sánchez, Carolina Sepúlveda, Jennie Risopatrón, Juana V. Villegas, Laura Cecilia GiojalasAbstract:Objective To verify whether Chemotaxis is in part an oxidative process mediated by reactive oxygen species (ROS). Design In this prospective study, after removal of seminal plasma, the Sperm suspension received no treatment (control), ROS formation by stimulation with phorbol 12-myristate 13-acetate (PMA), antioxidant treatment (with catalase), or PMA stimulus in the presence of catalase. At time zero and after 3 hours of incubation, the percentage of capacitated and oriented Spermatozoa and the ROS levels were determined. Setting Andrology laboratory in a medical research institution. Patient(s) Normal semen was obtained from eight men. Intervention(s) The semen samples were evaluated to determine the effect of ROS production by stimulation with PMA and/or antioxidant treatment (with catalase) on the percentage of capacitated and oriented Spermatozoa. Main Outcome Measure(s) The Sperm capacitation, Chemotaxis and reactive oxygen species were assessed before and after PMA and/or antioxidant treatment. Result(s) Prolonged exposure to high quantities of ROS decrease the Sperm chemotactic response, probably because of oxidative damage of the cell. However, this effect may be reduced by the addition of antioxidants like catalase. Conclusion(s) Similar to capacitation, Chemotaxis seems to depend on the production of ROS, but in the latter process there may be a critical level of ROS necessary for Chemotaxis to occur.
-
Progesterone from the Cumulus Cells Is the Sperm Chemoattractant Secreted by the Rabbit Oocyte Cumulus Complex
PloS one, 2008Co-Authors: Héctor Alejandro Guidobaldi, Maria E. Teves, Diego Rafael Uñates, Agustin Anastasia, Laura Cecilia GiojalasAbstract:Sperm Chemotaxis in mammals have been identified towards several female sources as follicular fluid (FF), oviduct fluid, and conditioned medium from the cumulus oophorus (CU) and the oocyte (O). Though several substances were confirmed as Sperm chemoattractant, Progesterone (P) seems to be the best chemoattractant candidate, because: 1) Spermatozoa express a cell surface P receptor, 2) capacitated Spermatozoa are chemotactically attracted in vitro by gradients of low quantities of P; 3) the CU cells produce and secrete P after ovulation; 4) a gradient of P may be kept stable along the CU; and 5) the most probable site for Sperm Chemotaxis in vivo could be near and/or inside the CU. The aim of this study was to verify whether P is the Sperm chemoattractant secreted by the rabbit oocyte-cumulus complex (OCC) in the rabbit, as a mammalian animal model. By means of videomicroscopy and computer image analysis we observed that only the CU are a stable source of Sperm attractants. The CU produce and secrete P since the hormone was localized inside these cells by immunocytochemistry and in the conditioned medium by enzyme immunoassay. In addition, rabbit Spermatozoa express a cell surface P receptor detected by western blot and localized over the acrosomal region by immunocytochemistry. To confirm that P is the Sperm chemoattractant secreted by the CU, the Sperm chemotactic response towards the OCC conditioned medium was inhibited by three different approaches: P from the OCC conditioned medium was removed with an anti-P antibody, the attractant gradient of the OCC conditioned medium was disrupted by a P counter gradient, and the Sperm P receptor was blocked with a specific antibody. We concluded that only the CU but not the oocyte secretes P, and the latter chemoattract Spermatozoa by means of a cell surface receptor. Our findings may be of interest in assisted reproduction procedures in humans, animals of economic importance and endangered species.
-
Progesterone at the picomolar range is a chemoattractant for mammalian Spermatozoa.
Fertility and sterility, 2006Co-Authors: Maria E. Teves, Héctor Alejandro Guidobaldi, Raúl Sánchez, Werner Miska, Flavia Barbano, Laura Cecilia GiojalasAbstract:By means of a videomicroscopy system and a computer image analysis, we performed Chemotaxis assays to detect true Chemotaxis in human Spermatozoa, in parallel to immunohistochemistry detection of progesterone inside the cumulus cells. Progesterone indeed chemotactically guides mammalian Spermatozoa at very low hormone concentrations, and the cumulus oophorus could be a potential place for Sperm Chemotaxis mediated by progesterone in vivo.
-
Human Sperm Chemotaxis: both the oocyte and its surrounding cumulus cells secrete Sperm chemoattractants
Human reproduction (Oxford England), 2004Co-Authors: Fei Sun, Ilan Tur-kaspa, Anat Bahat, Anna Gakamsky, Eliezer Girsh, Nathan Katz, Laura Cecilia Giojalas, Michael EisenbachAbstract:Background Human Sperm Chemotaxis to pre-ovulatory follicular fluid is well established in vitro. However, it is not known whether the female's oocyte-cumulus complex secretes Sperm chemoattractants subsequent to ovulation (for enabling Sperm Chemotaxis within the Fallopian tube) and, if so, which of these cell types--the oocyte or the cumulus oophorus--is the physiological origin of the secreted chemoattractant. Methods By employing a directionality-based Chemotaxis assay, we examined whether media conditioned with either individual, mature (metaphase II) human oocytes or the surrounding cumulus cells attract human Sperm by Chemotaxis. Results We observed Sperm Chemotaxis to each of these media, suggesting that both the oocyte and the cumulus cells secrete Sperm chemoattractants. Conclusions These observations suggest that Sperm chemoattractants are secreted not only prior to ovulation within the follicle, as earlier studies have demonstrated, but also after oocyte maturation outside the follicle, and that there are two chemoattractant origins: the mature oocyte and the surrounding cumulus cells.
Michael Eisenbach - One of the best experts on this subject based on the ideXlab platform.
-
Testing Human Sperm Chemotaxis: How to Detect Biased Motion in Population Assays
PloS one, 2012Co-Authors: Leah Armon, Michael Eisenbach, S. Roy Caplan, Benjamin M FriedrichAbstract:Biased motion of motile cells in a concentration gradient of a chemoattractant is frequently studied on the population level. This approach has been particularly employed in human Sperm chemotactic assays, where the fraction of responsive cells is low and detection of biased motion depends on subtle differences. In these assays, statistical measures such as population odds ratios of swimming directions can be employed to infer chemotactic performance. Here, we report on an improved method to assess statistical significance of experimentally determined odds ratios and discuss the strong impact of data correlations that arise from the directional persistence of Sperm swimming.
-
Behavioral Mechanism during Human Sperm Chemotaxis: Involvement of Hyperactivation
PloS one, 2011Co-Authors: Leah Armon, Michael EisenbachAbstract:When mammalian Spermatozoa become capacitated they acquire, among other activities, chemotactic responsiveness and the ability to exhibit occasional events of hyperactivated motility--a vigorous motility type with large amplitudes of head displacement. Although a number of roles have been proposed for this type of motility, its function is still obscure. Here we provide evidence suggesting that hyperactivation is part of the chemotactic response. By analyzing tracks of Spermatozoa swimming in a spatial chemoattractant gradient we demonstrate that, in such a gradient, the level of hyperactivation events is significantly lower than in proper controls. This suggests that upon sensing an increase in the chemoattractant concentration capacitated cells repress their hyperactivation events and thus maintain their course of swimming toward the chemoattractant. Furthermore, in response to a temporal concentration jump achieved by photorelease of the chemoattractant progesterone from its caged form, the responsive cells exhibited a delayed turn, often accompanied by hyperactivation events or an even more intense response in the form of flagellar arrest. This study suggests that the function of hyperactivation is to cause a rather sharp turn during the chemotactic response of capacitated cells so as to assist them to reorient according to the chemoattractant gradient. On the basis of these results a model for the behavior of Spermatozoa responding to a spatial chemoattractant gradient is proposed.
-
Human Sperm Chemotaxis: both the oocyte and its surrounding cumulus cells secrete Sperm chemoattractants
Human reproduction (Oxford England), 2004Co-Authors: Fei Sun, Ilan Tur-kaspa, Anat Bahat, Anna Gakamsky, Eliezer Girsh, Nathan Katz, Laura Cecilia Giojalas, Michael EisenbachAbstract:Background Human Sperm Chemotaxis to pre-ovulatory follicular fluid is well established in vitro. However, it is not known whether the female's oocyte-cumulus complex secretes Sperm chemoattractants subsequent to ovulation (for enabling Sperm Chemotaxis within the Fallopian tube) and, if so, which of these cell types--the oocyte or the cumulus oophorus--is the physiological origin of the secreted chemoattractant. Methods By employing a directionality-based Chemotaxis assay, we examined whether media conditioned with either individual, mature (metaphase II) human oocytes or the surrounding cumulus cells attract human Sperm by Chemotaxis. Results We observed Sperm Chemotaxis to each of these media, suggesting that both the oocyte and the cumulus cells secrete Sperm chemoattractants. Conclusions These observations suggest that Sperm chemoattractants are secreted not only prior to ovulation within the follicle, as earlier studies have demonstrated, but also after oocyte maturation outside the follicle, and that there are two chemoattractant origins: the mature oocyte and the surrounding cumulus cells.
-
Towards understanding the molecular mechanism of Sperm Chemotaxis.
The Journal of general physiology, 2004Co-Authors: Michael EisenbachAbstract:The awareness that, in most animal species, the prospects of the male's Spermatozoa to reach the female's eggs are very slim in the absence of some guidance mechanism (usually chemical in nature) has been acquired gradually; first, in marine species, where both types of gametes are released into sea
-
Lack of species-specificity in mammalian Sperm Chemotaxis
Developmental biology, 2003Co-Authors: Fei Sun, Ilan Tur-kaspa, Laura Cecilia Giojalas, Raúl Sánchez, Roberto A. Rovasio, Michael EisenbachAbstract:Attraction of Spermatozoa by way of Chemotaxis to substances secreted from the egg or its surrounding cells has been demonstrated in marine species, amphibians, and mammals. This process is species- or family-specific in marine invertebrates: a chemoattractant for one marine species is usually not recognized by another species or by a member of another family. It is not known whether this selectivity is also the rule in other phyla. Furthermore, it is not at all obvious that such selectivity would be advantageous to species with internal fertilization. Here, using a directionality-based assay for Chemotaxis, we studied in vitro the chemotactic response of human and rabbit Spermatozoa to human, rabbit, and bovine egg-related factors. We found that Spermatozoa from each of the two sources responded similarly well to egg-related factors obtained from any of the three species examined. These results indicate lack of Chemotaxis-related, species specificity between these species, suggesting that their Sperm chemoattractants are common or very similar. The findings further suggest that mammals do not rely on species specificity of Sperm Chemotaxis for avoidance of interspecies fertilization.
Manabu Yoshida - One of the best experts on this subject based on the ideXlab platform.
-
chapter 3 Sperm activation and Chemotaxis in invertebrates
2020Co-Authors: Jumpei Ikenaga, Manabu YoshidaAbstract:The gametes of aqua-living animals are equipped with several systems to ensure fertilization. Sperm activation and Chemotaxis toward the conspecific eggs—some factors from the eggs or female organs activate and attract conspecific Sperm—are the first two steps of authentication between Sperm and eggs. Phenomena and molecular mechanisms underlying Sperm activation and Chemotaxis are varied, even in the same taxa. Considering species specificity of Sperm Chemotaxis, the system may prevent crossbreeding. It is an interesting point why the system of Sperm activation and Chemotaxis has been evolved with such a high diversity. In this chapter, we reviewed the Sperm activation and Chemotaxis in aquatic invertebrates.
-
High potassium seawater inhibits ascidian Sperm Chemotaxis, but does not affect the male gamete Chemotaxis of a brown alga.
Zygote (Cambridge England), 2019Co-Authors: Nana Kinoshita-terauchi, Manabu Yoshida, Kogiku Shiba, Makoto Terauchi, Francisco J. Romero, Héctor Vincente Ramírez-gómez, Taizo Motomura, Hiroshi Kawai, Takuya NishigakiAbstract:Male gamete Chemotaxis towards the female gamete is a general strategy to facilitate the sexual reproduction in many marine eukaryotes. Biochemical studies of chemoattractants for male gametes of brown algae have advanced in the 1970s and 1980s, but the molecular mechanism of male gamete responses to the attractants remains elusive. In sea urchin, a K+ channel called the tetraKCNG channel plays a fundamental role in Sperm Chemotaxis and inhibition of K+ efflux through this channel by high K+ seawater blocks almost all cell responses to the chemoattractant. This signalling mechanism could be conserved in marine invertebrates as tetraKCNG channels are conserved in the marine invertebrates that exhibit Sperm Chemotaxis. We confirmed that high K+ seawater also inhibited Sperm Chemotaxis in ascidian, Ciona intestinalis (robusta), in this study. Conversely, the male gamete Chemotaxis towards the female gamete of a brown alga, Mutimo cylindricus, was preserved even in high K+ seawater. This result indicates that none of the K+ channels is essential for male gamete Chemotaxis in the brown alga, suggesting that the signalling mechanism for Chemotaxis in this brown alga is quite different from that of marine invertebrates. Correlated to this result, we revealed that the channels previously proposed as homologues of tetraKCNG in brown algae have a distinct domain composition from that of the tetraKCNG. Namely, one of them possesses two repeats of the six transmembrane segments (diKCNG) instead of four. The structural analysis suggests that diKCNG is a cyclic nucleotide-modulated and/or voltage-gated K+ channel.
-
¶Corresponding author:
2016Co-Authors: Manabu YoshidaAbstract:Sperm Chemotaxis and regulation of flagellar movement by Ca2
-
NEW RESEARCH HORIZON Review Sperm Chemotaxis and regulation of flagellar movement by Ca21
2016Co-Authors: Manabu Yoshida, Kaoru YoshidaAbstract:abstract: The Chemotaxis of Sperm towards eggs is a widespread phenomenon that occurs in most forms of life from lower plants to mammals and plays important roles in ensuring fertilization. In Spermatozoa, the attractants act as beacons, indicating the path leading to the eggs from the same species. The existence of species-specific Sperm Chemotaxis has been demonstrated in marine invertebrates; thus, Sperm Chemotaxis may be involved in preventing crossbreeding, especially in marine invertebrates with external fertilization. However, the mechanisms of Sperm Chemotaxis in mammalian species differ from those of marine invertebrates. In mammals, the attrac-tant source is not the egg, but follicular fluids or cumulus cells and chemotactic behaviour is shown only in small populations of Sperm. Nevertheless, the fundamental mechanisms underlying Sperm Chemotaxis are likely to be common among all species. Among these mech-anisms, intracellular Ca2+ concentration ([Ca2+]i) is an important factor for the regulation of chemotactic behaviour in Spermatozoa. Sperm attractants induce the entry of extracellular Ca2+, resulting in [Ca2+]i increase in the Sperm cells. Furthermore, [Ca 2+]i modulates Sperm flagellar movement. However, the relationship between [Ca2+]i and the chemotactic response of a Sperm flagellum is not well known. Investigation of the dynamic responses of Sperm cells to their attractants is important for our understanding of the regulation of fertilization. Here, we reviewed Sperm Chemotaxis focusing on the mechanisms that regulate Sperm flagellar beating during the chemo-tactic response. Key words: Ca2+ / Chemotaxis / fertilization / Sperm flagell
-
Sperm Chemotaxis: The First Authentication Events Between Conspecific Gametes Before Fertilization
Sexual Reproduction in Animals and Plants, 2014Co-Authors: Manabu YoshidaAbstract:Sperm Chemotaxis toward eggs before fertilization has been observed in many living organisms. Sperm Chemotaxis is the first communication or signaling event between male and female gametes in the process of fertilization, and species-specific events occur in many cases. Thus, Sperm Chemotaxis may act as a safety process for authenticating that fertilization occurs between conspecific egg and Sperm and helps to prevent crossbreeding. Here, we introduce mechanisms of Sperm Chemotaxis, focusing on cross-talk between gametes and species specificity. Furthermore, we discuss the interactions between Sperm-activating and Sperm-attracting factors (SAAFs) in the ascidian species and that SAAF receptors on Sperm cells are not all-or-none responses. The SAAF receptors may accept SAAFs of related species (closely related molecules), with different affinities.
Masaaki Morisawa - One of the best experts on this subject based on the ideXlab platform.
-
Na+/Ca2+ exchanger modulates the flagellar wave pattern for the regulation of motility activation and Chemotaxis in the ascidian Spermatozoa.
Cell motility and the cytoskeleton, 2006Co-Authors: Kogiku Shiba, Masaaki Morisawa, Teréz Márián, Zoltán Krasznai, Shoji A. Baba, Manabu YoshidaAbstract:Ion channels and ion exchangers are known to be important participants in various aspects of Sperm physiology, e.g. motility activation, Chemotaxis, the maintenance of motility and the acrosome reaction in the Sperm. We report here on a role of the K+-independent Na+/Ca2+ exchanger (NCX) on ascidian Sperm. Reverse-transcriptase PCR reveals that the NCX is expressed in the testis while immunoblotting and immunolocalization demonstrate that the NCX exists on the Sperm in the ascidian Ciona savignyi and C. intestinalis. A potent blocker of the NCX, KB-R7943 was found to block Sperm-activating and -attracting factor (SAAF)-induced motility activation, Sperm motility and Sperm Chemotaxis. We further analyzed the effects of this blocker on motility parameters such as the flagellar waveform, curvature, beat frequency, amplitude and wavelength of the Sperm flagella. Inhibition of the NCX caused two distinct effects: a low concentration of KB-R7943 induced symmetric bending, whereas a high concentration of KB-R7943 resulted in asymmetric flagellar bending. These findings suggest that the NCX plays important roles in the regulation of SAAF-induced Sperm Chemotaxis, motility activation and motility maintenance in the ascidian. This study provides new information toward an understanding of Ca2+ transport systems in Sperm motility and Chemotaxis. Cell Motil. Cytoskeleton 2006. © 2006 Wiley-Liss, Inc.
-
strategies for Sperm Chemotaxis in the siphonophores and ascidians a numerical simulation study
The Biological Bulletin, 2004Co-Authors: Makiko Ishikawa, Jacky Cosson, Hidekazu Tsutsui, Yoshitaka Oka, Masaaki MorisawaAbstract:Chemotactic swimming behaviors of Spermatozoa toward an egg have been reported in various species. The strategies underlying these behaviors, however, are poorly understood. We focused on two types of Chemotaxis, one in the siphonophores and the second in the ascidians, and then proposed two models based on experimental data. Both models assumed that the radius of the path curvature of a swimming Spermatozoon depends on [Ca2+]i, the intracellular calcium concentration. The Chemotaxis in the siphonophores could be simulated in a model that assumes that [Ca2+]i depends on the local concentration of the attractant in the vicinity of the Spermatozoon and that a substantial time period is required for the clearance of transient high [Ca2+]i. In the case of ascidians, trajectories similar to those in experiments could be adequately simulated by a variant of this model that assumes that [Ca2+]i depends on the time derivative of the attractant concentration. The properties of these strategies and future problems ...
-
Strategies for Sperm Chemotaxis in the Siphonophores and Ascidians: A Numerical Simulation Study
The Biological bulletin, 2004Co-Authors: Makiko Ishikawa, Jacky Cosson, Hidekazu Tsutsui, Yoshitaka Oka, Masaaki MorisawaAbstract:Chemotactic swimming behaviors of Spermatozoa toward an egg have been reported in various species. The strategies underlying these behaviors, however, are poorly understood. We focused on two types of Chemotaxis, one in the siphonophores and the second in the ascidians, and then proposed two models based on experimental data. Both models assumed that the radius of the path curvature of a swimming Spermatozoon depends on [Ca(2+)](i), the intracellular calcium concentration. The Chemotaxis in the siphonophores could be simulated in a model that assumes that [Ca(2+)](i) depends on the local concentration of the attractant in the vicinity of the Spermatozoon and that a substantial time period is required for the clearance of transient high [Ca(2+)](i). In the case of ascidians, trajectories similar to those in experiments could be adequately simulated by a variant of this model that assumes that [Ca(2+)](i) depends on the time derivative of the attractant concentration. The properties of these strategies and future problems are discussed in relation to these models.
-
A chemoattractant for ascidian Spermatozoa is a sulfated steroid
Proceedings of the National Academy of Sciences of the United States of America, 2002Co-Authors: Manabu Yoshida, Kazuo Inaba, Michio Murata, Masaaki MorisawaAbstract:Sperm Chemotaxis toward eggs before fertilization has been demonstrated in many animals and plants, and several peptides and small organic compounds acting as chemoattractants have been identified. We previously showed that Sperm of the ascidians Ciona intestinalis and Ciona savignyi are activated and then attracted toward the egg by a common factor released from the egg. In this study, we purified Sperm-activating and -attracting factor (SAAF) from the egg-conditioning medium of C. intestinalis by using several steps of column chromatography. Determination of the molecular structure by NMR and MS/MS analysis revealed that SAAF is a previously uncharacterized sulfated steroid: 3,4,7,26-tetrahydroxycholestane-3,26-disulfate. Furthermore, it was shown that the SAAF of C. savignyi was indistinguishable from that of C. intestinalis in terms of the chromatographic behavior and molecular weight, indicating that the same compound might be responsible for Sperm activation and Chemotaxis in both the species. Furthermore, we established a method for quantitative analysis of Sperm Chemotaxis and showed that the chemotactic behavior of Ciona Sperm is controlled by the "chemotactic turn" associated with decrease in the concentration of SAAF.
-
calcium and cyclic amp mediate Sperm activation but ca2 alone contributes Sperm Chemotaxis in the ascidian ciona savignyi ascidian Sperm motility Chemotaxis calcium camp
Development Growth & Differentiation, 1994Co-Authors: Manabu Yoshida, Kazuo Inaba, Katsumi Ishida, Masaaki MorisawaAbstract:Sperm-activating and -attracting factor (SAAF) released from the ascidian, Ciona savignyi, was partially purified from egg seawater with ethanol extraction and separation with the two-phase system of chloroform and water. SAAF did not activate Sperm motility and cAMP synthesis in calcium-free seawater (CaFSW), but activated the both in the presence of Ca2+. Sperm activation by SAAF in Ca2+-containing medium was inhibited by flunarizine, a T-type Ca2+channel antagonist, but L-type Ca2+channel specific antagonists had no effect. Theophylline, a phosphodiesterase inhibitor, induced the increase of cAMP level and Sperm activation in CaFSW without SAAF. On the other hand, the theophylline-activated Sperm in CaFSW did not exhibit Chemotaxis toward the tip of glass capillary containing SAAF, but upon the addition of Ca2+they were attracted toward SAAF in the same manner as Chemotaxis in normal artificial seawater. These results suggest that Sperm activation is induced by the increased cAMP level caused by Ca2+influx through T-type Ca2+channel, and that Ca2+alone mediates the Sperm Chemotaxis in Ciona.
Jeffrey A. Riffell - One of the best experts on this subject based on the ideXlab platform.
-
Sperm Chemotaxis promotes individual fertilization success in sea urchins.
The Journal of Experimental Biology, 2016Co-Authors: Yasmeen H. Hussain, Jeffrey S. Guasto, Richard K. Zimmer, Roman Stocker, Jeffrey A. RiffellAbstract:Reproductive success fundamentally shapes an organism's ecology and evolution, and gamete traits mediate fertilization, which is a critical juncture in reproduction. Individual male fertilization success is dependent on the ability of Sperm from one male to outcompete the Sperm of other males when searching for a conspecific egg. Sperm Chemotaxis, the ability of Sperm to navigate towards eggs using chemical signals, has been studied for over a century, but such studies have long assumed that this phenomenon improves individual male fitness without explicit evidence to support this claim. Here, we assessed fertilization changes in the presence of a chemoattractant-digesting peptidase and used a microfluidic device coupled with a fertilization assay to determine the effect of Sperm Chemotaxis on individual male fertilization success in the sea urchin Lytechinus pictus We show that removing chemoattractant from the gametic environment decreases fertilization success. We further found that individual male differences in Chemotaxis to a well-defined gradient of attractant correlate with individual male differences in fertilization success. These results demonstrate that Sperm Chemotaxis is an important contributor to individual reproductive success.
-
Sperm Chemotaxis, fluid shear, and the evolution of sexual reproduction
Proceedings of the National Academy of Sciences of the United States of America, 2011Co-Authors: Richard K. Zimmer, Jeffrey A. RiffellAbstract:Chemical communication is fundamental to sexual reproduction, but how Sperm search for and find an egg remains enigmatic. For red abalone (Haliotis rufescens), a large marine snail, the relationship between chemical signaling and fluid motion largely determines fertilization success. Egg-derived attractant plumes are dynamic, changing their size and shape in response to unique combinations of physical and chemical environmental features. Attractant plumes that promote sexual reproduction, however, are limited to a precise set of hydrodynamic conditions. Performance-maximizing shears are those that most closely match flows in native spawning habitats. Under conditions in which reproductive success is chronically limited by Sperm availability, gametes are under selection for mechanisms that increase Sperm-egg encounter. Here, chemoattraction is found to provide a cheap evolutionary alternative for enhancing egg target size without enlarging cytoplasmic and/or cell volume. Because egg signaling and Sperm response may be tuned to meet specific fluid-dynamic constraints, shear could act as a critical selective pressure that drives gamete evolution and determines fitness.
-
Sperm Chemotaxis as revealed with live and synthetic eggs
The Biological Bulletin, 2011Co-Authors: Julie E. Himes, Jeffrey A. Riffell, Cheryl Ann Zimmer, Richard K. ZimmerAbstract:Fertilization is one of the least understood fundamental biological processes. How Sperm search for and find an egg remains enigmatic. Sperm attraction to egg-derived chemical cues may be significant evolutionarily for maintaining species barriers and important ecologically for increasing gamete encounters. New tools are needed, however, to resolve the functional consequences of these dissolved signal molecules. Freshly spawned eggs from red abalone (Haliotis rufescens) naturally release l-tryptophan, which stimulates chemotactic responses by conspecific Sperm. Here, microspheres were manufactured to the approximate size and the same shape as female gametes and formulated to emit controlled doses of chemoattractant, imitating natural l-tryptophan release rates. When experimentally tested for effectiveness, male gametes did not distinguish between chemically impregnated mimics and live eggs, demonstrating that l-tryptophan alone is both necessary and sufficient to promote Chemotaxis, and confirming the ide...
-
Sperm Chemotaxis as revealed with live and synthetic eggs.
The Biological bulletin, 2011Co-Authors: Julie E. Himes, Jeffrey A. Riffell, Cheryl Ann Zimmer, Richard K. ZimmerAbstract:Fertilization is one of the least understood fundamental biological processes. How Sperm search for and find an egg remains enigmatic. Sperm attraction to egg-derived chemical cues may be significant evolutionarily for maintaining species barriers and important ecologically for increasing gamete encounters. New tools are needed, however, to resolve the functional consequences of these dissolved signal molecules. Freshly spawned eggs from red abalone (Haliotis rufescens) naturally release l-tryptophan, which stimulates chemotactic responses by conspecific Sperm. Here, microspheres were manufactured to the approximate size and the same shape as female gametes and formulated to emit controlled doses of chemoattractant, imitating natural l-tryptophan release rates. When experimentally tested for effectiveness, male gametes did not distinguish between chemically impregnated mimics and live eggs, demonstrating that l-tryptophan alone is both necessary and sufficient to promote Chemotaxis, and confirming the identity of a native Sperm attractant. The techniques that we describe can be used to create synthetic eggs for most animal and plant species, including humans. Egg mimics increase the capacity for experimental manipulation and enable realistic studies of Sperm behavior even in the absence of female gametes.
-
Identification of a testicular odorant receptor mediating human Sperm Chemotaxis.
Science (New York N.Y.), 2003Co-Authors: Marc Spehr, Richard K. Zimmer, Jeffrey A. Riffell, Günter Gisselmann, Alexandra Poplawski, Christian H. Wetzel, Hanns HattAbstract:Although it has been known for some time that olfactory receptors (ORs) reside in Spermatozoa, the function of these ORs is unknown. Here, we identified, cloned, and functionally expressed a previously undescribed human testicular OR, hOR17-4. With the use of ratiofluorometric imaging, Ca2+ signals were induced by a small subset of applied chemical stimuli, establishing the molecular receptive fields for the recombinantly expressed receptor in human embryonic kidney (HEK) 293 cells and the native receptor in human Spermatozoa. Bourgeonal was a powerful agonist for both recombinant and native receptor types, as well as a strong chemoattractant in subsequent behavioral bioassays. In contrast, undecanal was a potent OR antagonist to bourgeonal and related compounds. Taken together, these results indicate that hOR17-4 functions in human Sperm Chemotaxis and may be a critical component of the fertilization process.