Pavel Stopka
Charles University, Prague, Department of Zoology, Faculty Member
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- Most of our research focuses on lipocalins (OBP, MUP, LCN). We are interested in the evolution of chemical communicat... moreMost of our research focuses on lipocalins (OBP, MUP, LCN). We are interested in the evolution of chemical communication and immunity in mammals. Our favourite models are rodents (Mus, Apodemus). OUR NEW DEPARTMENT: http://www.biocev.eu/edit
Mammalian tears are produced by lacrimal glands to protect eyes and may function in chemical communication and immunity. Recent studies on the house mouse chemical signalling revealed that major urinary proteins (MUPs) are not... more
Mammalian tears are produced by lacrimal glands to protect eyes and may function in chemical communication and immunity. Recent studies on the house mouse chemical signalling revealed that major urinary proteins (MUPs) are not individually unique in Mus musculus musculus. This fact stimulated us to look for other sexually dimorphic proteins that may—in combination with MUPs—contribute to a pool of chemical signals in tears. MUPs and other lipocalins including odorant binding proteins (OBPs) have the capacity to selectively transport volatile organic compounds (VOCs) in their eight-stranded beta barrel, thus we have generated the tear proteome of the house mouse to detect a wider pool of proteins that may be involved in chemical signalling. We have detected significant male-biased (7.8%) and female-biased (7%) proteins in tears. Those proteins that showed the most elevated sexual dimorphisms were highly expressed and belong to MUP, OBP, ESP (i.e., exocrine gland-secreted peptides), and SCGB/ABP (i.e., secretoglobin) families. Thus, tears may have the potential to elicit sex-specific signals in combination by different proteins. Some tear lipocalins are not sexually dimorphic— with MUP20/darcin and OBP6 being good examples—and because all proteins may flow with tears through nasolacrimal ducts to nasal and oral cavities we suggest that their roles are wider than originally thought. Also, we have also detected several sexually dimorphic bactericidal proteins, thus further supporting an idea that males and females may have adopted alternative strategies in controlling microbiota thus yielding different VOC profiles. INTRODUCTION The genome of the mouse contains at least 55 genes for lipocalins and—due to their capacity to transport VOCs in their eight-stranded beta barrel—many of them are involved in chemical communication (Logan,
Mammalian olfaction depends on chemosensory neurons of the main olfactory epithelia (MOE), and/or of the accessory olfactory epithelia in the vomeronasal organ (VNO). Thus, we have generated the VNO and MOE transcriptomes and the nasal... more
Mammalian olfaction depends on chemosensory neurons of the main olfactory epithelia (MOE), and/or of the accessory olfactory epithelia in the vomeronasal organ (VNO). Thus, we have generated the VNO and MOE transcriptomes and the nasal cavity proteome of the house mouse, Mus musculus musculus. Both transcriptomes had low levels of sexual dimorphisms, while the soluble proteome of the nasal cavity revealed high levels of sexual dimorphism similar to that previously reported in tears and saliva. Due to low levels of sexual dimorphism in the olfactory receptors in MOE and VNO, the sex-specific sensing seems less likely to be dependent on receptor repertoires. However, olfaction may also depend on a continuous removal of background compounds from the sites of detection. Odorant binding proteins (OBPs) are thought to be involved in this process and in our study Obp transcripts were most expressed along other lipocalins (e.g., Lcn13, Lcn14) and antimicrobial proteins. At the level of proteome, OBPs were highly abundant with only few being sexually dimorphic. We have, however, detected the major urinary proteins MUP4 and MUP5 in males and females and the male-biased central/group-B MUPs that were thought to be abundant mainly in the urine. The exocrine gland-secreted peptides ESP1 and ESP22 were male-biased but not male-specific in the nose. For the first time, we demonstrate that the expression of nasal lipocalins correlates with antimicrobial proteins thus suggesting that their individual variation may be linked to evolvable mechanisms that regulate natural microbiota and pathogens that regularly enter the body along the 'eyes-nose-oral cavity' axis.
Recently, we showed that generation of tumours in syngeneic mice by cells devoid of mitochondrial (mt) DNA (r 0 cells) is linked to the acquisition of the host mtDNA. However, the mechanism of mtDNA movement between cells remains... more
Recently, we showed that generation of tumours in syngeneic mice by cells devoid of mitochondrial (mt) DNA (r 0 cells) is linked to the acquisition of the host mtDNA. However, the mechanism of mtDNA movement between cells remains unresolved. To determine whether the transfer of mtDNA involves whole mitochondria, we injected B16r 0 mouse melanoma cells into syngeneic C57BL/6N su9-DsRed2 mice that express red fluorescent protein in their mitochondria. We document that mtDNA is acquired by transfer of whole mitochondria from the host animal, leading to normalisation of mitochondrial respiration. Additionally, knockdown of key mitochondrial complex I (NDUFV1) and complex II (SDHC) subunits by shRNA in B16r 0 cells abolished or significantly retarded their ability to form tumours. Collectively, these results show that intact mitochondria with their mtDNA payload are transferred in the developing tumour, and provide functional evidence for an essential role of oxidative phosphorylation in cancer.
Female house mice produce pheromone-carrying major urinary proteins (MUPs) in a cycling manner, thus reaching the maximum urinary production just before ovulation. This is thought to occur to advertise the time of ovulation via deposited... more
Female house mice produce pheromone-carrying major urinary proteins (MUPs) in a cycling manner, thus reaching the maximum urinary production just before ovulation. This is thought to occur to advertise the time of ovulation via deposited urine marks. This study aimed to characterize the protein content from the house mouse vaginal flushes to detect putative vaginal-advertising molecules for a direct identification of reproductive states. Here we show that the mouse vaginal discharge contains lipocalins including those from the odorant binding (OBP) and major urinary (MUP) protein families. OBPs were highly expressed but only slightly varied throughout the cycle, whilst several MUPs were differentially abundant. MUP20 or 'darcin', was thought to be expressed only by males. However, in females it was significantly up-regulated during estrus similarly as the recently duplicated central/ group-B MUPs (sMUP17 and highly expressed sMUP9), which in the mouse urine are male biased. MUPs rise between proestrus and estrus, remain steady throughout metestrus, and are co-expressed with antimicrobial proteins. Thus, we suggest that MUPs and potentially also OBPs are important components of female vaginal advertising of the house mouse.
Chemical communication is mediated by sex-biased signals abundantly present in the urine, saliva and tears. Because most studies concentrated on the urinary signals, we aimed to determine the saliva proteome in wild Mus musculus musculus,... more
Chemical communication is mediated by sex-biased signals abundantly present in the urine, saliva and tears. Because most studies concentrated on the urinary signals, we aimed to determine the saliva proteome in wild Mus musculus musculus, to extend the knowledge on potential roles of saliva in chemical communication. We performed the gel-free quantitative LC-MS/MS analyses of saliva and identified 633 proteins with 134 (21%) of them being sexually dimorphic. They include proteins that protect and transport volatile organic compounds in their beta barrel including LCN lipocalins, major urinary proteins (MUPs), and odorant binding proteins (OBPs). To our surprise, the saliva proteome contains one MUP that is female biased (MUP8) and the two protein pheromones MUP20 (or 'Darcin') and ESP1 in individuals of both sex. Thus, contrary to previous assumptions, our findings reveal that these proteins cannot function as male-unique signals. Our study also demonstrates that many olfactory proteins (e.g. LCNs, and OBPs) are not expressed by submandibular glands but are produced elsewhere–in nasal and lacrimal tissues, and potentially also in other oro-facial glands. We have also detected abundant proteins that are involved in wound healing, immune and non-immune responses to pathogens, thus corroborating that saliva has important protective roles. The sequence of the mouse genome provided a tool to study blueprints for all RNAs and proteins in mice 1. Progenitors of modern laboratory mice were hybrids among Mus musculus domesticus, Mus musculus musculus and other subspecies. Though, laboratory mice have been widely and successfully used as experimental organisms in studies of biomarkers of physiological states 2 and of human pathological conditions, they may be less suitable to study chemical communication, a process which is driven by sexual selection. This is due to the differential contribution of blocks of genes from the two house-mouse subspecies M. m. domesticus and M. m. musculus to current laboratory strains 1 that may mask typical intra-and inter-specific differences. One of our aims, therefore, was to define the saliva proteome in M. m. musculus to provide the array of proteins and their quantity characteristic for saliva in a wild living mouse species. This study also represents a baseline for future comparative studies focusing on chemical communication and immunity. In mice, the most published studies in chemical communication focused on the major urinary proteins (MUPs) 3–7 , which are expressed by the liver and transport volatile organic compounds (VOCs) in their beta barrel structure to the urine 6–11. VOCs are slowly released from different urinary MUPs, and have been proposed to function in a variety of social signals, including identity, territorial marking, mate choice etc. 3,12–14. Thus, lipoca-lins and their specific ligands together form a signal 15. Differential ligand binding may have a potential influence on sub-species recognition between M. m. musculus and M. m. domesticus 16–18. These two sub-species have been previously shown to vary in the abundance of male VOCs 19 and in MUP expression between the two subspecies and individuals of the opposite sex 9. Moreover, scent signals have been shown to be an integral part of subspecies recognition and could play important roles in preventing interspecific mating between the two house mouse subspecies 18. Increasing number of papers, however, show that MUP expression is linked to reproduction and sociality, and not just to competitive ability 3,4,20–23. The expression of urinary MUPs is socially regulated in that males excrete
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A b s t r a c t . the presence of large amounts of proteins in mammal urine is usually associated with a pathological condition and indicates serious renal lesions. However, there are few species with obligate proteinuria indicating that... more
A b s t r a c t . the presence of large amounts of proteins in mammal urine is usually associated with a pathological condition and indicates serious renal lesions. However, there are few species with obligate proteinuria indicating that they must derive some benefit from this condition. Urinary proteins have been most extensively studied in the house mouse and the rat, and findings to date indicate that their function in intraspecific communication is complex and not yet fully understood. Other proteins of the same protein family as MUPs have been also found in urine of some other rodent species, and still less is known about these. In this study we demonstrate the existence of urinary lipocalins in Mastomys coucha for the first time. Our results support the hypothesis that urinary proteins may play an important role in chemical communication in species other than mice and rats. Information about the presence, concentration, and level of polymorphism of these proteins in different ...
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Pilot studies of KRUUK (1989) in the UK revealed that amongst Mustelidae badgers are unusual as they form large groups sharing a communal site. Although there is a profusion of studies on badgers from the UK, there is genuine lack of... more
Pilot studies of KRUUK (1989) in the UK revealed that amongst Mustelidae badgers are unusual as they form large groups sharing a communal site. Although there is a profusion of studies on badgers from the UK, there is genuine lack of supporting evidence that they are particularly social elsewhere in Europe, and densities are extremely variable. Such great geographic variation in behaviour provides an excellent opportunity to progress in testing models of social behaviour and cooperation in mammals. This area of research is also important because in Britain badgers have been linked to the spread of bovine tuberculosis. Whether this is likely to be a problem elsewhere in Europe largely depends on understanding the ecology and behaviour of badgers and their interacti- ons with other mammalian species. The aim of this paper is to highlight the recent developments in the study of the social biology of this species, with a view to encouraging more research in Europe.
Many biological processes involve globular transport proteins belonging to a family called lipocalins. The prominent feature in lipocalin structure is their specific tertiary conformation forming eight-stranded beta barrel with capacity... more
Many biological processes involve globular transport proteins belonging to a family called lipocalins. The prominent feature in lipocalin structure is their specific tertiary conformation forming eight-stranded beta barrel with capacity to bind various ligands inside. The importance of lipocalins is evident from the list of vital substances (hydrophobic ligands including vitamin A, steroids, bilins, lipids, pheromones etc.) that these proteins transport and from their high expression levels in various tissues. Among wide spectrum of lipocalins, Major Urinary Proteins (Mup) and Odorant Binding Proteins (Obp) are well known for their capacity to bind and carry odorants / pheromones and have been studied to detail in various mammalian models including mice, rats, and hamsters. However, many lipocalins (also including Mups) have previously been described with respect to their protective function in mammalian organism where they transport potentially harmful molecules to a degradation si...
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The Prisoner's Dilemma (PD) is a widely used paradigm to study cooperation in evolutionary biology, as well as in fields as diverse as moral philosophy, sociology, economics and politics. Players are typically assumed to have fixed... more
The Prisoner's Dilemma (PD) is a widely used paradigm to study cooperation in evolutionary biology, as well as in fields as diverse as moral philosophy, sociology, economics and politics. Players are typically assumed to have fixed payoffs for adopting certain strategies, which depend only on the strategy played by the opponent. However, fixed payoffs are not realistic in nature. Utility functions and the associated payoffs from pursuing certain strategies vary among members of a population with numerous factors. In biology such factors include size, age, social status and expected life span; in economics they include socio-economic status, personal preference and past experience; and in politics they include ideology, political interests and public support. Thus, no outcome is identical for any two different players. We show that relaxing the assumption of fixed payoffs leads to frequent violations of the payoff structure required for a Prisoner's Dilemma. With variance twi...
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During their movements in the wild, wood mice (Apodemus sylvaticus) distribute small objects, such as leaves or twigs, which are often visually conspicuous. Our experiments demonstrate that these marks serve as points of reference during... more
During their movements in the wild, wood mice (Apodemus sylvaticus) distribute small objects, such as leaves or twigs, which are often visually conspicuous. Our experiments demonstrate that these marks serve as points of reference during exploration. Way-marking, as we call it, may diminish the likelihood of losing an "interesting" location, perhaps following disturbance by, for example, a predator or conspecific. Way-marks, being readily portable, may be a less confusing method of marking ephemeral sites than scent marks. They may also be a safer option for local navigation insofar as scent marks can easily be detected by a predator. In an experiment, conspicuous natural candidate way-marks were removed from a simple arena and wood mice were given white plastic discs instead. The wood mice picked up these discs and re-distributed them about their arena; as the mice moved, they repeatedly re-positioned the discs and usually spent a considerable time near recently repositio...
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ABSTRACT There is evidence of possible correlation between mating behaviour, sperm morphology and sperm behaviour in the female reproductive tract prior to fertilization. As shown in A. sylvaticus (1), cooperation between spermatozoa of... more
ABSTRACT There is evidence of possible correlation between mating behaviour, sperm morphology and sperm behaviour in the female reproductive tract prior to fertilization. As shown in A. sylvaticus (1), cooperation between spermatozoa of an individual confers a significant advantage for fertilization, where inter-male sperm competition is intense. In our study we aimed to focus on three other species of rodent genus Apodemus; A. flavicolis, microps, agrarius versus A. sylvaticus, whose either promiscuous or monogamous mating behaviour has already been demonstrated (Stopka et al., unpublished). We placed spermatozoa from cauda epididymis of adult males of selected species into mouse in vitro fertilisation medium, and compared sperm behaviour of individual species. Surprisingly, despite monogamous or polygamous mating behaviour, sperm of all the above species rapidly aggregated into motile trains, as in A. sylvaticus, consisting of hundreds of cells. However, size and cell–cell coupling differed between each species. This may point to another aspect besides mating behaviour that may be involved in building up a mechanism for successful sperm delivery to the egg. These unique and organised aggregations can significantly increase sperm progressive motility. A detailed study of the main cytoskeletal proteins, using immunofluorescent methods, together with confocal microscopy, shows that in sperm-sperm binding especially protein actin plays an important role. According to in vitro experiments, we speculate that the viscous environment of the female reproductive tract may have played a crucial role in the evolution of sperm behaviour. Disintegration of motile sperm trains was associated with the majority of spermatozoa undergoing a premature acrosome reaction. However, the mechanism that triggers it remains to be determined. To conclude, it is likely that a myriad of changes in social behaviour of particular species were not accompanied by changes in sperm behaviour, but instead they retained original ancestral tactics typical for the genus Apodemus. (1) Moore, H., Dvorakova, K., Jenkins, N., Breed, W. (2002) Exceptional sperm cooperation in the wood mouse. Nature 418, 174–177.
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Research Interests: Chemical Ecology, Gene expression, Sexual dimorphism, Biological Sciences, Environmental Sciences, and 11 moreMice, Female, Animals, Male, Polymerase Chain Reaction, Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis, CHEMICAL SCIENCES, Proteinuria, Species Specificity, Base Sequence, and Mus Musculus
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A primary site of infection in mammals is the nostrils, representing the gate to the brain through olfactory and vomeronasal epithelia, eyes as a direct route to the brain via the optical nerve, and oral cavity representing the main route... more
A primary site of infection in mammals is the nostrils, representing the gate to the brain through olfactory and vomeronasal epithelia, eyes as a direct route to the brain via the optical nerve, and oral cavity representing the main route to the digestive tract. Similarly, pheromones, odorants and tastants enter animal bodies the same way. Therefore similar evolutionary forces might have shaped the evolution of systems for recognition of pathogens and chemical signals. This might have resulted in sharing various proteins among systems of recognition and filtering to decrease potential costs of evolving and utilizing unique biochemical pathways. This has been documented previously in, for example, multipurpose and widely distributed GPCRs (G-protein-coupled receptors). The aim of the present review is to explore potential functional overlaps or complementary functions of lipocalins in the system of perception of exogenous substances to reconstruct the evolutionary forces that might have shaped their synergistic functions.
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There is pronounced promiscuity and sperm competition in long-tailed field mice (Apodemus sylvaticus). These mice have evolved unusual sperm behaviour favouring rapid fertilisation, including dynamic formation of sperm trains and their... more
There is pronounced promiscuity and sperm competition in long-tailed field mice (Apodemus sylvaticus). These mice have evolved unusual sperm behaviour favouring rapid fertilisation, including dynamic formation of sperm trains and their subsequent dissociation. The cell surface complement regulatory (CReg) protein CD46 is broadly expressed in eutherian mammals other than rodents, in which it is expressed solely on the spermatozoal acrosomal membrane. Ablation of the CD46 gene has been associated with a faster acrosome reaction (AR) rate in inbred laboratory mice. Here, we demonstrate that wild-caught field mice of three species, A. sylvaticus, A. flavicollis and A. microps, exhibit a more rapid AR than wild-caught house mice Mus musculus or inbred laboratory BALB/c mice. We also demonstrate that wild-caught field mice of these three species, unlike house mice, produce alternatively spliced transcripts of testicular CD46 mRNA lacking exons 5–7 or 6–7, together with an extended 3 0-and often truncated 5 0-utr, leading to failure to express any sperm CD46 protein in both the testis and epididymis. Male field mice may therefore have traded expression of this CReg protein for acrosomal instability, providing a novel genus-specific strategy to favour rapid fertilisation and competitive advantage in the promiscuous reproductive behaviour of wild field mice.
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Research Interests: Fluorescence Microscopy, Biological Sciences, Mice, Animals, Male, and 11 moreAlternative splicing, Molecular endocrinology and reproductive biology, Time Factors, Protein Expression, Reproductive, Alternative Splicing, Amino Acid Sequence, Base Sequence, Spermatozoa, Cell Surface Markers, and Acrosome Reaction
Among members of the family Muridae, the herb-field mouse, Apodemus microps, is unique in that aggression is almost entirely lacking. This species, therefore, is a model organism for experimental studies of social behavior without the... more
Among members of the family Muridae, the herb-field mouse, Apodemus microps, is unique in that aggression is almost entirely lacking. This species, therefore, is a model organism for experimental studies of social behavior without the confounding influence of aggression. We used video surveillance cameras to assess the importance of self-grooming and allogrooming in the social life of this species. Detailed
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Toxoplasma gondii is a common protozoan parasite that infects warm-blooded animals throughout the world, including mice and humans. During infection, both, the parasite and the host, utilize various mechanisms to maximize their own... more
Toxoplasma gondii is a common protozoan parasite that infects warm-blooded animals throughout the world, including mice and humans. During infection, both, the parasite and the host, utilize various mechanisms to maximize their own reproductive success. Mice and humans are both the intermediate hosts for Toxoplasma gondii, which forms specialized vacuoles containing reproductive cysts in the formers' tissue. As half of the human population is infected, developing a disease called toxoplasmosis, along with an ever-growing number of couples suffering with idiopathic infertility, it is therefore surprising that there is a lack of research on how Toxoplasma gondii can alter reproductive parameters. In this study, a detailed histometric screening of the testicular function along with the levels of the pituitary luteinizing hormone (LH) were analysed in infected mice. Data on relative testis and epididymis weight, and sperm count were also collected. Based on the results obtained, the...
Research Interests: Engineering, Physics, Chemistry, Biology, Toxoplasma, and 17 moreMedicine, Gene expression, Multidisciplinary, Humans, Mice, Animals, Male, DNA methylation, CpG islands, Host-parasite interactions, Sertoli cells, PLoS one, Genetic Fitness, Spermatozoa, Epididymis, Luteinizing Hormone, and Seminiferous tubules
A primary site of infection in mammals is the nostrils, representing the gate to the brain through olfactory and vomeronasal epithelia, eyes as a direct route to the brain via the optical nerve, and oral cavity representing the main route... more
A primary site of infection in mammals is the nostrils, representing the gate to the brain through olfactory and vomeronasal epithelia, eyes as a direct route to the brain via the optical nerve, and oral cavity representing the main route to the digestive tract. Similarly, pheromones, odorants and tastants enter animal bodies the same way. Therefore similar evolutionary forces might have shaped the evolution of systems for recognition of pathogens and chemical signals. This might have resulted in sharing various proteins among systems of recognition and filtering to decrease potential costs of evolving and utilizing unique biochemical pathways. This has been documented previously in, for example, multipurpose and widely distributed GPCRs (G-protein-coupled receptors). The aim of the present review is to explore potential functional overlaps or complementary functions of lipocalins in the system of perception of exogenous substances to reconstruct the evolutionary forces that might h...
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Research Interests: Animal Behavior, Polymorphism, Chemical Ecology, Biological Sciences, Social behavior, and 17 moreEnvironmental Sciences, Chemical Communication, Social Context, Mice, Female, Animals, Male, Social Environment, Proteins, CHEMICAL SCIENCES, Social Behavior, Species Specificity, House Mouse, Polyacrylamide Gel Electrophoresis, SDS PAGE, Mus Musculus, and Down-Regulation
The mammalian female reproductive tract has an abundance of complement components, which play a vital role in protection against genital pathogens. Sperm may be protected against complement-mediated damage by complement regulatory... more
The mammalian female reproductive tract has an abundance of complement components, which play a vital role in protection against genital pathogens. Sperm may be protected against complement-mediated damage by complement regulatory proteins, including membrane cofactor protein (CD46), decay accelerating factor (CD55) and CD59. However, sperm from Apodemus (field mice) do not express CD46 protein. The aim of the present study was to determine whether Apodemus sperm may be protected against complement-mediated damage by expression of CD55 and CD59 in the absence of CD46. We demonstrate here that, like Mus musculus mice (house mice), wild-caught Apodemus flavicollis, Apodemus microps and Apodemus sylvaticus mice express both glycosylphosphatidylinositol (GPI)- and transmembrane (TM)-anchored testicular CD55 mRNA transcripts. In Mus, testicular GPI- and TM-CD55 transcripts are generated by two distinct but closely related genes. We show that in contrast to Mus, CD55 isoforms in A. sylvat...
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In rodents, the cell surface complement regulatory protein CD46 is expressed solely on the spermatozoal acrosome membrane. Ablation of the CD46 gene is associated with a faster acrosome reaction. Sperm from Apodemus flavicollis... more
In rodents, the cell surface complement regulatory protein CD46 is expressed solely on the spermatozoal acrosome membrane. Ablation of the CD46 gene is associated with a faster acrosome reaction. Sperm from Apodemus flavicollis (yellow-necked field mice), A. microps (pygmy field mice) and A. sylvaticus (European wood mice) fail to express CD46 protein and exhibit a more rapid acrosome reaction rate than Mus (house mice) or BALB/c mice. A. agrarius (striped field mice) belong to a different Apodemus subgenus and have pronounced promiscuity and large relative testis size. The aim of this study was to determine whether A. agrarius sperm fail to express CD46 protein and, if so, whether A. agrarius have a faster acrosome reaction than Mus.
Research Interests: Fluorescence Microscopy, Biological Sciences, Mice, Animals, Male, and 11 moreAlternative splicing, Molecular endocrinology and reproductive biology, Time Factors, Protein Expression, Reproductive, Alternative Splicing, Amino Acid Sequence, Base Sequence, Spermatozoa, Cell Surface Markers, and Acrosome Reaction
There is pronounced promiscuity and sperm competition in long-tailed field mice (Apodemus sylvaticus). These mice have evolved unusual sperm behaviour favouring rapid fertilisation, including dynamic formation of sperm trains and their... more
There is pronounced promiscuity and sperm competition in long-tailed field mice (Apodemus sylvaticus). These mice have evolved unusual sperm behaviour favouring rapid fertilisation, including dynamic formation of sperm trains and their subsequent dissociation. The cell surface complement regulatory (CReg) protein CD46 is broadly expressed in eutherian mammals other than rodents, in which it is expressed solely on the spermatozoal acrosomal membrane. Ablation of the CD46 gene has been associated with a faster acrosome reaction (AR) rate in inbred laboratory mice. Here, we demonstrate that wild-caught field mice of three species, A. sylvaticus, A. flavicollis and A. microps, exhibit a more rapid AR than wild-caught house mice Mus musculus or inbred laboratory BALB/c mice. We also demonstrate that wild-caught field mice of these three species, unlike house mice, produce alternatively spliced transcripts of testicular CD46 mRNA lacking exons 5-7 or 6-7, together with an extended 3'...