Gamete Production Research Articles

Divergent Gene Expression Following Duplication of Meiotic Genes in the Stick Insect Clitarchus hookeri

Some animal groups, such as stick insects (Phasmatodea), have repeatedly evolved alternative reproductive strategies, including parthenogenesis. Genomic studies have found modification of the genes underlying meiosis exists in some of these animals. Here we examine the evolution of copy number, evolutionary rate and gene expression in candidate meiotic genes of the New Zealand geographic parthenogenetic stick insect Clitarchus hookeri. We characterised 101 genes from a de novo transcriptome assembly from female and male gonads that have homology with meiotic genes from other arthropods. For each gene we determined copy number, the pattern of gene duplication relative to other arthropod orthologues and the potential for meiosis-specific expression. There are five genes duplicated in C. hookeri, including one also duplicated in the stick insect Timema cristinae, that are not or uncommonly duplicated in other arthropods. These included two sister chromatid cohesion associated genes (SA2 and SCC2), a recombination gene (HOP1), an RNA-silencing gene (AGO2) and a cell cycle regulation gene (WEE1). Interestingly, WEE1 and SA2 are also duplicated in the cyclical parthenogenetic aphid Acyrthosiphon pisum and Daphnia duplex, respectively, indicating possible roles in the evolution of reproductive mode. Three of these genes (SA2, SCC2 and WEE1) have one copy displaying gonad-specific expression and all genes, with the exception of WEE1, have significantly different non-synonymous/synonymous ratios between the gene duplicates, indicative of a shift in evolutionary constraints following duplication. These results suggest that stick insects may have evolved genes with novel functions in gamete production by gene duplication.

Seasonality of Gamete Production of Cyclonaias Species in Central Texas

Reproductive traits, which can impact population health, are important life-history characteristics for freshwater mussels. Little research has been done on the reproductive ecology of mussels, and crucial information is missing for many threatened and endangered species, especially in Texas. The objective of this study was to examine gamete production, parasitic infection rates, and sex ratios of two freshwater mussel species (Cyclonaias petrina and Cyclonaias pustulosa) in the Llano and San Saba rivers in central Texas. Gamete densities and egg diameters of C. petrina in the Llano River varied seasonally, with peak gamete densities occurring in December and February 2017 and being significantly lower from June through September 2017, while the relative abundance of the largest size classes of eggs was highest in February 2018. Few to no differences were detected in gamete production and egg diameter sizes for C. petrina between rivers. Cyclonaias pustulosa had significantly higher sperm densities and smaller egg diameters compared to C. petrina but exhibited similar egg densities in the San Saba River. There were no significant differences in gamete densities between rivers and no significant correlations between shell length and gamete density. Infection rates of parasitic trematodes varied from <1% to 14%, with the highest infection rates occurring in C. petrina in the San Saba River. Sex ratio of C. petrina was slightly skewed toward females in the Llano River and toward males in the San Saba River, with C. pustulosa having a 1:1 sex ratio in the San Saba River. The high percentage of samples without gametes suggests that the reproductive outputs of Cyclonaias appear to be more limited in the San Saba River due to several potential stressors. Further research will need to investigate the relative importance of the various stressors that affect the reproductive ecology of mussels and their persistence.

Toads use the subsurface thermal gradient for temperature regulation underground

As ectotherms with moist, permeable skins, amphibians continually seek a physiological balance between maintaining hydration and optimizing body temperature. Laboratory studies have suggested that dehydrated and starved amphibians should select cooler temperatures to slow the rate of water loss and reduce metabolism. However, much less is known about amphibian thermoregulatory behaviour in the wild, where environmental conditions and constraints may be more variable. In seasonally cold environments, where animals must maximize growth, gamete production and/or fat storage for winter dormancy over a short active season, maintaining a high metabolic rate may be primary. We investigated the thermoregulatory behaviour of the Fowler's Toads, Anaxyrus fowleri, in the wild at their northern range limit at Long Point, Ontario. We outfitted adult toads with small temperature loggers and radio-tracked them for periods of 24 hours. Simultaneously, we also recorded air and subsurface temperatures to a depth of 18.6cm. When active at night, toads rapidly equilibrated with ambient air temperatures. However, during the day, resting toads selected and maintained body temperatures around 30°C during the heat of the day by adjusting the depth to which they were buried. This strongly suggests that they behaviourally thermoregulate during their resting hours to maintain a high metabolic rate without regard to the dryness of their immediate surroundings.

RNA kinase CLP1/Cbc regulates meiosis initiation in spermatogenesis.

CLP1, TSEN complex, and VCP are evolutionarily conserved proteins whose mutations are associated with neurodegenerative diseases. In this study, we have found that they are also involved in germline differentiation. To optimize both quantity and quality in gametes production, germ cells expand themselves through limited mitotic cycles prior to meiosis. Stemming from our previous findings on the correlation between mRNA 3′-processing and meiosis entry, here we identify that the RNA kinase Cbc, the Drosophila member of the highly conserved CLP1 family, is a component of the program regulating the transition from mitosis to meiosis. Using genetic manipulations in Drosophila testis, we demonstrate that nuclear Cbc is required to promote meiosis entry. Combining biochemical and genetic methods, we reveal that Cbc physically and/or genetically intersects with Tsen54 and TER94 (VCP ortholog) in this process. The C-terminal half of Tsen54 is both necessary and sufficient for its binding with Cbc. Further, we illustrate the functional conservation between Cbc and mammalian CLP1 in the assays of subcellular localization and Drosophila fertility. As CLP1, TSEN complex, and VCP have also been identified in neurodegenerations of animal models, a mechanism involving these factors seems to be shared in gametogenesis and neurogenesis.

Phospho-Regulation of Meiotic Prophase.

Germ cells undergoing meiosis rely on an intricate network of surveillance mechanisms that govern the production of euploid gametes for successful sexual reproduction. These surveillance mechanisms are particularly crucial during meiotic prophase, when cells execute a highly orchestrated program of chromosome morphogenesis and recombination, which must be integrated with the meiotic cell division machinery to ensure the safe execution of meiosis. Dynamic protein phosphorylation, controlled by kinases and phosphatases, has emerged as one of the main signaling routes for providing readout and regulation of chromosomal and cellular behavior throughout meiotic prophase. In this review, we discuss common principles and provide detailed examples of how these phosphorylation events are employed to ensure faithful passage of chromosomes from one generation to the next.

Tell the Difference Between Mitosis and Meiosis: Interplay Between Chromosomes, Cytoskeleton, and Cell Cycle Regulation.

Meiosis is a specialized style of cell division conserved in eukaryotes, particularly designed for the production of gametes. A huge number of studies to date have demonstrated how chromosomes behave and how meiotic events are controlled. Yeast substantially contributed to the understanding of the molecular mechanisms of meiosis in the past decades. Recently, evidence began to accumulate to draw a perspective landscape showing that chromosomes and microtubules are mutually influenced: microtubules regulate chromosomes, whereas chromosomes also regulate microtubule behaviors. Here we focus on lessons from recent advancement in genetical and cytological studies of the fission yeast Schizosaccharomyces pombe, revealing how chromosomes, cytoskeleton, and cell cycle progression are organized and particularly how these are differentiated in mitosis and meiosis. These studies illuminate that meiosis is strategically designed to fulfill two missions: faithful segregation of genetic materials and production of genetic diversity in descendants through elaboration by meiosis-specific factors in collaboration with general factors.

Factor de crecimiento ligado a la insulina en la reproducción animal

The development of female gametes production (gametogenesis) occurs in an interesting way, as its process depends of many combined factors. This review will approach these morphofunction mechanisms of the ovary and the folliculogenesis, correlating the function of Insulin-Like Growth Factors (IGFs), which will influence in the production of steroids hormones, in the maintenance follicular maturation, and still elucidate how the diet assists better in this phases. Besides that, with the new researches in animal reproduction, it is important emphasize the role and assists of Insulin-Like Growth Factors during these physiologic process, showing all its potential for a more efficient follicular dynamics in any species.

The Physiology of Reproduction - Quo vadis?

The reproductive system in males and females reflects a highly dynamic underlying physiology. Yet our current understanding of this system is still largely based upon relatively simplistic snapshots of individual component cells and tissues. Gamete production as well as gonadal hormone synthesis and its influence are the manifestations of dynamic and redundant informational networks and processes, whose qualitative and quantitative dimensions, especially through development from embryo through puberty and adulthood into ageing, are still largely uncharted. Whilst the recent huge advances in molecular science have helped to describe the components of the reproductive system in ever greater detail, how these interact and function in space and time dimensions is still largely obscure. Recent developments in microfluidics, stem cell biology, and the integration of single-cell transcriptomics with tissue dynamics are offering possible methodological solutions to this issue. Such knowledge is essential if we are to understand not only the normal healthy functioning of this system, but also how and why it is affected in disease or by external impacts such as those from environmental endocrine disruptors, or in ageing. Moreover, operating within a complex network of other physiological systems, its integrational capacity is much more than the generation of male and female gametes and their roles in fertility and infertility; rather, it represents the underpinning support for health and well-being across the lifespan, through pregnancy, puberty, and adulthood, into old age.

Photoperiod in aquaculture of the sea urchin Arbacia dufresnii (Echinodermata: Echinoidea): Effects on gamete production and maturity

Introduction: Photoperiod is, together with temperature and food availability, one of the main stimuli in the regulation of gametogenesis in a wide variety of species. Objective: To evaluate the effect of photoperiod on the production of mature gametes in cultured Arbacia dufresnii. Methods: An experiment was carried out with three varying light-dark regimes/treatments: constant light (24 h light), neutral photoperiod (12 h light, 12 h darkness), and constant darkness (24 h darkness). Twenty females were used in each treatment. All were induced to spawn and, ten randomly selected females from each treatment were induced to spawn again after 30 days. After 60 days, spawning was induced in the remaining females. The gametes were collected in filtered seawater, fixed in Davidson solution, quantified and measured per individual in triplicate in a Sedgewick-Rafter chamber. To determine maturation, fertilization success was evaluated 30 minutes after fertilization. Results: Our results showed that in the aquaculture system, after only two months, mature gametes were obtained, and in the neutral light regime there were 10 times more gametes than the number produced in wild sea urchins during the spawning period in question. We also found that with a greater exposure to light, a lower number of mature gametes was produced. Conclusions: This study suggests the viability of the production of mature gametes in a short period of time as regards Arbacia dufresnii.

Nutrient restriction synergizes with retinoic acid to induce mammalian meiotic initiation in vitro

The molecular machinery and chromosome structures carrying out meiosis are frequently conserved from yeast to mammals. However, signals initiating meiosis appear divergent: while nutrient restriction induces meiosis in the yeast system, retinoic acid (RA) and its target Stra8 have been shown to be necessary but not sufficient to induce meiotic initiation in mammalian germ cells. Here, we use primary culture of mouse undifferentiated spermatogonia without the support of gonadal somatic cells to show that nutrient restriction in combination with RA is sufficient to induce Stra8- and Spo11-dependent meiotic gene and chromosome programs that recapitulate the transcriptomic and cytologic features of in vivo meiosis. We demonstrate that neither nutrient restriction nor RA alone exerts these effects. Moreover, we identify a distinctive network of 11 nutrient restriction-upregulated transcription factor genes, which are associated with early meiosis in vivo and whose expression does not require RA. Our study proposes a conserved model, in which nutrient restriction induces meiotic initiation by upregulating key transcription factor genes for the meiotic gene program and provides an in vitro platform for meiotic induction that could facilitate research and haploid gamete production.

Testicular subcutaneous allografting followed by immunosuppressive treatment promotes maintenance of spermatogonial cells in rainbow trout (Oncorhynchus mykiss)

Germ cell transplantation and testis graft represent promising biotechnologies that can be applied for the reproduction of commercial or endangered species. However, mechanisms of rejection from the host immune system might remove the transplanted donor cells/tissues and limit the surrogate production of gametes. In this work, we administered emulsion containing-immunosuppressants to verify whether they are capable to prevent immune rejection and promote survival of testis allografts in rainbow trout. In the first part of this study, we demonstrated in vitro that tacrolimus and cyclosporine were able to affect viability, inhibit leucocyte proliferation, and suppress il2 expression in vitro. In in vivo experiments, both doses of tacrolimus (0.5 and 1.5 mg/kg) and the lower dose of cyclosporine (20 mg/kg) significantly inhibited the expression of il2 in head kidney, three days post-injection. A higher dose of cyclosporine (40 mg/kg) was able to inhibit il2 expression for up to seven days post-injection. In the second part, testis allografts were conducted in fish treated weekly with emulsion containing-tacrolimus. Immunohistochemical, conventional histology, and qRT-PCR (vasa) analysis demonstrated the presence of spermatogonial cells by the fifth week, in animals treated with 0.5 mg/kg of tacrolimus similar as found in autografted group. In the group treated with the highest tacrolimus dose (1.5 mg/kg) and in the non-treated group (without immunosuppressant), no germ cells or their respective markers were detected. il2 expression in head kidney was also suppressed in grafted animals treated with tacrolimus compared to non-treated group. These results suggest that tacrolimus may be a promising immunosuppressant for testis allografts or germ cell transplantation in rainbow trout. Co-administration combining tacrolimus (at lower dose) with other immunosuppressive drugs for inhibiting other activation pathways of the immune system, as performed in human organ transplantation, could be an alternative approach to optimize the immunosuppressive effects in host organisms.

Morphometry and histology to assess the maturity stage of three endangered devil ray species (Elasmobranchii: Mobulidae) from the Gulf of California

Abstract Devil rays of the genus Mobula are subject to fishing exploitation worldwide and are considered vulnerable to overexploitation due to population reduction, which is evidenced by a decline in the number of catches of these animals. Limited biological knowledge on these species has forced the use of precautionary conservation measures in countries where intensive fishing occurs. This study aimed to describe biological data of interest for estimating the feasibility of the recovery of Mobula populations, emphasizing the reproductive activity of three endangered species of the genus Mobula (Mobula munkiana, Mobula thurstoni, and Mobula mobular) in the Gulf of California. Reproductive organs were collected during 7 years of commercial fishing (2001–2007), and data on population structure, sex ratio, gamete production, and the number of offspring per breeding period were obtained. Maturity stages were determined through histological analysis of the gonads for both sexes, and the size at maturity was estimated based on anatomical and histological characteristics of the specimens caught. Considering the wide global distribution of Mobula species, there is an urgent need to apply strict conservation measures, such as established fishery closures during the breeding season or the establishment of catch periods after specimens have reached sexual maturity, especially in the countries where these animals are caught.

Cystic proliferation of germline stem cells is necessary to reproductive success and normal mating behavior in medaka

The production of an adequate number of gametes is necessary for normal reproduction, for which the regulation of proliferation from early gonadal development to adulthood is key in both sexes. Cystic proliferation of germline stem cells is an especially important step prior to the beginning of meiosis; however, the molecular regulators of this proliferation remain elusive in vertebrates. Here, we report that ndrg1b is an important regulator of cystic proliferation in medaka. We generated mutants of ndrg1b that led to a disruption of cystic proliferation of germ cells. This loss of cystic proliferation was observed from embryogenic to adult stages, impacting the success of gamete production and reproductive parameters such as spawning and fertilization. Interestingly, the depletion of cystic proliferation also impacted male sexual behavior, with a decrease of mating vigor. These data illustrate why it is also necessary to consider gamete production capacity in order to analyze reproductive behavior.

Influence of maternal weight, age, larval feeding and their interactions on the hatchery outcomes of an Indian major carp (Labeo rohita, Hamilton 1822)

Broodstocks’ size (weight or length), age and larval feeding are crucial in the production of good quality gametes and larvae in any fish. Therefore, this study was conducted with two experiments to understand 1) effects of maternal weight and age, and 2) effects of maternal weight, age, larval feeding and their interactions on egg and larval traits using the Indian major carp (Labeo rohita). In both experiments, females were divided into two size groups based on their body weights (‘large’ and ‘small’) to obtain eggs and larvae. In experiment-1, parameters of egg quality such as egg weight, egg number, egg diameter, egg area and hatching rate were assessed, and larvae were reared up to two weeks with optimum feeds to evaluate their traits such as deformation rate, survival rate, total length and body area. In experiment-2, only the three-day old larvae were randomly assigned into two feeding regimes (‘everyday’ and ‘every other day’) up to two weeks to assess their fitness. The results revealed that egg weight, hatching rate, larval total length, body area increased significantly (P <0.05) and hatchling deformation rate decreased significantly (P <0.05) with the increase of female age, whereas only egg weight was linearly related to female weight (R2 = 0.47, P <0.05) in experiment-1. The experiment-2 showed that everyday fed larvae had significantly (P <0.05) higher survival rate, total length and body area than those fed every other day. The dietary treatment found no significant effects of maternal age, weight and their interactions with larval feeding. Thus, the study showed that maternal body weight, age and larval feeding may influence some traits of egg and larval fitness. The overall findings suggest that maternal weight, age and regular larval feeding must be considered to produce good quality of gametes and larvae for sustainable production of this species.

Reduced fertility caused by meiotic defects and micronuclei formation during microsporogenesis in xBrassicoraphanus

BackgroundHybridization and polyploidization events are important driving forces in plant evolution. Allopolyploids formed between different species can be naturally or artificially created but often suffer from genetic instability and infertility in successive generations. xBrassicoraphanus is an intergeneric allopolyploid obtained from a cross between Brassica rapa and Raphanus sativus, providing a useful resource for genetic and genomic study in hybrid species.ObjectiveThe current study aims to understand the cause of hybrid sterility and pollen abnormality in different lines of synthetic xBrassicoraphanus from the cytogenetic perspective.MethodsAlexander staining was used to assess the pollen viability. Cytogenetic analysis was employed to monitor meiotic chromosome behaviors in pollen mother cells (PMCs). Origins of parental chromosomes in xBrassicoraphanus meiocytes were determined by genome in situ hybridization analysis.ResultsThe xBrassicoraphanus lines BB#4 and BB#6 showed high rates of seed abortion and pollen deformation. Abnormal chromosome behaviors were observed in their PMCs, frequently forming univalents and inter-chromosomal bridges during meiosis. A positive correlation also exists between meiotic defects and the formation of micronuclei, which is conceivably responsible for unbalanced gamete production and pollen sterility.ConclusionThese results suggest that unequal segregation of meiotic chromosomes, due in part to non-homologous interactions, is responsible for micronuclei and unbalanced gamete formation, eventually leading to pollen degeneration and inferior fertility in unstable xBrassicoraphanus lines.

Cloning and characterization of rec8 gene in orange-spotted grouper (Epinephelus coioides) and Dmrt1 regulation of rec8 promoter activity

Meiosis is a specialized type of cell division critical for gamete production during sexual reproduction in eukaryotes. The meiotic recombination protein Rec8 has been identified as an important factor in germ cell meiotic initiation in vertebrates; however, its equivalent role in teleosts is poorly characterized. In this study, we cloned and sequenced the rec8 gene from orange-spotted grouper (Epinephelus coioides). The cDNA sequence consisted of 2244 base pairs (bp), including a 5' untranslated region (UTR) of 198bp and a 3'UTR of 284bp. The open reading frame of grouper rec8 was 1752bp, encoding 584 amino acids. Expression levels of rec8 were higher in the ovary, intersex gonad, and testis. A neighbor-joining phylogenetic tree based on the deduced amino acid sequence indicated a common origin for grouper and other teleost rec8 molecules. Immunohistochemistry using a polyclonal anti-Rec8 antibody localized the protein in the oogonia and primary oocytes in the ovary and in spermatogonia and spermatocytes in the intersex gonad and testis, suggesting that Rec8 may play an important role in the meiotic division and the development of grouper germ cells. In addition, we found that the transcription factor Dmrt1 increased rec8 promoter activity through the second binding site, based on dual-luciferase assays. Together, these results suggest that Rec8 plays a crucial role in meiosis and may be regulated by Dmrt1 to affect meiosis in groupers.

Artificially produced gametes in mice, humans and other species.

The production of gametes from pluripotent stem cells in culture, also known as invitro gametogenesis, will make an important contribution to reproductive biology and regenerative medicine, both as a unique tool for understanding germ cell development and as an alternative source of gametes for reproduction. Invitro gametogenesis was developed using mouse pluripotent stem cells but is increasingly being applied in other mammalian species, including humans. In principle, the entire process of germ cell development is nearly reconstitutable in culture using mouse pluripotent stem cells, although the fidelity of differentiation processes and the quality of resultant gametes remain to be refined. The methodology in the mouse system is only partially applicable to other species, and thus it must be optimised for each species. In this review, we update the current status of invitro gametogenesis in mice, humans and other animals, and discuss challenges for further development of this technology.

The Role of Extracellular Vesicles in Sperm Function and Male Fertility.

Within the reproductive tract, distinct cell types must have precisely controlled communication for complex processes such as gamete production, fertilisation and implantation. Intercellular communication in many physiological processes involves extracellular vesicles (EVs). In reproductive systems, EVs have been implicated in many aspects, from gamete maturation to embryo development. Sperm develop within the testis and then exit into the epididymis in an immature form, lacking motility and fertilising capabilities. Due to their small size, compact nature of the nucleus and the lack of specific organelles, sperm are unable to perform de novo protein synthesis, and thus rely on extrinsic signals delivered from the external milieu to gain full function. Mounting evidence points to EVs as being a major provider of these signals, not just within the male reproductive tract but also within the female as the sperm make their way through a seemingly hostile environment to the oocyte. In this chapter, we review the current knowledge on EVs as mediators of sperm maturation and function and highlight their potential roles in male fertility.

Decellularization Methods of Ovary in Tissue Engineering.

The ovaries or female gonads are situated in the ovarian fossa of the abdominal cavity. These are paired, almond-shaped organs measuring about 3.5cm long and 1.5cm thick and exist out of a central medullary zone and a peripheral cortex that are enclosed in a fibrous capsule called the tunica albuginea. The ovaries serve 2 main functions, the first one being the production of female gametes called oocytes (oogenesis). Interestingly, the number of primary oocytes that reside in the ovary is determined at birth. About 400 oocyte-containing follicles successfully go through all the developmental stages from this limited pool during folliculogenesis throughout the female reproductive life. In this process, primordial follicles grow and advance until forming a mature or Graafian follicle; during ovulation, secondary oocytes are released and the remaining follicular wall collapses and forms the highly vascularized corpus luteum or luteal gland. This ovarian cycle is regulated by several hormones secreted from the adenohypophysis and lasts about 28days. During this cycle, the ovaries also serve as endocrine glands and produce female sex hormones such as estrogens and progesterone (steroidogenesis), influencing the growth and development of tissues sensitive to these hormones such as the endometrium. Hence, the endometrial cycle goes synchronized with the ovarian cycle.

Regulation of Human Spermatogenesis.

Human spermatogenesis (HS) is an intricate network of sequential processes responsible for the production of the male gamete, the spermatozoon. These processes take place in the seminiferous tubules (ST) of the testis, which are small tubular structures considered the functional units of the testes. Each human testicle contains approximately 600-1200 STs [1], and are capable of producing up to 275 million spermatozoa per day [2].