Expression of sex-specific molecular markers by Babesia bovis gametes

BACKGROUND

Bovine babesiosis caused by Babesia bovis is one of the most important tick-borne diseases of cattle in tropical and subtropical regions. Babesia bovis parasites have a complex lifecycle, including development within the mammalian host and tick vector. In the tick midgut, extracellular Babesia parasites transform into gametes that fuse to form zygotes. To date, little is known about genes and proteins expressed by male gametes.

METHODS AND RESULTS

We developed a method to separate male gametes from in vitro induced B. bovis culture. Separation enabled the validation of sex-specific markers. Collected male gametocytes were observed by Giemsa-stained smear and live-cell fluorescence microscopy. Babesia male gametes were used to confirm sex-specific markers by quantitative real-time PCR. Some genes were found to be male gamete specific genes including pka, hap2, α-tubulin II and znfp2. However, α-tubulin I and ABC transporter, trap2-4 and ccp1-3 genes were found to be upregulated in culture depleted of male gametes (female-enriched). Live immunofluorescence analysis using polyclonal antibodies confirmed surface expression of HAP2 by male and TRAP2-4 by female gametes. These results revealed strong markers to distinguish between B. bovis male and female gametes.

CONCLUSIONS

Herein, we describe the identification of sex-specific molecular markers essential for B. bovis sexual reproduction. These tools will enhance our understanding of the biology of sexual stages and, consequently, the development of additional strategies to control bovine babesiosis.

Preservation of fertility in female and male prepubertal patients diagnosed with cancer

Over the past two decades, the importance of fertility preservation has grown not only in the realm of medical and clinical patient care, but also in the field of basic and applied research in human reproduction. With advancements in cancer treatments resulting in higher rates of patient survival, it is crucial to consider the quality of life post-cure. Therefore, fertility preservation must be taken into account prior to antitumor treatments, as it can significantly impact a patient's future fertility. For postpubertal patients, gamete cryopreservation is the most commonly employed preservation strategy. However, for prepubertal patients, the situation is more intricate. Presently, ovarian tissue cryopreservation is the standard practice for prepubertal girls, but further scientific evidence is required in several aspects. Testicular tissue cryopreservation, on the other hand, is still experimental for prepubertal boys. The primary aim of this review is to address the strategies available for possible fertility preservation in prepubertal girls and boys, such as ovarian cryopreservation/transplantation, in vitro follicle culture and meiotic maturation, artificial ovary, transplantation of cryopreserved spermatogonia, and cryopreservation/grafting of immature testicular tissue and testicular organoids.

Influences of habitat and seasonal changes on gonadal maturation of Echinometra mathaei (Echinodermata: Echinoidea) and Tridacna squamosa (Mollusca: Bivalvia) in the Red Sea, Egypt

The present work is aimed at investigating the effects of seasonal changes and habitat conditions on reproductive state and gonadal development of two macrobenthic fauna. Echinometra mathaei and Tridacna squamosa were collected seasonally (summer and winter) in July 2019 and January 2020 from three sites along the Red Sea coast, Egypt: Hamraween, Sedy Malek, and Porto Ghalb. Sexual differences and gonadal maturation in the two species were determined by performing biopsies of their gonads followed by morphologic analyses. Hematoxylin and eosin-stained gonadal sections were examined and analyzed. In E. mathaei, reproductive behavior was more active in the summer than in the winter; in T. squamosa, reproductive behavior was active almost all the year, especially during the winter. The reproductive activity and gonadal maturation of both species were affected by environmental factors. The results indicated that temperature is a vital factor affecting the reproductive activity of both species. This study concluded that temperature fluctuations may pose significant challenges to coastal marine ecosystems.

Voices from Health Care Providers: Assessing the Impact of the Indian Assisted Reproductive Technology (Regulation) Act, 2021 on the Practice of IVF in India

The regulatory vacuum in the field of ART in India was filled when in December 2021, the Assisted Reproductive Technology (Regulation) Act, 2021 (ART Act) (https://egazette.nic.in/WriteReadData/2021/232025.pdf) and the Surrogacy (Regulation) Act, 2021 (SR Act) were passed. We surveyed medical professionals to understand their knowledge, attitude and perception towards the Acts and to offer an initial, snapshot assessment of their impact on the medical community. The government has already signalled its intent to implement the Acts and has published several notifications/gazettes to clarify and amend the issues surrounding the Acts (https://artsurrogacy.gov.in/NationalArtSurrogacy/faces/HomePage.xhtml#). We hope that these responses will help to voice the thoughts, concerns and suggestions from of ART service providers for ART to further clarify and rationalise the laws. Infertility is already a much stigmatised problem which deserves to be a higher public health priority. While the laws are a welcome step, changes in both laws is are the need of the hour to make ART more accessible, available and affordable to the millions of couples who need these services and for the health care providers who to be able to deliver them.

Effect of cryopreservation on post-thaw motility and viability of Grey mullet, Mugil cephalus sperm (Linnaeus, 1758)

In this study, we optimized a simple method of cryopreservation for Mugil cephalus sperm based on post-thaw motility and viability. A series of experiments were conducted by changing the extender, cryoprotectant and freezing height above the liquid nitrogen (LN) surface. First, we carried out the cryopreservation using the extender V2E and cryoprotective agents (CPAs) namely, propylene glycol (PG), methanol (MeOH), glycerol (GLY), ethylene glycol (EG), dimethylsulfoxide (Me2SO) and dimethylacetamide (DMA) at a final concentration of 5% and 10%. We found that 10% of GLY, EG and Me2SO were more suitable compared to other CPAs. Then, different freezing heights (6, 8, 10 and 12 cm) above the LN surface were experimented with extender V2E and optimized CPAs. Then, 0.3 M of glucose, sucrose and trehalose were tested as extender along with optimized CPAs and freezing height. Additionally, the effect of fast-rate freezing and storage days (7, 30 and 180) on post-thaw sperm quality was documented using the factors optimized in earlier experiments. For all experiments, the fresh sperm was diluted at a ratio of 1:1 with cryomedium (CPA + extender), loaded into cryovials (2.0 mL) and frozen. The cryopreserved sperm was thawed at 30 °C for 90-120 s and their quality was evaluated. Among the experimented factors, sperm diluted in cryomedium (0.3 M glucose + 10% EG) and frozen at 4 cm above the LN surface registered significantly (P < 0.05) highest post-thaw motility (73 ± 2%) and (71 ± 1%) viability. Fast-rate freezing has resulted in lower (about 30%) post-thaw motility and viability of sperm. The storage days (7, 30 and 180) did not have a significant effect on post-thaw sperm quality. Overall results show that using the factors optimized through this study, high-quality sperm can be obtained after cryopreservation.

Distribution of tetraspanins in bovine ovarian tissue and fresh/vitrified oocytes

Tetraspanin proteins are mostly known as organizers of molecular complexes on cell membranes, widely expressed on the surface of most nucleated cells. Although tetraspanins participate in many physiological processes of mammals, including reproduction, their relevance to the processes of folliculogenesis and oogenesis has not yet been fully elucidated. We bring new information regarding the distribution of tetraspanins CD9, CD81, CD151, CD82, and CD63 at different stages of follicular development in cattle. The found distribution of tetraspanin CD9, CD63, and integrin alpha V in similar areas of ovarian tissue outlined their possible cooperation. We also describe yet-unknown distribution patterns of CD151, CD82, and CD63 on immature and mature bovine oocytes. The unique localization of tetraspanins CD63 and CD82 in the zona pellucida of bovine oocytes suggested their involvement in transzonal projections. Furthermore, we present an unchanged distribution pattern of the studied tetraspanins in vitrified mature bovine oocytes. The immunofluorescent analysis was supplemented by in silico data addressing tetraspanins expression in the ovarian cells and oocytes across several species. The obtained results suggest that in the study of the oocyte development and potentially the fertilization process of cattle, the role of tetraspanins and integrins should also be taken into account.

Ex vivo exposure to titanium dioxide and silver nanoparticles mildly affect sperm of gilthead seabream (Sparus aurata) - A multiparameter spermiotoxicity approach

Nanoparticles (NP) are potentially reprotoxic, which may compromise the success of populations. However, the reprotoxicity of NP is still scarcely addressed in marine fish. Therefore, we evaluated the impacts of environmentally relevant and supra environmental concentrations of titanium dioxide (TiO₂: 10 to 10,000 μg·L^-1) and silver NP (Ag: 0.25 to 250 μg·L^-1) on the sperm of gilthead seabream (Sparus aurata). We performed short-term direct exposures (ex vivo) and evaluated sperm motility, head morphometry, mitochondrial function, antioxidant responses and DNA integrity. No alteration in sperm motility (except for supra environmental Ag NP concentration), head morphometry, mitochondrial function, and DNA integrity occurred. However, depletion of all antioxidants occurred after exposure to TiO₂ NP, whereas SOD decreased after exposure to Ag NP (lowest and intermediate concentration). Considering our results, the decrease in antioxidants did not indicate vulnerability towards oxidative stress. TiO₂ NP and Ag NP induced low spermiotoxicity, without proven relevant ecological impacts.

Revisiting selected ethical aspects of current clinical in vitro fertilization (IVF) practice

Ethical considerations are central to all medicine though, likely, nowhere more essential than in the practice of reproductive endocrinology and infertility. Through in vitro fertilization (IVF), this is the only field in medicine involved in creating human life. IVF has, indeed, so far led to close to 10 million births worldwide. Yet, relating to substantial changes in clinical practice of IVF, the medical literature has remained surprisingly quiet over the last two decades. Major changes especially since 2010, however, call for an updated commentary. Three key changes deserve special notice: Starting out as a strictly medical service, IVF in recent years, in efforts to expand female reproductive lifespans in a process given the term “planned” oocyte cryopreservation, increasingly became more socially motivated. The IVF field also increasingly underwent industrialization and commoditization by outside financial interests. Finally, at least partially driven by industrialization and commoditization, so-called add-ons, the term describing mostly unvalidated tests and procedures added to IVF since 2010, have been held responsible for worldwide declines in fresh, non-donor live birthrates after IVF, to levels not seen since the mid-1990s. We here, therefore, do not offer a review of bioethical considerations regarding IVF as a fertility treatment, but attempt to point out ethical issues that arose because of major recent changes in clinical IVF practice.

Effects on reproductive, biochemical and genotoxic parameters of herbicides 2,4-D and glyphosate in silver catfish (Rhamdia quelen)

The objective of this work was to evaluate the effects of the herbicides 2,4-D, glyphosate and the mixture of both on oxidative stress, genotoxicity and the rates of fertilization, hatching and larval normality in silver catfish. Exposure to glyphosate and the mixture of herbicides significantly decreased the fertilization of oocytes and the hatching of eggs. The different concentrations of 2,4-D and glyphosate, in addition to the mixture of both, did not affect the rates of larval normality, the activity of CAT, GST, LPO, and PCO. SOD activity was not evident in any of the treatments. Exposure to 2,4-D and the mixture of herbicides caused damage to the genetic material of larvae silver catfish. Our results show that although high concentrations of the herbicides were used, changes caused by them were detected in only some of the tested biomarkers.

[Impact of SARS-CoV-2 on fertility, gametes' quality and Assisted Reproduction Technology]

Le contexte actuel de pandémie conduit à s’interroger sur les conséquences de la COVID-19 en Assistance médicale à la procréation (AMP). En effet, suite aux premières recommandations de l’Agence de la biomédecine en mars 2020, les centres d’AMP ont suspendu leurs activités. La reprise progressive des tentatives en mai 2020 s’est accompagnée de nombreux questionnements, concernant les effets directs et indirects du SARS-CoV-2 sur la qualité des gamètes, la gamétogenèse, la fertilité, la grossesse et la santé néonatale. L’objectif de cette revue de la littérature est de synthétiser les données disponibles, pour informer les patient(e)s pris(es) en charge et adapter les pratiques d’AMP en cette période de la COVID-19. La plupart des études récentes se basent sur l’évaluation des effets du syndrome infectieux, sur l’analyse des facteurs hormonaux, et sur l’expression des protéines d’entrée virale (ACE2 et TMPRSS2) au niveau des cellules impliquées dans la gamétogenèse pour évaluer les répercussions de la COVID-19. La transmission materno-fœtale du SARS-CoV-2 n’a pas pu être démontrée à ce jour, mais l’infection néonatale reste possible. Néanmoins, les hommes seraient plus à risque d’être infectés par le SARS-CoV-2, d’être symptomatiques et la spermatogenèse est vraisemblablement affectée. La présence du virus dans le sperme est un évènement rare, mais l’ensemble de ces paramètres sont à prendre en compte dans la prise en charge des couples en AMP. Cependant, aucune conséquence sur la qualité des gamètes féminins n’a été mise en évidence jusqu’à présent.

Impact on Fertility Rate and Embryo-Larval Development Due to the Association Acidification, Ocean Warming and Lead Contamination of a Sea Urchin Echinometra lucunter (Echinodermata: Echinoidea)

Ocean warming and acidification can cause deleterious effects on marine biota, which may be potentialized when associated with metal pollution. Thus, the aim of this work was to evaluate the effects of pH decrease, temperature increase and lead contamination on fertility rate and embryo-larval development of Echinometra lucunter. Gametes and embryos were exposed at pH 8.2 (control) and 7.5; at 26°C (control) and 28°C; and at lead concentrations of 0 (control), 125, 250 and 500 μg/L. These conditions were tested individually and in combination. The fertilization rate of E. lucunter was only significantly reduced in the treatments where temperature was increased and in the treatment where pH decreased. However, the development rate of the pluteus larvae was significantly affected in the majority of treatments: metal contamination in the higher concentration; decreased pH in all metal concentrations; increased temperature in the highest metal concentration; decreased pH and increased temperature and all variables combined, which is decreased pH, increased temperature and metal contamination in relation to the control group (C). The development test was shown to be more sensitive than the fertilization test in all the studied scenarios. In general, the present study suggests that pH decrease, temperature increase and metal pollution may have a significant impact on E. lucunter reproductive cycle.

MTHFR (methylenetetrahydrofolate reductase: EC 1.5.1.20) SNPs (single-nucleotide polymorphisms) and homocysteine in patients referred for investigation of fertility

Purpose

MTHFR, one of the major enzymes in the folate cycle, is known to acquire single-nucleotide polymorphisms that significantly reduce its activity, resulting in an increase in circulating homocysteine. Methylation processes are of crucial importance in gametogenesis, involved in the regulation of imprinting and epigenetic tags on DNA and histones. We have retrospectively assessed the prevalence of MTHFR SNPs in a population consulting for infertility according to gender and studied the impact of the mutations on circulating homocysteine levels.

Methods

More than 2900 patients having suffered at least two miscarriages (2 to 9) or two failed IVF/ICSI (2 to 10) attempts were included for analysis of MTHFR SNPs C677T and A1298C. Serum homocysteine levels were measured simultaneously.

Results

We observed no difference in the prevalence of different genetic backgrounds between men and women; only 15% of the patients were found to be wild type. More than 40% of the patients are either homozygous for one SNP or compound heterozygous carriers. As expected, the C677T SNP shows the greatest adverse effect on homocysteine accumulation. The impact of MTHFR SNPs on circulating homocysteine is different in men than in women.

Conclusions

Determination of MTHFR SNPs in both men and women must be seriously advocated in the presence of long-standing infertility; male gametes, from MTHFR SNPs carriers, are not exempted from exerting a hazardous impact on fertility. Patients should be informed of the pleiotropic medical implications of these SNPs for their own health, as well as for the health of future children.

The sexual side of parasitic protists

Much of the vast evolutionary landscape occupied by Eukaryotes is dominated by protists. Though parasitism has arisen in many lineages, there are three main groups of parasitic protists of relevance to human and livestock health: the Apicomplexa, including the malaria parasite Plasmodium and coccidian pathogens of livestock such as Eimeria; the excavate flagellates, encompassing a diverse range of protist pathogens including trypanosomes, Leishmania, Giardia and Trichomonas; and the Amoebozoa, including pathogenic amoebae such as Entamoeba. These three groups represent separate, deep branches of the eukaryote tree, underlining their divergent evolutionary histories. Here, I explore what is known about sex in these three main groups of parasitic protists.

Copper and cadmium impair sperm performance, fertilization and hatching of oocytes from Amazonian fish Colossoma macropomum

The contamination of aquatic environments by transition metals can have a direct influence on the reproductive process of several organisms in the aquatic biota. This study aimed to evaluate the effect of cadmium and copper on the sperm of tambaqui (Colossoma macropomum). Male (n = 4) and female (n = 4) specimens of C. macropomum were induced to spermiation and ovulation, with sperm being activated in the following media: 0; 0.6; 1.2 and 1.8 mg/L of cadmium (CdCl₂) and 0; 0.4; 0.8 and 1.2 mg/L of copper (CuCl₂). Sperm quality was assessed through time (s) and motility rate (%), superoxide dismutase (SOD) and glutathione S-transferase (GST) activities, lipoperoxidation levels (LPO), and morphological characteristics. In parallel, the effects of these metals on the rate of fertilization and hatching of the oocytes were evaluated. The duration and motility rate of sperm were longer in the control treatment, 85.67 ± 11.01 s; 90 ± 0.01%, and progressively decreased to 44.67 ± 4.16 s and 60 ± 5%, respectively, in concentrations of 1.8 mg/L (44.67 ± 4.16 s; 60 ± 5%) of CdCl₂ and to 65.67 ± 3.30 s; 70 ± 5%, respectively, in concentrations of 0.8 mg/L of CuCl₂. We observed an increase in the activity of the SOD enzyme in sperm cells exposed to 1.2 mg/L of CdCl₂. The LPO levels were increased significantly in sperm cells exposed to 1.2 and 1.8 mg/L of CdCl₂ and 0.8 mg/L of CuCl₂. Fertilization and hatching were severely impaired in the presence of Cd and Cu. These data indicate that environments contaminated with cadmium and copper harm the gametes of C. macropomum.

Maternal pineal melatonin in gestation and lactation physiology, and in fetal development and programming

Pregnancy and lactation are reproductive processes that rely on physiological adaptations that should be timely and adequately triggered to guarantee both maternal and fetal health. Pineal melatonin is a hormone that presents daily and seasonal variations that synchronizes the organism's physiology to the different demands across time through its specific mechanisms and ways of action. The reproductive system is a notable target for melatonin as it actively participates on reproductive physiology and regulates the hypothalamus-pituitary-gonads axis, influencing gonadotropins and sexual hormones synthesis and release. For its antioxidant properties, melatonin is also vital for the oocytes and spermatozoa quality and viability, and for blastocyst development. Maternal pineal melatonin blood levels increase during pregnancy and triggers the maternal physiological alterations in energy metabolism both during pregnancy and lactation to cope with the energy demands of both periods and to promote adequate mammary gland development. Moreover, maternal melatonin freely crosses the placenta and is the only source of this hormone to the fetus. It importantly times the conceptus physiology and influences its development and programing of several functions that depend on neural and brain development, ultimately priming adult behavior and energy and glucose metabolism. The present review aims to explain the above listed melatonin functions, including the potential alterations observed in the progeny gestated under maternal chronodisruption and/or hypomelatoninemia.

Structural and functional characterization of buffalo oviduct-specific glycoprotein (OVGP1) expressed during estrous cycle

Oviduct-specific glycoprotein (OVGP1) is a high molecular weight chitinase-like protein belonging to GH18 family. It is secreted by non-ciliated epithelial cells of oviduct during estrous cycle providing an essential milieu for fertilization and embryo development. The present study reports the characterization of buffalo OVGP1 through structural modeling, carbohydrate-binding properties and evolutionary analysis. Structural model displayed the typical fold of GH18 family members till the boundary of chitinase-like domain further consisting of a large (β/α)₈ TIM barrel sub-domain and a small (α+β) sub-domain. Two critical catalytic residues were found substituted in the catalytic centre (Asp to Phe118, Glu to Leu120) compared with the active chitinase. The carbohydrate-binding groove in TIM barrel was lined with various conserved aromatic residues. Molecular docking with different sugars revealed the involvement of various residues in hydrogen-bonding and non-bonded contacts. Most of the substrate-binding residues were conserved except for a few replacements (Ser13, Lys48, Asp49, Pro50, Asp167, Glu199, Gln272 and Phe275) in comparison with other GH18 members. The residues Trp10, Trp79, Asn80, Gln272, Phe275 and Trp334 were involved in recognition of all six ligands. The α+β sub-domain participated in sugar-binding through Thr270, Gln272, Tyr242 and Phe275. The binding assays revealed significant sugar-binding with purified native and recombinant OVGP1. Phylogenetic analysis revealed that OVGP1 was closely related to AMCases followed by other CLPs and evolution of OVGP1 occurred through several gene duplications. This is the first study describing the structural characteristics of OVGP1 that will further help to understand its interaction with gametes to perform crucial reproductive functions.

Porcine oviductal extracellular vesicles interact with gametes and regulate sperm motility and survival

Once in the female reproductive tract, spermatozoa undergo several modifications to acquire their complete fertilizing ability. Interactions between the oviductal fluid (OF) and gametes contribute to a successful fertilization. Recently, oviductal extracellular vesicles have been identified as an important part of the OF but their interactions with gametes are not fully understood. In the present study, we aim at determining the patterns of interactions between porcine oviductal extracellular vesicles (poEVs) and gametes (spermatozoa and oocytes). Moreover, we evaluate the effect of poEVs on sperm survival and motility to better understand the mechanisms by which poEVs modulate the processes leading to fertilization. Evaluation of poEVs uptake by spermatozoa showed that poEVs bind to spermatozoa in a time and dose dependent manner. Co-incubation of spermatozoa with poEVs (0.2 μg/μL) increased fresh and frozen sperm survival after 6 and 17 h, respectively. By contrast, poEVs supplementation reduced the total and progressive sperm motility after 2 h. Additionally, we demonstrated that poEVs interacted with the cumulus cells, zona pellucida (ZP) and oocyte, being able to cross the ZP. Besides, we showed that poEVs delivered their cargo into the oocyte, by the transfer of OVGP1 protein. In conclusion, our results demonstrated that poEVs are able to interact with both gametes. Besides, the findings from the present study showed that poEVs may participate in maintaining sperm viability and reducing motility, functions associated with the oviduct sperm reservoir. Although further investigations are needed, our results indicate that poEVs can be a potential tool to improve sperm life span during sperm handling and enhance IVF outcomes.

Characterization of Cystoisospora suis sexual stages in vitro

BACKGROUND

The porcine coccidium Cystoisospora suis is characterized by a complex life-cycle during which asexual multiplication is followed by sexual development with two morphologically distinct cell types, the micro- and macrogametes. Genes related to the sexual stages and cell cycle progression were previously identified in related Apicomplexa. Dynein light chain type 1 and male gamete fusion factor HAP2 are restricted to microgametes. Tyrosine-rich proteins and oocyst wall proteins are a part of the oocyst wall. The Rad51/Dmc1-like protein and Nima-related protein kinases are associated with the cell cycle and fertilization process. Here, the sexual stages of C. suis were characterized in vitro morphologically and for temporal expression changes of the mentioned genes to gain insight into this poorly known phase of coccidian development.

METHODS

Sexual stages of C. suis developing in vitro in porcine intestinal epithelial cells were examined by light and electron microscopy. The transcriptional levels of genes related to merozoite multiplication and sexual development were evaluated by quantitative real-time PCR at different time points of cultivation. Transcription levels were compared for parasites in culture supernatants at 6-9 days of cultivation (doc) and intracellular parasites at 6-15 doc.

RESULTS

Sexual stage of C. suis was detected during 8-11 doc in vitro. Microgamonts (16.8 ± 0.9 µm) and macrogamonts (16.6 ± 1.1 µm) are very similar in shape and size. Microgametes had a round body (3.5 ± 0.5 µm) and two flagella (11.2 ± 0.5 µm). Macrogametes were spherical with a diameter of 12.1 ± 0.5 µm. Merozoite gene transcription peaked on 10 doc and then declined. Genes related to the sexual stages and cell cycle showed an upregulation with a peak on 13 doc, after which they declined.

CONCLUSIONS

The present study linked gene expression changes to the detailed morphological description of C. suis sexual development in vitro, including fertilization, meiosis and oocyst formation in this unique model for coccidian parasites. Following this process at the cellular and molecular level will elucidate details on potential bottlenecks of C. suis development (applicable for coccidian parasites in general) which could be exploited as a novel target for control.

[Importance of the determination of MTHFR SNPs (Methylene Tetrahydrofolate Reductase Single Nucleotide Polymorphisms) in couple infertility]

OBJECTIVE

MTHFR SNPs (Methylene Tetrahydrofolate reductase Single Nucleotide polymorphisms) are biochemical modifications decreasing the capacity to form 5 MTHF 5 methyltetrahydrofolate (5MTHF). Their presence reduces the capacity of the One Carbon cycle, and so the regeneration of Homocysteine (Hcy) and in fine strongly perturbs all the methylation processes. As methylation processes are major regulators in gametogenesis and embryogenesis. We have determined the prevalence of the 2 most important SNPs A1298C and C677T in our population of patients consulting for infertility.

METHODS

Determination of the MTHFR SNPs A1298C and C677T, by hybridization using the LAMP Human MTHFR mutation KITs.

RESULTS

Only 15.8% of our patients (861) do not carry any SNP (WT wid type). Close to 20% of the patients are homozygotes for one mutation or the other. A total of 19.7% are composite heterozygous. A total of 43% of our population is considered "at risk", based on observations collected for the repeat miscarriages.

CONCLUSIONS

Determination of the 2 major MTHFR SNPs is not a "first row" choice, but it must not be neglected and should be carried out in case of repeat ART failures and repeat miscarriages. Some simple therapeutic options can be proposed: they are based on the use of 5MTHF (5MethyleneTetraHydroFolate) the compound downstream the MTHFR.

5-Methyltetrahydrofolate reduces blood homocysteine level significantly in C677T methyltetrahydrofolate reductase single-nucleotide polymorphism carriers consulting for infertility

PURPOSE

Methyltetrahydrofolate reductase (MTHFR) C677T (ala222Val) is a single-nucleotide polymorphism (SNP) that affects the formation of 5-methyltetrahydrofolate (5-MTHF), the active folate that allows the recycling of homocysteine (Hcy) to Methionine. Hcy is at the epicentre of oxidative stress and DNA methylation errors. This SNP often increases the circulating Hcy levels and consequently reduces the methylation process, which is involved in the epigenesis and imprinting of markings in gametes. This study aimed to investigate decreases in Hcy levels in MTHFR SNP carriers.

PROCEDURE

Eighty-nine couples with fertility problems for at least 3 years were included in this program. The women were systematically tested for the MTHFR C 677T isoform. If the woman tested positive, testing of the male partner was proposed. All the carriers had well-controlled blood Hcy levels before and after treatment (600μg of 5-MTHF/day, with a backup of one carbon cycle during at least 3 months).

FINDINGS

As expected, the circulating Hcy level was higher in the homozygous patients than in the heterozygous and wild-type patients. The treatments caused a significant decrease of the circulating Hcy in the SNP carriers group.

CONCLUSIONS

Couples with a long history of infertility should be analysed for MTHFR SNP and homocysteine and should be treated with physiological doses of 5-MTHF instead of high doses of folic acid.

Procuring animals and culturing of eggs and embryos

Echinoderms and especially echinoids have a rich history as model systems for the study of oogenesis, fertilization, and early embryogenesis. The ease of collecting and maintaining adults, as well as in obtaining gametes and culturing large quantities of synchronous embryos, is complemented by the ability to do biochemistry, reverse genetics, embryo manipulations and study gene regulatory networks. The diversity of species and developmental modes as well as unparalleled transparency in early developmental stages also makes echinoderms an excellent system in which to study evolutionary aspects of developmental biology. This chapter provides a practical guide to experimental methods for procuring adults and gametes, achieving synchronous in vitro fertilization, and culturing embryos through early larval stages for several echinoderm species representing four classes (Echinoidea, Asteroidea, Ophiuroidea, and Holothuroidea). We provide specific examples of protocols for obtaining adults and gametes and for culturing embryos of a selected number of species for experimental analysis of their development. The species were chosen to provide breadth across the phylum Echinodermata, as well as to provide practical guidelines for handling some of the more commonly studied species. For each species, we highlight specific advantages, and special note is made of key issues to consider when handling adults, collecting gametes, or setting and maintaining embryo cultures. Finally, information regarding interspecific crosses is provided.

The dinoflagellate Alexandrium minutum affects development of the oyster Crassostrea gigas, through parental or direct exposure

Harmful algal blooms are a threat to aquatic organisms and coastal ecosystems. Among harmful species, the widespread distributed genus Alexandrium is of global importance. This genus is well-known for the synthesis of paralytic shellfish toxins which are toxic for humans through the consumption of contaminated shellfish. While the effects of Alexandrium species upon the physiology of bivalves are now well documented, consequences on reproduction remain poorly studied. In France, Alexandrium minutum blooms have been recurrent for the last decades, generally appearing during the reproduction season of most bivalves including the oyster Crassostrea gigas. These blooms could not only affect gametogenesis but also spawning, larval development or juvenile recruitment. This study assesses the effect of toxic A. minutum blooms on C. gigas reproduction. Adult oysters were experimentally exposed to A. minutum, at environmentally realistic concentrations (10² to 10³ cells mL^-1) for two months during their gametogenesis and a control group, not exposed to A. minutum was fed with a non-toxic dinoflagellate. To determine both consequences to next generation and direct effects of A. minutum exposure on larvae, the embryo-larval development of subsequent offspring was conducted with and without A. minutum exposure at 10² cells mL^-1. Effects at each stage of the reproduction were investigated on ecophysiological parameters, cellular responses, and offspring development. Broodstock exposed to A. minutum produced spermatozoa with decreased motility and larvae of smaller size which showed higher mortalities during settlement. Embryo-larval exposure to A. minutum significantly reduced growth and settlement of larvae compared to non-exposed offspring. This detrimental consequence on larval growth was stronger in larvae derived from control parents compared to offspring from exposed parents. This study provides evidence that A. minutum blooms, whether they occur during gametogenesis, spawning or larval development, can either affect gamete quality and/or larval development of C. gigas, thus potentially impacting oyster recruitment.

Step-by-step protocols for rice gamete isolation

A detailed, step-by-step protocol for isolation of rice gametes for transcriptional profiling, with a general workflow that includes controls for RNA contamination from surrounding cells and tissues is presented. Characterization of the transcriptome and other -omics studies of flowering plant gametes are challenging as a consequence of the small sizes and relative inaccessibility of these cells. Collecting such poorly represented cells is also complicated by potential contamination from surrounding sporophytic, adjacent gametophytic tissues and difficulties in extracting high-quality intact cells. Here we present detailed, step-by-step procedures for collecting intact, unfixed rice (Oryza sativa) egg cells and sperm cells without enzymatic treatments. In addition, we also present a general workflow for assessing sample purity by RT-PCR, using primers specific for marker genes preferentially expressed in surrounding cells and tissues. These protocols should facilitate future studies of genome-scale characterization of gametes in this important model crop.

A brown algal sex pheromone reverses the sign of phototaxis by cAMP/Ca2+-dependent signaling in the male gametes of Mutimo cylindricus (Cutleriaceae)

Male gametes of the brown alga Mutimo cylindricus show positive phototaxis soon after spawning in seawater but gradually change the sign of phototaxis with time. This conversion appears to need the decrease of intracellular Ca2+ concentration. In this study, we revealed that the conversion of male gamete phototactic sign, positive to negative, was accelerated by mixing with female gametes. The supernatant after the centrifugation of female gamete suspension showed the same activity to change the phototactic sign, suggesting that a factor released from female gametes was responsible for the reaction. A known brown algal sex pheromone, ectocarpene, induced chemotaxis of male gametes of M. cylindricus. The addition of this compound induced the change of phototactic sign, clearly indicating that a sex pheromone is essential for the reversal. An inhibitor of phosphodiesterase, theophylline, inhibited the chemotaxis and phototactic sign reversion by a factor released from female gametes and ectocarpene. Measurements of cyclic nucleotides showed that the increase in intracellular concentration of cAMP, not cGMP, was parallel to the change of phototactic sign. The inhibition of phototactic sign by theophylline was not observed in low Ca2+ sea water. These results suggest that a signaling pathway mediated by cAMP and Ca2+ concentrations drives the interconversion between two important behaviors of male gametes, phototaxis and chemotaxis.

Fluorescent proteins reveal what trypanosomes get up to inside the tsetse fly

The discovery and development of fluorescent proteins for the investigation of living cells and whole organisms has been a major advance in biomedical research. This approach was quickly exploited by parasitologists, particularly those studying single-celled protists. Here we describe some of our experiments to illustrate how fluorescent proteins have helped to reveal what trypanosomes get up to inside the tsetse fly. Fluorescent proteins turned the tsetse fly from a “black box” into a bright showcase to track trypanosome migration and development within the insect. Crosses of genetically modified red and green fluorescent trypanosomes produced yellow fluorescent hybrids and established the “when” and “where” of trypanosome sexual reproduction inside the fly. Fluorescent-tagging endogenous proteins enabled us to identify the meiotic division stage and gametes inside the salivary glands of the fly and thus elucidate the mechanism of sexual reproduction in trypanosomes. Without fluorescent proteins we would still be in the “dark ages” of understanding what trypanosomes get up to inside the tsetse fly.

The evolution and patterning of male gametophyte development

The reproductive adaptations of land plants have played a key role in their terrestrial colonization and radiation. This encompasses mechanisms used for the production, dispersal and union of gametes to support sexual reproduction. The production of small motile male gametes and larger immotile female gametes (oogamy) in specialized multicellular gametangia evolved in the charophyte algae, the closest extant relatives of land plants. Reliance on water and motile male gametes for sexual reproduction was retained by bryophytes and basal vascular plants, but was overcome in seed plants by the dispersal of pollen and the guided delivery of non-motile sperm to the female gametes. Here we discuss the evolutionary history of male gametogenesis in streptophytes (green plants) and the underlying developmental biology, including recent advances in bryophyte and angiosperm models. We conclude with a perspective on research trends that promise to deliver a deeper understanding of the evolutionary and developmental mechanisms of male gametogenesis in plants.

Restoration of cellular integrity following "ballistic" pronuclear exchange during Tetrahymena conjugation

During sexual reproduction or conjugation, ciliates form a specialized cell adhesion zone for the purpose of exchanging gametic pronuclei. Hundreds of individual membrane fusion events transform the adhesion zone into a perforated membrane curtain, the mating junction. Pronuclei from each mating partner are propelled through this fenestrated membrane junction by a web of short, cris-crossing microtubules. Pronuclear passage results in the formation of two breaches in the membrane junction. Following pronuclear exchange and karyogamy (fertilization), cells seal these twin membrane breaches thereby re-establishing cellular independence. This would seem like a straightforward problem: simply grow membrane in from the edges of each breach in a fashion similar to how animal cells "grow" their cytokinetic furrows or how plant cells construct a cell wall during mitosis. Serial section electron microscopy and 3-D electron tomography reveal that the actual mechanism is less straightforward. Each of the two membrane breaches transforms into a bowed membrane assembly platform. The resulting membrane protrusions continue to grow into the cytoplasm of the mating partner, traverse the cytoplasm in anti-parallel directions and make contact with the plasma membrane that flanks the mating junction. This investigation reveals the details of a novel, developmentally-induced mechanism of membrane disruption and restoration associated with pronuclear exchange and fertilization in the ciliate, Tetrahymena thermophila.

Nanoplastics impaired oyster free living stages, gametes and embryos

In the marine environment, most bivalve species base their reproduction on external fertilization. Hence, gametes and young stages face many threats, including exposure to plastic wastes which represent more than 80% of the debris in the oceans. Recently, evidence has been produced on the presence of nanoplastics in oceans, thus motivating new studies of their impacts on marine life. Because no information is available about their environmental concentrations, we performed dose-response exposure experiments with polystyrene particles to assess the extent of micro/nanoplastic toxicity. Effects of polystyrene with different sizes and functionalizations (plain 2-μm, 500-nm and 50-nm; COOH-50 nm and NH₂-50 nm) were assessed on three key reproductive steps (fertilization, embryogenesis and metamorphosis) of Pacific oysters (Crassostrea gigas). Nanoplastics induced a significant decrease in fertilization success and in embryo-larval development with numerous malformations up to total developmental arrest. The NH₂-50 beads had the strongest toxicity to both gametes (EC₅₀ = 4.9 μg/mL) and embryos (EC₅₀ = 0.15 μg/mL), showing functionalization-dependent toxicity. No effects of plain microplastics were recorded. These results highlight that exposures to nanoplastics may have deleterious effects on planktonic stages of oysters, presumably interacting with biological membranes and causing cyto/genotoxicity with potentially drastic consequences for their reproductive success.

[Impact of air quality on practices and results in the IVF laboratory]

The concept of Air Quality often refers to particulate and microbiological contamination of ambiant air. European Directive 2006/86/CE encompass the IVF process and specify a class A air quality for manipulation of tissue and cells, in a class D environment (A over D rule). Recognizing the paramount importance of ensuring the highest microbiological and particulate safety in the IVF laboratory, it is equally important to take into account practicability issues and the financial burden of these recommendations, as well as the utter need to protect gametes and embryo viability during their IVF journey. The usefulness of such stringent recommendations may also be questionned given the absence of published cases of airborne contaminations and related patients infections after embryo transfer. The European directive stems from pharmaceutical standards and were not specifically designed for human IVF. Gametes and embryos are indeed extremely sensitive to physical and chemical stress and require strict temperature, osmolarity and pH control, as well as an absence of chemical contamination during manipulation and culture. These conditions are hardly obtained when using laminar flow hoods. Following concerns raised by many experts in the field, exceptions to the A over D rule were added in the 2006/86/CE Directives. This narrative review discusses all these aspects in a critical way and compare scientific and legal requirements applying to IVF practices in different regions of the world.

DNA fragmentation in epididymal freeze-dried ram spermatozoa impairs embryo development

Sperm freeze-drying is a revolutionary technique, which has been gaining prominence in recent years. The first related significant result was Wakayama and Yanagimachi's demonstration in 1998 of the birth of healthy mouse offspring by Intracytoplasmic Sperm Injection (ICSI), using epididymal freeze-dried spermatozoa. Mouse, rat, and hamster models were the first small mammals born from lyophilized epididymal spermatozoa, whereas most other studies in this field used ejaculated spermatozoa. In this work, we applied this technique to ram epididymal spermatozoa, checking the correlation between DNA integrity and embryo development following ICSI. To do this, epididymal sperm from four rams was lyophilized in a trehalose, glucose, KCl, HEPES, and Trolox media. To evaluate DNA damage and fragmentation after rehydration, samples were processed for Sperm Chromatin Dispersion test (SCD), Two-Tailed Comet Assay, and were used for ICSI. Ram #2 had a higher rate of spermatozoa with intact DNA compared with rams #1, #3, and #4 (28% vs. 3.8%, 2.8%, and 5%, respectively) and the lowest rate of Single-Strand Breaks (SSBs) (70% vs. 95.9%, 92.6%, and 93% respectively). Ram #3 had a higher level of Double-Strand Breaks (DSBs) compared to Ram #1 (4.6% vs. 0.33%, respectively). Embryo development to the blastocyst stage following ICSI was only reached from rams whose sperm had higher level of intact DNA - Rams #2 and #4 (6%, 5/147 and 6.3%, 4/64, respectively). Definitively, the impact of sperm DNA damage on embryonic development depends on the balance between sperm DNA fragmentation extent, fragmentation type (SSBs or DSBs), and the oocyte's repair capacity.

Cellular responses of Pacific oyster (Crassostrea gigas) gametes exposed in vitro to polystyrene nanoparticles

While the detection and quantification of nano-sized plastic in the environment remains a challenge, the growing number of polymer applications mean that we can expect an increase in the release of nanoplastics into the environment by indirect outputs. Today, very little is known about the impact of nano-sized plastics on marine organisms. Thus, the objective of this study was to investigate the toxicity of polystyrene nanoplastics (NPs) on oyster (Crassostrea gigas) gametes. Spermatozoa and oocytes were exposed to four NPs concentrations ranging from 0.1 to 100 mg L^-1 for 1, 3 and 5 h. NPs coated with carboxylic (PS-COOH) and amine groups (PS-NH₂) were used to determine how surface properties influence the effects of nanoplastics. Results demonstrated the adhesion of NPs to oyster spermatozoa and oocytes as suggested by the increase of relative cell size and complexity measured by flow-cytometry and confirmed by microscopy observations. A significant increase of ROS production was observed in sperm cells upon exposure to 100 mg L^-1 PS-COOH, but was not observed with PS-NH₂, suggesting a differential effect according to the NP-associated functional group. Altogether, these results demonstrate that the effects of NPs occur rapidly, are complex and are possibly associated with the cellular eco-corona, which could modify NPs behaviour and toxicity.

The landscape of mitochondrial small non-coding RNAs in the PGCs of male mice, spermatogonia, gametes and in zygotes

Background

Mitochondria are organelles that fulfill a fundamental role in cell bioenergetics, as well as in other processes like cell signaling and death. Small non-coding RNAs (sncRNA) are now being considered as pivotal post-transcriptional regulators, widening the landscape of their diversity and functions. In mammalian cells, small RNAs encoded by the mitochondrial genome, mitosRNAs were discovered recently, although their biological role remains uncertain.

Results

Here, using specific bioinformatics analyses, we have defined the diversity of mitosRNAs present in early differentiated germ cells of male mice (PGCs and spermatogonia), and in the gametes of both sexes and in zygotes. We found strong transcription of mitosRNAs relative to the size of the mtDNA, and classifying these mitosRNAs into different functional sncRNA groups highlighted the predominance of Piwi-interacting RNAs (piRNAs) relative to the other types of mitosRNAs. Mito-piRNAs were more abundant in oocytes and zygotes, where mitochondria fulfill key roles in fecundation process. Functional analysis of some particular mito-piRNAs (mito-piR-7,456,245), also expressed in 3T3-L1 cells, was assessed after exposure to RNA antagonists.

Conclusions

As far as we are aware, this is the first integrated analysis of sncRNAs encoded by mtDNA in germ cells and zygotes. The data obtained suggesting that mitosRNAs fulfill key roles in gamete differentiation and fertilization.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-5020-3) contains supplementary material, which is available to authorized users.

MTHFR isoform carriers. 5-MTHF (5-methyl tetrahydrofolate) vs folic acid: a key to pregnancy outcome: a case series

PURPOSE

To evaluate the possibility of correcting metabolic defects in gametes and embryos due to methylene tetra hydrofolate reductase (MTHFR) isoforms C677T and A1298C, by supplementation with 5-methyl THF instead of synthetic folic acid. In these couples, high doses of folic acid lead to UMFA (un-metabolized folic acid) syndrome.

METHODS

Thirty couples with fertility problems lasting for at least 4 years, such as recurrent fetal loss, premature ovarian insufficiency, or abnormal sperm parameters, with two thirds of them having failed assisted reproductive technology (ART) attempts were included in this program. For all couples, at least one of the partners was a carrier of one of the two main MTHFR isoforms. Most of the women had been previously treated unsuccessfully with high doses of folic acid (5 mg/day), according to what is currently proposed in the literature. The couples carrying one of the isoforms were treated for 4 months with 5-MTHF, at a dose of 600 micrograms per day, before attempting conception or starting another attempt at ART. The duration of treatment corresponding to an entire cycle of spermatogenesis is approximately 74 days.

RESULTS

In this first series of 33 couples, one couple was not followed-up, and two are still currently under treatment. No adverse effects were observed. Thirteen of the couples conceived spontaneously, the rest needing ART treatment in order to achieve pregnancy. Only three couples have, so far, not succeeded.

CONCLUSION

The conventional use of large doses of folic acid (5 mg/day) has become obsolete. Regular doses of folic acid (100-200 μg) can be tolerated in the general population but should be abandoned in the presence of MTHFR mutations, as the biochemical/genetic background of the patient precludes a correct supply of 5-MTHF, the active compound. A physiological dose of 5-MTHF (800 μg) bypasses the MTHFR block and is suggested to be an effective treatment for these couples. Moreover, it avoids potential adverse effects of the UMFA syndrome, which is suspected of causing immune dysfunction and other adverse pathological effects such as cancer (especially colorectal and prostate).

Expected advances in human fertility treatments and their likely translational consequences

BACKGROUND

Due to rapid research progress in reproductive biology and reproductive clinical endocrinology, many human infertility treatments are close to potential breakthroughs and translational applications. We here review current barriers, where such breakthroughs will likely come from, what they will entail, and their potential clinical applications.

MAIN TEXT

The radical nature of change will primarily benefit older women, reduce fertility treatment costs and thereby expand access to treatment. A still widely overlooked prerequisite for implantation and normal pregnancy maintenance is timely development of maternal immunological tolerance toward an implanting paternal semi-allograft, if malfunctioning associated with implantation failure and pregnancy loss, while premature termination of tolerance appears associated with premature labor, pre-eclampsia/eclampsia and gestoses of pregnancy. Common denominators between pregnancy and invasive malignancies have again been attracting attention, suggesting that, like in malignant tumors, degrees of embryo aneuploidy may affect invasiveness and ability to "disarm" the immune system's innate response against implanting embryos. Linking tolerance to implantation, we offer evidence that the so-called "implantation window" is likely immunological rather than hormonally defined.

CONCLUSIONS

Because many here outlined treatment changes will disproportionally benefit older women, they will exert a pronounced effect on society, as increasing numbers of women at grandparental ages will become mothers.

Thermal resistances and acclimation potential during coral larval ontogeny in Acropora pulchra

Rising temperature can adversely affect specific functions of corals. Coral gametes and planulae of Acropora pulchra were evaluated to determine their temperature resistances, and the potential of developmental thermal acclimation was examined on gametes. Results highlight that fertilization success displays a relatively high thermal resistance at ET₅₀ (median effective temperature) 31.5 ± 0.5 °C after 4 h and 30 min. Additionally, probability of larval survival is halved at LT₅₀ (median lethal temperature) 28.4 ± 0.42 °C after 14 days. The pre-exposure of oocytes to 30 °C and 32 °C for 1 h increases the cell development pace during fertilization at ambient temperature. Pre-exposure of gametes, separately at 32 °C for 1 h, increases fertilization success rate by 63% at 32°C, conversely, pre-exposure to 30 °C induces more variable results. These results evidenced the occurrence of developmental thermal acclimation as a result of thermal pre-exposure of oocytes.

Grooves surrounding the micropyle decrease the inseminating dose in fish

In fish with external fertilization, sperm must reach the oocyte through the micropyle to enter the cytoplasm. Fertilization success is then influenced by characteristics of oocytes or sperm. In this study, we evaluated oocyte morphology and sperm motility parameters and their effects on the inseminating dose in a teleost fish Astyanax altiparanae. Interestingly, we found one of the lowest yet described inseminating doses in teleosts (2390 spermatozoa oocyte-1 ml-1). Such a fertilization efficacy may be explained by the long duration of sperm motility (>75 s), the small oocyte diameter (695.119 µm), large micropyle diameter (7.57 µm), and the presence of grooves on the oocyte surface that guides spermatozoon to the fertilization area. Additionally, we have described for the first time a structure that combines grooves on the chorion surface and a ridge in the micropylar area.

Making gametes from alternate sources of stem cells: past, present and future

Infertile couples including cancer survivors stand to benefit from gametes differentiated from embryonic or induced pluripotent stem (ES/iPS) cells. It remains challenging to convert human ES/iPS cells into primordial germ-like cells (PGCLCs) en route to obtaining gametes. Considerable success was achieved in 2016 to obtain fertile offspring starting with mouse ES/iPS cells, however the specification of human ES/iPS cells into PGCLCs in vitro is still not achieved. Human ES cells will not yield patient-specific gametes unless and until hES cells are derived by somatic cell nuclear transfer (therapeutic cloning) whereas iPS cells retain the residual epigenetic memory of the somatic cells from which they are derived and also harbor genomic and mitochondrial DNA mutations. Thus, they may not be ideal starting material to produce autologus gametes, especially for aged couples. Pluripotent, very small embryonic-like stem cells (VSELs) have been reported in adult tissues including gonads, are relatively quiescent in nature, survive oncotherapy and can be detected in aged, non-functional gonads. Being developmentally equivalent to PGCs (natural precursors to gametes), VSELs spontaneously differentiate into gametes in vitro. It is also being understood that gonadal stem cells niche is compromised by oncotherapy and with age. Improving the gonadal somatic niche could regenerate non-functional gonads from endogenous VSELs to restore fertility. Niche cells (Sertoli/mesenchymal cells) can be directly transplanted and restore gonadal function by providing paracrine support to endogenous VSELs. This strategy has been successful in several mice studies already and resulted in live birth in a woman with pre-mature ovarian failure.

Phototaxis and chemotaxis of brown algal swarmers

Brown algae exhibit three patterns of sexual reproduction: isogamy, anisogamy, and oogamy. Unicellular swarmers including gametes and zoospores bear two heterogenous flagella, an anterior flagellum with mastigonemes (fine tripartite hairs) and a posterior one. In seawater, these flagellates usually receive physico-chemical signals for finding partners and good habitats. It is well known that brown algal swarmers change their swimming direction depending on blue light (phototaxis), and male gametes do so, based on the sex pheromones from female gametes (chemotaxis). In recent years, the comparative analysis of chemotaxis in isogamy, anisogamy, and oogamy has been conducted. In this paper, we focused on the phototaxis and chemotaxis of brown algal gametes comparing the current knowledge with our recent studies.

Chapter 1 Historical Background on Gamete and Embryo Cryopreservation

This chapter describes the development of the science of cryopreservation of gametes and embryos of various species including human. It attempts to record in brief the main contributions of workers in their attempts to cryopreserve gametes and embryos. The initial difficulties faced and subsequent developments and triumphs leading to present-day state of the art are given in a concise manner. The main players and their contributions are mentioned and the authors' aim is to do justice to them. This work also attempts to ensure that credit is correctly attributed for significant advances in gamete and embryo cryopreservation. In general this chapter has tried to describe the historical development of the science of cryopreservation of gametes and embryos as accurately as possible without bias or partiality.

Quantification of coral sperm collected during a synchronous spawning event

Most studies of coral reproductive biology to date have focused on oocyte numbers and sizes. Only one (ex situ) study has enumerated sperm numbers, even though these data have multiple potential applications. We quantified total coral sperm and eggs per gamete bundle collected from six species in situ during a synchronous spawning event in Singapore. Egg-sperm bundles were captured midwater as they floated towards the surface after being released by the colony. For each sample, a semi-transparent soft plastic bottle was squeezed and released to create a small suction force that was used to ‘catch’ the bundles. This technique provided several advantages over traditional methods, including low cost, ease of use, no diving prior to the night of collection needed, and the ability to target specific areas of the colony. The six species sampled were Echinophyllia aspera, Favites abdita, F. chinensis, Merulina ampliata, M. scabricula and Platygyra pini. The mean number of sperm packaged within one egg-sperm bundle ranged from 2.04 × 10⁶ to 1.93 × 10⁷. The mean number of eggs per egg-sperm bundle ranged from 26.67 (SE ± 3.27) to 85.33 (SE ± 17.79). These data are critical for fertilisation success models, but the collection technique described could also be applied to studies requiring in situ spawning data at the polyp level.

Effects of field and laboratory exposure to the toxic dinoflagellate Karenia brevis on the reproduction of the eastern oyster, Crassostrea virginica, and subsequent development of offspring

Blooms of the brevetoxin-producing dinoflagellate, Karenia brevis, are a recurrent and sometimes devastating phenomenon in the Gulf of Mexico. The eastern oyster, Crassostrea virginica, is exposed regularly to these blooms, yet little is known about the impacts of K. brevis upon this important species. The present study considered the effects of exposure to both a natural bloom and cultured K. brevis on the reproductive development of C. virginica. Oysters had been exposed to a bloom of K. brevis that occurred in Lee County, Florida, from September 2012 through May 2013, during a period of gametogenesis and gamete ripening. Ripe adult oysters were collected from this bloom-exposed site and from a site 200 miles north which was not exposed to any bloom. In addition, responses to two 10-day laboratory exposures of either unripe or ripe adult oysters to whole cells of K. brevis at high bloom concentrations (1000 and 5000cellsmL^-1) were determined. Both field- and laboratory-exposed adult oysters accumulated PbTx (attaining ∼22×10³ngg^-1 and 922ngg^-1 PbTx-3 equivalents in the laboratory and the field, respectively), and significant mucal, edematous, and inflammatory features, indicative of a defense response, were recorded in adult tissues in direct contact with K. brevis cells. Laboratory-exposed oysters also showed an increase in the total number of circulating hemocytes suggesting that: (1) new hemocytes may be moving to sites of tissue inflammation, or, (2) hemocytes are released into the circulatory system from inflamed tissues where they may be produced. The area of oyster tissue occupied by gonad (representative of reproductive effort) and reactive oxygen species production in the spermatozoa of oysters exposed to the natural bloom of K. brevis were significantly lower compared to oysters that were not exposed to K. brevis. Additionally, following 10-day exposure of ripe oysters, a significant, 46% reduction in the prevalence of individuals with ripe gametes was obtained in the 5000cellsmL^-1K. brevis treatment. Brevetoxin (PbTx) was recorded within the spermatozoa and oocytes of naturally exposed oysters and was estimated to be 18 and 26% of the adult PbTx load, respectively. Larvae derived from gametes containing PbTx showed significantly higher mortalities and attained a smaller larval size for the first 6 days post-fertilization. These negative effects on larval development may be due to the presence of PbTx in the lipid droplets of the oocytes, which is mobilized by the larvae during embryonic and lecithotrophic larval development. Provision of a non-contaminated food source to larvae however, appeared to mitigate the early negative effects of this neonatal PbTx exposure. Results herein show that adult eastern oysters and their offspring are susceptible to exposure to K. brevis. Caution should therefore be exercised when identifying oyster reef restoration areas and in efforts to establish aquaculture in areas prone to red tides.

Germ Line Mechanics--And Unfinished Business

Primordial germ cells are usually made early in the development of an organism. These are the mother of all stem cells that are necessary for propagation of the species, yet use highly diverse mechanisms between organisms. How they are specified, and when and where they form, are central to developmental biology. Using diverse organisms to study this development is illuminating for understanding the mechanics these cells use in this essential function and for identifying the breadth of evolutionary changes that have occurred between species. This essay emphasizes how echinoderms may contribute to the patchwork quilt of our understanding of germ line formation during embryogenesis.

Retracted article: In vitro derivation of mammalian germ cells from stem cells and their potential therapeutic application

Pluripotent stem cells (PSCs) are a unique type of cells because they exhibit the characteristics of self-renewal and pluripotency. PSCs may be induced to differentiate into any cell type, even male and female germ cells, suggesting their potential as novel cell-based therapeutic treatment for infertility problems. Spermatogenesis is an intricate biological process that starts from self-renewal of spermatogonial stem cells (SSCs) and leads to differentiated haploid spermatozoa. Errors at any stage in spermatogenesis may result in male infertility. During the past decade, much progress has been made in the derivation of male germ cells from various types of progenitor stem cells. Currently, there are two main approaches for the derivation of functional germ cells from PSCs, either the induction of in vitro differentiation to produce haploid cell products, or combination of in vitro differentiation and in vivo transplantation. The production of mature and fertile spermatozoa from stem cells might provide an unlimited source of autologous gametes for treatment of male infertility. Here, we discuss the current state of the art regarding the differentiation potential of SSCs, embryonic stem cells, and induced pluripotent stem cells to produce functional male germ cells. We also discuss the possible use of livestock-derived PSCs as a novel option for animal reproduction and infertility treatment.

Hyposalinity stress compromises the fertilization of gametes more than the survival of coral larvae

The life cycle of coral is affected by natural and anthropogenic perturbations occurring in the marine environment. In the context of global changes, it is likely that rainfall events will be more intense and that coastal reefs will be exposed to sudden drops in salinity. Therefore, a better understanding of how corals-especially during the pelagic life stages-are able to deal with declines in salinity is crucial. To fill this knowledge gap, this work investigated how gametes and larva stages of two species of Acropora (Acropora cytherea and Acropora pulchra) from French Polynesia cope with drops in salinity. An analysis of collected results highlights that both Acropora coral gametes displayed the same resistance to salinity changes, with 4h30-ES50 (effective salinity that decrease by 50% the fertilization success after 4h30 exposure) of 26.6 ± 0.1 and 27.5 ± 0.3‰ for A. cytherea and A. pulchra, respectively. This study also revealed that coral gametes were more sensitive to decreases in salinity than larvae, for which significant changes are only observed at 26‰ for A. cytherea after 14 d of exposure. Although rising seawater temperatures and ocean acidification are often perceived as the main threat for the survival of coral reefs, our work indicates that 70% of the gametes could be killed during a single night of spawning by a rainfall event that decreases salinity to 26‰. This suggests that changes in the frequency and intensity of rainfall events associated with climate changes should be taken seriously in efforts to both preserve coral gametes and ensure the persistence and renewal of coral populations.

Acute hypoxic exposure affects gamete quality and subsequent fertilization success and embryonic development in a serpulid polychaete

Hypoxia likely compromises the reproductive success of those marine organisms carrying out external fertilization because their gametes and embryos are inevitably exposed to the external environment. Hydroides elegans, a dominant serpulid polychaete in Hong Kong waters, can spawn throughout the year but the number of recruits drops during summer when hypoxia commonly occurs. This study attempted to explain such observation by investigating the gamete quality, including sperm motility, egg size, complexity and viability, after 1-h hypoxic exposure (1 mg O2 l(-1)). In addition, how gamete quality affects fertilization success and embryonic development was examined. After 1-h hypoxic exposure, sperm motility was significantly reduced, compromising fertilization success. Although the eggs remained viable, more malformed embryos and retarded embryonic development were observed. We interpreted that the harmful effect of hypoxia on embryonic development was attributed to the teratogenicity and induced oxidative stress, ultimately causing the reduction in recruitment during summer.

5-Hydroxymethylation marks a class of neuronal gene regulated by intragenic methylcytosine levels

We recently identified a class of neuronal gene inheriting high levels of intragenic methylation from the mother and maintaining this through later development. We show here that these genes are implicated in basic neuronal functions such as post-synaptic signalling, rather than neuronal development and inherit high levels of 5mC, but not 5hmC, from the mother. 5mC is distributed across the gene body and appears to facilitate transcription, as transcription is reduced in DNA methyltransferase I (Dnmt1) knockout embryonic stem cells as well as in fibroblasts treated with a methyltransferase inhibitor. However in adult brain, transcription is more closely associated with a gain in 5hmC, which occurs without a measurable loss of 5mC. These findings add to growing evidence that there may be a role for 5mC in promoting transcription as well as its classical role in gene silencing.

The dynamic DNA methylation cycle from egg to sperm in the honey bee Apis mellifera

In honey bees (Apis mellifera), the epigenetic mark of DNA methylation is central to the developmental regulation of caste differentiation, but may also be involved in additional biological functions. In this study, we examine the whole genome methylation profiles of three stages of the haploid honey bee genome: unfertilised eggs, the adult drones that develop from these eggs and the sperm produced by these drones. These methylomes reveal distinct patterns of methylation. Eggs and sperm show 381 genes with significantly different CpG methylation patterns, with the vast majority being more methylated in eggs. Adult drones show greatly reduced levels of methylation across the genome when compared with both gamete samples. This suggests a dynamic cycle of methylation loss and gain through the development of the drone and during spermatogenesis. Although fluxes in methylation during embryogenesis may account for some of the differentially methylated sites, the distinct methylation patterns at some genes suggest parent-specific epigenetic marking in the gametes. Extensive germ line methylation of some genes possibly explains the lower-than-expected frequency of CpG sites in these genes. We discuss the potential developmental and evolutionary implications of methylation in eggs and sperm in this eusocial insect species.

Epigenetic effects of methoxychlor and vinclozolin on male gametes

Imprinting is an epigenetic form of gene regulation that mediates a parent-of-origin-dependent expression of the alleles of a number of genes. Imprinting, which occurs at specific sites within or surrounding the gene, called differentially methylated domains, consists in a methylation of CpGs. The appropriate transmission of genomics imprints is essential for the control of embryonic development and fetal growth. A number of endocrine disruptors (EDs) affect male reproductive tract development and spermatogenesis. It was postulated that the genetic effects of EDs might be induced by alterations in gene imprinting. We tested two EDs: methoxychlor and vinclozolin. Their administration during gestation induced in the offspring a decrease in sperm counts and significant modifications in the methylation pattern of a selection of paternally and maternally expressed canonical imprinted genes. The observation that imprinting was largely untouched in somatic cells suggests that EDs exert their damaging effects via the process of reprogramming that is unique to gamete development. Interestingly, the effects were transgenerational, although disappearing gradually from F1 to F3. A systematic analysis showed a heterogeneity in the CpG sensitivity to EDs. We propose that the deleterious effects of EDs on the male reproductive system are mediated by imprinting defects in the sperm. The reported effects of EDs on human male spermatogenesis might be mediated by analogous imprinting alterations.

Effect of parental hypoxic exposure on embryonic development of the offspring of two serpulid polychaetes: Implication for transgenerational epigenetic effect

Sperm production and motility, fecundity, and egg size, complexity and viability of serpulid polychaetes Hydroides elegans and Hydroides diramphus after 2-week treatment to hypoxia (2 mg O2 l(-1)) was compared with those under normoxia (6 mg O2 l(-1)). Despite reduced fecundity, the effect of parental hypoxic exposure on gamete quality was not discernible for both species. However, regardless of their subsequent dissolved oxygen environment, eggs spawned by H. elegans after hypoxic exposure were found to have lower fertilization success, slower embryonic development and a significantly higher yield of malformed embryos than those with a parental normoxic treatment. In contrast, neither fertilization success nor rate of embryonic development was affected for H. diramphus. The results implied that hypoxia was a potential stress reducing the recruitment of H. elegans through non-adaptive epigenetic effect, whereas H. diramphus was a more tolerant species to survive hypoxic events.

Environmental concentrations of irgarol, diuron and S-metolachlor induce deleterious effects on gametes and embryos of the Pacific oyster, Crassostrea gigas

Irgarol and diuron are the most representative "organic booster biocides" that replace organotin compounds in antifouling paints, and metolachlor is one of the most extensively used chloroacetamide herbicides in agriculture. The toxicity of S-metolachlor, irgarol and diuron was evaluated in Pacific oyster (Crassostrea gigas) gametes or embryos exposed to concentrations of pesticides ranging from 0.1× to 1000×, with 1× corresponding to environmental concentrations of the three studied pesticides in Arcachon Bay (France). Exposures were performed on (1) spermatozoa alone (2) oocytes alone and (3) both spermatozoa and oocytes, and adverse effects on fertilization success and offspring development were recorded. The results showed that the fertilizing capacity of spermatozoa was significantly affected after gamete exposure to pesticide concentrations as low as 1× of irgarol and diuron and 10× of metolachlor. The offspring obtained from pesticide-exposed spermatozoa displayed a dose-dependent increase in developmental abnormalities. In contrast, treating oocytes with pesticide concentrations up to 10× did not alter fertilization rate and offspring quality. However, a significant decline in fertilization success and increase in abnormal D-larvae prevalence were observed at higher concentrations 10× (0.1 μg L(-1)) for S-metolachlor and 100× for irgarol (1.0 μg L(-1)) and diuron (4.0 μg L(-1)). Irgarol, diuron and S-metolachlor also induced a dose-dependent increase in abnormal D-larvae prevalence when freshly fertilized embryos were treated with pesticide concentrations as low as concentration of 1× (0.01 μg L(-1) for irgarol or S-metolachlor, and 0.04 μg L(-1) for diuron). The two bioassays on C. gigas spermatozoa and embryos displayed similar sensitivities to the studied pesticides while oocytes were less sensitive. Diuron, irgarol and S-metolachlor induced spermiotoxicity and embryotoxicity at environmentally relevant concentrations and therefore might be a threat to oyster recruitment in coastal areas facing chronic inputs of pesticides.