Review: A barnyard in the lab: prospect of generating animal germ cells for breeding and conservation

In vitro gametogenesis (IVG) offers broad opportunities for gaining detailed new mechanistic knowledge of germ cell biology that will enable progress in the understanding of human infertility, as well as for applications in the conservation of endangered species and for accelerating genetic selection of livestock. The realisation of this potential depends on overcoming key technical challenges and of gaining more detailed knowledge of the ontogeny and developmental programme in different species. Important differences in the molecular mechanisms of germ cell determination and epigenetic reprogramming between mice and other animals have been elucidated in recent years. These must be carefully considered when developing IVG protocols, as cellular kinetics in mice may not accurately reflect mechanisms in other mammals. Similarly, diverse stem cell models with potential for germ cell differentiation may reflect alternative routes to successful IVG. In conclusion, the fidelity of the developmental programme recapitulated during IVG must be assessed against reference information from each species to ensure the production of healthy animals using these methods, as well as for developing genuine models of gametogenesis.

Efficacy and Safety of Paliperidone Palmitate 6-Month versus Paliperidone Palmitate 3-Month Long-Acting Injectable in European Patients with Schizophrenia: A Post Hoc Analysis of a Global Phase-3 Double-Blind Randomized Non-Inferiority Study

Purpose

To examine efficacy and safety of paliperidone palmitate (PP) 6-month (PP6M) vs PP3-month (PP3M) long acting injectable (LAI) in patients with schizophrenia from European sites previously stabilized on PP3M or PP1-month (PP1M).

Methods

This post-hoc subgroup analysis used data from a global phase-3 double-blind (DB) randomized non-inferiority study (NCT03345342). Patients were randomized (2:1, respectively) to receive dorsogluteal injections of PP6M (700 mg eq. or 1000 mg eq.) or PP3M (350 mg eq. or 525 mg eq.) in the 12-month DB phase. Primary endpoint was time-to-relapse during the DB phase, using a Kaplan-Meier cumulative survival estimate (non-inferiority margin 95% CI lower bound larger than prespecified as -10%). Treatment emergent adverse events (TEAEs), physical examinations, and laboratory tests were also evaluated.

Results

A total of 384 patients who entered the DB phase were included in European sites (PP6M, n = 260; PP3M, n = 124) with a mean age similar in both groups (mean age [SD] years: PP6M, 40.0 [11.39]; PP3M, 38.8 [10.41]). Baseline characteristics were similar across both groups. The number of patients who experienced a relapse during DB phase were PP6M: 18 (6.9%) vs PP3M: 3 (2.4%) with percentage relapse-free difference of -4.9% (95% CI: -9.2%, -0.5%), thus achieving non-inferiority criteria. Secondary efficacy endpoints indicated comparable improvements. Incidence of TEAEs was similar between PP6M (58.8%) and PP3M (54.8%) groups. Nasopharyngitis, headache, increased weight, and injection-site pain were the most common TEAEs.

Conclusion

The efficacy of PP6M was non-inferior to that of PP3M in preventing relapse in the European subgroup previously treated with PP1M or PP3M, which was consistent with the global study. No new safety signals were identified.

45 Embryonic disc development invitro in ovine embryos

Embryonic mortality during the second week of pregnancy has an important economic impact on farming. At this time, the embryo undergoes critical developmental events that cannot be recapitulated invitro, limiting our understanding of these pregnancy losses. After the blastocyst stage, the hypoblast migrates to cover the inner surface of the embryo and the epiblast forms a flat embryonic disc (ED) that initiates gastrulation. The aim of this study was to develop an invitro culture system to support sheep embryo development after the blastocyst stage. Day 6/7 invitro-produced blastocysts were cultured over agarose gels to prevent attachment and allocated to different media: synthetic oviductal fluid with 10% fetal bovine serum (SOF-FBS, n=52), an invitro culture medium (hIVC, n=35) supporting ED formation in human embryos (Deglincerti et al. 2016 Nature 533, 251-254; https://doi.org/10.1038/nature17948), and chemically defined N2B27 medium (n=38) supporting ED formation in bovine embryos (Ramos-Ibeas et al. 2020 Reproduction 160, 579-589, https://doi.org/10.1530/REP-20-0243). At Day 14, survival and embryo area were recorded, the abundance of transcripts encoding interferon Tau (TP1) and metabolic enzymes was analysed by RT-qPCR, and the development of epiblast and hypoblast was assessed by immunostaining for SOX2 and SOX17. Embryo survival and size and the percentage of embryos achieving complete hypoblast migration were significantly reduced in SOF-FBS (Chi-squared test and one-way ANOVA; P<0.05). Only N2B27 medium supported epiblast survival in 11/28 embryos. TP1 expression increased at Day 14 in all culture conditions and metabolism-related genes revealed a shift from anaerobic glycolysis to oxidative phosphorylation after culture in hIVC and N2B27. Next, to promote epiblast development, we allocated blastocysts to N2B27 medium supplemented with activin A (n=45), rho-associated protein kinase (ROCK) inhibitor (ROCKi, n=42), or insulin growth factor 1 (IGF1, n=29). IGF1 reduced significantly the percentage of embryos showing an ED-like structure, whereas activin A supplementation significantly increased epiblast survival (Chi-squared test; P<0.05) and SOX2+ cell number was higher in embryos cultured with ROCK inhibitor. When we combined activin A and ROCKi supplementation (N2B27+A+R, n=151), SOX2+ cell number and the percentage of embryos showing an ED-like structure increased significantly (165.1±53.1 and 31/35 embryos with SOX2+ epiblast cells; ∼89%) compared with N2B27 alone (49.4±12.7 and 5/11; ∼45%) (one-way ANOVA and Chi-squared test; P<0.05). Moreover, 18/31 (∼58%) ED-like structures developed in N2B27+A+R lost the Rauber’s layer (polar trophoblast), and BRACHYURY expression, denoting the onset of gastrulation, was observed in 3/14. In conclusion, we have developed a culture system that supports complete hypoblast migration and ED development invitro, which represents a valuable tool to explore early embryo mortality in livestock species without the need for experimental animals.

163 Treatment with gonadotrophin-releasing hormone at the time of AI in beef heifers that fail to express oestrus after an estradiol-based synchronisation protocol improves pregnancies per AI

Oestrus expression between progesterone (P4) withdrawal and fixed-time AI (FTAI) has been shown to improve pregnancies per AI (P/AI) by 27% in beef cattle. As a result, cattle that do not express oestrus after P4 withdrawal present a challenge to the efficiency of FTAI. The present study was designed to test the hypothesis that administration of gonadotrophin-releasing hormone (GnRH) at the time of AI in heifers that do not express oestrus can improve fertility. Two-year-old Angus heifers (n=1032) with a condition score of 2.75 to 3.5 at two locations in Argentina were used. On Day 0, heifers received an intravaginal device containing 0.5g of P4 (Cronipres, Biogenesis) and 2mg of oestradiol benzoate intramuscularly (Bioestrogen, Biogenesis). On Day 8, devices were removed and heifers received 150µg of d-cloprostenol intramuscularly (Enzaprost, Biogenesis), 0.5mg of oestradiol cipionate intramuscularly (Croni-Cip, Biogenesis), and an oestrus detection patch (Estrotect, Rockway Inc.). On Day 10, AI was performed in all heifers 50 to 54h after device removal. Heifers were categorised based on oestrus expression, and those that did not express oestrus were randomised to receive 100µg of gonadorelin acetate intramuscularly (Gonasyn, Syntex; n=158) concurrent with AI or remain as untreated controls (n=151). Pregnancy was determined using ultrasonography at Days 38 and 111 after AI. Differences in fertility were evaluated using generalised linear mixed models, and the results are shown in Table 1. Oestrus expression between device removal and FTAI was 70.1% (723/1032). Pregnancies per AI at Days 38 and 111 were different between groups (P<0.01). Heifers that expressed oestrus had greater P/AI than those that did not regardless of treatment (P<0.01). However, in heifers that did not express oestrus, treatment with GnRH at the time of AI resulted in greater P/AI than in control heifers (P=0.004). Similarly, P/AI at Day 111 were greater in heifers that expressed oestrus than in those that did not regardless of treatment (P<0.01). Heifers that did not express oestrus and were treated with GnRH had greater P/AI than those that did not express oestrus and remained as controls (P=0.02). Pregnancy loss between Days 38 and 111 was not different between groups; however, there was a tendency (P=0.06) for greater pregnancy loss in heifers that did not express oestrus and were treated with GnRH compared with heifers that expressed oestrus. In summary, treatment with GnRH at the time of AI is a suitable strategy to improve P/AI in heifers that fail to exhibit oestrus after an oestradiol-based synchronisation protocol. However, this strategy appears to increase pregnancy loss, and thus further research is needed to confirm this observation and the mechanisms underlying it. Table 1.Pregnancies per AI (P/AI) and pregnancy loss (%; no. in parentheses) in Angus heifers based on oestrus expression and treatment with GnRH Group P/AI Day 38 P/AI Day 111 Pregnancy loss Oestrus 68.9 (498/723)A 65.2 (471/723)A 5.4 (27/498) No oestrus control 29.8 (45/151)B 28.5 (43/151)B 4.4 (2/45) No oestrus + GnRH 45.6 (72/158)C 40.5 (64/158)C 11.1 (8/72) P-value <0.001 <0.001 0.15 A-CValues within a column with different superscripts differ significantly (P<0.05).

86 Difficulty of Transfer of In Vivo-Derived Bovine Embryos and Route of Administration of Flunixin Meglumine at the Time of Transfer may Affect Pregnancy Rate

Recipient handling during embryo transfer (ET) induces prostaglandin F2α (PGF2α) production in 2 periods: an early transient and rapid increase around the time of ET, followed by another 2 to 4 h later. This PGF2α is associated with embryonic loss during early gestation by affecting both the embryo and the corpus luteum. To control this, antiprostaglandins such as flunixin meglumine (FM) have been applied IM at the time of ET with varying results. In such studies, the interaction of IM administration of FM and difficulty of transfer has not always been evaluated, possibly confusing the interpretation of the results. Furthermore, IV FM injection at ET and its relationship with pregnancy rates (PR) has not been determined. The objectives were (1) to determine the relationship between difficulty of ET and PR; and (2) to evaluate the efficacy of IM v. IV FM on pregnancy outcomes. One hundred and ten crossbred (Bos taurus × Bos indicus) heifers (18-24 months old) from 3 farms were used as recipients. Two evaluation systems of ET difficulty were used: (1) duration of transfer (objective determination of the elapsed time measured in seconds between the introduction of the catheter and embryo release), and (2) level of difficulty experienced by the practitioner (subjective determination; 1 = minimum and 2 = medium to extreme manipulation). Quality 1 and 2 fresh embryos from superovulated cows were transferred by the same practitioner. At ET, recipients were randomly divided into 3 groups: (1) Control (no treatment, n = 31); (2) FM-IM (n = 39): injected IM with 2.2 mg kg−1 FM at ET; and (3) FM-IV (N = 40): injected with 2.2 mg kg−1 FM IV at ET. Pregnancy was diagnosed at 30 to 40 and 60 to 90 days after ET. Spearman’s test was performed to determine the correlation between duration and difficulty at ET and Chi-square test was used to compare PR. The mean duration of transfer for all heifers was 62.3 ± 57.5 s (11 to 357 s; median: 44.5 s). There was a high correlation (0.8; P < 0.001) between the ET difficulty evaluation systems. Overall, ET difficulty 1 had higher PR than ET difficulty 2 (64.2 v. 40.7; P = 0.013). The PR was significantly improved (P < 0.01) in the FM-IV group (75 and 70% at 30 and 60 days after ET) compared with control (45.2 and 32.3%) and FM-IM (33.3 and 30.7%). In conclusion, results indicate that the difficulty of transfer affects PR achieved following the transfer of in vivo-derived bovine embryos. Treatment with FM-IV following transfer resulted in significantly higher PR compared with control and FM-IM recipients. The IV injection of FM may antagonize the very early and transient increase of PGF2α caused by genital tract manipulation (even gently performed) at embryo transfer. Further research is necessary to confirm the results of the present study.

Epigenetics and developmental programming of welfare and production traits in farm animals

The concept that postnatal health and development can be influenced by events that occur in utero originated from epidemiological studies in humans supported by numerous mechanistic (including epigenetic) studies in a variety of model species. Referred to as the 'developmental origins of health and disease' or 'DOHaD' hypothesis, the primary focus of large-animal studies until quite recently had been biomedical. Attention has since turned towards traits of commercial importance in farm animals. Herein we review the evidence that prenatal risk factors, including suboptimal parental nutrition, gestational stress, exposure to environmental chemicals and advanced breeding technologies, can determine traits such as postnatal growth, feed efficiency, milk yield, carcass composition, animal welfare and reproductive potential. We consider the role of epigenetic and cytoplasmic mechanisms of inheritance, and discuss implications for livestock production and future research endeavours. We conclude that although the concept is proven for several traits, issues relating to effect size, and hence commercial importance, remain. Studies have also invariably been conducted under controlled experimental conditions, frequently assessing single risk factors, thereby limiting their translational value for livestock production. We propose concerted international research efforts that consider multiple, concurrent stressors to better represent effects of contemporary animal production systems.

Improve intra-uterine insemination in rabbits using ultra-high temperature skim milk as extender to keep semen at room temperature

Two experiments were carried out to examine in vitro quality and in vivo fertility of rabbit semen diluted in ultra-high temperature (UHT) skim milk. In the first experiment, pooled ejaculates of 10 adult rabbits were divided in three aliquots. Each aliquot was diluted in saline solution, TrisC or UHTm extender and kept at room temperature for 24 h. Sperm quality assessment was performed during all the incubation periods. In the second experiment, 27 adult rabbit does were inseminated with semen incubated for 5 h. Embryo recovery was performed 96 h after insemination. Results showed that treatments diluted in UHTm registered the highest values of spermatozoon with total motility, intact and functional plasma membrane and greater number of embryos recovered in rabbit does. We conclude that UHT skim milk would be a good extender for improved intra-uterine insemination in rabbits and to keep sperm cells for several hours at room temperature.

Vaginal histological changes after using intravaginal sponges for oestrous synchronization in anoestrous ewes

To characterize the histological and cytological vaginal changes generated by the use of intravaginal sponge (IS) applied in oestrous synchronization treatments in ewes during mid-non-breeding season. Thirty-five multiparous ewes were allocated to three experimental groups according to the moment in which the samples were taken: (i) ewes treated with IS containing 60 mg of medroxyprogesterone acetate for 14 days, sampled the day of IS removal (group ISR; n = 10), (ii) or after sponge removal at time of oestrus or 72 h after removal (group AR; n = 14) and (iii) ewes without sponge treatment that were sampled at the day of IS removal of the other groups (group CG; n = 11). Vaginal biopsies and cytological samples were taken from the anterior vaginal fornix area. The vagina of the CG group had a stratified squamous epithelium with a moderate degree of cellular infiltration with lymphocytes and plasma cells in the lamina propia. Treated ewes (ISR and AR) had epithelial hyperplasia and hypertrophy. ISR ewes had haemorrhage and perivascular infiltrate and an increased number of epithelial cells, neutrophils, macrophages and erythrocytes at IS removal. The use of IS generated histological and cytological alterations in the vaginal wall when used for oestrous synchronization in anoestrous ewes.

Recent advances in stem and germ cell research: implications for the derivation of pig pluripotent cells

Pluripotent stem cells have the unique capacity to contribute to all the tissues of an adult animal after transfer into a host embryo. How pluripotency is acquired during early development and how it is maintained in stem cells have attracted the interest of many scientists for over three decades. Much progress in our understanding of how stem cells arise in culture and the signals required for homoeostasis has enabled the derivation of pluripotent cells in multiple species. Here, we discuss recent developments in stem cell biology that will impact the generation of pluripotent cells from different embryonic origins and will contribute to increase our capacity for generating transgenic animals.

Changes in the aerobic vaginal bacteria load and antimicrobial susceptibility after different oestrous synchronisation treatments in goats

The objectives of this study were to determine (i) the variation in the bacterial population, (ii) the changes in the number of aerobic bacteria, and (iii) in vitro bacterial susceptibility to different antibiotics after the use of two different intravaginal devices (silicone devices or polyurethane sponges) for 6 or 11 days in goats. During the breeding season, 25 multiparous Saanen goats were randomly allocated to four treatments. Group IS-6 (n = 6) and Group IS-11 (n = 6) goats received a polyurethane intravaginal sponge (60 mg medroxyprogesterone acetate with oxytetracycline in powder) during 6 or 11 days, respectively. Goats from groups SD-6 (n = 7) and SD-11 (n = 6) received an intravaginal silicone device (0.3 g progesterone) during 6 or 11 days, respectively. Before the introduction of the devices, at device withdrawal, and the day of oestrus we performed standard bacteriological procedures on vaginal mucus samples. The predominant bacterial flora at device insertion was gram-positive (77%), and the most frequent strain was Bacilllus sp. The samples obtained on Day 6 [SD-6: 9/12 (75.0%); IS-6: 5/9 (55.5%)] and Day 11 [SD-11: 3/4 (75.0%); IS-11: 5/5 (100%)] were predominantly gram-negative, and the most frequently isolated bacteria was Arcanobacterium pyogenes. The total number of aerobic bacteria forming colony units (CFU/mL) was greater in goats treated with inert silicon device that those treated with intravaginal sponges (P = 0.028). On device removal (Days 6 and 11), we observed more CFU/mL than on device insertion. We observed no difference in CFU/mL on day of oestrus with respect to the day of device insertion (Day 0: 41.1 ± 19.3; Day 6: 187.1 ± 51.3; Day 11: 169.1 ± 27.8; day of oestrus: 20.1 ± 25.8 CFU × 103/mL; P < 0.05). The in vitro studies demonstrated that most samples were resistant to oxytetracycline. We concluded that the use of intravaginal devices, regardless of their composition, provoked an increase in the normal vaginal bacterial flora, but values returned to pre-insertion numbers by the day of oestrus. According to in vitro results, amoxicillin, ampicillin and streptomycin were the most effective antibiotics to prevent vaginal bacterial growth.

18 TOTAL PARENTERAL NUTRITION DURING NEONATAL CARE OF THE FIRST BITRANSGENIC FEMALE BOVINE CLONE

This work describes the treatment with total parenteral nutrition (TPN) of a 37-day cloned calf after suffering ruminal acidosis by ingestion of milk. Cells for SCNT were obtained by using a bicistronic vector for human lysozyme and lactoferrin. We obtained 7 embryos and 2 pregnancies. Only one fetus was born alive weighing 47 kg and it was presented to the neonatal unit of INTA showing a deep depression, diarrhoea, dehydration (10%), hyperthermia and inability to stand (Table 1). A 20-cm-length 20-Ga-diameter catheter (Arrow) was placed in the jugular vein. Blood samples from catheter and brachial artery showed leukocytosis, hypoglycemia and metabolic acidosis (Table 1). Esophageal tube was placed to remove 5 L of ruminal content and for the administration of 2 L of a solution of sodium bicarbonate (40 g L–1 of water). Saline (NaCl, 9 g L–1), sodium bicarbonate (8.4 g/100 mL) and 10% dextrose were administered IV until dehydration; blood pH and glucose were corrected. Ceftriaxone 1 g IM/12 h (Acantex, Roche) to prevent bacterial translocation, 1.175 mg of flunixin meglumine (PharmaVet) as anti-endotoxic dose and 80 mg of ranitidine IV/12h (Vetanco) to prevent laminitis were also administered. Two litres of bovine plasma were administered during the first 2 days and, after this, we began with a TPN regimen due to lack of sucking reflex and animal anorexia. Kabiven (Fresenius Kabi AV) was administered at 1 g of lipids/kg/24 h by a regimen of 18 drops min–1 to prevent hyperlipidemia at the recommended dose for humans. For this reason, we also administered dextrose 25% 12.5 drops min–1 and amino acids 11.5% 504 mL (Rivero), to reach a dose of 10 g/kg/24 h and 2 g/kg/24 h, respectively. Saline (NaCl, 9 g L–1) and vitamin complex (Rivial Paediatrics, Rivero) was also administered to cover water and vitamin requirements. The TPN therapy lasted 24 days during which the animal regularized its metabolic functions, reversed signs of ruminal acidosis and learned to eat a balanced ration and hay. To our knowledge, no information is available on such a long period of TPN in bovine neonates. This work shows that TPN can increase the survival chances of high risk animals and thus the final efficiency of cloning and transgenesis. Table 1.Clinical and haematological responses to 24-day total parenteral nutrition in a 37-day cloned female calf The authors thank Fresenius Kavi and Rivero Laboratories for their support.

The Sda/GM2-glycan is a carbohydrate marker of porcine primordial germ cells and of a subpopulation of spermatogonia in cattle, pigs, horses and llama

Spermatogonia are a potential source of adult pluripotent stem cells and can be used for testis germ cell transplantation. Markers for the isolation of these cells are of great importance for biomedical applications. Primordial germ cells and prepubertal spermatogonia in many species can be identified by their binding of Dolichos biflorus agglutinin (DBA). This lectin binds to two different types of glycans, which are α-linked N-acetylgalactosamine (GalNac) and β-linked GalNac, if this is part of the Sda or GM2 glycotopes. We used the MAB CT1, which is specific for the trisaccharides motif NeuAcα2-3(GalNAcβ1-4)Galβ1-, which is common to both Sda and GM2 glycotopes, to further define the glycosylation of DBA binding germ cells. In porcine embryos, CT1 bound to migratory germ cells and gonocytes. CT1/DBA double staining showed that the mesonephros was CT1 negative but contained DBA-positive cells. Gonocytes in the female gonad became CT1 negative, while male gonocytes remained CT1 positive. In immunohistological double staining of cattle, pig, horse and llama testis, DBA and CT1 staining was generally colocalised in a subpopulation of spermatogonia. These spermatogonia were mainly single, sometimes paired or formed chains of up to four cells. Our data show that the Sda/GM2 glycotope is present in developing germ cells and spermatogonia in several species. Owing to the narrower specificity of the CT1 antibody, compared with DBA, the former is likely to be a useful tool for labelling and isolation of these cells.

Effect of progesterone administration on the ovarian response to superovulatory treatments in cattle

To evaluate ovarian response in Angus cows previously treated with progesterone (P4), animals were randomly assigned to two groups: T600 group (n=14), 600 mg of P4/day. P4 was injected from days 3 to 7 of the estrous cycle. On day 7, superovulatory treatments began. The control group (n=12) was given vehicle only. The superovulatory treatments in the control group began on days 7-9 of the estrous cycle. The superovulatory total treatment dose of 400mg NIH FSH P1 was given twice a day over a 4-day period. Ultrasonography of the ovaries was conducted 3 days preceding the initiation of superovulatory treatment, every 24h. In both groups, an additional ultrasonographic evaluation was made at 24h after the end of superovulatory treatment. Blood samples were collected 4 days preceding the initiation of superovulatory treatment, every 24h. Additional samples were taken from the P600 group for 12 day after of initiation of superovulatory treatment every 24h, except on the fifth day after the initiation of superovulatory treatment. In the P600 group, P4 concentrations were greater than in the control group (P<0.01) and remained over 1 ng/ml up to day 11 after beginning of superovulatory treatment. The diameter of the dominant follicle was larger in the animals of the control group (P<0.01). Cows of the P600 group had a greater number of Class I (3-4mm) follicles (P<0.01). A significant day and treatment effect (P<0.01) were observed in Class II (5-9 mm) follicles. Effects due to treatment on the number of Class III follicles (P<0.05) were observed. In the P600 group, no estrous post-superovulatory was observed and there were no ovulations that occurred. Conversely, 100% of the cows of the control group showed estrous. In the P600 group, there were a greater number of Class III follicles (P<0.01) and a lesser number of Class II follicles (P<0.05) at 24h after the end of superovulatory. In the control group, 66.7% of the cows responded to superovulatory treatments. In conclusion, the daily administration of 600 mg of P4, from days 3 to 7 of the estrous cycle, produces an increase of plasma concentrations of this hormone from day 4, resulting in changes in follicular dynamics (absence of follicles greater than 10mm of diameter and an increase of the population of Class I follicles). As to the ovarian stimulation using Folltropin V in animals receiving a daily injection of 600 mg of P4 from days 3 to 7 of the estrous cycle, a greater population of follicles>or=10mm developed by 24h after superovulatory treatments were completed.

Timing of emergence of ovulatory follicles in polyovulatory goats

The current study characterized the timing of emergence of ovulatory follicles during the follicular phase of the estrous cycle in polyovulatory does and assessed whether selection may influence ovulation rate through differences in ovarian follicular dynamics, by characterizing preovulatory follicular emergence and growth in two ecotypes of Neuquen-Criollo Argentinean goats (Short-Hair, n=11 and Long-Hair, n=9). During the breeding season, the time of estrus was synchronized in all does with two doses of a prostaglandin analogue. Ovarian laparoscopies were performed on days 17 and 19 after the induced estrus (day 0) and 7-15 h after the beginning of the subsequent estrus. Results indicate that both ecotypes of goats have common features in the ovarian follicular population and in the patterns of preovulatory follicular enlargement. In all the goats, most of the preovulatory follicles arose from the pool of follicles present in the ovary between days 17 and 19 of the estrous cycle. These follicles were all larger than 2mm at emergence, being the largest growing follicle present in the ovaries on days 17 and 19 in 56.5 and 78.6% of the does, respectively. The appearance of new follicles remained unaffected, while the mean number of small growing follicles decreased (P<0.05) during the follicular phase, indicating that preovulatory follicles do not suppress the emergence of new follicles but inhibit the growth of small follicles. A separate analysis of single and double ovulating does showed that 75% of the second ovulatory follicles in polyovulatory goats was present on the ovarian surface between days 17 and 19 of the estrous cycle, but appeared later in the other 25% of the estrous cycles. These findings support the hypothesis that follicular dominance effects are exerted during the preovulatory period, when the growth of follicles other than the ovulatory is inhibited, and that increases in ovulation rate in small ruminants are related to a reduced incidence of follicular atresia and an extended period of ovulatory follicle recruitment.

45 NUCLEAR LAMIN A/C EXPRESSION IN BOVINE PARTHENOTES AND NUCLEAR TRANSFER EMBRYOS

Despite the apparent successes of nuclear transfer (NT) technology, numerous recent reports have indicated de-regulation of key gene expression patterns in NT embryos as compared to their in vivo and IVF counterparts. Aberrant expression of lamin A/C has been reported in mouse (Moreira et al. 2003 J. Cell Sci. 116, 3713-3720) and bovine (Sullivan et al. 2004 Biol. Rep. 70, 146-153) NT embryos, leading to the hypothesis that the presence of lamin A/C might affect subsequent development. Lamin A/C expression is a potential marker for reprogramming due to the induced expression and remodeling during differentiation. Previously using immunofluorescence in bovine IVF embryos, we have demonstrated the persistence of lamin A/C until the 2-cell stage (Kelly et al. 2005 Reprod. Fertil. Dev. 17, 205-206). The present study was initiated to further characterize lamin A/C expression in bovine parthenogenetic and NT embryos using a monoclonal antibody specific to lamin A/C. Bovine oocytes were matured in vitro as previously described (Fouladi-Nashta et al. 1998 Biol. Rep. 59, 255-262). NT embryos were constructed using lamin A/C-positive primary bovine fetal fibroblasts and in vitro-matured, enucleated MII bovine oocytes. Oocyte cell couplets were fused at 24 h post onset of maturation 1 h prior to activation. Oocyte activation was achieved with 7% ethanol for 7 min followed by a 6 h incubation in mSOF containing 10 �g/mL cycloheximide and 7.5 �g/mL cytochalasin B for the production of both NT and parthenogenetic embryos. Embryos were cultured in mSOF supplemented with 10% FCS and collected at various stages for immunofluorescence staining. Prior to fixation, embryos were incubated in 2 mg/mL protease to remove the zona pellucida. Samples were fixed in 100% methanol at -20�C for 20 min and then blocked for 1 h (4% goat serum in PBS) at RT. Embryos were then incubated overnight at 4�C with mouse anti-lamin A/C antibody (IgM; Santa Cruz Biotechnology, Santa Cruz, CA, USA) or with blocking solution as a control. Following the primary incubation, embryos were washed extensively in 1% BSA in PBS and then incubated with Cy3 goat anti-mouse IgM (1:400) (Chemicon International, Inc., Temecula, CA, USA) for 1 h at RT. Unbound secondary antibody was removed by washing with 1% BSA in PBS, and embryos were mounted in VectaShield mounting medium containing 42,6-diamidino-1-phenylindole (DAPI) (Vector Laboratories, Burlingame, CA, USA). Images were viewed using epifluorescence (Leica DMR; Leica Microsystems, Wetzlar, Germany) and confocal microscopy (Leica TCS). Inhibiting protein synthesis during the activation period with cycloheximide had no effect on lamin A/C assembly in 6 h post activation (hpa) parthenogenetic (35/35) and NT (7/7) embryos. The pronuclei of parthenogenetic (30/30) and NT (15/15) zygotes at 22 hpa were also positively labeled for lamin A/C. Nuclear labeling was observed in both parthenogenetic (25/25) and NT (12/12) 2-cell embryos. All parthenogenetic and NT embryos examined from the 4-cell stage through to blastocysts were stained negatively for lamin A/C. These results suggest that lamin A/C present in bovine NT zygotes is not due to aberrant reprogramming and that remodeling of the nuclear lamina occurs correctly in bovine NT embryos.

121 DEMETHYLATION OF MAMMALIAN SOMATIC DNA BY XENOPUS EGG AND OOCYTE EXTRACTS

In mammals, the successful development of live offspring by somatic cell nuclear transfer (SCNT) has demonstrated the ability of oocyte or egg cytoplasm to reprogram the differentiated status of somatic DNA. However, the efficiency of development is low, and this has been attributed to incomplete or inappropriate reprogramming of epigenetic status. One such epigenetic marker is methylation of genomic DNA at CpG islands. In SCNT, derived embryo abnormal DNA methylation patterns have been reported by a number of groups; in particular, it has been observed that the methylation pattern of embryonic cells resembles that of the donor cell (Santos et al. 2003 Curr. Biol. 13, 1116-1121). One strategy to improve reprogramming and, hence, development is to erase or reprogram the epigenetic status of the donor cell prior to nuclear transfer. We have previously reported that Xenopus egg and oocyte extracts show a differential effect on transcription. In oocyte extracts Pol I and II transcripts are maintained in the somatic cells; in egg extracts, these are abolished (Alberio et al. 2005 Exp. Cell. Res. 307, 131-141). To extend these studies, we have investigated the ability of oocyte and egg extracts to demethylate bovine somatic DNA. Preparation of Xenopus oocyte and egg extracts, culture, permeabilization of donor cells, and incubation conditions were all as previously described (Alberio et al. 2005 Exp. Cell. Res. 307, 131-141). Cells were incubated in extracts for 1 and 3 h at 21�C, centrifuged onto glass slides fixed in 4% Para formaldehyde for 15 min, followed by 4 M HCL for 1 h at 39�C, and blocked for 1 h. Cells were stained with mouse monoclonal anti-1MeC (1:50) overnight at 4�C followed by FITC-conjugated goat anti-mouse antibody (1:20) for 1 h at room temperature and mounted in Vectashied containing 10 �g of propidium iodide/mL. Nuclei were scored as positive or negative for 5MeC staining. In control cells, 90% of nuclei stained positively for 5MeC. In both oocyte and egg extracts the number of positive nuclei decreased with time showing demethylation of the somatic DNA 68 and 58% and 38 and 42% positive, respectively, after 1 and 3 h of incubation. Addition of apyrase (2%) to hydrolyze ATP inhibited demethylation in both extracts (90% nuclei positive). High rates of DNA replication were observed in somatic cells in egg extracts in contrast to no replication in oocyte extracts. Aphidicolin (1 �g/20 �L) was added to egg extracts to inhibit DNA replication, and under these conditions, DNA demethylation was abolished, suggesting a passive DNA demethylation mechanism as a result of DNA replication. In conclusion, Xenopus laevis oocyte and egg extracts can demethylate mammalian somatic DNA in an energy-dependent manner. In oocyte extracts, demethylation is independent of DNA replication, suggesting an active mechanism. In egg extracts, DNA replication is required, suggesting a passive mechanism. These studies further demonstrate the differences in reprogramming activities between oocyte and egg cytoplasm and suggest that interspecies extracts may provide a tool for nuclear reprogramming.

Cloning: Eight Years After Dolly

It is now 8 years since the birth of Dolly, the first animal produced by nuclear transfer using a donor cell population established from an adult animal. During this time, the technique of nuclear transfer has been successfully applied to a range of mammalian species for the production of offspring using a plethora of donor cell types derived from both foetal and adult tissues. In addition, when coupled with genetic manipulation of the donor cells, transgenic offspring have been produced with a range of genetic modifications including gene knockouts and gene knockings. Despite the apparent successes of the technology, the efficiency of development to live offspring has remained low and developmental abnormalities still occur. The objectives of this paper are to review some of the successes and failures of the nuclear transfer procedure since the production of Dolly. In particular, we will review the major steps in the procedure and discuss studies from our laboratory and others which have modified the procedure in ways which may impact on development.

Influence of different doses of progesterone treatments on ovarian follicle status in beef cows

To determine a dose of progesterone (P4) that allow ovarian follicular wave control, Aberdeen Angus cows were randomly assigned into four groups: T600 (n=5), 600 mg of P4/day; T400 (n=5), 400 mg of P4/day; T200 (n=4), 200mg of P4/day and Control (n=4) (excipient only). Progesterone was injected from day 3 to 9 of estrous cycle. Ultrasonographies and blood sample collections were performed daily from day 2 to 10 and on day 15 of the estrous cycle. Additionally, an ultrasonographic study was conducted on day 13. Progesterone concentrations were different among all groups (P<0.01). The diameter of the dominant follicle was greater for control than for T200, T400 and T600 groups (P<0.01); there was no difference between T200 and T400 (P>0.05), but they had a greater diameter follicle than the T600 group (P<0.01). The growth rate of the dominant follicle between day 3 and 7 of estrous cycle was greater for control group (1.63+/-0.3 mmday(-1)) than for T200 (0.56+/-0.19 mmday(-1), P<0.05), T400 (0.6+/-0.23 mmday(-1), P<0.05) and T600 (0.11+/-0.13 mmday(-1), P<0.01) groups. The mean number of class I follicles (3-4mm) per day for the entire experimental period was less for the control group than for T200 (P<0.05), T400 and T600 (P<0.01) groups (3.7+/-1.3; 5.3+/-1.3; 6.6+/-1.8 and 8.1+/-1.9, respectively). The mean number for the T200 group was less than for T600 (P<0.05) and similar for T400 and T600 groups (P>0.05). The number of class III follicles was greater for control group than for the other groups (P<0.01). T200 and T400 groups had similar numbers of class III follicles (P>0.05) and both had greater numbers of follicles than the T600 group (P<0.05). The diameter of the corpus luteum of the T600 group (15.8+/-1.6 mm) was less than for control (21.0+/-2.5 mm, P<0.01), T200 (19.3+/-2.7 mm, P<0.01) and T400 (20.0+/-2.2 mm) groups (P<0.05). The mean diameter of corpus luteum of T200 was similar to T400 (P>0.05), but different from the control group (P<0.05). In conclusion, the daily intramuscular administration of 200mg or more of progesterone from day 3 to 9 of the estrous cycle indicates that plasma concentrations of progesterone can be used to modify the pattern of follicular development during the follicular wave. From day 5 of the estrous cycle, progesterone concentrations greater than 15 ng/ml (T600 group: 600 mg/day of progesterone from day 3 to 9 of the estrous cycle) inhibit dominant follicle development, increase the class I follicle populations (3-4 mm) and diminish the development of the corpus luteum.

110 NUCLEAR LAMIN A/C EXPRESSION IN BOVINE IVF EMBRYOS

Lamin A/C expression is generally associated with terminally differentiated cell types; however, numerous conflicting reports in the literature demonstrate the presence of lamins A/C in pluripotent cells of pre-implantation embryos. This study characterized lamin A/C expression in bovine pre-implantation embryos using two monoclonal lamin A/C antibodies: anti-A/C IgM (A/C1) and anti-A/C IgG (A/C2) (Santa Cruz, California). Bovine embryos were produced as previously described (Fouladi-Nashta et al. 1998 Biol. Rep. 59, 255–262) and collected at various stages for immunofluorescence staining. Embryos were fixed in 100% methanol at −20°C for 20 min and then blocked for 1 h (4% goat serum in PBS) at RT. Samples were then incubated overnight at 4°C with mouse lamin A/C antibodies or with blocking solution as a control. Following the primary incubation, embryos were washed extensively in 1% BSA in PBS and then incubated with rabbit anti-mouse immunoglobulins (1:20) (DAKO, Denmark) for 1 h at RT. Unbound secondary antibody was removed by washing with 1% BSA in PBS, and embryos were counter-stained with 4',6-diamidino-2-phenylindole (2 μg/mL). Bovine fetal fibroblasts (BFF1) and human embryonic teratocarcinoma cells (EC1 and EC2) were processed identically to the embryos and used as positive and negative controls, respectively (Stewart and Burke 1987 Cell 51, 383–392). Images were viewed using epifluorescence (Leica DMR, Germany) and confocal microscopy (Leica TCS). BFF1 cells reacted with both lamin A/C1 and A/C2 antibodies. EC1 and EC2 stained positively for A/C2 whereas A/C1 was negative in both. All germinal vesicle (GV)-stage oocytes stained strongly for A/C2; however, for A/C1 only 67.5% were positive, and staining intensity was variable. Metaphase II oocytes stained negatively for both antibodies. One-cell zygotes exhibited a variable staining pattern similar to that of GV-stage oocytes. In contrast, all embryos from the 2-cell to blastocyst stage were negative for A/C1 but positive for A/C2. Our observations in embryos and EC cells indicate that the mouse anti-lamin A/C1 is specifically binding to lamin A/C whereas A/C2 is cross-reacting with other nuclear envelope proteins, possibly lamin B1/B2. The cross-reactivity of A/C2 has led to contradicting results in previous reports on lamin A/C expression in pre-implantation embryos. Our results with A/C1 show that lamin A/C is present in GV oocytes and 1-cell zygotes, suggesting that lamin A is important for pronuclear formation after fertilization. These results suggest that active remodelling of the nuclear envelope occurs during the early stages of bovine embryo development. RK is supported by a BBSRC postgraduate studentship. RA is a Marie-Curie Fellow.

Differential staining combined with TUNEL labelling to detect apoptosis in preimplantation bovine embryos

Development of accurate laboratory methods to assess embryo quality will improve the efficiency of embryo production from in-vitro culture systems. Currently, the techniques of TdT (terminal deoxynucleotidyl transferase)-mediated dUDP nick-end (TUNEL) labelling for the detection of apoptosis, and differential staining for determining the ratio of inner cell mass (ICM) to trophectoderm (TE) cells, are used separately to assess embryo quality in a range of different species. This paper reports a unique, simple and fast method for the assessment of embryo quality using differential staining of TE and ICM, but combined with TUNEL labelling (DST staining). This technique was used to investigate the effect of serum supplementation on total cell number, ICM:TE ratio and apoptosis index after in-vitro production of bovine embryos. Serum supplementation increased total cell number (P < 0.01), but reduced the ratio of ICM:TE cells. No differences were observed in the number of apoptotic nuclei between treatments, or in the localization of the apoptotic nuclei. However, more apoptotic nuclei were observed in ICM than TE cells in both culture groups. In conclusion, using DST, it has been possible to carry out both a qualitative and quantitative analysis of embryos produced using the two different methods. DST provides a means of assessing the effect of culture conditions on cell number of both embryo compartments (ICM and TE), as well as providing information on the localization of apoptotic nuclei within the blastocyst.

95 EFFECT OF ESTROUS COW SERUM ON SURVIVAL OF IN VITRO-PRODUCED BOVINE EMBRYOS AFTER SLOW FREEZING OR VITRIFICATION

Until now, the major obstacle associated with the extensive use of in vitro-produced bovine embryos is the lack of suitable methods to cryopreserve them. At least two approaches exist for overcoming this problem. One is to adjust cryopreservation methods to the requirements of these embryos, and the other is to improve embryo quality by using an appropriate in vitro environment for embryo production. The objective of this study was to determine the effect of estrous cow serum (ECS) during in vitro culture on embryo survival after cryopreservation by slow freezing or vitrification. Cumulus-oocytes complexes were in vitro-matured and fertilized as previously described (Ferre et al. 2003 Theriogenology 59, 301 abst). Presumptive zygotes were denuded from cumulus cells and cultured in groups of 50 in 400 μL drops of CR1aa medium. Seventy-two hour post-insemination (PI) embryos were randomly separated into three groups. Each group was then cultured in CR1aa + 5% ECS (without BSA; CR1-ECS), CR1aa + 3 mg/mL BSA (CR1-BSA), or CR1aa + 5% ECS + 3 mg/mL BSA (CR1-ECS-BSA). Embryos were cultured under 38.5°C, 5% CO2, 5% O2, and 90% N2. At 7.5 days PI, blastocysts from each group were double stained using propidium iodide and bisbenzimide (Hoechst 33342) to determine damaged cells and total cell number. The remaining embryos were randomly cryopreserved by freezing (1.5 M ethylene glycol; cooled at 0.5°C/min to −35°C) or vitrification (open pulled straw, Vajta et al. 1998 Mol. Reprod. Dev. 51, 53–58). After thawing or warming, embryos were cultured in CR1-ECS-BSA to evaluate embryo survival (hatching rate). Data were analyzed by χ2, ANOVA and Student's t-test (SAS Institute, Inc., Cary, NC, USA). Total cell number was higher in embryos cultured in CR1-ECS than in CR1-BSA or CR1-ECS-BSA (CR1-ECS: 142.1 ± 4.7, n = 23 vs. CR1-BSA 124.7 ± 4.9, n = 21, and CR1-ECS-BSA 125.8 ± 4.5, n = 25; t-test, P < 0.05). No differences were found in percent of damaged cells (CR1-ECS: 0.7%; CR1-BSA: 1.8%; CR1-ECS-BSA: 0.7%). Blastocyst survival after thawing was affected by cryopreservation methods and culture media (P < 0.01, Table 1). No interaction was found between both factors. In conclusion, under our experimental conditions elimination of ECS from CR1aa medium improves embryo cryotolerance. Vitrification allows for higher survival rates, regardless of the presence of serum during embryo culture. Table 1. Effect of cryopreservation method and serum supplementation during embryo culture on survival rate of in vitro-produced bovine embryos

Relationship between low-molecular-weight insulin-like growth factor-binding proteins, caspase-3 activity, and oocyte quality

Bovine follicular atresia is associated with the apoptosis of granulosa cells and the subsequent loss of oocyte competence through the reduction of cellular contact (e.g., gap junctions). Several components of the insulin-like growth factor (IGF) system are thought to affect follicular atresia. Whereas the IGF-binding proteins (IGFBPs) are present in varying quantities throughout follicular development, IGFBP-5 appears to be present only during atresia, in parallel with its regulation in other tissue remodeling systems. However, to our knowledge, no connection has yet been made between atresia, low-molecular-weight IGFBP content, and oocyte quality in the bovine ovary. Caspases are actively involved in ovarian follicular atresia, and apoptosis in antral follicles is caspase-3-dependent. Hence, the aim of the present study was to investigate the use of these factors in the assessment of oocyte quality and developmental potential. Oocytes were aspirated, morphologically classified, and individually matured in vitro. The follicular fluid and granulosa cells of these follicles were analyzed for IGFBP profile and caspase-3 activity, respectively. A significant correlation was found between the presence of low-molecular-weight IGFBPs in bovine follicular fluid and caspase-3 activity of granulosa cells isolated from individual follicles. The highest percentage of development to the blastocyst stage was observed in oocytes from slightly atretic follicles. This group of oocytes contained an equal proportion of oocytes at grades 1-3. These data demonstrate that low-molecular-weight IGFBP profile is a more reliable method than the traditional morphological assessment of oocytes and can be used as an effective marker of developmentally competent oocytes. Importantly, these results have implications for the use of noninvasive follicular fluid markers in the selection of competent oocytes to improve outcomes of in vitro fertilization.

54THE DEVELOPMENT AND CHARACTERIZATION OF MITOCHONDRIAL DNA (MTDNA)-DEPLETED CAPRA HIRCUS FETAL FIBROBLASTS: CANDIDATE DONORS FOR SOMATIC CELL NUCLEAR TRANSFER (SCNT)

Mammalian mtDNA is approximately 16.6kb in size. It has 37 genes, 13 of which encode protein subunits of the oxidative phosphorylation (OXPHOS) system, the major ATP-generating pathway of the cell. Normally, mammals inherit a single mtDNA genome (homoplasmy) from their mother. Somatic cell nuclear transfer (SCNT) violates this strict maternal, homoplasmic inheritance of mtDNA as cytoplasm is transferred along with the nucleus, which often results in an oocyte harboring both donor and recipient mtDNA genomes (heteroplasmy). This been previously reported (reviewed St. John JC 2002 Theriogenology 57, 109–123). To overcome the problem of donor mtDNA transmission, we have developed and characterized mtDNA-depleted C. hircus (goat) cells for use as donors in SCNT. C. hircus primary foetal fibroblast cells were established in culture and depleted of their mtDNA by supplementing their growth medium with a low concentration, 50ngmL−1, of ethidium bromide (EthBr). Conventional PCR, using a series of primers designed specifically for goat mtDNA, was used to screen for the presence of mtDNA during the EthBr treatment. In addition, mitochondrial organization, activity and morphology in the cells were analyzed using the mitochondrial specific fluoroprobe JC1. mtDNA-encoded and mitochondrial transcription factor A (mtTFA) transcript levels were analysed using RTPCR. Furthermore, both mtDNA depleted and non-depleted cells were characterised using immunocytochemistry to detect the expression of specific protein subunits of the OXPHOS system. Progressive mtDNA depletion was observed, using conventional PCR, in cells treated for 3 to 25 days with EthBr, while 42 days of culture resulted in complete depletion. RTPCR showed a progressive reduction followed by complete elimination of the mtDNA-encoded ND1, ND2, ND3, COX I and mtTFA transcripts. In addition, the expression of mtDNA-encoded protein subunits, e.g. COXI, of the OXPHOS system were reduced following mtDNA depletion whereas the expression of nuclear-DNA encoded protein subunits, e.g. COXVic, were unaltered. We hypothesize that the elimination of mtDNA and mtDNA transcripts from the donor cells will facilitate normal mtDNA replication and transcription in SCNT embryos, thus maintaining the strict unimaternal transmission of mtDNA to the offspring. Consequently, genetically identical offspring will be generated which have identical nuclear and mitochondrial DNA content, assuming oocytes from the same ovary are used. This technique is important for the generation of offspring for the livestock industry and animal models for the analysis of single gene disorders as well as the propagation of endangered species.

151A SIMPLE AND FAST METHOD FOR CONCURRENT DIFFERENTIAL STAINING AND TUNEL LABELLING OF BOVINE BLASTOCYSTS

Currently techniques of TUNEL labelling for detection of apoptosis and differential staining for counting the ratio of inner cell mass (ICM) to trophoectoderm (TE) cells are used separately for assessment of embryo quality in different species. The majority of these techniques are antibody-based, and time-consuming, frequently giving inconsistent results. Here we report on the development of a simple and fast method for simultaneous differential staining and TUNEL labelling of bovine embryos. Cleaved embryos produced from in vitro-matured and fertilized oocytes were cultured to the blastocyst stage in synthetic oviductal fluid culture medium (SOF) supplemented with 4mgmL−1 BSA and 5% FCS. Embryos were partially permeabilized in 0.5% Triton X-100 solution containing 2μMmL−1 TOTO-3 dye (Molecular Probes, Eugene, OR, USA) for 30s. TOTO-3 is a cell-impermeant nucleic acid dye; thus only permeabilized cells are stained red. The embryos were then quickly washed in PBS containing 3mgmL−1 PVA, fixed for 15min at RT in 4% paraformaldehyde containing 10μgmL−1 Hoescht, and TUNEL-labelled using a Cell Death Kit (Roche Applied Science, East Sussex, UI) for 30min at 37°C in a humid chamber. The embryos were then treated with RNase A (50UmL−1) for 30min at 37°C, washed and mounted in a small drop of glycerol on a glass slide. RQ1-DNase (3UmL−1)-treated embryos were used as a positive control. After three-dimensional reconstruction using a Leica TCS SP2 confocal microscope, we determined the number of ICM (blue), TE (red) and apoptotic nuclei (green). Only peripheral cells of the blastocysts were labelled red, indicating that TE cells were permeabilized by the short exposure to the detergent Triton. ICM cells were consistently stained blue by the cell permeant dye Hoechst. Apoptotic nuclei were found in both types of cells. More consistent differential staining was observed in hatched blastocysts (n=30) than in zona-enclosed blastocysts (n=35); also, more apoptotic nuclei were observed. No differences were found in the consistency of the technique for embryos grown with or without FCS. When compared to dual staining without Tunel, no differences in cell number (74±22) , and ICM/TE ratio (0.28±0.06) were detected, indicating that the Tunel procedure does not affect the labeling of the DNA. Preliminary observations also indicate that this method can be successfully applied to porcine and ovine embryos. This technique has the advantage of being fast and can be applied for assessment of embryo quality. It can also be used to determine the time and origin of ICM and TE differentiation while monitoring the degree of apoptosis in different culture systems and in different species. This work was in part supported by Department of Environment Food and Rural Affairs (Defra) UK.

23REPROGRAMMING MAMMALIAN CELLS IN XENOPUS EGG EXTRACTS: ROLE OF EMBRYONIC LAMIN B3

The generation of animals by nuclear transplantation has demonstrated that a fully differentiated cell can be reversed into totipotency when transferred into an oocyte. Identification of oocyte specific molecules responsible for the reprogramming of somatic cells may contribute to the understanding of cell differentiation and embryo development. We have developed a heterologous system to investigate the effect of lamin B3, a major component of Xenopus laevis egg cytoplasm, on DNA replication of mammalian somatic cells. Bovine fetal fibroblasts were arrested at G1/S by incubation in aphidicolin for 18h. After permeabilization with digitonin, the cells were incubated in either (1) lamin B3 depleted, or (2) whole Xenopus egg extracts (1000 cells μL−1 extract) supplemented with an energy regenerating system for a period of 3h at 21°C. Xenopus lamin B3-depleted egg extracts were prepared by three rounds of incubation with Dynabeads coated with a mouse monoclonal lamin B3 antibody (mAbLB3). Immunodepletion was confirmed by western blotting. Purified lamin B3 was obtained by dialysis of the beads after immunodepletion, and the purified lamin B3 was used for rescue experiments. DNA replication of cells incubated in the extracts was assessed by adding 25μM Biotin-11-dUTP for 3h. After treatment cells were fixed in 70% methanol at −20°C and incubated in mAbLB3 for 30min at 37°C. This was followed by incubation in FITC-conjugated sheep anti-mouse antibody and in 5mgmL−1 Texas Red-conjugated Streptavidin for 40min at 37°C. After three hours’ incubation in egg extracts, DNA replication was detected in 60% of cells and more than 95% of cells were lamin B3 positive. In contrast, DNA replication in immunodepleted extracts was significantly lower (P≤0.01, by one-way ANOVA) than in cells incubated in whole extracts and was coincident with the few lamin B3-positive cells observed. More than 95% of cells were lamin B3-negative and did not replicate DNA. When purified lamin B3 was re-added to depleted extracts, DNA replication was detected in 60% of cells. DNA synthesis resumed in 93% of control cells 3h after release from aphidicolin into culture medium at 39°C. These experiments show that somatic nuclei, which possess a nuclear envelope with somatic variants of lamins, are able to synthesize DNA in egg extracts only when Xenopus lamin B3 is incorporated into the nuclear envelope. This heterologous system provides new information on the role of an embryonic molecule, namely Xenopus lamin B3, in the reprogramming of DNA replication of somatic cells incubated in egg environment. These results open new questions as to whether embryonic lamins also exist in mammals, and whether failure in development of cloned animals is in part due to abnormal or incomplete replacement of somatic variants of proteins with their embryonic counterparts.

6ACETYLATION OF HISTONE H4 LYSINE-5 AND LYSINE-8 DURING DEVELOPMENT OF IN VITRO-PRODUCED BOVINE EMBRYOS

The oocyte is remarkable in its ability to remodel the parental genomes following fertilization and to reprogram somatic nuclei as in nuclear transfer. While significant research has been carried out on DNA methylation patterns in the early embryo, increased interest in histone acetylation is more recent. The objective of this study was to characterize the pattern of acetylation of histone H4 lysine-5 (H4L5) and lysine-8 (H4L8) in the early pre-implantation bovine embryo. Bovine embryos were produced as previously described (Fouladi Nashta AA et al., 1998 Biol. Rep. 59, 255–262) and collected at different developmental stages, 1-cell (20h), 2-cell (30h), 4- and 8-cell (Day 2), 16-cell (Day 4), and blastocyst (Days 7–8) with an average of 6 embryos per group in two replicates. Embryos were fixed in 2.5% paraformaldehyde, 15min at room temperature (RT), stained with polyclonal rabbit antibodies against H4L5 (1:800) and H4L8 (1:600) residues (Serotec, UK) at 4°C overnight. A polyclonal swine anti-rabbit (1:200; Dako, Denmark) was used as secondary antibody for 40min at RT. Images were examined using a fluorescent microscope (Leica DMR, Germany). Image analysis and quantification were performed using Simple PCI software (Compix Imaging Systems, USA). Changes in intensities within and between different embryo stages were recorded as a ratio of red stain to blue counterstain. Data were corrected for confounding area and absorbance and analysed using a multivariate linear regression model. The intensity of staining for H4L5 appeared higher in 8-cell embryos than 2- and 4-cell embryos but not to a significant level (P≥0.05); 8-cell embryos also appeared higher in stain intensity than 16-cell but of borderline significance (P=0.073). Staining intensity decreased between the 8-cell and blastocyst stage (P≤0.05). In contrast, the intensity of acetylation staining for H4L8 residue decreased slightly between the 1- and 4-cell stages and then decreased significantly between the 4- and 8-cell stages (P≤0.05), increasing significantly by the 16-cell stage (P≤0.05). A significant decrease in staining intensity was observed at the blastocyst stage (P≤0.05). In blastocyst-stage embryos both lysine-5 and lysine-8 showed a differential staining of inner cell mass (ICM) and trophectoderm (TE) cells. ICM cells showed intense staining and TE cells stained very weakly. The intensity results presented are cumulative of ICM and TE intensities, which explains the overall low levels of acetylation in blastocysts when compared to the earlier stages. Acetylation of H4L5 starts high in 1-cell embryo, as it is necessary for protamine replacement (Adenot et al., 1997 Development 124, 4615–4625), decreases when methylation is high and increases when methylation is low (as in the 8-cell stage which corresponds with zygotic gene activation). Acetylation of H4L8 decreases between the 1-and 8-cell stages; however, its association with changes in DNA methylation has yet to be determined.

Reprogramming the genome: role of the cell cycle

In nuclear transfer reconstructed embryos, the co-ordination of donor nuclear and recipient cytoplasmic cell cycle phases is essential to maintain ploidy and prevent DNA damage. However, the stage of the cell cycle at the time of reconstruction and the method of reconstruction may also have a significant impact on the subsequent development of the embryo and fetus through a number of other mechanisms. This paper reviews some of the information currently available and proposes that consideration of the cell cycle may lead to improvement of methods for embryo reconstruction.

Nuclear transfer in practice

The technique of nuclear transfer (NT) allows the production of embryos, fetuses, and offspring from a range of embryonic, fetal, and adult derived cell types in a range of species. Successful development is dependent upon numerous factors, including type of recipient cell, source of recipient cell, method of reconstruction, activation, embryo culture, donor cell type, and donor and recipient cell cycle stages. The present review will discuss the uses of NT, the techniques presently available, and the factors affecting subsequent development.

Accumulation of the proteolytic marker peptide ubiquitin in the trophoblast of mammalian blastocysts

Ubiquitination is a universal protein degradation pathway in which the molecules of 8.5-kDa proteolytic peptide ubiquitin are covalently attached to the epsilon-amino group of the substrate's lysine residues. Little is known about the importance of this highly conserved mechanism for protein recycling in mammalian gametogenesis and fertilization. The data obtained by the students and faculty of the international training course Window to the Zygote 2000 demonstrate the accumulation of ubiquitin-cross-reactive structures in the trophoblast, but not in the inner cell mass of the expanding bovine and mouse blastocysts. This observation suggests that a major burst of ubiquitin-dependent proteolysis occurs in the trophoblast of mammalian peri-implantation embryos. This event may be important for the success of blastocyst hatching, differentiation of embryonic stem cells into soma and germ line, and/or implantation in both naturally conceived and reconstructed mammalian embryos.

Nuclear transfer in cattle with non-transfected and transfected fetal or cloned transgenic fetal and postnatal fibroblasts

The efficiency of nuclear transfer (NT) using two primary cultures of fetal fibroblasts (FF1 and FF2) was compared vs. the same cultures transfected with an expression vector in which the bovine prochymosin coding sequence is placed under the control of the bovine alpha(S1)-casein promoter (TFF1 and TFF2). In addition, fibroblasts of a cloned transgenic fetus (TRFF1) derived from TFF1 and ear skin fibroblasts of a 1-month-old cloned transgenic calf (TRCF1) derived from TRFF1 were used as nuclear donors. Embryos reconstructed from FF1 (44%) and FF2 (52%) developed to the blastocyst stage at a significantly (P < 0.05) higher rate than those derived from TFF1 (24%) and TFF2 (27%). The proportions of cleaved embryos and blastocysts were significantly (P < 0.05) higher with TRFF1 than with TRCF1 used as nuclear donors (75 vs. 66% and 33 vs. 16%, respectively). Transfer of NT embryos derived from FF2 and TFF2 to recipients resulted in similar pregnancy rates on day 30 (52 and 48%, respectively). However, with TFF2 embryos, the majority of pregnancies (8/11; 73%) was lost in the first and second trimesters of gestation, whereas 4/11 (36%) pregnancies with FF2 embryos were lost during the full period of in vivo development. Of 11 FF2 and 6 TFF2 born calves (25 and 13% of transferred embryos, respectively), 6 and 3 survived including one oversized FF2 calf. After transfer of TRFF1 and TRCF1 NT embryos to recipients, initial pregnancy rate was as a tendency higher in the TRFF1 (49%) than in the TRCF1 group (30%). The majority (14/17) of TRFF1 pregnancies and all TRCF1 pregnancies were lost in the first and second trimester. A high proportion of TRFF1 calves (5/8) showed increased body weights, and only two calves which were also large survived. These findings demonstrate that (i) extended culture associated with transfection and selection procedures may induce changes of donor cells which markedly decrease the efficiency of nuclear transfer and (ii) these changes are not reversed by recloning.

Mammalian oocyte activation: lessons from the sperm and implications for nuclear transfer

Events after fertilisation have been carefully studied in the last decades. However, there are still several questions to be clarified in relation to the signalling pathway initiated by the sperm, the identification of proteins or factors involved in the activation of the arrested oocyte, and the inactivation of specific molecules involved in the meiotic arrest. The present state of knowledge in mammalian fertilisation allows the development of activation protocols that closely mimic the events initiated by the sperm according to certain major factors (MPF activity and MAPk activity). These protocols are successfully used for the activation of oocytes after NT giving rise to offspring. Few cloned animals have yet been produced. However, the pregnancy and the survival rates after birth are not significantly different when different activation protocols are compared. This fact argues fora major reason forthe low success in the efficiency of NT. Eventually, factors related to the recipient oocyte, the donor cell or the culture conditions are part of these major problems that the reconstructed embryo has to overcome to develop into a normal offspring. Nonetheless, the development of activation protocols that closely imitate the mechanism of activation initiated by the sperm are of special interest to improve the developmental potential of cloned embryos.

Remodeling of donor nuclei, DNA-synthesis, and ploidy of bovine cumulus cell nuclear transfer embryos: effect of activation protocol

The purpose of this study was to investigate the effects of two activation protocols on nuclear remodeling, DNA synthesis during the first cell cycle, chromosome segregation after first mitosis and development to blastocyst of embryos produced by somatic nuclear transfer. Pronuclear formation was significantly higher when activation lasted 5 hr compared to 3 hr for both ethanol-cycloheximide and ionomycin-bohemine treatment. However, the presence of a single nucleus was significantly higher in embryos activated for 3 hr in bohemine. Initiation of DNA synthesis was delayed in ethanol-cycloheximide group, however, after 12 hr labeling 100% of embryos synthesized DNA in both groups. Embryos activated with ethanol-cycloheximide developed to blastocysts at a significantly higher rate than those activated with ionomycin-bohemine. Analysis of 2-cell embryos with DNA probes for chromosome 6, 7, and 15 by fluorescence in situ hybridization showed that at least 50% of NT embryos were of normal ploidy independent of the activation stimulus. The results presented in this study show differences between the protocols compared on the nuclear events during the first cell cycle and on the development to blastocyst. Mol. Reprod. Dev. 59: 371-379, 2001.

Intracytoplasmic sperm injection in bovine: effects of oocyte activation, sperm pretreatment and injection technique

Intracytoplasmic sperm injection (ICSI) is a very important technique for treating male subfertility and for basic research. The efficiency of ICSI in bovine is very limited because of the necessity for additional oocyte activation before or after the ICSI procedure. In this study, we compared the effects of seven different protocols on activation and fertilization rates of bovine oocytes after ICSI and on their subsequent development under in vitro conditions. The protocols include 1) different chemical activation of oocytes, 2) pretreated or nonpretreated sperm, and 3) conventional or Piezo-driven injection techniques. In all three groups, ICSI, sham-injected, and noninjected, the highest activation rates were obtained after treatment of oocytes with ionomycin followed by 6-dimethylaminopurine (6-DMAP). Using this treatment for oocyte activation, 59% of oocytes were activated and 31% of oocytes were fertilized using dithiothreitol (DTT) pretreated spermatozoa and Piezo-driven injection. Using the protocols with the same oocyte activation or activation with calcium ionophore (Ca-I) and cycloheximide (CHX), nonpretreated sperm, and conventional injection technique, early cleavage rate (79.6% and 77.6%, respectively) were significantly (P <0.01) higher when compared with all other protocols. The latter protocol resulted in 8% blastocyst and 90% of the obtained blastocysts were found to be diploid. Our results demonstrate that activation of oocytes, sperm treatment, and injection technique separately or together could improve the success of bovine ICSI.

Behavior of M-phase synchronized blastomeres after nuclear transfer in cattle

M-phase synchronized bovine blastomeres were used to study the effect of nuclear-cytoplasmic synchronization on the developmental potential after nuclear transfer (NT). The capacity of nocodazole and benomyl to reversibly synchronize blastomeres from embryos in M-phase was evaluated. Nocodazole reversibly arrested bovine embryos at the studied stages and induced high rates of M-phases in morulae and compact morulae. In contrast, benomyl was less efficient than nocodazole to synchronize in M-phase. After transfer of an M-phase blastomere, premature chromatin condensation was the prevalent finding 1 hr post-fusion (hpf). Condensed chromosomes non-arranged in the equatorial plate (1-3 hpf) that acquired an organized structure over time (3-7 hpf) were subsequently observed. Anaphase-telophase structures were predominantly recorded at 4-9 hpf. About 50% of the embryos activated at both 3-4 and 6-7 hpf extruded a polar body-like structure 5 hr after activation, but this was not observed in embryos activated immediately after fusion. A significantly lower activation rate was observed for oocytes activated 3-4 hpf compared to those activated 6-7 hpf. However, the ability to undergo first cleavage was significantly lower in the latter group. Reconstructed embryos activated immediately after fusion showed no difference in the rate of activation compared to those activated 6-7 hpf, although the cleavage rate was higher. DNA synthesis was observed at a significantly higher rate in embryos activated both immediately and 3-4 hpf that did not extrude a PB-like structure than in those activated 3-4 hpf that extruded a polar body-like structure. Under the conditions tested M-phase donor cells cannot be properly remodeled after NT in cattle to trigger normal embryonic development. Our observations of chromatin structures together with DNA synthesis suggest that the failure in the development may be due to improper chromatin remodeling of mitotic nuclei after NT, which may result in chromosomal abnormalities incompatible with normal embryo development.

Activation of bovine oocytes by specific inhibition of cyclin-dependent kinases

Activation of bovine oocytes by experimental procedures that closely mimic normal fertilization and allow to obtain haploid oocytes is essential both for intracytoplasmic sperm injection (ICSI) and for nuclear transfer. Therefore, with the goal of producing haploid activated oocytes, this study evaluated whether bohemine, either alone or in combination with ionomycin, is able to activate young matured bovine oocytes. Furthermore, the effect of bohemine on the patterns of DNA synthesis after pronuclear formation as well as changes in histone H1 kinase and MAP kinase activities during the process of activation were studied. Our results with bohemine show that the specific inhibition of CDKs in metaphase II bovine oocytes induces parthenogenetic activation in a dose-dependent manner (25, 50, and 100 microM, respectively), either alone (3%, 30%, and 50%) or in combination with ionomycin (30%, 70%, and 87.5%). A single pronucleus and extrusion of the second polar body was observed (97%) when Ca(2+) influx was stimulated in the presence of bohemine, although pronuclear formation without polar body extrusion was observed when bohemine was used alone. Bohemine-activated oocytes started to synthesize DNA in the first hour (37%) after their removal from bohemine-supplemented medium (6-7 hr post-activation; hpa). A high synchrony in the S-phase was registered with more than 85% of parthenotes actively synthesizing DNA 8 hpa. By contrast, DNA synthesis was absent in oocytes cultured for 4, 6, and 8 hpa in the presence of bohemine and a low rate was observed by those cultured for 18 hr (30%) in bohemine-supplemented medium. This confirms the ability of the inhibitor to arrest the cell cycle in the G1/S boundary for at least 8 hr. A drop in histone H1 kinase activity was observed in bohemine-activated oocytes. The activity of MBP kinase decreased later than histone H1 kinase and even 4 hr after inomycin-bohemine treatment at least half of this activity was still detectable. Then, the MBP kinase activity decreased and the lowest level could be seen 6-8 hpa. In summary, our study shows that in vitro matured bovine oocytes can be successfully activated by a synthetic inhibitor of CDKs. This effect can be improved by combination with ionomycin. The targeting of CDKs in the way to activate bovine oocytes can be an approach to improve the efficiency of mammalian oocyte activation.

Adult cloning in cattle: potential of nuclei from a permanent cell line and from primary cultures

Nuclear transfer was used to evaluate the developmental potential of nuclei from a spontaneously immortalized bovine mammary gland epithelial cell line (MECL) and from primary cultures of mammary gland cells (PMGC) and ear skin fibroblasts (PESF) established from 3-year-old cows. Cell proliferation was investigated by incorporation and detection of 5-bromo-2'-deoxyuridine (BrdU). The proportion of cells in S-phase was significantly (P < 0.05) higher for MECL cells than for PMGC and PESF, both in the presence of serum (90% vs. 28% and 15%) and following serum starvation (27% vs. 6% and 3%). Nuclei from PESF supported the development of reconstructed embryos to the blastocyst stage significantly better than those of PMGC (60% vs. 26%; P < 0.05). Embryos reconstructed with cells from MECL failed to develop to blastocysts. After transfer of embryos derived from PMGC and PESF, respectively, 2/2 and 5/12 recipients were pregnant on day 42. On day 90, the corresponding pregnancy rates were 2/2 and 3/12. One live calf derived from a PMGC was born at day 287 of gestation. Another live PESF-derived calf was delivered by caesarean section at day 286 of gestation. Our study suggests that nuclei from primary cultures of adult cells can be successfully reprogrammed by nuclear transfer, whereas nuclei from a permanent cell line failed to support the development of nuclear transfer embryos.

Pubertal traits and seasonal variation of the sexual activity in Brahman, Hereford and crossbred heifers

Age and weight at puberty and the pattern of ovulatory activity from puberty to 26 mo of age were studied in a total of 55 Brahman (B), Hereford (H), 5/8B-3/8H (B(5)H(3)) and 5/16B-11/16H (B(5)H(11)) heifers. The trial was conducted over two years. Heifers were kept during the whole experimental period on a paddock of native pasture at a stocking rate of 0.5 animals per hectare. Vasectomized bulls were used for estrus detection and blood was collected from the heifers twice weekly to monitor ovulatory activity through progesterone level as determinated by RIA. In addition to age and weight at puberty, the weights and dates at the time of cessation and resumption of ovulatory activity were also considered. There were significant effects (P<0.05 or P<0.01) of genetic group (purebreds vs crossbreds) for age and weight at puberty; the difference being 60 d and 18 kg, respectively, favoring the crossbred groups. After puberty attainment, an anestrous period was detected in all Brahman (118.6 d) and B(5)H(3) (113.4 d) heifers; anestrus was observed in only 14% of B(5)H(11) heifers and for a shorter (43.5 days) period. Hereford heifers did not exhibit interruption of ovulatory activity. In Brahman and B(5)H(3) heifers, the pattern of interruption and resumption of estrus and ovulatory activity correlated closely (0.89 and 0.95 for Brahman and B(5)H(3) heifers, respectively) with the photoperiod curve, suggesting the probable influence of this environmental factor on the regulation of estrous cycle activity in heifers with a higher proportion of Bos indicus genes. Thus, the genetic factor needs be taken into account when establishing programs in reproductive management.