CRISPR/Cas9-mediated generation of biallelic F0 anemonefish (Amphiprion ocellaris) mutants.

Genomic manipulation is a useful approach for elucidating the molecular pathways underlying aspects of development, physiology, and behaviour. However, a lack of gene-editing tools appropriated for use in reef fishes has meant the genetic underpinnings for many of their unique traits remain to be investigated. One iconic group of reef fishes ideal for applying this technique are anemonefishes (Amphiprioninae) as they are widely studied for their symbiosis with anemones, sequential hermaphroditism, complex social hierarchies, skin pattern development, and vision, and are raised relatively easily in aquaria. In this study, we developed a gene-editing protocol for applying the CRISPR/Cas9 system in the false clown anemonefish, Amphiprion ocellaris. Microinjection of zygotes was used to demonstrate the successful use of our CRISPR/Cas9 approach at two separate target sites: the rhodopsin-like 2B opsin encoding gene (RH2B) involved in vision, and Tyrosinase-producing gene (tyr) involved in the production of melanin. Analysis of the sequenced target gene regions in A. ocellaris embryos showed that uptake was as high as 73.3% of injected embryos. Further analysis of the subcloned mutant gene sequences combined with amplicon shotgun sequencing revealed that our approach had a 75% to 100% efficiency in producing biallelic mutations in F0 A. ocellaris embryos. Moreover, we clearly show a loss-of-function in tyr mutant embryos which exhibited typical hypomelanistic phenotypes. This protocol is intended as a useful starting point to further explore the potential application of CRISPR/Cas9 in A. ocellaris, as a platform for studying gene function in anemonefishes and other reef fishes.

Organ Fabrication Using Pigs as An in Vivo Bioreactor.

We present the most recent research results on the creation of pigs that can accept human cells. Pigs in which grafted human cells can flourish are essential for studies of the production of human organs in the pig and for verification of the efficacy of cells and tissues of human origin for use in regenerative therapy. First, against the background of a worldwide shortage of donor organs, the need for future medical technology to produce human organs for transplantation is discussed. We then describe proof-of-concept studies in small animals used to produce human organs. An overview of the history of studies examining the induction of immune tolerance by techniques involving fertilized animal eggs and the injection of human cells into fetuses or neonatal animals is also presented. Finally, current and future prospects for producing pigs that can accept human cells and tissues for experimental purposes are discussed.

Effective gene editing by high-fidelity base editor 2 in mouse zygotes.

Targeted point mutagenesis through homologous recombination has been widely used in genetic studies and holds considerable promise for repairing disease-causing mutations in patients. However, problems such as mosaicism and low mutagenesis efficiency continue to pose challenges to clinical application of such approaches. Recently, a base editor (BE) system built on cytidine (C) deaminase and CRISPR/Cas9 technology was developed as an alternative method for targeted point mutagenesis in plant, yeast, and human cells. Base editors convert C in the deamination window to thymidine (T) efficiently, however, it remains unclear whether targeted base editing in mouse embryos is feasible. In this report, we generated a modified high-fidelity version of base editor 2 (HF2-BE2), and investigated its base editing efficacy in mouse embryos. We found that HF2-BE2 could convert C to T efficiently, with up to 100% biallelic mutation efficiency in mouse embryos. Unlike BE3, HF2-BE2 could convert C to T on both the target and non-target strand, expanding the editing scope of base editors. Surprisingly, we found HF2-BE2 could also deaminate C that was proximal to the gRNA-binding region. Taken together, our work demonstrates the feasibility of generating point mutations in mouse by base editing, and underscores the need to carefully optimize base editing systems in order to eliminate proximal-site deamination.

Differential regulation of receptivity in two uterine horns of a recipient mouse following asynchronous embryo transfer.

Receptivity is a limited time in which uterine endometrium can establish a successful dialogue with blastocyst. This study was to investigate the effect of asynchronous embryo transfer on uterine receptivity in mice. Embryos under different stages were transferred into two oviduct sides of a recipient mouse on day 1 of pseudopregnancy. Our results showed the asynchronously transferred embryos can implant in all groups. Compared to zygote-transfer group, the length of implanted embryos is longer in 8-cell embryo- or blastocyst-transfer group. The levels of Snail and COX-2 immunostaining in blastocyst-transfer group are significantly stronger than that in zygote-transfer group. Embryos in blastocyst-transfer group migrate faster than that in zygote-transfer group within uterus. Blastocysts are in a state of developmental delay after they are transferred into oviducts, and they are reactivated and implanted rapidly in uterus. The developmental rate to newborn in zygote-transfer group is obviously higher than that in blastocyst-transfer group, suggesting that a delay in embryo development and implantation will lead to a decrease of litter size. These results indicated that the window of implantation is differentially regulated in two uterine horns of a recipient by embryos at different stages.

Limited implantation success of direct-cleaved human zygotes: a time-lapse study.

OBJECTIVE: To evaluate embryos with direct cleavage (≤5 hours) from two to three cells (DC2-3) and correlate this morphokinetic parameter to implantation and ongoing pregnancy. DESIGN: Clinical multicenter retrospective study. SETTING: Private in vitro fertilization (IVF) centers. PATIENT(S): From three clinics, a total of 979 treatments including 5,225 embryos using autologous or donated oocytes, of which 1,659 embryos were transferred. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Clinical pregnancy confirmed by ultrasound in week 7. RESULT(S): Of the total embryo cohort, 715 (13.7%) underwent direct cleavage from two to three cells, 1,659 embryos were transferred to recipients, and 109 of the transferred embryos cleaved directly from two to three cells (6.6%). Only one DC2-3 embryo was known to result in a clinical pregnancy (1%) and 80 (73.4%) DC2-3 embryos did not implant. Of the 1,550 embryos transferred not showing DC2-3, 203 embryos were from treatments with 100% implantation (13.1%), and 804 (51.8%) embryos did not implant. The known implantation rate of DC2-3 embryos was statistically significantly lower than for embryos with a normal cleavage pattern (1.2% vs. 20.2%, respectively). CONCLUSION(S): Embryos with DC2-3 had a statistically significantly lower implantation rate than embryos with a normal cleavage pattern, suggesting that rejection of these embryos for transfer could improve the implantation rate.

Characterization of a recurrent poor-quality embryo morphology phenotype and zygote transfer as a rescue strategy.

Some patients in IVF programmes repeatedly display an abnormal embryonic development characterized as soon as day 2 post fertilization by a high rate (>60%) of highly fragmented embryos (⩾40% of cytoplasmic fragments) leading to recurrent IVF failures. This study postulated that, for various maternal reasons, some embryos were unable to withstand the in-vitro environment and an early pronucleate-stage transfer was proposed to these couples. Fifty-three patients with recurrent IVF failures (a mean of 2.8±1.0 previous attempts) characterized by low embryonic quality (a mean of 62.7% of the embryos with extended fragmentation) were included this transfer protocol. As in previous cycles, the mean number of oocytes retrieved and the fertilization rate were normal. The mean number of zygotes per transfer was 2.24. Fourteen clinical pregnancies were obtained, representing a pregnancy rate and a delivery rate per oocyte retrieval of 26.4% and 18.9%, respectively. Recurrent heavy and early embryo fragmentation in vitro characterizes around 3% of IVF couples and leads to lack of transfer or implantation failure. These data on fresh zygote transfers are encouraging and may provide a valid alternative solution for some of these patients. Some patients in IVF programmes repeatedly display an abnormal embryonic development characterized as soon as day 2 post fertilization by a high rate of highly fragmented embryos, leading to recurrent IVF failures. We hypothesized that, for various reasons, some embryos were unable to withstand the in-vitro environment and an early pronucleate stage transfer was proposed to these couples. Fifty-three patients with recurrent IVF failures characterized by low embryonic quality were included in this transfer protocol. As in previous cycles, the mean number of oocytes retrieved and the fertilization rate were normal. The mean number of zygotes per transfer was 2.24. Fourteen clinical pregnancies were obtained, representing a pregnancy rate and a delivery rate per oocyte retrieval of 26.4% and 18.9%, respectively. Recurrent early and heavy embryo fragmentation in vitro characterizes around 3% of IVF couples and leads to lack of transfer or implantation failure. Our data on fresh zygote transfers are encouraging and may provide a valid alternative solution for these patients.

Double activation improves rabbit freeze-thawed oocytes developmental potential.

OBJECTIVE: To investigate the effects of various activation methods on freeze-thawed rabbit oocytes developmental potential. METHODS: Rabbit oocytes were vitrified by cryoleafs and cryoprotected with ethylene glycol and propanediol. After thawing, the oocytes were fertilized by intracytoplasmic sperm injection (ICSI). Surviving oocytes after ICSI were divided into five groups at random. Group 1: Oocytes (n = 30) activated 1 h after ICSI by calcium ionomycin (I0634); Group 2: Oocytes (n = 26) activated by strontium chloride an hour after ICSI; Group 3: Oocytes (n = 33) activated by I0634 twice; Group 4: Oocytes (n = 28) were activated by strontium chloride twice; CONTROL GROUP: Inactivated oocytes (n = 39). Blastocysts derived from each group were transplanted to recipient rabbits. RESULTS: Rates of fertilization, cleavage and blastocyst formation of Group 3 were higher than those of Group 1 and Group 2 (81.8% vs 33.3% vs 53.8%, 54.5% vs 16.7% vs 26.9%, p < 0.05; 15.2% vs 3.3% vs 7.7%, p > 0.05). The rabbit transplanted with embryos derived from Group 3 became pregnant. Embryos derived from double activation could implant into endometrium. CONCLUSION: Double activation may increase freeze-thawed oocytes developmental potential. After activation, oocytes cleavage velocity may be faster than that of oocytes without activation.

How to repair the oocyte and zygote?

The supply of human oocytes is very limited. This restricts not only certain assisted reproduction procedures in IVF clinics where recipients wait for oocytes from donors, but also development of some promising approaches, like therapeutic nuclear transfer with subsequent derivation of patient compatible embryonic stem cells. Moreover, in some patients, collected oocytes exhibit certain specific defects, and logically, we can expect that after fertilization, the embryos arising from these defective oocytes may not develop or that their development might eventually be compromised. For this reason, an increased effort to determine how to repair oocytes is evident in the literature. In general, abnormalities (defects) can be detected in different oocyte components, the zona pellucida, cytoplasm, nucleus (chromosomes) and nucleolus. Whereas defects of a nuclear component are impossible (nuclear DNA) or very hard to repair (nucleolus), zona pellucida abnormalities and cytoplasm defects (for example, if containing mutated mitochondrial DNA, mtDNA) can be repaired in some cases with the help of micromanipulation schemes. In the present article, we will briefly outline the current methodological approaches that can be used to repair the oocyte or one-cell stage embryo.

One-cell zygote transfer from diabetic to nondiabetic mouse results in congenital malformations and growth retardation in offspring.

Fetuses of type 1 and 2 diabetic women experience higher incidences of malformations and fetal death as compared with nondiabetics, even when they achieve adequate glycemic control during the first trimester. We hypothesize that maternal diabetes adversely affects the earliest embryonic stage after fertilization and programs the fetus to experience these complications. To test this hypothesis, we transferred either one-cell mouse zygotes or blastocysts from either streptozotocin-induced diabetic or control mice into nondiabetic pseudopregnant female recipients. We then evaluated the fetuses at embryonic d 14.5 to assess fetal growth and the presence or absence of malformations. We found that fetuses from the diabetic mice transferred at the blastocyst stage but also as early as the one-cell zygote stage displayed significantly higher rates of malformations consistent with neural tube closure problems and abdominal wall and limb deformities. In addition, both these groups of fetuses were significantly growth retarded. To determine if this phenomenon was due to high glucose concentrations, two-cell embryos were cultured to a blastocyst stage in 52 mm D-glucose or L-glucose as an osmotic control, transferred into nondiabetic pseudopregnant mice, and examined at embryonic d 14.5. These embryos did not demonstrate any evidence of malformations, however, they did experience significantly higher rates of resorptions, lower implantation rates, and they were significantly smaller at embryonic d 14.5. In summary, exposure to maternal diabetes during oogenesis, fertilization, and the first 24 h was enough to program permanently the fetus to develop significant morphological changes.

Timing intra-Fallopian transfer procedures.

With the gradual decline in the use of zygote intra-Fallopian transfer (ZIFT), current practice is to offer ZIFT almost exclusively to patients with repeated implantation failure (RIF). For practical reasons, the procedure is sometimes deferred by 1 day and embryo intra-Fallopian transfer (EIFT) is performed. The aim of the present study was to compare the reproductive outcome of ZIFT versus EIFT. In a retrospective analysis, 176 patients who failed in 7.65 +/- 3.7 previous IVF cycles underwent 200 ZIFT and 73 EIFT procedures. Implantation and live birth rates were compared for both groups. Patients in both groups were found comparable for demographic and clinical parameters. Similar numbers of oocytes were retrieved and fertilized in both groups, and 5.2 +/- 1.2 zygotes/embryos were transferred. Implantation and live birth rates (10.5 and 26.5% versus 10.9 and 24.7% for ZIFT and EIFT respectively) were comparable. It is concluded that tubal transfer of zygotes and day-2 cleavage stage embryos are equally effective.

Limited importance of pre-embryo pronuclear morphology (zygote score) in assisted reproduction outcome in the absence of embryo cryopreservation.

OBJECTIVE: To investigate the hypothesis that Z-score criteria represent a reliable predictor of implantation rate and pregnancy outcome in in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) cycles, excluding the possibility of embryo selection before the embryo transfer. DESIGN: Retrospective clinical study. SETTING: Centre of Reproductive Medicine, Department of Obstetrics and Gynecology, Arcispedale S. Maria Nuova (ASMN), Reggio Emilia, Italy. PATIENT(S): We analyzed 393 pregnancies obtained by IVF or ICSI cycles. INTERVENTION(S): Morphologic evaluations of Z-score in pre-embryos obtained from IVF or ICSI cycles. MAIN OUTCOME MEASURE(S): Evaluations of Z-scores, implantation rate, and clinical pregnancy outcome. RESULT(S): We did not find any statistically significant correlation between the Z-score of 1032 embryos transferred in 393 embryo transfers and the implantation rate or the pregnancy outcome. In particular, the best Z-score identified (Z1, 7.2%) did not seem to correlate with embryo implantation rate or pregnancy outcomes any better than those with worse scores (Z2, 6.9% and Z3, 85.9%). CONCLUSION(S): Our results seem to confirm that Z-score alone cannot be considered a better tool than standard morphologic criteria for identifying, controlling, or selecting embryos with a better chance of successful ongoing pregnancy.

Serial nuclear transfer improves the developmental potential of mouse embryos cloned from oocytes matured in a protein-free medium.

Germinal vesicle (GV) oocytes matured in vitro are an alternative source for cytoplasmic recipients of nuclear transfer (NT). However, the developmental potential of oocytes matured in vitro is limited. In this study, we developed a protein-free maturation medium for mouse GV oocytes. Following parthenogenetic activation, the oocytes matured in the protein-free medium develop to blastocyst stage with a high efficiency, even up to the rate obtained from in vivo MII-oocytes (90.6% vs. 92.8%). Using the oocytes matured in the protein-free medium as the recipient, NT embryos develop to the blastocyst stage (17.6%). To further improve the developmental potential of NT embryos, we performed serial NT and compared the effect of three different activated cytoplasm samples derived from in vitro matured oocytes as the second recipient, that is, the effect of in vitro fertilized (IVF) zygote, the preactivated cytoplast and the IVF cytoplast, on the development of NT embryos. We found that when the pronucleus of NT zygote was transferred into the cytoplasm of the IVF zygote, the blastocyst formation increased to 39.4%. This is the first report to demonstrate the IVF zygote from oocytes matured in protein-free medium can be used successfully as the recipient for serial NT to enhance the developmental potential of mouse NT embryos from oocytes matured in the protein-free medium.

Biotechnological and clinical outcome of in vitro fertilization in non-obese patients with polycystic ovarian syndrome.

INTRODUCTION: Polycystic ovarian syndrome (PCOS) is a hormonal and metabolic disorder which poses problems with controlled ovarian stimulation (COH). It has been also postulated that PCOS patients have oocytes and embryos with poorer quality which affects IVF results. AIM: To verify IVF outcome in non-obese patients with PCOS. MATERIALS AND METHODS: IVF results of 71 non-obese PCOS patients with 243 non-obese non-POCS patients, regardless of stimulation protocol, from years 2004-2006 were compared. RESULTS: Biotechnological results of PCOS patients in opposition to non-PCOS patients were respectively as follows: higher average number (10.19 vs. 7.61; p=0.001) and percentage (82.34% vs. 76.25%; p=0.025) of retrieved mature M2 oocytes; similar (77.01% vs. 76.75%; p=0.835) fertilization rate with higher average number of embryos (7.633 vs. 5.650 p=0.003); higher average number (4.830 vs. 3.304; p=0.001) and percentage (65.66% vs. 60.57%; p=0.006) of embryos with optimal Z1 and Z2 pronuclei pattern according to Scott; higher average number of class Aembryos (3.57 vs. 2.34; p=0.001). Similar number of embryos were transferred in both groups (2.408 vs. 2.485, p=0.552). Clinical results in PCOS and non-PCOS patients were as follows: similar stimulation duration (10.53 days vs. 10.31 days; p=0.639) with significant less gonadotropin total usage (1866.54 IU vs. 2276.18 IU; p=0.001). Also clinical pregnancy per transfer (57.75% vs. 41.98%; p=0.021) and delivery per transfer (45.07% vs. 32.51%; p=0.066) were more often in PCOS patients with comparable miscarriages (12,68% vs. 6,58%; p=0.131) and ectopic pregnancy (0.00% vs. 2.06%; p=0.591) rates, respectively. CONCLUSION: PCOS in non-obese patients is linked with good biotechnological and clinical IVF outcome.

[Analysis of transfer of microinjected zygotes in production of transgenic mice].

The data on transfer of mouse eggs microinjected with DNA during production of transgenic mice were analyzed. The transfer of mouse eggs into both oviducts did not lead to a reliably higher birth rate. It did not affect the frequency of recipients' pregnancy and, although somewhat increased the frequency of multiple birth, led, finally, to unjustified loss of the major part of viable DNA-injected eggs. We recommend transferring no less than 15 microinjected eggs only in one oviduct of each recipient. The transfer into another oviduct is acceptable if the transfer into the first oviduct failed or its outcome is doubtful.

Highly efficient transgenesis in Xenopus tropicalis using I-SceI meganuclease.

In this study, we report a highly efficient transgenesis technique for Xenopus tropicalis based on a method described first for Medaka. This simple procedure entails co-injection of meganuclease I-SceI and a transgene construct flanked by two I-SceI sites into fertilized eggs. Approximately 30% of injected embryos express transgenes in a promoter-dependent manner. About 1/3 of such embryos show incorporation of the transgene at the one-cell stage and the remainder are 'half-transgenics' suggesting incorporation at the two-cell stage. Transgenes from both classes of embryos are shown to be transmitted and expressed in offspring. The procedure also works efficiently in Xenopus laevis. Because the needle injection procedure does not significantly damage embryos, a high fraction develop normally and can, as well, be injected with a second reagent, for example an mRNA or antisense morpholino oligonucleotide, thus allowing one to perform several genetic manipulations on embryos at one time. This simple and efficient technique will be a powerful tool for high-throughput transgenesis assays in founder animals, and for facilitating genetic studies in the fast-breeding diploid frog, X. tropicalis.

Aberrant heteroplasmic transmission of mtDNA in cloned pigs arising from double nuclear transfer.

Double nuclear transfer begins with the transfer of nuclear DNA from a donor cell into an enucleated recipient oocyte. This reconstructed oocyte is allowed to develop to the pronuclear stage, where the pronuclei are transferred into an enucleated zygote. This reconstructed zygote is then transferred to a surrogate sow. The genetic integrity of cloned offspring can be compromised by the transmission of mitochondrial DNA from the donor cell, the recipient oocyte and the recipient zygote. We have verified through the use of sequence analysis, restriction fragment length polymorphism analysis, allele specific PCR and primer extension polymorphism analysis that following double nuclear transfer the donor cell mtDNA is eliminated. However, it is likely that the recipient oocyte and zygote mitochondrial DNA are transmitted to the offspring, indicating bimaternal mitochondrial DNA transmission. This pattern of mtDNA inheritance is similar to that observed following cytoplasmic transfer and violates the strict unimaternal inheritance of mitochondrial DNA to offspring. This form of transmission raises concerns regarding the genetic integrity of cloned offspring and their uses in studies that require metabolic analysis or a stable genetic environment where only one variable is under analysis, such as in knockout technology.

Obtaining mice that carry human mitochondrial DNA transmitted to the progeny.

To study human diseases associated with mutations in mitochondrial DNA one needs an animal model in which the distribution of abnormal mtDNA and its impact on the phenotype might be followed. We isolated human mitochondria from HepG2 cell culture and microinjected them into murine zygotes, upon which those were transplanted to the pseudopregnant mice. PCR with species-specific primers allowed detecting human mtDNA in the tissues of 7-13-day embryos. No serious alterations in the development of transmitochondrial embryos were noticed. Among various organs/tissues of the 13-day embryos, human mtDNA was detected only in the heart, skeletal muscles, and stomach, which is in line with its uneven distribution among the blastomeres of an early mouse embryo that we described previously. In four recipient females, the microinjected zygotes were allowed to develop to term, the four neonate males of their joint litter were sacrificed, and in three of them human mtDNA was detected in the heart, skeletal muscles, stomach, brain, testes, and bladder. Six females of that joint litter were grown and mated to intact males. In the progeny (F1) of one of the females two mice were carrying human mtDNA in the heart, skeletal muscles, stomach, brain, lungs, uterus, ovaries, and kidneys. The study confirms the possibility to obtain transmitochondrial mice carrying human mtDNA that is transmitted to the animals of the next generation. Our results also indicate that among the organs to which human mtDNA is distributed some are more likely to receive it than others.

Transgenic mouse production by zygote injection.

This unit describes methods for the production of transgenic mice by injection of DNA into zygotes, including fertilized-egg isolation, zygote injection, and oviduct reimplantation. Methods for the preparation of plasmid and BAC DNA suitable for microinjection are also presented.