Transgene transmission in South American catfish (Rhamdia quelen) larvae by sperm-mediated gene transfer

Comparison of two methods of sperm- and testis-mediated gene transfer in production of transgenic animals: A systematic review

Transgenic (Tg) animal technology is one of the growing areas in biology. Various Tg technologies, each with its own advantages and disadvantages, are available for generating Tg animals. These include zygote microinjection, electroporation, viral infection, embryonic stem cell or spermatogonial stem cell-mediated production of Tg animals, sperm-mediated gene transfer (SMGT), and testis-mediated gene transfer (TMGT). However, there are currently no comprehensive studies comparing SMGT and TMGT methods, selecting appropriate gene delivery carriers (such as nanoparticles and liposomes), and determining the optimal route for gene delivery (SMGT and TMGT) for producing Tg animal. Here we aim to provide a comprehensive assessment comparing SMGT and TMGT methods, and to introduce the best carriers and gene transfer methods to sperm and testis to generate Tg animals in different species. From 2010 to 2022, 47 studies on SMGT and 25 studies on TMGT have been conducted. Mice and rats were the most commonly used species in SMGT and TMGT. Regarding the SMGT approach, nanoparticles, streptolysin-O, and virus packaging were found to be the best gene transfer methods for generating Tg mice. In the TMGT method, the best gene transfer methods for generating Tg mice and rats were virus packaging, dimethyl sulfoxide, electroporation, and liposome. Our study has shown that the efficiency of producing Tg animals varies depending on the species, gene carrier, and method of gene transfer.

ZIF-8 Nanoparticle: A Valuable Tool for Improving Gene Delivery in Sperm-Mediated Gene Transfer

Metal-organic frameworks (MOFs) are porous materials with unique characteristics that make them well-suited for drug delivery and gene therapy applications. Among the MOFs, zeolitic imidazolate framework-8 (ZIF-8) has emerged as a promising candidate for delivering exogenous DNA into cells. However, the potential of ZIF-8 as a vector for sperm-mediated gene transfer (SMGT) has not yet been thoroughly explored.This investigation aimed to explore the potential of ZIF-8 as a vector for enhancing genetic transfer and transgenesis rates by delivering exogenous DNA into sperm cells. To test this hypothesis, we employed ZIF-8 to deliver a plasmid expressing green fluorescent protein (GFP) into mouse sperm cells and evaluated the efficiency of DNA uptake. Our findings demonstrate that ZIF-8 can efficiently load and deliver exogenous DNA into mouse sperm cells, increasing GFP expression in vitro. These results suggest that ZIF-8 is a valuable tool for enhancing genetic transfer in SMGT, with important implications for developing genetically modified animals for research and commercial purposes. Additionally, our study highlights the potential of ZIF-8 as a novel class of vectors for gene delivery in reproductive biology.Overall, our study provides a foundation for further research into using ZIF-8 and other MOFs as gene delivery systems in reproductive biology and underscores the potential of these materials as promising vectors for gene therapy and drug delivery.

Efficiency and cell viability implications using tip type electroporation in zebrafish sperm cells

Sperm-mediated gene transfer (SMGT) has a potential use for zebrafish transgenesis. However, transfection into fish sperm cells still needs to be improved. The objective was to demonstrate the feasibility of tip type electroporation in zebrafish sperm, showing a protocol that provide high transfection efficiency, with minimal side-effects. Sperm was transfected with a Cy3-labelled DNA using tip type electroporation with voltages ranging from 500 to 1500 V. Sperm kinetics parameters were assessed using Computer Assisted Semen Analysis (CASA) and cell integrity, reactive oxygen species (ROS), mitochondrial functionality and transfection rate were evaluated by flow cytometry. The transfection rates were positively affected by tip type electroporation, reaching 64.9% ± 3.6 in the lowest voltage used (500 V) and 86.6% ± 1.9 in the highest (1500 V). The percentage of overall motile sperm in the electrotransfected samples was found to decrease with increasing field strength (P < 0.05). Increase in the sperm damaged plasma membrane was observed with increasing field strength (P < 0.05). ROS and sperm mitochondrial functionality did not present a negative response after the electroporation (P > 0.05). Overall results indicate that tip type electroporation enhances the internalization of exogenous DNA into zebrafish sperm cells with minimal harmful effects to sperm cells.

Protein evolution revisited

Antifreeze proteins (AFPs) protect marine fishes from freezing in icy seawater. They evolved relatively recently, most likely in response to the formation of sea ice and Cenozoic glaciations that occurred less than 50 million years ago, following a greenhouse Earth event. Based on their diversity, AFPs have independently evolved on many occasions to serve the same function, with some remarkable examples of convergent evolution at the structural level, and even instances of lateral gene transfer. For some AFPs, the progenitor gene is recognizable. The intense selection pressure exerted by icy seawater, which can rapidly kill unprotected fish, has led to massive AFP gene amplification, as well as some partial gene duplications that have increased the size and activity of the antifreeze. The many protein evolutionary processes described in Gordon H. Dixon's Essays in Biochemistry article will be illustrated here by examples from studies on AFPs. Abbreviations: AFGP: antifreeze glycoproteins; AFP: antifreeze proteins; GHD: Gordon H. Dixon; SAS: sialic acid synthase; TH: thermal hysteresis.

Progress and biotechnological prospects in fish transgenesis

The history of transgenesis is marked by milestones such as the development of cellular transdifferentiation, recombinant DNA, genetic modification of target cells, and finally, the generation of simpler genetically modified organisms (e.g. bacteria and mice). The first transgenic fish was developed in 1984, and since then, continuing technological advancements to improve gene transfer have led to more rapid, accurate, and efficient generation of transgenic animals. Among the established methods are microinjection, electroporation, lipofection, viral vectors, and gene targeting. Here, we review the history of animal transgenesis, with an emphasis on fish, in conjunction with major developments in genetic engineering over the past few decades. Importantly, spermatogonial stem cell modification and transplantation are two common techniques capable of revolutionizing the generation of transgenic fish. Furthermore, we discuss recent progress and future biotechnological prospects of fish transgenesis, which has strong applications for the aquaculture industry. Indeed, some transgenic fish are already available in the current market, validating continued efforts to improve economically important species with biotechnological advancements.

Bacterial magnetic particles improve testes-mediated transgene efficiency in mice

Nano-scaled materials have been proved to be ideal DNA carriers for transgene. Bacterial magnetic particles (BMPs) help to reduce the toxicity of polyethylenimine (PEI), an efficient gene-transferring agent, and assist tissue transgene ex vivo. Here, the effectiveness of the BMP-PEI complex-conjugated foreign DNAs (BPDs) in promoting testes-mediated gene transfer (TMGT) in mouse was compared with that of liposome-conjugated foreign DNAs. The results proved that through testes injection, the clusters of BPDs successfully reached the cytoplasm and the nuclear of spermatogenesis cell, and expressed in testes of transgene founder mice. Additionally, the ratio of founder mice obtained from BPDs (88%) is about 3 times higher than the control (25%) (p < 0.05). Interestingly, the motility of sperms recovered from epididymis of the founder mice from BPD group were significantly improved, as compared with the control (p < 0.01). Based on classic breeding, the ratio of transgene mice within the first filial was significantly higher in BPDs compared with the control (73.8% versus 11.6%, p < 0.05). TMGT in this study did not produce visible histological changes in the testis. In conclusion, nano-scaled BPDs could be an alternative strategy for efficiently producing transgene mice in vivo.

Potential toxicity of engineered nanoparticles in mammalian germ cells and developing embryos: treatment strategies and anticipated applications of nanoparticles in gene delivery

BACKGROUND

Engineered nanoparticles (ENPs) offer technological advantages for a variety of industrial and consumer products as well as show promise for biomedical applications. Recent progress in the field of nanotechnology has led to increased exposure to nanoparticles by humans. To date, little is known about the adverse effects of these ENPs on reproductive health, although interest in nanotechnology area is growing. A few biocompatible ENPs have a high loading capacity for exogenous substances, including drugs, DNA or proteins, and can selectively deliver molecular cargo into cells; however, they represent a potential tool for gene delivery into gametes and embryos.

OBJECTIVE AND RATIONALE

Understanding the reprotoxicological aspects of these ENPs is of the utmost importance to reliably estimate its potential impact on human health. In addition, a search for protective agents to combat ENP-mediated reproductive toxicity is warranted. Therefore, in this review we summarize the toxic effects of a few ENPs (metal and metal oxides, carbon-based nanoparticles, quantum dots and chitosan) in mammalian germ cells and developing embryos, and propose some treatment strategies that could mitigate nanoparticle-mediated toxicity. In addition, we outline the anticipated applications of ENPs in transgenic animal production in order to generate models for investigations into the mechanisms for human disease.

SEARCH METHODS

A literature search was performed using the National Center for Biotechnology Information PubMed database up until March 2016 and relevant keywords were used to obtain information regarding mammalian germ cell-specific toxicity and embryotoxicity of ENPs, possible treatment strategies, as well as the anticipated applications of nanoparticles in gene delivery in germ cells and embryos. Only English language publications were included.

OUTCOMES

Here, we demonstrate the toxicological effects of ENPs in mammalian germ cells and developing embryos by considering both in vitro and in vivo experimental models based on the existing literature. The biodistribution and cellular uptake of ENPs and the observed toxicities are mostly dependent on ENP size and surface-coating agents (surface functional groups/surface charge). ENPs have been shown to induce toxicity via oxidative stress, inflammation and DNA damage in both human and mouse germ cells. Use of antioxidant, anti-inflammatory drugs and selective metal chelators would be beneficial against nanoparticle-induced toxicity.

WIDER IMPLICATIONS

Our review provides the reproductive scientists a mechanistic insight into the reprotoxicological aspects of ENPs to reliably estimate its potential impact on human health and help to select/design protective agents to combat ENP-mediated toxicity. Furthermore, research regarding the detailed mechanism(s) of ENP toxicity in mammalian germ cells and developing embryos as well as the search for protective agents to combat ENP-mediated reproductive toxicity is warranted. Furthermore, we anticipate that investigations into the possibility of applying nanovectors to gene delivery in germ cells and early embryos will open new horizons in reproductive biology.

Editing of the Luteinizing Hormone Gene to Sterilize Channel Catfish, Ictalurus punctatus, Using a Modified Zinc Finger Nuclease Technology with Electroporation

Channel catfish (Ictalurus punctatus) is the most important freshwater aquaculture species in the USA. Genetically enhanced fish that are sterile could both profit the catfish industry and reduce potential environmental and ecological risks. As the first step to generate sterile channel catfish, three sets of zinc finger nuclease (ZFN) plasmids targeting the luteinizing hormone (LH) gene were designed and electroporated into one-cell embryos, different concentrations were introduced, and the Cel-I assay was conducted to detect mutations. Channel catfish carrying the mutated LH gene were sterile, as confirmed by DNA sequencing and mating experiments. The overall mutation rate was 19.7 % for 66 channel catfish, and the best treatment was ZFN set 1 at the concentration 25 μg/ml. To our knowledge, this is the first instance of gene editing of fish via plasmid introduction instead of mRNA microinjection. The introduction of the ZFN plasmids may have reduced mosaicism, as mutated individuals were gene edited in every tissue evaluated. Apparently, the plasmids were eventually degraded without integration, as they were not detectable in mutated individuals using PCR. Carp pituitary extract failed to induce spawning and restoration of fertility, indicating the need for developing other hormone therapies to achieve reversal of sterility upon demand. This is the first sterilization achieved using ZFN technology in an aquaculture species and the first successful gene editing of channel catfish. Our results will help understand the roles of the LH gene, purposeful sterilization of teleost fishes, and is a step towards control of domestic, hybrid, exotic, invasive, and transgenic fishes.

Effects of transgenic sterilization constructs and their repressor compounds on hatch, developmental rate and early survival of electroporated channel catfish embryos and fry

Channel catfish (Ictalurus punctatus) embryos were electroporated with sterilization constructs targeting primordial germ cell proteins or with buffer. Some embryos then were treated with repressor compounds, cadmium chloride, copper sulfate, sodium chloride or doxycycline, to prevent expression of the transgene constructs. Promoters included channel catfish nanos and vasa, salmon transferrin (TF), modified yeast Saccharomyces cerevisiae copper transport protein (MCTR) and zebrafish racemase (RM). Knock-down systems were the Tet-off (nanos and vasa constructs), MCTR, RM and TF systems. Knock-down genes included shRNAi targeting 5' nanos (N1), 3' nanos (N2) or dead end (DND), or double-stranded nanos RNA (dsRNA) for overexpression of nanos mRNA. These constructs previously were demonstrated to knock down nanos, vasa and dead end, with the repressors having variable success. Exogenous DNA affected percentage hatch (% hatch), as all 14 constructs, except for the TF dsRNA, TF N1 (T), RM DND (C), vasa DND (C), vasa N1 (C) and vasa N2 (C), had lower % hatch than the control electroporated with buffer. The MCTR and RM DND (T) constructs resulted in delayed hatch, and the vasa and nanos constructs had minimal effects on time of hatch (P < 0.05). Cadmium chloride appeared to counteract the slow development caused by the TF constructs in two TF treatments (P < 0.05). The 4 ppt sodium chloride treatment for the RM system decreased % hatch (P < 0.05) and slowed development. In the case of nanos constructs, doxycycline greatly delayed hatch (P < 0.05). Adverse effects of the transgenes and repressors continued for several treatments for the first 6 days after hatch, but only in a few treatments during the next 10 days. Repressors and gene expression impacted the yield of putative transgenic channel catfish fry, and need to be considered and accounted for in the hatchery phase of producing transgenically sterilized catfish fry and their fertile counterparts. This fry output should be considered to ensure that sufficient numbers of transgenic fish are produced for future applications and for defining repressor systems that are the most successful.

Interaction of diet and the masou salmon Δ5-desaturase transgene on Δ6-desaturase and stearoyl-CoA desaturase gene expression and N-3 fatty acid level in common carp (Cyprinus carpio)

The masou salmon Δ5-desaturase-like gene (D5D) driven by the common carp β-actin promoter was transferred into common carp (Cyprinus carpio) that were fed two diets. For P1 transgenic fish fed a commercial diet, Δ6-desaturase-like gene (D6D) and stearoyl-CoA desaturase (SCD) mRNA levels in muscle were up-regulated (P < 0.05) 12.7- and 17.9-fold, respectively, and the D6D mRNA level in the gonad of transgenic fish was up-regulated 6.9-fold (P < 0.05) compared to that of non-transgenic fish. In contrast, D6D and SCD mRNA levels in transgenic fish were dramatically down-regulated (P < 0.05), 50.2- and 16.7-fold in brain, and 5.4- and 2.4-fold in liver, respectively, in comparison with those of non-transgenic fish. When fed a specially formulated diet, D6D and SCD mRNA levels in muscle of transgenic fish were up-regulated (P < 0.05) 41.5- and 8.9-fold, respectively, and in liver 6.0- and 3.3-fold, respectively, compared to those of non-transgenic fish. In contrast, D6D and SCD mRNA levels in the gonad of transgenic fish were down-regulated (P < 0.05) 5.5- and 12.4-fold, respectively, and D6D and SCD mRNA levels in the brain were down-regulated 14.9- and 1.4-fold (P < 0.05), respectively, compared to those of non-transgenic fish. The transgenic common carp fed the commercial diet had 1.07-fold EPA, 1.12-fold DPA, 1.07-fold DHA, and 1.07-fold higher observed total omega-3 fatty acid levels than non-transgenic common carp. Although these differences were not statistically different (P > 0.05), there were significantly (P < 0.10) higher omega-3 fatty acid levels when considering the differences for all of the individual omega-3 fatty acids. The genotype × diet interactions observed indicated that the potential of desaturase transgenesis cannot be realized without using a well-designed diet with the needed amount of substrates.

The impact of exogenous DNA on the structure of sperm of olive flounder (Paralichthys olivaceus)

Sperm-mediated gene transfer (SMGT) is a promising transgenic technology that relies on the capability of sperm to internalize exogenous DNA. In marine fish, however, the interaction between sperm and exogenous DNA appears to be deficient. Here, we demonstrated significant DNase activity in the seminal plasma of the olive flounder. When incubated with naked-DNA, the spermatozoa lost their structural integrity, including the head, mitochondria and flagellum, in an incubation time-dependent manner. However, internalization of a liposome-DNA complex resulted in the structural integrity of the spermatozoa being maintained, even when using incubation times of up to 50min. We concluded that in the olive flounder, SMGT is possible by integrating liposome-DNA complexes, rather than naked-DNA alone, into the sperm. In brief, removal of the seminal plasma and packaging the exogenous DNA were necessary for successful SMGT in the olive flounder.

Sperm nuclear transfer and transgenic production in the fish medaka

Sperm nuclear transfer or intracytoplasmic sperm injection (ICSI) is a powerful assisted reproductive technology (ART) for treating human male infertility. Controversial reports of increased birth defects have raised concerns about the ART's safety. The cause for birth defects, however, has remained elusive for analysis in human because of the sample size, male infertility genetics, physiological heterogeneity and associated procedures such as embryo manipulations. Animal models are required to evaluate factors leading to the increased birth defects. Here we report the establishment of medakafish model for ICSI and transgenic production. This small laboratory fish has high fecundity and easy embryology. We show that ICSI produced a 5% high percentage of fertile animals that exhibited both paternal and maternal contribution as evidenced by the pigmentation marker. Furthermore, when sperm were pre-incubated with a plasmid ubiquitously expressing RFP and subjected to ICSI, 50% of sperm nuclear transplants showed germline transmission. We conclude that medaka is an excellent model for ICSI to evaluate birth defects and that sperm nuclear transfer can mediate stable gene transfer at high efficiency. Although more demanding for experimentation, sperm-mediated transgenesis should be particularly applicable for aquaculture species with a lengthy generation time and/or a large adult body size.