Production of transgenic pigs mediated by pseudotyped lentivirus and sperm

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.

Genetically modified animals for use in biopharmacology: from research to production

Introduction: In this review, the analysis of technologies for obtaining biologically active proteins from various sources is carried out, and the comparative analysis of technologies for creating producers of biologically active proteins is presented. Special attention is paid to genetically modified animals as bioreactors for the pharmaceutical industry of a new type. The necessity of improving the technology of development transgenic rabbit producers and creating a platform solution for the production of biological products is substantiated.

The advantages of using TrB for the production of recombinant proteins: The main advantages of using TrB are the low cost of obtaining valuable complex therapeutic human proteins in readily accessible fluids, their greater safety relative to proteins isolated directly from human blood, and the greater safety of the activity of the native protein.

The advantages of the mammary gland as a system for the expression of recombinant proteins: The mammary gland is the organ of choice for the expression of valuable recombinant proteins because milk is easy to collect in large volumes.

Methods for obtaining transgenic animals: The modern understanding of the regulation of gene expression and the discovery of new tools for gene editing can increase the efficiency of creating bioreactors for animals and help to obtain high concentrations of the target protein.

The advantages of using rabbits as bioreactors producing recombinant proteins in milk: The rabbit is a relatively small animal with a short duration of gestation, puberty and optimal size, capable of producing up to 5 liters of milk per year per female, receiving up to 300 grams of the target protein.

Laser-assisted Lentiviral Gene Delivery to Mouse Fertilized Eggs

Lentiviruses are efficient vectors for gene delivery to mammalian cells. Following transduction, the lentiviral genome is stably incorporated into the host chromosome and is passed on to progeny. Thus, they are ideal vectors for creation of stable cell lines, in vivo delivery of indicators, and transduction of single cell fertilized eggs to create transgenic animals. However, mouse fertilized eggs and early stage embryos are protected by the zona pellucida, a glycoprotein matrix that forms a barrier against lentiviral gene delivery. Lentiviruses are too large to penetrate the zona and are typically delivered by microinjection of viral particles into the perivitelline cavity, the space between the zona and the embryonic cells. The requirement for highly skilled technologists and specialized equipment has minimized the use of lentiviruses for gene delivery to mouse embryos. This article describes a protocol for permeabilizing the mouse fertilized eggs by perforating the zona with a laser. Laser-perforation does not result in any damage to embryos and allows lentiviruses to gain access to embryonic cells for gene delivery. Transduced embryos can develop into blastocyst in vitro, and if implanted in pseudopregnant mice, develop into transgenic pups. The laser used in this protocol is effective and easy to use. Genes delivered by lentiviruses stably incorporate into mouse embryonic cells and are germline transmittable. This is an alternative method for creation of transgenic mice that requires no micromanipulation and microinjection of fertilized eggs.

En masse lentiviral gene delivery to mouse fertilized eggs via laser perforation of zona pellucida

Lentiviruses are highly efficient vehicles for delivering genes into cells. They readily transduce primary and immortalized cells in vivo and in vitro. Genes delivered by lentiviruses are incorporated and replicated as part of their host genome and therefore offer a powerful tool for creation of stable cell lines and transgenic animals. However, the zona pellucida surrounding the fertilized eggs acts as a barrier and hinders lentiviral transduction of embryos. Here, we utilize a laser, typically used to perforate the zona pellucida for in vitro fertilization, to permeabilize the zona for lentiviral gene delivery. A single hole in the zona is sufficient for the lentivirus to gain access to fertilized eggs without the need for microinjection for en masse gene delivery. Embryos generated by this method elicit no damage and can develop to term for creation of transgenic animals.

Production of germline transgenic pigs co-expressing double fluorescent proteins by lentiviral vector

Genomic integration of transgene by lentiviral vector has been proved an efficient method to produce single-transgenic animals. But it failed to create multi-gene transgenic offspring. Here, we have exploited lentivirus to generate the double-transgenic piglets through the female germline. The recombinant lentivirus containing fluorescent proteins genes (DsRed1 and Venus) were injected into the perivitelline space of 2-cell stage in vitro porcine embryos. Compared to control group, there was no significantly decreased in the proportion of blastocysts, and the two fluorescent protein genes were co-expressed in almost all the injected embryos. Total of 32 injected in vitro embryos were transferred to 2 recipients. One recipient gave birth of three live offspring, and one female piglet was identified as genomic transgene integration by PCR analysis. Subsequently, the female transgenic founder was mated naturally with a wild-type boar and gave birth of two litters of total 23 F(1) generation piglets, among which Venus and DsRed1 genes were detected in 11 piglets and 10 kinds of organs by PCR and RT-PCR respectively. The co-expression of two fluorescent proteins was visible in four different frozen tissue sections from the RT-PCR positive piglets, and 3 to 5 copies of the transgenes were detected to be integrated into the second generation genome by southern blotting analysis. The transgenes were heritable and stably integrated in the F(1) generation. The results indicated for the first time that lentiviral vector combined with natural mating has the potential to become a simple and practical technology to create germline double-transgenic livestock or biomedical animals.

Transgenic bovine as bioreactors: Challenges and perspectives

The use of recombinant proteins has increased in diverse commercial sectors. Various systems for protein production have been used for the optimization of production and functional protein expression. The mammary gland is considered to be a very interesting system for the production of recombinant proteins due to its high level of expression and its ability to perform post-translational modifications. Cows produce large quantities of milk over a long period of lactation, and therefore this species is an important candidate for recombinant protein expression in milk. However, transgenic cows are more difficult to generate due to the inefficiency of transgenic methodologies, the long periods for transgene detection, recombinant protein expression and the fact that only a single calf is obtained at the end of each pregnancy. An increase in efficiency for transgenic methodologies for cattle is a big challenge to overcome. Promising methodologies have been proposed that can help to overcome this obstacle, enabling the use of transgenic cattle as bioreactors for protein production in milk for industry.

An efficient strategy for generation of transgenic mice by lentiviral transduction of male germline stem cells in vivo

Background

Male germline stem cells (MGSCs) are a subpopulation of germ cells in the testis tissue. MGSCs are capable of differentiation into spermatozoa and thus are perfect targets for genomic manipulation to generate transgenic animals.

Method

The present study was to optimize a protocol of production of transgenic mice through transduction of MGSCs in vivo using lentiviral-based vectors. The recombinant lentiviral vectors with either EF-1 or CMV promoter to drive the expression of enhanced green fluorescent protein (eGFP) transgene were injected into seminiferous tubules or inter-tubular space of 7-day-old and 28-day-old mouse testes. At 5 or 6 wk post-surgery, these pre-founders were mated with wild-type C57BL/6J female mice (1.5 to 2.0-month-old).

Results

Sixty-seven percent of F1 generation and 55.56 % of F2 offspring were positive for eGFP transgene under the control of EF-1 promoter via PCR analysis. The transgenic pups were generated in an injection site-and age-independent manner. The expression of transgene was displayed in the progeny derived from lentiviral vector containing CMV promoter to drive transgene, but it was silenced or undetectable in the offspring derived from lentiviral vector with transgene under EF-1 promoter. The methylation level of gDNA in the promoter region of transgene was much higher in the samples derived lentiviral vectors with EF-1 promoter than that with CMV promoter, suggesting eGFP transgene was suppressed by DNA methylation in vivo.

Conclusion

This research reported here an effective strategy for generation of transgenic mice through transduction of MGSCs in vivo using lentivirus vectors with specific promoters, and the transgenic offspring were obtained in an injection site-and age-independent manner. This protocol could be applied to other animal species, leading to advancement of animal transgenesis in agricultural and biomedical fields.

Electronic supplementary material

The online version of this article (doi:10.1186/s40104-015-0058-4) contains supplementary material, which is available to authorized users.

Germline modification of domestic animals

Genetically-modified domestic animal models are of increasing significance in biomedical research and agriculture. As authentic ES cells derived from domestic animals are not yet available, the prevailing approaches for engineering genetic modifications in those animals are pronuclear microinjection and somatic cell nuclear transfer (SCNT, also known as cloning). Both pronuclear microinjection and SCNT are inefficient, costly, and time-consuming. In animals produced by pronuclear microinjection, the exogenous transgene is usually inserted randomly into the genome, which results in highly variable expression patterns and levels in different founders. Therefore, significant efforts are required to generate and screen multiple founders to obtain animals with optimal transgene expression. For SCNT, specific genetic modifications (both gain-of-function and loss-of-function) can be engineered and carefully selected in the somatic cell nucleus before nuclear transfer. SCNT has been used to generate a variety of genetically modified animals such as goats, pigs, sheep and cattle; however, animals resulting from SCNT frequently suffer from developmental abnormalities associated with incomplete nuclear reprogramming. Other strategies to generate genetically-modified animals rely on the use of the spermatozoon as a natural vector to introduce genetic material into the female gamete. This sperm mediated DNA transfer (SMGT) combined with intracytoplasmatic sperm injection (ICSI) has relatively high efficiency and allows the insertion of large DNA fragments, which, in turn, enhance proper gene expression. An approach currently being developed to complement SCNT for producing genetically modified animals is germ cell transplantation using genetically modified male germline stem cells (GSCs). This approach relies on the ability of GSCs that are genetically modified in vitro to colonize the recipient testis and produce donor derived sperm upon transplantation. As the genetic change is introduced into the male germ line just before the onset of spermatogenesis, the time required for the production of genetically modified sperm is significantly shorter using germ cell transplantation compared to cloning or embryonic stem (ES) cell based technology. Moreover, the GSC-mediated germline modification circumvents problems associated with embryo manipulation and nuclear reprogramming. Currently, engineering targeted mutations in domestic animals using GSCs remains a challenge as GSCs from those animals are difficult to maintain in vitro for an extended period of time. Recent advances in genome editing techniques such as Zinc-Finger Nucleases (ZFNs), Transcription Activator-like Effector Nucleases (TALENs) and Clustered Regularly Interspaced Short Palindromic Repeats (CRISPRs) greatly enhance the efficiency of engineering targeted genetic change in domestic animals as demonstrated by the generation of several gene knock-out pig and cattle models using those techniques. The potential of GSC-mediated germline modification in making targeted genetic modifications in domestic animal models will be maximized if those genome editing techniques can be applied in GSCs.

Novel potential targets for prevention of arterial restenosis: insights from the pre-clinical research

Restenosis is the pathophysiological process occurring in 10-15% of patients submitted to revascularization procedures of coronary, carotid and peripheral arteries. It can be considered as an excessive healing reaction of the vascular wall subjected to arterial/venous bypass graft interposition, endarterectomy or angioplasty. The advent of bare metal stents, drug-eluting stents and of the more recent drug-eluting balloons, have significantly reduced, but not eliminated, the incidence of restenosis, which remains a clinically relevant problem. Biomedical research in pre-clinical animal models of (re)stenosis, despite its limitations, has contributed enormously to the identification of processes involved in restenosis progression, going well beyond the initial dogma of a primarily proliferative disease. Although the main molecular and cellular mechanisms underlying restenosis have been well described, new signalling molecules and cell types controlling the progress of restenosis are continuously being discovered. In particular, microRNAs and vascular progenitor cells have recently been shown to play a key role in this pathophysiological process. In addition, the advanced highly sensitive high-throughput analyses of molecular alterations at the transcriptome, proteome and metabolome levels occurring in injured vessels in animal models of disease and in human specimens serve as a basis to identify novel potential therapeutic targets for restenosis. Molecular analyses are also contributing to the identification of reliable circulating biomarkers predictive of post-interventional restenosis in patients, which could be potentially helpful in the establishment of an early diagnosis and therapy. The present review summarizes the most recent and promising therapeutic strategies identified in experimental models of (re)stenosis and potentially translatable to patients subjected to revascularization procedures.

Precision editing of large animal genomes

Transgenic animals are an important source of protein and nutrition for most humans and will play key roles in satisfying the increasing demand for food in an ever-increasing world population. The past decade has experienced a revolution in the development of methods that permit the introduction of specific alterations to complex genomes. This precision will enhance genome-based improvement of farm animals for food production. Precision genetics also will enhance the development of therapeutic biomaterials and models of human disease as resources for the development of advanced patient therapies.