Adenovirus-mediated introduction of DNA into pig sperm and offspring

Cloning, expression pattern analysis, and subcellular localization of Capra hircus SCD1 gene with production of transgenic mice

This study aimed to clone the Stearoyl-CoA desaturase 1 (SCD1) gene derived from Xuhuai goat (Capra hircus), and analyze the sub-cellular localization in cells and tissues. The cDNA was cloned by reverse transcription polymerase chain reaction (RT-PCR). pEGFP-SCD1 vector was constructed to detect sub-cellular localization and tissue distribution. pEGFP-SCD1 was transfected into NIH-3T3 cells using polyethylene imine (PEI) and observed under fluorescence inversion microscope system 48 h after transfection. The expression level of SCD1 was detected by RT-PCR. Testicular injection was used to produce transgenic mice with goat SCD1 gene. DNA and protein were extracted from the tail tissue of F₁ mice. The expression of exogenous gene in the F₁ generation was detected in both DNA and protein. The results showed that the coding sequence (CDS) fragments of C. hircus SCD1 gene was 1074 bp and encodes 360 amino acids. RT-PCR results showed that SCD1 could be expressed successfully in NIH-3T3 cells in vitro. Sub-cellular localization analysis showed that pEGFP-SCD1 fusion protein located in the cytoplasm. It can be concluded that transgenic mice with goat SCD1 expressed in sperm and tail tissue was successfully produced in the F₁ mice generation.

[Generation of goat H-FABP overexpression transgenic mice by testicular injection]

To explore the possibility of transgenic animals by testicular injection, the goat heart-type fatty acid binding protein (H-FABP) expression vector pEGFP-H-FABP was injected into the testis of 6 mice randomly by liposome mediated transfection. By detection of testis slice, sperm fluorescence and sperm DNA PCR, the exogenous gene was expressed in the parental mice. The exogenous gene was expressed at different levels in both the F1 generation mice gave birthed by treated male mice and normal female mice and the F2 generation mice generated by mating F1 could be detected that the exogenous gene expressed at different levels with the positive rates of 4% and 30.23%, respectively. The results suggested that testicu-lar injection, as an effective method to generate transgenic animal, could realize the stable integration of exogenous gene. The amelioration and maturity of testicular injection provides theoretical and practical significance in generation of trans-genic animals and even in the animal trait improvement and breeding.

Sperm and testis mediated DNA transfer as a means of gene therapy

Assisted reproductive technologies (ART) have revolutionized the treatment of infertility. However, many types of infertility may still not be addressable by ART. With recent successes in identifying many of the genetic factors responsible for male infertility and the future prospect of whole individual human genome sequencing to identify disease causing genes, the possible use of gene therapy for treating infertility deserves serious consideration. Gene therapy in the sperm and testis offers both opportunities and obstacles. The opportunities stem from the fact that numerous different approaches have been developed for introducing transgenes into the sperm and testis, mainly because of the interest in using sperm mediated gene transfer and testis mediated gene transfer as ways to generate transgenic animals. The obstacles arise from the fact that it may be very difficult to carry out gene therapy of the testis and sperm without also affecting the germline. Here we consider new developments in both sperm and testis mediated gene transfer, including the use of viral vectors, as well as the technical and ethical challenges facing those who would seek to use these approaches for gene therapy as a way to treat male infertility.

Production of transgenic rabbit embryos through intracytoplasmic sperm injection

The objective of this study was to test if intracytoplasmic sperm injection (ICSI)-mediated gene transfer was an effective method in the production of transgenic rabbit embryos. Rabbit sperm diluted in different media with various pH were treated by freezing without cryoprotectant, and their ability for DNA uptake was determined. In these experiments using production of transgenic rabbit embryos by ICSI, exogenous genes at three concentrations and of two conformation types were used. The rate of DNA association to the sperm seen by rhodamine-tagged DNA encoding green fluorescent protein (GFP) was 90.0%, 92.7%, 91.0%, 91.7%, and 92.3%, respectively in TCM199, DM, DPBS, CZB, and HCZB media. The DNA attachment to sperm was not affected by media pH within the range of 5.4-9.4 (p > 0.05). Expression of GFP first occurred at the 2-cell stage and continued to blastocyst formation. DNA concentration (between 5, 10, and 20 ng/μl) or conformation (linear and circular) had no effect on the production rate of transgenic embryos. These results indicated that genetically modified rabbit blastocysts can be efficiently produced by ICSI technique.

Efficient and simple production of transgenic mice and rabbits using the new DMSO-sperm mediated exogenous DNA transfer method

A high efficient and simple transgenic technology on mice and rabbits to transfect spermatozoa with exogenous DNA/DMSO complex to obtain transgenic offspring, which is namely called DMSO-sperm mediated gene transfer (SMGT). Mouse sperm could be either directly transfected via injection into testis or cultured in vitro with the plasmed DNA containing the enhanced green fluorescent protein (EGFP) that could be expressed in the embryos and offspring. Then, 36 living transgenic rabbits were produced using the same technology, and the transgenic ratio of 56.3% was detected using PCR and Southern blot. As the controls, the transgenic ratios of 39.6% and 47.8% have also been tested using the liposomes mediated technology of Tfx-50 Reagent or Lipefectamin-2000, respectively. The results show that the female transgenic rabbits, as the mammary gland bioreactor models, could express the human tissue plasminogen activator mutant (htPAm) in their mammary cells when they are adult.

Endocrine aspects of cancer gene therapy

The field of cancer gene therapy is in continuous expansion, and technology is quickly moving ahead as far as gene targeting and regulation of gene expression are concerned. This review focuses on the endocrine aspects of gene therapy, including the possibility to exploit hormone and hormone receptor functions for regulating therapeutic gene expression, the use of endocrine-specific genes as new therapeutic tools, the effects of viral vector delivery and transgene expression on the endocrine system, and the endocrine response to viral vector delivery. Present ethical concerns of gene therapy and the risk of germ cell transduction are also discussed, along with potential lines of innovation to improve cell and gene targeting.

High Toxicity, Low Receptor Density, and Low Integration Frequency Severely Impede the Use of Adenovirus Vectors for Production of Transgenic Mice

Although many methods are available for introducing genes into the mammalian germ line, none is ideal for genetic manipulation of livestock or primates. These organisms produce relatively few offspring in each reproductive cycle and they have long generation times. For these reasons, a recent report that adenovirus vectors can efficiently insert genes into the mouse germ line by embryo infection is of considerable interest. Adenovirus vectors have a high cloning capacity, can be produced in high titers, and can infect a wide variety of cell types. We have investigated in more detail the potential for such vectors to infect embryos and integrate their DNA into the genome. We exposed mouse embryos to adenovirus vectors that express bacterial beta-galactosidase (LacZ), and studied expression in the preimplantation period, toxicity of the vectors, and the frequency with which fetuses and pups integrate vector DNA. Our findings indicate that fully functional adenovirus receptor does not appear until the two-cell stage of development. Successful infection is associated with high toxicity, such that viral titers must be balanced to achieve high infection with tolerable levels of toxicity. Screening of 94 animals after embryo infection revealed a single positive polymerase chain reaction signal, which is indicative of the presence of the lacZ gene. This finding could not be confirmed by Southern blotting, which indicates that the founder animal was a genetic mosaic for the exogenous DNA. We conclude from these experiments that adenovirus gene transfer vectors are not readily usable for germ line gene insertion.

Regulation of foreign DNA uptake by mouse spermatozoa

We have studied some features of DNA uptake in both mature and immature mammalian spermatozoa. Mature sperm collected from the cauda epididymis are able to incorporate foreign DNA in a buffer containing only salts and calcium. Immature spermatozoa, however, are unable to bind DNA. This seems to be caused by the lack of a functional receptor in the sperm membrane since once this membrane is disrupted by sonication, DNA can be detected in the postacrosome region of the sperm nucleus, matching the distribution of the mature spermatozoa. Comparison between the DNA binding proteins of mature and immature spermatozoa allowed us to identify two bands that could be part of the putative membrane receptor for the DNA. On the other hand, DNA uptake in mature sperm is prevented by the seminal plasma. We have identified two components of the seminal plasma, a calcium-dependent DNase present in the seminal vesicle fluid and several DNA binding proteins secreted by the ventral prostate, that could account for the inhibitory activity. Taken as a whole, our results indicate that DNA uptake by the mammalian spermatozoa is a very specific and highly regulated phenomenon.

Direct exposure of mouse spermatogenic cells to high doses of adenovirus gene therapy vector does not result in germ cell transduction

The potential for adenovirus gene therapy vectors to gain access to male germ cells was rigorously tested in the mouse by injecting high titers of the vector directly into the testis and epididymis, or by exposing sperm to the vector immediately prior to or during in vitro fertilization. The adenovirus vector carried the bacterial lacZ gene (Adbeta-Gal) driven by the Rous sarcoma virus (RSV) promoter, and infection was assessed by testing for lacZ expression, either with antibodies to LacZ protein or by staining for LacZ enzymatic activity. A total of 109 plaque-forming units (PFU) was inserted into the testis or epididymis, and in vitro fertilization was performed after sperm were exposed either to 10 or 100 PFU per sperm cell. lacZ expression was examined within testes for several weeks after injection, and in preimplantation embryos produced by in vitro fertilization with sperm exposed to the gene therapy vector. Direct injection of Adbeta-Gal into either the testis or epididymis resulted in lacZ expression only within the interstitium of the testis and not within seminiferous tubules. Despite direct exposure of spermatogenic cells or mature sperm to high titers of virus, lacZ expression was likewise not detected in embryos. These findings are consistent with the conclusion that the risk is minimal for germ line integration of adenovirus vectors exposed to male reproductive cells.