Resurrection of an alpha-1,3-galactosyltransferase gene-targeted miniature pig by recloning using postmortem ear skin fibroblasts

Cloned Foal Born from Postmortem-Obtained Ear Sample Refrigerated for 5 Days Before Fibroblast Isolation and Decontamination of the Infected Monolayer Culture

A 6-year-old mare, a valuable polo horse, died of complications following postcolic surgery. To preserve its genetics, ear skin samples were collected immediately after death and stored in an equine embryo transfer medium at 4°C for 5 days. After trypsin digestion, monolayer fibroblast cultures were established, but signs of massive bacterial infection were found in all of them. As an ultimate attempt for rescue, rigorously and repeatedly washed cells were individually cultured in all wells of four 96-well dishes. New monolayers were established from the few wells without contamination and used for somatic cell nuclear transfer. Four of the six Day 7 blastocysts derived from 14 reconstructed zygotes were transferred in four naturally cycling mares on Day 5 after ovulation. The embryo transfers resulted in 2 pregnancies, one from a fresh and one from a vitrified blastocyst. The vitrified embryo transfer resulted in a healthy offspring, now 21 months old, genetically and phenotypically identical to the somatic cell donor animal.

Identification of the Porcine Vascular Endothelial Cell-Specific Promoter ESAM1.0 Using Transcriptome Analysis

The vascular endothelium of xenografted pig organs represents the initial site of rejection after exposure to recipient immune cells. In this study, we aimed to develop a promoter specific to porcine vascular endothelial cells as a step toward overcoming xenograft rejection. Transcriptome analysis was performed on porcine aortic endothelial cells (PAECs), ear skin fibroblasts isolated from GGTA knockout (GTKO) pigs, and the porcine renal epithelial cell line pk-15. RNA sequencing confirmed 243 differentially expressed genes with expression changes of more than 10-fold among the three cell types. Employing the Human Protein Atlas database as a reference, we identified 34 genes exclusive to GTKO PAECs. The endothelial cell-specific adhesion molecule (ESAM) was selected via qPCR validation and showed high endothelial cell specificity and stable expression across tissues. We selected 1.0 kb upstream sequences of the translation start site of the gene as the promoter ESAM1.0. A luciferase assay revealed that ESAM1.0 promoter transcriptional activity was significant in PAECs, leading to a 2.8-fold higher level of expression than that of the porcine intercellular adhesion molecule 2 (ICAM2) promoter, which is frequently used to target endothelial cells in transgenic pigs. Consequently, ESAM1.0 will enable the generation of genetically modified pigs with endothelium-specific target genes to reduce xenograft rejection.

Developmental analysis of reconstructed embryos of second-generation cloned transgenic goats

To improve the efficiency of the production of transgenic cloned goats by somatic cell nuclear transfer (SCNT), the development of reconstructed embryos of first-generation (G1) and second-generation (G2) cloned transgenic goats were compared and analyzed. Primary transgenic fetal fibroblasts were used as donor cells for G1 somatic cell nuclear transfer (SCNT). When the G1 transgenic embryos developed to 35 days in the recipient goats, transgenic fetal fibroblasts were isolated from them and used as donor cells for the G2 clone. In the G1 clones, the average fusion rate of reconstructed embryos was 73.62±2.9%, the average development rate (2-4 cells) was 33.96±2.36%, and the pregnancy rate of transplant recipients was 31.91%. In the G2 clones, the average fusion rate of the reconstructed embryos was 90.29±2.03%, the average development rate was 66.46±3.30%, and the pregnancy rate was 58.14%. These results indicate that in the G2 clones, the fusion rate of eggs, the development rate of reconstructed embryos, and the pregnancy rate of transplant recipients were significantly higher than those of G1 clones. We believe these results will lay a solid foundation for the efficient production of transgenic cloned animals in the future.

Comprehensive Analysis of Cardiac Xeno-Graft Unveils Rejection Mechanisms

Porcine heart xenotransplantation is a potential treatment for patients with end-stage heart failure. To understand molecular mechanisms of graft rejection after heart transplantation, we transplanted a 31-day-old alpha-1,3-galactosyltransferase knockout (GTKO) porcine heart to a five-year-old cynomolgus monkey. Histological and transcriptome analyses were conducted on xenografted cardiac tissue at rejection (nine days after transplantation). The recipient monkey's blood parameters were analyzed on days -7, -3, 1, 4, and 7. Validation was conducted by quantitative real-time PCR (qPCR) with selected genes. A non-transplanted GTKO porcine heart from an age-matched litter was used as a control. The recipient monkey showed systemic inflammatory responses, and the rejected cardiac graft indicated myocardial infarction and cardiac fibrosis. The transplanted heart exhibited a total of 3748 differentially expressed genes compared to the non-transplanted heart transcriptome, with 2443 upregulated and 1305 downregulated genes. Key biological pathways involved at the terminal stage of graft rejection were cardiomyopathies, extracellular interactions, and ion channel activities. The results of qPCR evaluation were in agreement with the transcriptome data. Transcriptome analysis of porcine cardiac tissue at graft rejection reveals dysregulation of the key molecules and signaling pathways, which play relevant roles on structural and functional integrities of the heart.

Transdifferentiation of α-1,3-galactosyltransferase knockout pig bone marrow derived mesenchymal stem cells into pancreatic β-like cells by microenvironment modulation

OBJECTIVE

To evaluate the pancreatic differentiation potential of α-1,3-galactosyltransferase knockout (GalTKO) pig-derived bone marrow-derived mesenchymal stem cells (BM-MSCs) using epigenetic modifiers with different pancreatic induction media.

METHODS

The BM-MSCs have been differentiated into pancreatic β-like cells by inducing the overexpression of key transcription regulatory factors or by exposure to specific soluble inducers/small molecules. In this study, we evaluated the pancreatic differentiation of GalTKO pig-derived BM-MSCs using epigenetic modifiers, 5-azacytidine (5-Aza) and valproic acid (VPA), and two types of pancreatic induction media - advanced Dulbecco's modified Eagle's medium (ADMEM)-based and N2B27-based media. GalTKO BM-MSCs were treated with pancreatic induction media and the expression of pancreas-islets-specific markers was evaluated by real-time quantitative polymerase chain reaction, Western blotting, and immunofluorescence. Morphological changes and changes in the 5'-C-phosphate-G-3' (CpG) island methylation patterns were also evaluated.

RESULTS

The expression of the pluripotent marker (POU class 5 homeobox 1 [OCT4]) was upregulated upon exposure to 5-Aza and/or VPA. GalTKO BM-MSCs showed increased expression of neurogenic differentiation 1 in the ADMEM-based (5-Aza) media, while the expression of NK6 homeobox 1 was elevated in cells induced with the N2B27-based (5-Aza) media. Moreover, the morphological transition and formation of islets-like cellular clusters were also prominent in the cells induced with the N2B27-based media with 5-Aza. The higher insulin expression revealed the augmented trans-differentiation ability of GalTKO BM-MSCs into pancreatic β-like cells in the N2B27-based media than in the ADMEM-based media.

CONCLUSION

5-Aza treated GalTKO BM-MSCs showed an enhanced demethylation pattern in the second CpG island of the OCT4 promoter region compared to that in the GalTKO BM-MSCs. The exposure of GalTKO pig-derived BM-MSCs to the N2B27-based microenvironment can significantly enhance their trans-differentiation ability into pancreatic β-like cells.

Introduction of a plasmid and a protein into bovine and swine cells by water-in-oil droplet electroporation

Instrument cost is a major problem for the transduction of DNA fragments and proteins into cells. Water-in-oil droplet electroporation (droplet-EP) was recently invented as a low-cost and effective method for the transfection of plasmids into cultured human cells. We here applied droplet-EP to livestock animal cells. Although it is difficult to transfect plasmids into bovine fibroblasts using conventional lipofection methods, droplet-EP enabled us to introduce an enhanced green fluorescent protein (EGFP)-expressing plasmid into bovine earlobe fibroblasts. The optimal transfection condition was 3.0 kV, which allowed 19.1% of the cells to be transfected. For swine earlobe fibroblasts, the maximum transfection efficacy was 14.0% at 4.0 kV. After transfection with droplet-EP, 69.1% of bovine and 76.5% of swine cells were viable. Furthermore, droplet-EP successfully transduced Escherichia coli recombinant EGFP into frozen-thawed bovine sperm at 1.5 kV. Flow cytometry analysis revealed that 71.5% of spermatozoa exhibited green fluorescence after transfection. Overall, droplet-EP is suitable for the transfection of plasmids and proteins into cultured livestock animal cells.

A functional regulatory variant of MYH3 influences muscle fiber-type composition and intramuscular fat content in pigs

Muscle development and lipid accumulation in muscle critically affect meat quality of livestock. However, the genetic factors underlying myofiber-type specification and intramuscular fat (IMF) accumulation remain to be elucidated. Using two independent intercrosses between Western commercial breeds and Korean native pigs (KNPs) and a joint linkage-linkage disequilibrium analysis, we identified a 488.1-kb region on porcine chromosome 12 that affects both reddish meat color (a*) and IMF. In this critical region, only the MYH3 gene, encoding myosin heavy chain 3, was found to be preferentially overexpressed in the skeletal muscle of KNPs. Subsequently, MYH3-transgenic mice demonstrated that this gene controls both myofiber-type specification and adipogenesis in skeletal muscle. We discovered a structural variant in the promotor/regulatory region of MYH3 for which Q allele carriers exhibited significantly higher values of a* and IMF than q allele carriers. Furthermore, chromatin immunoprecipitation and cotransfection assays showed that the structural variant in the 5'-flanking region of MYH3 abrogated the binding of the myogenic regulatory factors (MYF5, MYOD, MYOG, and MRF4). The allele distribution of MYH3 among pig populations worldwide indicated that the MYH3 Q allele is of Asian origin and likely predates domestication. In conclusion, we identified a functional regulatory sequence variant in porcine MYH3 that provides novel insights into the genetic basis of the regulation of myofiber type ratios and associated changes in IMF in pigs. The MYH3 variant can play an important role in improving pork quality in current breeding programs.

Immune molecular profiling of whole blood drawn from a non-human primate cardiac xenograft model treated with anti-CD154 monoclonal antibodies

Most studies of xenografts have been carried out with complex immunosuppressive regimens to prevent immune rejection; however, such treatments may be fatal owing to unknown causes. Here, we performed immune molecular profiling following anti-CD154 monoclonal antibody (mAb) treatment in heterotopic abdominal cardiac xenografts from α-1,3-galactosyltransferase-knockout pigs into cynomolgus monkeys to elucidate the mechanisms mediating the undesirable fatal side effects of immunosuppressive agents. Blood samples were collected from healthy monkeys as control and then at 2 days after xenograft transplantation and just before humane euthanasia; 94 genes related to the immune system were analyzed. The basic immunosuppressive regimen included cobra venom factor, anti-thymocyte globulin, and rituximab, with and without anti-CD154 mAbs. The maintenance therapy was followed with tacrolimus, MMF, and methylprednisolone. The number of upregulated genes was initially decreased on Day 2 (-/+ anti-CD154 mAb, 22/13) and then increased before euthanasia in recipients treated with anti-CD154 mAbs (-/+ anti-CD154 mAb, 30/37). The number of downregulated genes was not affected by anti-CD154 mAb treatment. Additionally, the number of upregulated genes increased over time for both groups. Interestingly, treatment with anti-CD154 mAbs upregulated coagulation inducers (CCL2/IL6) before euthanasia. In conclusion, immunosuppressive regimens used for cardiac xenografting affected upregulation of 6 inflammation genes (CXCL10, MPO, MYD88, NLRP3, TNFα, and TLR1) and downregulation of 8 genes (CCR4, CCR6, CD40, CXCR3, FOXP3, GATA3, STAT4, and TBX21).

Generation of α-1,3-galactosyltransferase knocked-out transgenic cloned pigs with knocked-in five human genes

Recent progress in genetic manipulation of pigs designated for xenotransplantation ha6s shown considerable promise on xenograft survival in primates. However, genetic modification of multiple genes in donor pigs by knock-out and knock-in technologies, aiming to enhance immunological tolerance against transplanted organs in the recipients, has not been evaluated for health issues of donor pigs. We produced transgenic Massachusetts General Hospital piglets by knocking-out the α-1,3-galactosyltransferase (GT) gene and by simultaneously knocking-in an expression cassette containing five different human genes including, DAF, CD39, TFPI, C1 inhibitor (C1-INH), and TNFAIP3 (A20) [GT^{−(DAF/CD39/TFPI/C1-INH/TNFAIP3)/+}] that are connected by 2A peptide cleavage sequences to release individual proteins from a single translational product. All five individual protein products were successfully produced as determined by western blotting of umbilical cords from the newborn transgenic pigs. Although gross observation and histological examination revealed no significant pathological abnormality in transgenic piglets, hematological examination found that the transgenic piglets had abnormally low numbers of platelets and WBCs, including neutrophils, eosinophils, basophils, and lymphocytes. However, transgenic piglets had similar numbers of RBC and values of parameters related to RBC compared to the control littermate piglets. These data suggest that transgenic expression of those human genes in pigs impaired hematopoiesis except for erythropoiesis. In conclusion, our data suggest that transgenic expression of up to five different genes can be efficiently achieved and provide the basis for determining optimal dosages of transgene expression and combinations of the transgenes to warrant production of transgenic donor pigs without health issues.

Molecular immunology profiles of monkeys following xenografting with the islets and heart of α-1,3-galactosyltransferase knockout pigs

Effective immunosuppression strategies and genetically modified animals have been used to prevent hyperacute and acute xenograft rejection; however, the underlying mechanisms remain unknown. In this study, we evaluated the expression of a comprehensive set of immune system-related genes (89 genes, including five housekeeping genes) in the blood of cynomolgus monkeys (~5 yr old) used as graft recipients, before and after the xenografting of the islets and heart from single and double α-1,3-galactosyltransferase (GalT) knockout (KO) pigs (<6 weeks old). The immunosuppressive regimen included administration of cobra venom factor, anti-thymocyte globulin, rituximab, and anti-CD154 monoclonal antibodies to recipients before and after grafting. Islets were xenografted into the portal vein in type 1 diabetic monkeys, and the heart was xenografted by heterotopic abdominal heart transplantation. Genes from recipient blood were analyzed using RT(2) profiler PCR arrays and the web-based RT(2) profiler PCR array software v.3.5. Recipients treated with immunosuppressive agents without grafting showed significant downregulation of CCL5, CCR4, CCR6, CD4, CD40LG, CXCR3, FASLG, CXCR3, FOXP3, GATA3, IGNG, L10, IL23A, TRAF6, MAPK8, MIF, STAT4, TBX21, TLR3, TLR7, and TYK2 and upregulation of IFNGR1; thus, genes involved in protection against viral and bacterial infection were downregulated, confirming the risk of infection. Notably, C3-level control resulted in xenograft failure within 2 days because of a 7- to 11-fold increase in all xenotransplanted models. Islet grafting using single GalT-KO pigs resulted in upregulation of CXCL10 and MX1, early inflammation, and acute rejection-associated signals at 2 days after xenografting. We observed at least 5-fold upregulation in recipients transplanted with islets grafts from single (MX1) or double (C3, CCR8, IL6, IL13, IRF6, CXCL10, and MX1) GalT-KO pigs after 77 days; single GalT-KO incurred early losses owing to immune attacks. Our results suggest that this novel, simple, non-invasive, and time-efficient procedure (requiring only 1.5 ml blood) for evaluating graft success, minimizing immune rejection, and blocking infection.

Complete reduction of p53 expression by RNA interference following heterozygous knockout in porcine fibroblasts

Tumor suppressor p53 plays a critical role in the regulation of cell cycle and apoptosis in mammals. Mutations of p53 often cause various cancers. Murine models have improved our understanding on tumorigenesis associated with p53 mutations. However, mice and humans are different in many ways. For example, the short lifespans of mice limit the clinical application of the data obtained from this species. Porcine model could be an alternative as pigs share many anatomical and physiological similarities with humans. Here, we modified the expression levels of p53 messenger RNA (mRNA) and protein in porcine fetal fibroblasts using a combination of gene targeting and RNA interference. First, we disrupted the p53 gene to produce p53 knockout (KO) cells. Second, the p53 shRNA expression vector was introduced into fibroblasts to isolate p53 knockdown (KD) cells. We obtained p53 KO, KD, and KO + KD fibroblasts which involve p53 KO and KD either separately or simultaneously. The mRNA expression of p53 in p53 KO fibroblasts was similar to that in the wild-type control. However, the mRNA expression levels of p53 in KD and KO + KD cells were significantly decreased. The p53 protein level significant reduced in p53 KD. Interestingly, no p53 protein was detected in KO + KD, suggesting a complete reduction of the protein by synergistic effect of KO and KD. This study demonstrated that various expression levels of p53 in porcine fibroblasts could be achieved by gene targeting and RNA interference. Moreover, complete abolishment of protein expression is feasible using a combination of gene targeting and RNA interference.

Alpha-1,3-galactosyltransferase-deficient miniature pigs produced by serial cloning using neonatal skin fibroblasts with loss of heterozygosity

Objective

Production of alpha-1,3-galactosyltransferase (αGT)-deficient pigs is essential to overcome xenograft rejection in pig-to-human xenotransplantation. However, the production of such pigs requires a great deal of cost, time, and labor. Heterozygous αGT knockout pigs should be bred at least for two generations to ultimately obtain homozygote progenies. The present study was conducted to produce αGT-deficient miniature pigs in much reduced time using mitotic recombination in neonatal ear skin fibroblasts.

Methods

Miniature pig fibroblasts were transfected with αGT gene-targeting vector. Resulting gene-targeted fibroblasts were used for nuclear transfer (NT) to produce heterozygous αGT gene-targeted piglets. Fibroblasts isolated from ear skin biopsies of these piglets were cultured for 6 to 8 passages to induce loss of heterozygosity (LOH) and treated with biotin-conjugated IB4 that binds to galactose-α-1,3-galactose, an epitope produced by αGT. Using magnetic activated cell sorting, cells with monoallelic disruption of αGT were removed. Remaining cells with LOH carrying biallelic disruption of αGT were used for the second round NT to produce homozygous αGT gene-targeted piglets.

Results

Monoallelic mutation of αGT gene was confirmed by polymerase chain reaction in fibroblasts. Using these cells as nuclear donors, three heterozygous αGT gene-targeted piglets were produced by NT. Fibroblasts were collected from ear skin biopsies of these piglets, and homozygosity was induced by LOH. The second round NT using these fibroblasts resulted in production of three homozygous αGT knockout piglets.

Conclusion

The present study demonstrates that the time required for the production of αGT-deficient miniature pigs could be reduced significantly by postnatal skin biopsies and subsequent selection of mitotic recombinants. Such procedure may be beneficial for the production of homozygote knockout animals, especially in species, such as pigs, that require a substantial length of time for breeding.

Generation of Fibroblasts Lacking the Sal-like 1 Gene by Using Transcription Activator-like Effector Nuclease-mediated Homologous Recombination

The Sal-like 1 gene (Sall1) is essential for kidney development, and mutations in this gene result in abnormalities in the kidneys. Mice lacking Sall1 show agenesis or severe dysgenesis of the kidneys. In a recent study, blastocyst complementation was used to develop mice and pigs with exogenic organs. In the present study, transcription activator-like effector nuclease (TALEN)-mediated homologous recombination was used to produce Sall1-knockout porcine fibroblasts for developing knockout pigs. The vector targeting the Sall1 locus included a 5.5-kb 5′ arm, 1.8-kb 3′ arm, and a neomycin resistance gene as a positive selection marker. The knockout vector and TALEN were introduced into porcine fibroblasts by electroporation. Antibiotic selection was performed over 11 days by using 300 μg/mL G418. DNA of cells from G418-resistant colonies was amplified using polymerase chain reaction (PCR) to confirm the presence of fragments corresponding to the 3′ and 5′ arms of Sall1. Further, mono- and bi-allelic knockout cells were isolated and analyzed using PCR–restriction fragment length polymorphism. The results of our study indicated that TALEN-mediated homologous recombination induced bi-allelic knockout of the endogenous gene.

Knock-in fibroblasts and transgenic blastocysts for expression of human FGF2 in the bovine β-casein gene locus using CRISPR/Cas9 nuclease-mediated homologous recombination

Many transgenic domestic animals have been developed to produce therapeutic proteins in the mammary gland, and this approach is one of the most important methods for agricultural and biomedical applications. However, expression and secretion of a protein varies because transgenes are integrated at random sites in the genome. In addition, distal enhancers are very important for transcriptional gene regulation and tissue-specific gene expression. Development of a vector system regulated accurately in the genome is needed to improve production of therapeutic proteins. The objective of this study was to develop a knock-in system for expression of human fibroblast growth factor 2 (FGF2) in the bovine β-casein gene locus. The F2A sequence was fused to the human FGF2 gene and inserted into exon 3 of the β-casein gene. We detected expression of human FGF2 mRNA in the HC11 mouse mammary epithelial cells by RT-PCR and human FGF2 protein in the culture media using western blot analysis when the knock-in vector was introduced. We transfected the knock-in vector into bovine ear fibroblasts and produced knock-in fibroblasts using the clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 system. Moreover, the CRISPR/Cas9 system was more efficient than conventional methods. In addition, we produced knock-in blastocysts by somatic cell nuclear transfer using the knock-in fibroblasts. Our knock-in fibroblasts may help to create cloned embryos for development of transgenic dairy cattle expressing human FGF2 protein in the mammary gland via the expression system of the bovine β-casein gene.

Production of Cloned Korean Native Pig by Somatic Cell Nuclear Transfer

The Korean native pig (KNP) have been considered as animal models for animal biotechnology research because of their relatively small body size and their presumably highly inbred status due to the closed breeding program. However, little is reported about the use of KNP for animal biotechnology researches. This study was performed to establish the somatic cell nuclear transfer (SCNT) protocol for the production of swine leukocyte antigens (SLA) homotype-defined SCNT KNP. The ear fibroblast cells originated from KNP were cultured and used as donor cell. After thawing, the donor cells were cultured for 1 hour with 15 μM roscovitine prior to the nuclear transfer. The numbers of reconstructed and parthenogenetic embryos transferred were 98 ± 35.2 and 145 ± 11.2, respectively. The pregnancy and delivery rate were 3/5 (60%) and 2/5 (40%). One healthy SLA homotype-defined SCNT KNP was successfully generated. The recipient-based individual cloning efficiency ranged from 0.65 to 1.08%. Taken together, it can be postulated that the methodological establishment of the production of SLA homotype-defined cloned KNP can be applied to the generation of transgenic cloned KNP as model animals for human disease and xenotransplantation researches.

Comparative N-linked glycan analysis of wild-type and α1,3-galactosyltransferase gene knock-out pig fibroblasts using mass spectrometry approaches

Carbohydrate antigens expressed on pig cells are considered to be major barriers in pig-to-human xenotransplantation. Even after α1,3-galactosyltransferase gene knock-out (GalT-KO) pigs are generated, potential non-Gal antigens are still existed. However, to the best of our knowledge there is no extensive study analyzing N-glycans expressed on the GalT-KO pig tissues or cells. Here, we identified and quantified totally 47 N-glycans from wild-type (WT) and GalT-KO pig fibroblasts using mass spectrometry. First, our results confirmed the absence of galactose-alpha-1,3-galactose (α-Gal) residue in the GalT-KO pig cells. Interestingly, we showed that the level of overall fucosylated N-glycans from GalT-KO pig fibroblasts is much higher than from WT pig fibroblasts. Moreover, the relative quantity of the N-glycolylneuraminic acid (NeuGc) antigen is slightly higher in the GalT-KO pigs. Thus, this study will contribute to a better understanding of cellular glycan alterations on GalT-KO pigs for successful xenotransplantation.

Procedure used for denuding pig oocytes influences oocyte damage, and development of in vitro and nuclear transfer embryos

The effects of different denuding procedures used during the in vitro culture of porcine embryos on oocyte damage and aspects of porcine embryo development were investigated in a series of studies. Oocytes were denuded by vortexing or pipetting after 44h in vitro maturation (IVM) or pre-denuded after 22h IVM. The total oocyte death rate was significantly (P<0.05) higher for pre-denuded (27.3±1.4%) than for vortexed (20.3±1.2%) or pipetted (16.2±2.2%) oocytes. There was no significant difference between the treatments in the percentage of oocytes that extruded the first polar body. The type I cortical granule distribution (reflecting complete maturity) and normal spindle formation rates were significantly lower in the pre-denuding than in the vortexing and pipetting treatments. Blastocyst formation rates were significantly lower for the pre-denuding treatment in PA (25.7±4.5%) and IVF (6.1±1.5%) culture than in the vortexing (PA 42.0±4.5%; IVF 11.2±0.5%) and pipetting (PA 43.4±3.1%; IVF 9.4±1.6%) treatments. The proportion of oocytes developing to blastocysts in SCNT culture was not significantly different between treatments ranging from 9.9±1.8% for pre-denuding to 12.3±2.7% for vortexing. No significant differences in apoptosis or embryonic fragmentation were observed. This study shows that the denuding procedure used for porcine oocytes during the in vitro production of embryos can significantly affect oocyte damage, spindle patterns, oocyte maturation, embryo development but not embryonic apoptosis or the frequency of fragmentation.

Knock-in of Enhanced Green Fluorescent Protein or/and Human Fibroblast Growth Factor 2 Gene into β-Casein Gene Locus in the Porcine Fibroblasts to Produce Therapeutic Protein

Transgenic animals have become important tools for the production of therapeutic proteins in the domestic animal. Production efficiencies of transgenic animals by conventional methods as microinjection and retrovirus vector methods are low, and the foreign gene expression levels are also low because of their random integration in the host genome. In this study, we investigated the homologous recombination on the porcine β-casein gene locus using a knock-in vector for the β-casein gene locus. We developed the knock-in vector on the porcine β-casein gene locus and isolated knock-in fibroblast for nuclear transfer. The knock-in vector consisted of the neomycin resistance gene (neo) as a positive selectable marker gene, diphtheria toxin-A gene as negative selection marker, and 5′ arm and 3′ arm from the porcine β-casein gene. The secretion of enhanced green fluorescent protein (EGFP) was more easily detected in the cell culture media than it was by western blot analysis of cell extract of the HC11 mouse mammary epithelial cells transfected with EGFP knock-in vector. These results indicated that a knock-in system using β-casein gene induced high expression of transgene by the gene regulatory sequence of endogenous β-casein gene. These fibroblasts may be used to produce transgenic pigs for the production of therapeutic proteins via the mammary glands.

Targeted disruption of Ataxia-telangiectasia mutated gene in miniature pigs by somatic cell nuclear transfer

Ataxia telangiectasia (A-T) is a recessive autosomal disorder associated with pleiotropic phenotypes, including progressive cerebellar degeneration, gonad atrophy, and growth retardation. Even though A-T is known to be caused by the mutations in the Ataxia telangiectasia mutated (ATM) gene, the correlation between abnormal cellular physiology caused by ATM mutations and the multiple symptoms of A-T disease has not been clearly determined. None of the existing ATM mouse models properly reflects the extent to which neurological degeneration occurs in human. In an attempt to provide a large animal model for A-T, we produced gene-targeted pigs with mutations in the ATM gene by somatic cell nuclear transfer. The disrupted allele in the ATM gene of cloned piglets was confirmed via PCR and Southern blot analysis. The ATM gene-targeted pigs generated in the present study may provide an alternative to the current mouse model for the study of mechanisms underlying A-T disorder and for the development of new therapies.

Porcine Knock-in Fibroblasts Expressing hDAF on α-1,3-Galactosyltransferase (GGTA1) Gene Locus

The Galactose-α1,3-galactose (α1,3Gal) epitope is responsible for hyperacute rejection in pig-to-human xenotransplantation. Human decay-accelerating factor (hDAF) is a cell surface regulatory protein that serves as a complement inhibitor to protect self cells from complement attack. The generation of α1,3-galactosyltransferase (GGTA1) knock-out pigs expressing DAF is a necessary step for their use as organ donors for humans. In this study, we established GGTA1 knock-out cell lines expressing DAF from pig ear fibroblasts for somatic cell nuclear transfer. hDAF expression was detected in hDAF knock-in heterozygous cells, but not in normal pig cells. Expression of the GGTA1 gene was lower in the knock-in heterozygous cell line compared to the normal pig cell. Knock-in heterozygous cells afforded more effective protection against cytotoxicity with human serum than with GGTA1 knock-out heterozygous and control cells. These cell lines may be used in the production of GGTA1 knock-out and DAF expression pigs for xenotransplantation.

Improvement of cloning efficiency in minipigs using post-thawed donor cells treated with roscovitine

Massachusetts General Hospital miniature pigs (MGH minipigs) have been established for organ transplantation studies across the homozygous major histocompatibility complex, but cloning efficiency of MGH minipigs is extremely low. This study was designed to increase the productivity of MGH minipigs by nuclear transfer of post-thaw donor cells after 1 h co-incubation with roscovitine. The MGH minipig cells were genetically modified with GT KO (alpha1,3-galactosyltransferase knock-out) and hCD46 KI (human CD46 knock-in) and used as donor cells. The GT KO/hCD46 KI donor cells were cultured for either 3 days (control group) or 1 h after thawing with 15 μM roscovitine (experimental group) prior to the nuclear transfer. The relative percentage of the transgenic donor cells that entered into G0/G1 was 93.7 % (±2.54). This was different from the donor cells cultured for 1 h with the roscovitine-treated group (84.6 % ±4.6) (P < 0.05) and without roscovitine (78.6 % ±5.5) (P < 0.01), respectively. The pregnancy rate and delivery rate in the roscovitine group (8/12 and 6/8, respectively) were significantly higher (P < 0.01) than those in the control group (6/19 and 3/6, respectively). In the experimental group, 12 GT KO/hCD46 KI transgenic minipigs were successfully generated, and five minipigs among them survived for more than 6 months so far. The recipient-based individual cloning efficiency ranged from 0.74 to 2.54 %. In conclusion, gene-modified donor cells can be used for cloning of MGH minipigs if the cells are post-thawed and treated with roscovitine for 1 h prior to nuclear transfer.

Production of biallelic CMP-Neu5Ac hydroxylase knock-out pigs

After the knock-out (KO) of α1,3 galactosyltransfease (Gal-T), the Hanganutziu-Deicher antigen became a major antigen of the "non-Gal antigen" that is implicated in subsequent xenograft rejection. For deletion of non-Gal antigen, we successfully produced zinc finger nuclease (ZFN)-mediated monoallelic/biallelic male and female CMP-N-acetylneuraminic acid hydroxylase (CMAH) KO miniature pigs: the efficiency of the gene targeting (41.7%) was higher when donor DNA was used with the ZFN than those of ZFN alone (9.1%). Monoallelic KO pigs had no integration of exogenous DNA into their genome, indicating that this technique would provide a new avenue to reduce the risk of antibiotics resistance when organs from genetically modified pigs are transplanted into patients. Until now, both monoallelic and biallelic CMAH KO pigs are healthy and show no sign of abnormality and off-target mutations. Therefore, these CMAH null pigs on the Gal-T KO background could serve as an important model for the xenotransplantation.

Nucleofection-mediated α1,3-galactosyltransferase gene inactivation and membrane cofactor protein expression for pig-to-primate xenotransplantation

Xenotransplantation of pig organs into primates leads to hyperacute rejection (HAR). Functional ablation of the pig α 1,3-galactosyltransferase (GalT) gene, which abrogates expression of the Gal α 1-3Gal β 1-4GlcNAc-R (Gal) antigen, which inhibits HAR. However, antigens other than Gal may induce immunological rejection by their cognate antibody responses. Ultimately, overexpression of complement regulatory proteins reduces acute humoral rejection by non-Gal antibodies when GalT is ablated. In this study, we developed a vector-based strategy for ablation of GalT function and concurrent expression of membrane cofactor protein (MCP, CD46). We constructed an MCP expression cassette (designated as MCP-IRESneo) and inserted between the left and the right homologous arms to target exon 9 of the GalT gene. Nucleofection of porcine ear skin fibroblasts using the U-023 and V-013 programs resulted in high transfection efficiency and cell survival. We identified 28 clones in which the MCP-IRESneo vector had been successfully targeted to exon 9 of the GalT gene. Two of those clones, with apparent morphologically mitotic fibroblast features were selected through long-term culture. GalT gene expression was downregulated in these 2 clones. Importantly, MCP was shown to be efficiently expressed at the cell surface and to efficiently protect cell lysis against normal human complement serum attack in vitro.

Production of cloned NIBS (Nippon Institute for Biological Science) and α-1, 3-galactosyltransferase knockout MGH miniature pigs by somatic cell nuclear transfer using the NIBS breed as surrogates

BACKGROUND

Nuclear transfer (NT) technologies offer a means for producing the genetically modified pigs necessary to develop swine models for mechanistic studies of disease processes as well as to serve as organ donors for xenotransplantation. Most previous studies have used commercial pigs as surrogates.

METHOD AND RESULTS

In this study, we established a cloning technique for miniature pigs by somatic cell nuclear transfer (SCNT) using Nippon Institute for Biological Science (NIBS) miniature pigs as surrogates. Moreover, utilizing this technique, we have successfully produced an α-1, 3-galactosyltransferase knockout (GalT-KO) miniature swine. Fibroblasts procured from a NIBS miniature pig fetus were injected into 1312 enucleated oocytes. The cloned embryos were transferred to 11 surrogates of which five successfully delivered 13 cloned offspring; the production efficiency was 1.0% (13/1312). In a second experiment, lung fibroblasts obtained from neonatal GalT-KO MGH miniature swine were used as donor cells and 1953 cloned embryos were transferred to 12 surrogates. Six cloned offspring were born from five surrogates, a production efficiency of 0.3% (6/1953).

CONCLUSIONS

These results demonstrate successful establishment of a miniature pig cloning technique by SCNT using NIBS miniature pigs as surrogates. To our knowledge, this is the first demonstration of successful production of GalT-KO miniature swine using miniature swine surrogates. This technique could help to ensure a stable supply of the cloned pigs through the use of miniature pig surrogates and could expand production in countries with limited space or in facilities with special regulations such as specific pathogen-free or good laboratory practice.

Developmental potential of pig embryos reconstructed by use of sow versus pre-pubertal gilt oocytes after somatic cell nuclear transfer

In this study, the developmental ability of cloned embryos using gilt versus sow oocytes was evaluated under the hypothesis that the efficiency of nuclear transfer using gilt oocytes was lower than that of sow oocytes, but that it could be optimized. Five experiments were performed with routine production of cloned embryos with sow oocytes serving as the control. Results showed that: Experiment 1: Blastocyst rates of cloned embryos with gilt oocytes was about half compared with control. Experiment 2: An extended maturation time of 48 h used for gilt oocytes resulted in lower blastocyst rates after cloning. Experiment 3: Development of cloned embryos with gilt oocytes was improved by co-culture with sow oocytes. Experiment 4: After maturation of gilt oocytes using follicular fluid from gilt instead of sow, the oocytes were sorted into large and small oocytes, and after cloning, blastocyst rates were higher using large gilt oocytes compared with small oocytes; however, the rate remained lower compared with control. Experiment 5: Six sow recipients received a total of 503 morulae and blastocysts cloned from gilt oocytes (four recipients) and 190 cloned from sow oocytes (two recipients). All recipients became pregnant and went to term, resulting in 26 (gilt oocytes) and six (sow oocytes) piglets. In conclusion, results confirmed that nuclear transfer efficiency was higher using sow versus gilt oocytes, but the use of gilt oocytes can be optimized by sorting after ooplasm size following maturation and by maturing gilt and sow oocytes together.

Inheritance of mitochondrial DNA in serially recloned pigs by somatic cell nuclear transfer (SCNT)

Somatic cell nuclear transfer (SCNT) has been established for the transmission of specific nuclear DNA. However, the fate of donor mitochondrial DNA (mtDNA) remains unclear. Here, we examined the fate of donor mtDNA in recloned pigs through third generations. Fibroblasts of recloned pigs were obtained from offspring of each generation produced by fusion of cultured fibroblasts from a Minnesota miniature pig (MMP) into enucleated oocytes of a Landrace pig. The D-loop regions from the mtDNA of donor and recipient differ at nucleotide sequence positions 16050 (A→T), 16062 (T→C), and 16135 (G→A). In order to determine the fate of donor mtDNA in recloned pigs, we analyzed the D-loop region of the donor's mtDNA by allele-specific PCR (AS-PCR) and real-time PCR. Donor mtDNA was successfully detected in all recloned offspring (F1, F2, and F3). These results indicate that heteroplasmy that originate from donor and recipient mtDNA is maintained in recloned pigs, resulting from SCNT, unlike natural reproduction.

Recloned transgenic pigs possess normal reproductive performance and stable genetic transmission capacity

The present study investigated whether a recloning procedure would affect the reproductive performance or the germline transmission capacity of recloned transgenic pigs. This study has also laid the foundation for the development of elite transgenic swine breeds in the future. Recloned transgenic pigs were developed from ear tissue fibroblasts of primary transgenic cloned pigs using a recloning procedure, and their reproductive performance and exogenous gene transmission were analyzed. Two transgenic cell lines with different genetic backgrounds (derived from a female miniature pig and a male Landrace pig) with stable expression of green fluorescent protein (GFP) were established successfully. Furthermore, recloned transgenic embryos were developed to full term successfully. One female Chinese experimental miniature piglet (CEMP) (GFP+) and three male Landrace piglets (GFP+) were delivered naturally. Furthermore, the index values for the reproductive characteristics of the recloned transgenic pigs, such as puberty, gestation period, sperm volume and sperm concentration, were not significantly different from those of conventionally bred pigs. In addition, 53% of the F1 offspring of the recloned transgenic pigs were GFP positive. These results demonstrate that ear tissue fibroblasts from primary transgenic cloned pigs efficiently support the full-term development of recloned transgenic embryos. Furthermore, recloned transgenic pigs maintain normal reproductive performance and stable germline (genetic) transmission capacities.

α1,3-galactosyltransferase deficiency in germ-free miniature pigs increases N-glycolylneuraminic acids as the xenoantigenic determinant in pig-human xenotransplantation

In this study, we examined whether Hanganutziu-Deicher (H-D) antigens are important as an immunogenic non-α1,3-galactose (Gal) epitope in pigs with a disrupted α1,3-galactosyltransferase gene. The targeting efficiency of the AO blood genotype was achieved (2.2%) in pig fibroblast cells. A total of 1800 somatic cell nuclear transfer (SCNT) embryos were transferred to 10 recipients. One recipient developed to term and naturally delivered two piglets. The α1,3-galactosyltransferase activity in lung, liver, spleen, and testis of heterozygote α1,3-galactosyltransferase gene knockout (GalT-KO) pigs was significantly decreased, whereas brain and heart showed very low decreasing levels of α1,3-galactosyltransferase activity when compared to those of control. Enzyme-linked lectinosorbent assay showed that the heterozygote GalT-KO pig had more sialylα2,6- and sialylα2,3-linked glycan than the control. Furthermore, the heart, liver, and kidney of the heterozygote GalT-KO pig had a higher N-glycolylneuraminic acid (Neu5Gc) content than the control, whereas the lung of the heterozygote GalT-KO pig had Neu5Gc content similar to the control. Collectively, the data strongly indicated that Neu5Gc is a more critical xenoantigen to overcoming the next acute immune rejection in pig to human xenotransplantation.

Blastocysts cloned from the Putian Black pig ear tissues frozen without cryoprotectant at -80 and -196 degrees Celsius for 3 yrs

The Putian Black pig, as one of elite cultivars of endemic species in China, has been on the verge of extinction and urgently needs protection. Somatic cell nuclear transfer (SCNT) and noncryoprotected frozen tissue technology have successfully resurrected several mammalian species. Therefore, this study explored the primary feasibility of conserving this breed using a combination of both technologies. Skin tissues obtained from the ears of adult Putian Black boars were frozen without cryoprotectant at -20, -80, or -196 °C and stored for 3 yrs. Primary cell culture, passage and subculture were performed on frozen samples after being rapidly thawed at 39 °C and on fresh pig ear tissues (control). Cloned embryos were reconstructed using fibroblasts (from frozen and fresh tissues) with enucleated oocytes. Live cell lines were obtained from tissues frozen at -80 and at -196 °C and appeared to have normal proliferative activity after passage; furthermore, they directed cloned embryos to develop to the blastocyst stage after nuclear transfer. We concluded that the population of Putian Black pig might be increased in the future by transferring cloned blastocysts into synchronized recipient pigs.

Alpha 1,3-galactosyltransferase deficiency in pigs increases sialyltransferase activities that potentially raise non-gal xenoantigenicity

We examined whether deficiency of the GGTA1 gene in pigs altered the expression of several glycosyltransferase genes. Real-time RT-PCR and glycosyltransferase activity showed that 2 sialyltransferases [α2,3-sialyltransferase (α2,3ST) and α2,6-sialyltransferase (α2,6ST)] in the heterozygote GalT KO liver have higher expression levels and activities compared to controls. Enzyme-linked lectin assays indicated that there were also more sialic acid-containing glycoconjugate epitopes in GalT KO livers than in controls. The elevated level of sialic-acid-containing glycoconjugate epitopes was due to the low level of α-Gal in heterozygote GalT KO livers. Furthermore, proteomics analysis showed that heterozygote GalT KO pigs had a higher expression of NAD⁺-isocitrate dehydrogenase (IDH), which is related to the CMP-N-acetylneuraminic acid hydroxylase (CMAH) enzyme reaction. These findings suggest the deficiency of GGTA1 gene in pigs results in increased production of N-glycolylneuraminic acid (Neu5Gc) due to an increase of α2,6-sialyltransferase and a CMAH cofactor, NAD⁺-IDH. This indicates that Neu5Gc may be a critical xenoantigen. The deletion of the CMAH gene in the GalT KO background is expected to further prolong xenograft survival.