Engraftment of human iPS cells and allogeneic porcine cells into pigs with inactivated RAG2 and accompanying severe combined immunodeficiency.

Pigs with severe combined immunodeficiency (SCID) may provide useful models for regenerative medicine, xenotransplantation, and tumor development and will aid in developing therapies for human SCID patients. Using a reporter-guided transcription activator-like effector nuclease (TALEN) system, we generated targeted modifications of recombination activating gene (RAG) 2 in somatic cells at high efficiency, including some that affected both alleles. Somatic-cell nuclear transfer performed with the mutated cells produced pigs with RAG2 mutations without integrated exogenous DNA. Biallelically modified pigs either lacked a thymus or had one that was underdeveloped. Their splenic white pulp lacked B and T cells. Under a conventional housing environment, the biallelic RAG2 mutants manifested a "failure to thrive" phenotype, with signs of inflammation and apoptosis in the spleen compared with age-matched wild-type animals by the time they were 4 wk of age. Pigs raised in a clean environment were healthier and, following injection of human induced pluripotent stem cells (iPSCs), quickly developed mature teratomas representing all three germ layers. The pigs also tolerated grafts of allogeneic porcine trophoblast stem cells. These SCID pigs should have a variety of uses in transplantation biology.

Piglets produced from cloned blastocysts cultured in vitro with GM-CSF.

In general, pig embryos established by somatic cell nuclear transfer (SCNT) are transferred at the one-cell stage because of suboptimal embryo culture conditions. Improvements in embryo culture can increase the practical application of late embryo transfer. The goal of this study was to evaluate embryos cultured with granulocyte-macrophage colony-stimulating factor (GM-CSF) in vitro, and to track the in vivo developmental competency of SCNT-derived blastocysts from these GM-CSF embryos. The receptor for GM-CSF was up-regulated in in vitro-produced embryos when compared to in vivo-produced cohorts, but the level decreased when GM-CSF was present. In vitro fertilized (IVF) embryos, supplemented with GM-CSF (2 or 10 ng/ml), showed a higher frequency of development to the blastocyst stage compared to controls. The total cell numbers of the blastocysts also increased with supplementation of GM-CSF. Molecular analysis demonstrates that IVF-derived blastocysts cultured with GM-CSF exhibit less apoptotic activity. Similarly, an increase in development to the blastocyst stage and an increase in the average total-cell number in the blastocysts were observed when SCNT-derived embryos were cultured with either concentration of GM-CSF (2 or 10 ng/ml). When SCNT-derived embryos, cultured with 10 ng/ml GM-CSF, were transferred into six surrogates at Day 6, five of the surrogates became pregnant and delivered healthy piglets. Our findings suggest that supplementation of GM-CSF can provide better culture conditions for IVF- and SCNT-derived embryos, and pig SCNT-derived embryos cultured with GM-CSF in vitro can successfully produce piglets when transferred into surrogates at the blastocyst stage. Thus, it may be practical to begin performing SCNT-derived embryo transfer at the blastocyst stage.

Glycolysis in preimplantation development is partially controlled by the Warburg Effect.

Glucose metabolism in preimplantation embryos has traditionally been viewed from a somatic cell viewpoint. Here, we show that gene expression in early embryos is similar to rapidly dividing cancer cells. In vitro-produced pig blastocysts were subjected to deep-sequencing, and were found to express two gene variants that have been ascribed importance to cancer cell metabolism (HK2 and the M2 variant of PKM2). Development was monitored and gene expression was quantified in additional embryos cultured in low or high O(2) (5% CO(2), 5% O(2), 90% N(2) vs. 5% CO(2) in air). Development to the blastocyst stage in the two atmospheres was similar, except low O(2) resulted in more total and inner cell mass nuclei than high O(2). Of the 15 candidate genes selected that are involved in glucose metabolism, only TALDO1 and PDK1 were increased in the low O(2) environment. One paradigm that has been used to explain glycolysis under low oxygen tension is the Warburg Effect (WE). The WE predicts that expression of both HK2 and PKM2 M2 results in a slowing of glucose metabolism through the TCA cycle, thereby forcing the products of glycolysis to be metabolized through the pentose phosphate pathway and to lactic acid. This charging of the system is apparently so important to the early embryo that redundant mechanisms are present, that is, a fetal form of PKM2 and high levels of PDK1. Here, we set the framework for using the WE to describe glucose metabolism and energy production during preimplantation development.

Partial loss of interleukin 2 receptor gamma function in pigs provides mechanistic insights for the study of human immunodeficiency syndrome.

In this study, we described the phenotype of monoallelic interleukin 2 receptor gamma knockout (mIL2RG+/Δ69-368 KO) pigs. Approximately 80% of mIL2RG+/Δ69-368 KO pigs (8/10) were athymic, whereas 20% (2/10) presented a rudimentary thymus. The body weight of IL2RG+/Δ69-368KO pigs developed normally. Immunological analysis showed that mIL2RG+/Δ69-368 KO pigs possessed CD25+CD44- or CD25-CD44+ cells, whereas single (CD4 or CD8) or double (CD4/8) positive cells were lacking in mIL2RG+/Δ69-368 KO pigs. CD3+ cells in the thymus of mIL2RG+/Δ69-368 KO pigs contained mainly CD44+ cells and/or CD25+ cells, which included FOXP3+ cells. These observations demonstrated that T cells from mIL2RG+/Δ69-368 KO pigs were able to develop to the DN3 stage, but failed to transition toward the DN4 stage. Whole-transcriptome analysis of thymus and spleen, and subsequent pathway analysis revealed that a subset of genes differentially expressed following the loss of IL2RG might be responsible for both impaired T-cell receptor and cytokine-mediated signalling. However, comparative analysis of two mIL2RG+/Δ69-368 KO pigs revealed little variability in the down- and up-regulated gene sets. In conclusion, mIL2RG+/Δ69-368 KO pigs presented a T-B+NK- SCID phenotype, suggesting that pigs can be used as a valuable and suitable biomedical model for human SCID research.

Dickkopf-related protein 1 inhibits the WNT signaling pathway and improves pig oocyte maturation.

The ability to mature oocytes in vitro provides a tool for creating embryos by parthenogenesis, fertilization, and cloning. Unfortunately the quality of oocytes matured in vitro falls behind that of in vivo matured oocytes. To address this difference, transcriptional profiling by deep sequencing was conducted on pig oocytes that were either matured in vitro or in vivo. Alignment of over 18 million reads identified 1,316 transcripts that were differentially represented. One pathway that was overrepresented in the oocytes matured in vitro was for Wingless-type MMTV integration site (WNT) signaling. In an attempt to inhibit the WNT pathway, Dickkopf-related protein 1 was added to the in vitro maturation medium. Addition of Dickkopf-related protein 1 improved the percentage of oocytes that matured to the metaphase II stage, increased the number of nuclei in the resulting blastocyst stage embryos, and reduced the amount of disheveled segment polarity protein 1 protein in oocytes. It is concluded that transcriptional profiling is a powerful method for detecting differences between in vitro and in vivo matured oocytes, and that the WNT signaling pathway is important for proper oocyte maturation.

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.