Chloride channel accessory 1 gene deficiency causes selective loss of mucus production in a new pig model.

Morbidity and mortality of respiratory diseases are linked to airway obstruction by mucus but there are still no specific, safe, and effective drugs to correct this phenotype. The need for better treatment requires a new understanding of the basis for mucus production. In that regard, studies of human airway epithelial cells in primary culture show that a mucin granule constituent known as chloride channel accessory 1 (CLCA1) is required for inducible expression of the inflammatory mucin MUC5AC in response to potent type 2 cytokines. However, it remained uncertain whether CLCLA1 is necessary for mucus production in vivo. Conventional approaches to functional biology using targeted gene knockout were difficult due to the functional redundancy of additional Clca genes in mice not found in humans. We reasoned that CLCA1 function might be better addressed in pigs that maintain the same four-member CLCA gene locus and the corresponding mucosal and submucosal populations of mucous cells found in humans. Here we develop to our knowledge the first CLCA1-gene-deficient (CLCA1-/-) pig and show that these animals exhibit loss of MUC5AC+ mucous cells throughout the airway mucosa of the lung without affecting comparable cells in the tracheal mucosa or MUC5B+ mucous cells in submucosal glands. Similarly, CLCA1-/- pigs exhibit loss of MUC5AC+ mucous cells in the intestinal mucosa without affecting MUC2+ mucous cells. These data establish CLCA1 function for controlling MUC5AC expression as a marker of mucus production and provide a new animal model to study mucus production at respiratory and intestinal sites.

Disrupting porcine glutaminase does not block preimplantation development and elongation nor decrease mTORC1 activation in conceptuses†.

Elongation of pig conceptuses is a dynamic process, requiring adequate nutrient provisions. Glutamine is used as an energy substrate and is involved in the activation of mechanistic target of rapamycin complex 1 (mTORC1) during porcine preimplantation development. However, the roles of glutamine have not been extensively studied past the blastocyst stage. Therefore, the objective of the current study was to determine if glutaminase (GLS), which is the rate-limiting enzyme in glutamine metabolism, was necessary for conceptus elongation to proceed and was involved in mTORC1 activation. The CRISPR/Cas9 system was used to induce loss-of-function mutations in the GLS gene of porcine fetal fibroblasts. Wild type (GLS+/+) and knockout (GLS-/-) fibroblasts were used as donor cells for somatic cell nuclear transfer, and GLS+/+ and GLS-/- blastocyst-stage embryos were transferred into surrogates. On day 14 of gestation, GLS+/+ conceptuses primarily demonstrated filamentous morphologies, and GLS-/- conceptuses exhibited spherical, ovoid, tubular, and filamentous morphologies. Thus, GLS-/- embryos were able to elongate despite the absence of GLS protein and minimal enzyme activity. Furthermore, spherical GLS-/- conceptuses had increased abundance of transcripts related to glutamine and glutamate metabolism and transport compared to filamentous conceptuses of either genotype. Differences in phosphorylation of mTORC1 components and targets were not detected regarding conceptus genotype or morphology, but abundance of two transcriptional targets of mTORC1, cyclin D1, and peroxisome proliferator-activated receptor gamma coactivator 1-alpha was increased in spherical conceptuses. Therefore, porcine GLS is not essential for conceptus elongation and is not required for mTORC1 activation at this developmental timepoint.

Deciphering the functional role of EGR1 in Prostaglandin F2 alpha induced luteal regression applying CRISPR in corpus luteum of buffalo.

BACKGROUND: PGF2α is essential for the induction of the corpus luteum regression which in turn reduces progesterone production. Early growth response (EGR) proteins are Cys2-His2-type zinc-finger transcription factor that are strongly linked to cellular proliferation, survival and apoptosis. Rapid elevation of EGR1 was observed after luteolytic dose of PGF2α. EGR1 is involved in the transactivation of many genes, including TGFß1, which plays an important role during luteal regression. METHODS: The current study was conducted in buffalo luteal cells with the aim to better understand the role of EGR1 in transactivation of TGFß1 during PGF2α induced luteal regression. Luteal cells from mid stage corpus luteum of buffalo were cultured and treated with different doses of PGF2α for different time durations. Relative expression of mRNAs encoding for enzymes within the progesterone biosynthetic pathway (3ßHSD, CYP11A1 and StAR); Caspase 3; AKT were analyzed to confirm the occurrence of luteolytic event. To determine if EGR1 is involved in the PGF2α induced luteal regression via induction of TGFß1 expression, we knocked out the EGR1 gene by using CRISPR/Cas9. RESULT: The present experiment determined whether EGR1 protein expression in luteal cells was responsive to PGF2α treatment. Quantification of EGR1 and TGFß1 mRNA showed significant up regulation in luteal cells of buffalo at 12 h post PGF2α induction. In order to validate the role of PGF2α on stimulating the expression of TGFß1 by an EGR1 dependent mechanism we knocked out EGR1. The EGR1 ablated luteal cells were stimulated with PGF2α and it was observed that EGR1 KO did not modulate the PGF2α induced expression of TGFß1. In PGF2α treated EGR1 KO luteal cell, the mRNA expression of Caspase 3 was significantly increased compared to PGF2α treated wild type luteal cells maintained for 12 h. We also studied the influence of EGR1 on steroidogenesis. The EGR1 KO luteal cells with PGF2α treatment showed no substantial difference either in the progesterone concentration or in StAR mRNA expression with PGF2α-treated wild type luteal cells. CONCLUSION: These results suggest that EGR1 signaling is not the only factor which plays a role in the regulation of PGF2α induced TGFß1 signaling for luteolysis.

Transcriptional Regulation of Thrombospondins and Its Functional Validation through CRISPR/Cas9 Mediated Gene Editing in Corpus Luteum of Water Buffalo (Bubalus Bubalis).

BACKGROUND/AIMS: Thrombospondins (TSPs) are large multi-modular proteins, identified as natural angiogenesis inhibitors that exert their activity by binding to CD36 and CD47 receptors. The anti-angiogenic effect of TSPs in luteal regression of water buffalo has not been addressed. The present study characterized the expression pattern and localization of TSPs and their receptors in ovarian corpus luteum during different stages of development in buffalo. This study also elucidated the effect of exogenous Thrombospondin1 (TSP1) or the knocking out of the endogenous protein on luteal cell viability and function. Further, the in vitro transcriptional interaction of TSP1 with hormones, LH, PGF2α and angiogenic growth factors, VEGF and FGF2 were also evaluated. METHODS: First, the CLs were classified into four groups based on macroscopic observation and progesterone concentration. mRNA expression of examined factors was measured by qPCR, localization by immunoblotting and immunohistochemistry. TSP1 was knocked out (KO) in cultured luteal cells isolated from late luteal stage CLs (day 1116) by CRISPR/Cas9 mediated gene editing technology in order to functionally validate the TSP1 gene. Isolated cells from late stage CLs were also stimulated with different doses of TSP1, LH, PGF2α, VEGF and FGF2 for various time intervals to determine transcriptional regulation of thrombospondins. RESULTS: mRNA expression of TSPs and their receptors were found to be significantly higher in late and regressed stage of CL as compared to other groups which was consistent with the findings of immunoblotting and immunolocalization experiments. It was observed that TSP1 induced apoptosis, down regulated angiogenic growth factors, VEGF and FGF2 and attenuated progesterone production in cultured luteal cells. However, knocking out of endogenous TSP1 with CRISPR/Cas9 system improved the viability of luteal cells, progesterone synthesis and upregulated the expression of VEGF and FGF2 in the KO luteal cells. PGF2α induced the upregulation of TSPs and Caspase 3 transcripts, whereas treatment with LH and angiogenic growth factors (VEGF and FGF2) down regulated the TSP system in luteal cells. CONCLUSION: Collectively, these data provide evidence that thrombospondins along with their receptors are expressed at varying levels in different stages of CL progression with maximum expression during the late and regressing stages. These results are consistent with the hypothesis that thrombospondins stimulated by PGF2α plays an essential modulatory role in bringing about structural and functional luteolysis in buffalo.

New perspective on conceptus estrogens in maternal recognition and pregnancy establishment in the pig†.

The proposed signal for maternal recognition of pregnancy in pigs is estrogen (E2), produced by the elongating conceptuses between days 11 to 12 of pregnancy with a more sustained increase during conceptus attachment and placental development on days 15 to 30. To understand the role of E2 in porcine conceptus elongation and pregnancy establishment, a loss-of-function study was conducted by editing aromatase (CYP19A1) using CRISPR/Cas9 technology. Wild-type (CYP19A1+/+) and (CYP19A1-/-) fibroblast cells were used to create embryos through somatic cell nuclear transfer, which were transferred into recipient gilts. Elongated and attaching conceptuses were recovered from gilts containing CYP19A1+/+ or CYP19A1-/- embryos on day 14 and 17 of pregnancy. Total E2 in the uterine flushings of gilts with CYP19A1-/- embryos was lower than recipients containing CYP19A1+/+ embryos with no difference in testosterone, PGF2α, or PGE2 on either day 14 or 17. Despite the loss of conceptus E2 production, CYP19A1-/- conceptuses were capable of maintaining the corpora lutea. However, gilts gestating CYP19A1-/- embryos aborted between days 27 and 31 of gestation. Attempts to rescue the pregnancy of CYP19A1-/- gestating gilts with exogenous E2 failed to maintain pregnancy. However, CYP19A1-/- embryos could be rescued when co-transferred with embryos derived by in vitro fertilization. Endometrial transcriptome analysis revealed that ablation of conceptus E2 resulted in disruption of a number biological pathways. Results demonstrate that intrinsic E2 conceptus production is not essential for pre-implantation development, conceptus elongation, and early CL maintenance, but is essential for maintenance of pregnancy beyond 30 days .

Improvement of in vitro and early in utero porcine clone development after somatic donor cells are cultured under hypoxia.

Genetically engineered pigs serve as excellent biomedical and agricultural models. To date, the most reliable way to generate genetically engineered pigs is via somatic cell nuclear transfer (SCNT), however, the efficiency of cloning in pigs is low (1-3%). Somatic cells such as fibroblasts frequently used in nuclear transfer utilize the tricarboxylic acid cycle and mitochondrial oxidative phosphorylation for efficient energy production. The metabolism of somatic cells contrasts with cells within the early embryo, which predominately use glycolysis. We hypothesized that fibroblast cells could become blastomere-like if mitochondrial oxidative phosphorylation was inhibited by hypoxia and that this would result in improved in vitro embryonic development after SCNT. In a previous study, we demonstrated that fibroblasts cultured under hypoxic conditions had changes in gene expression consistent with increased glycolytic/gluconeogenic metabolism. The goal of this pilot study was to determine if subsequent in vitro embryo development is impacted by cloning porcine embryonic fibroblasts cultured in hypoxia. Here we demonstrate that in vitro measures such as early cleavage, blastocyst development, and blastocyst cell number are improved (4.4%, 5.5%, and 17.6 cells, respectively) when donor cells are cultured in hypoxia before nuclear transfer. Survival probability was increased in clones from hypoxic cultured donors compared to controls (8.5 vs. 4.0 ± 0.2). These results suggest that the clones from donor cells cultured in hypoxia are more developmentally competent and this may be due to improved nuclear reprogramming during somatic cell nuclear transfer.

Resistance to coronavirus infection in amino peptidase N-deficient pigs.

The alphacoronaviruses, transmissible gastroenteritis virus (TGEV) and Porcine epidemic diarrhea virus (PEDV) are sources of high morbidity and mortality in neonatal pigs, a consequence of dehydration caused by the infection and necrosis of enterocytes. The biological relevance of amino peptidase N (ANPEP) as a putative receptor for TGEV and PEDV in pigs was evaluated by using CRISPR/Cas9 to edit exon 2 of ANPEP resulting in a premature stop codon. Knockout pigs possessing the null ANPEP phenotype and age matched wild type pigs were challenged with either PEDV or TGEV. Fecal swabs were collected daily from each animal beginning 1 day prior to challenge with PEDV until the termination of the study. The presence of virus nucleic acid was determined by PCR. ANPEP null pigs did not support infection with TGEV, but retained susceptibility to infection with PEDV. Immunohistochemistry confirmed the presence of PEDV reactivity and absence of TGEV reactivity in the enterocytes lining the ileum in ANPEP null pigs. The different receptor requirements for TGEV and PEDV have important implications in the development of new genetic tools for the control of enteric disease in pigs.

Replacement of Porcine CD163 Scavenger Receptor Cysteine-Rich Domain 5 with a CD163-Like Homolog Confers Resistance of Pigs to Genotype 1 but Not Genotype 2 Porcine Reproductive and Respiratory Syndrome Virus.

CD163 knockout (KO) pigs are resistant to infection with genotype 2 (type 2) porcine reproductive and respiratory syndrome virus (PRRSV). Furthermore, the substitution of CD163 scavenger receptor cysteine-rich (SRCR) domain 5 with a homolog of human CD163-like (hCD163L1) SRCR 8 domain confers resistance of transfected HEK cells to type 1 PRRSV. As a means to understand the role of domain 5 in PRRSV infection with both type 1 and type 2 viruses, pigs were genetically modified (GM) to possess one of the following genotypes: complete knockout (KO) of CD163, deletions within SRCR domain 5, or replacement (domain swap) of SRCR domain 5 with a synthesized exon encoding a homolog of hCD163L1 SRCR domain 8. Immunophenotyping of porcine alveolar macrophages (PAMs) showed that pigs with the KO or SRCR domain 5 deletion did not express CD163. When placed in culture, PAMs from pigs with the CD163 KO phenotype were completely resistant to a panel consisting of six type 1 and nine type 2 isolates. PAMs from pigs that possessed the hCD163L1 domain 8 homolog expressed CD163 and supported the replication of all type 2 isolates, but no type 1 viruses. Infection of CD163-modified pigs with representative type 1 and type 2 viruses confirmed the in vitro results. The results confirm that CD163 is the likely receptor for all PRRS viruses. Even though type 1 and type 2 viruses are considered phenotypically similar at several levels, there is a distinct difference between the viral genotypes in the recognition of CD163. IMPORTANCE: Genetic modification of the CD163 gene creates the opportunity to develop production animals that are resistant to PRRS, the costliest viral disease to ever face the swine industry. The results create further opportunities to develop refinements in the modification of CD163 with the goal of making pigs refractory to infection while retaining important CD163 functions.

Zygote injection of RNA encoding Cre recombinase results in efficient removal of LoxP flanked neomycin cassettes in pigs.

Genetically engineered pigs are often created with a targeting vector that contains a loxP flanked selectable marker like neomycin. The Cre-loxP recombinase system can be used to remove the selectable marker gene from the resulting offspring or cell line. Here is described a new method to remove a loxP flanked neomycin cassette by direct zygote injection of an mRNA encoding Cre recombinase. The optimal concentration of mRNA was determined to be 10 ng/µL when compared to 2 and 100 ng/µL (P < 0.0001). Development to the blastocyst stage was 14.1% after zygote injection with 10 ng/µL. This method successfully removed the neomycin cassette in 81.9% of injected in vitro derived embryos; which was significantly higher than the control (P < 0.0001). Embryo transfer resulted in the birth of one live piglet with a Cre deleted neomycin cassette. The new method described can be used to efficiently remove selectable markers in genetically engineered animals without the need for long term cell culture and subsequent somatic cell nuclear transfer.

Gene editing as applied to prevention of reproductive porcine reproductive and respiratory syndrome.

Porcine Reproductive and Respiratory Syndrome (PRRS) causes severe reproductive failure in sows as well as transplacental transfer of PRRS virus (PRRSV) to late-gestation fetuses, resulting in abortions, early farrowing, increased number of stillborn piglets, and weak neonatal piglets. PRRSV-infected boars present with anorexia and lethargy, and have decreased sperm quality. The gene for the cellular receptor that the PRRSV uses, Cluster of differentiation 163 (CD163), was edited using Clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 gene-editing technology to create biallelic DNA edits to the CD163 gene in 100% of the offspring. CD163-null pigs challenged with virus were completely resistant to both Type 1 and Type 2 PRRSV isolates, as measured by clinical signs, viremia, antibody response, and lung histopathology. In vitro studies showed that CD163-null alveolar macrophages were also not permissive to infection by a panel of six Type 1 and nine Type 2 viral isolates. Thus, DNA editing of the CD163 gene prevented PRRSV infection and reproductive losses associated with infection.

Zygote injection of CRISPR/Cas9 RNA successfully modifies the target gene without delaying blastocyst development or altering the sex ratio in pigs.

The CRISPR/Cas9 genome editing tool has increased the efficiency of creating genetically modified pigs for use as biomedical or agricultural models. The objectives were to determine if DNA editing resulted in a delay in development to the blastocyst stage or in a skewing of the sex ratio. Six DNA templates (gBlocks) that were designed to express guide RNAs that target the transmembrane protease, serine S1, member 2 (TMPRSS2) gene were in vitro transcribed. Pairs of CRISPR guide RNAs that flanked the start codon and polyadenylated Cas9 were co-injected into the cytoplasm of zygotes and cultured in vitro to the blastocyst stage. Blastocysts were collected as they formed on days 5, 6 or 7. PCR was performed to determine genotype and sex of each embryo. Separately, embryos were surgically transferred into recipient gilts on day 4 of estrus. The rate of blastocyst development was not significantly different between CRISPR injection embryos or the non-injected controls at day 5, 6 or 7 (p = 0.36, 0.09, 0.63, respectively). Injection of three CRISPR sets of guides resulted in a detectable INDEL in 92-100 % of the embryos analyzed. There was not a difference in the number of edits or sex ratio of male to female embryos when compared between days 5, 6 and 7 to the controls (p > 0.22, >0.85). There were 12 resulting piglets and all 12 had biallelic edits of TMRPSS2. Zygote injection with CRISPR/Cas9 continues to be a highly efficient tool to genetically modify pig embryos.

Glycine supplementation in vitro enhances porcine preimplantation embryo cell number and decreases apoptosis but does not lead to live births.

Most in vitro culture conditions are less-than-optimal for embryo development. Here, we used a transcriptional-profiling database to identify culture-induced differences in gene expression in porcine blastocysts compared to in vivo-produced counterparts. Genes involved in glycine transport (SLC6A9), glycine metabolism (GLDC, GCSH, DLD, and AMT), and serine metabolism (PSAT1, PSPH, and PHGDH) were differentially expressed. Addition of 10 mM glycine to the culture medium (currently containing 0.1 mM) reduced the abundance of SLC6A9 transcript and increased total cell number, primarily in the trophectoderm lineage (P = 0.003); this was likely by decreasing the percentage of apoptotic nuclei. As serine and glycine can be reversibly metabolized by serine hydroxymethyltransferase 2 (SHMT2), we assessed the abundance of SHMT2 transcript as well as its functional role by inhibiting it with aminomethylphosphonic acid (AMPA), a glycine analog, during in vitro culture. Both AMPA supplementation and elevated glycine decreased the mRNA abundance of SHMT2 and tumor protein p53 (TP53), which is activated in response to cellular stress, compared to controls (P ≤ 0.02). On the other hand, mitochondrial activity of blastocysts, mtDNA copy number, and abundance of mitochondria-related transcripts did not differ between control and 10 mM glycine culture conditions. Despite improvements to these metrics of blastocyst quality, transfer of embryos cultured in 10 mM glycine did not result in pregnancy whereas the transfer of in vitro-produced embryos cultured in control medium yielded live births. Mol. Reprod. Dev. 83: 246-258, 2016. © 2016 The Authors.

Dynamics of TET family expression in porcine preimplantation embryos is related to zygotic genome activation and required for the maintenance of NANOG.

Dynamic changes in DNA methylation are observed during embryo development. Recent studies show that the TET family is involved in these changes by converting 5-methylcytosine (5mec) to 5-hydroxymethylcytosine (5hmec). Specifically, TET3 is responsible for the conversion in the early stages, and then TET1 is a key regulator at later stages of embryo development. From previous mouse reports and our preliminary data in porcine embryos, we hypothesized that TET1 becomes the main regulator at the time of the maternal to zygotic transition (MZT). Transcript abundance of TET3 was high only at the zygote and 2-cell stage. The abundance of TET1 mRNA was high in the blastocysts and TET1 protein was present at the 4-cell stage and the blastocysts. The dynamic was similar in porcine somatic cell nuclear transfer (SCNT) embryos however; abnormally upregulated TET3 was detected at the 4-cell stage. When transcription or translation was blocked at the 2-cell stage, TET3 mRNA remained high at the 4-cell stage suggesting that degradation of TET3 is related to the MZT. Downregulation of TET3 before fertilization resulted in the reduction of 5hmec in zygotes indicating that TET3 is a key molecule for 5hmec synthesis. This misregulation of 5hmec in zygotes also affected the level of NANOG expression in the blastocysts. We show here that the porcine TET family shows dynamic expression patterns during embryogenesis, and is responsible for the appearance of 5hmec in the zygotes by TET3. This appearance of 5hmec in zygote is important for the expression of NANOG in the blastocysts.

Impairment of preimplantation porcine embryo development by histone demethylase KDM5B knockdown through disturbance of bivalent H3K4me3-H3K27me3 modifications.

KDM5B (JARID1B/PLU1) is a H3K4me2/3 histone demethylase that is implicated in cancer development and proliferation and is also indispensable for embryonic stem cell self-renewal, cell fate, and murine embryonic development. However, little is known about the role of KDM5B during preimplantation embryo development. Here we show that KDM5B is critical to porcine preimplantation development. KDM5B was found to be expressed in a stage-specific manner, consistent with demethylation of H3K4me3, with the highest expression being observed from the 4-cell to the blastocyst stages. Knockdown of KDM5B by morpholino antisense oligonucleotides injection impaired porcine embryo development to the blastocyst stage. The impairment of embryo development might be caused by increased expression of H3K4me3 at the 4-cell and blastocyst stages, which disturbs the balance of bivalent H3K4me3-H3K27me3 modifications at the blastocyst stage. Decreased abundance of H3K27me3 at blastocyst stage activates multiple members of homeobox genes (HOX), which need to be silenced for faithful embryo development. Additionally, the histone demethylase KDM6A was found to be upregulated by knockdown of KDM5B, which indicated it was responsible for the decreased abundance of H3K27me3 at the blastocyst stage. The transcriptional levels of Ten-Eleven Translocation gene family members (TET1, TET2, and TET3) are found to be increased by knockdown of KDM5B, which indicates cross talk between histone modifications and DNA methylation. The studies above indicate that KDM5B is required for porcine embryo development through regulating the balance of bivalent H3K4me3-H3K27me3 modifications.

PS48 can replace bovine serum albumin in pig embryo culture medium, and improve in vitro embryo development by phosphorylating AKT.

The application of embryo-related technology is dependent on in vitro culture systems. Unfortunately, most culture media are suboptimal and result in developmentally compromised embryos. Since embryo development is partially dependent upon Warburg Effect-like metabolism, our goal was to test the response of embryos treated with compounds that are known to stimulate or enhance this Effect. One such compound is 5-(4-chloro-phenyl)-3-phenyl-pent-2-enoic acid (PS48). When added during oocyte maturation, the quality of the resultant embryos was compromised, whereas when added to the culture medium after fertilization, PS48 improved both the percentage of embryos that reach the blastocyst stage and the number of nuclei in those blastocysts. Embryonic PS48 treatment resulted in more phosphorylated v-akt murine thymoma viral oncogene homolog (AKT) in blastocyst-stage embryos as compared to the controls. Further, PS48 could replace bovine serum albumin in embryo culture medium, as demonstrated by high-quality embryos that were developmentally competent. The action of PS48 appears to be via stimulation of phosphoinositide-3 kinase and phosphorylation of AKT, which is consistent with stimulation of the Warburg Effect.

Use of the CRISPR/Cas9 system to produce genetically engineered pigs from in vitro-derived oocytes and embryos.

Targeted modification of the pig genome can be challenging. Recent applications of the CRISPR/Cas9 system hold promise for improving the efficacy of genome editing. When a designed CRISPR/Cas9 system targeting CD163 or CD1D was introduced into somatic cells, it was highly efficient in inducing mutations. When these mutated cells were used with somatic cell nuclear transfer, offspring with these modifications were created. When the CRISPR/Cas9 system was delivered into in vitro produced presumptive porcine zygotes, the system was effective in creating mutations in eGFP, CD163, and CD1D (100% targeting efficiency in blastocyst stage embryos); however, it also presented some embryo toxicity. We could also induce deletions in CD163 or CD1D by introducing two types of CRISPRs with Cas9. The system could also disrupt two genes, CD163 and eGFP, simultaneously when two CRISPRs targeting two genes with Cas9 were delivered into zygotes. Direct injection of CRISPR/Cas9 targeting CD163 or CD1D into zygotes resulted in piglets that have mutations on both alleles with only one CD1D pig having a mosaic genotype. We show here that the CRISPR/Cas9 system can be used by two methods. The system can be used to modify somatic cells followed by somatic cell nuclear transfer. System components can also be used in in vitro produced zygotes to generate pigs with specific genetic modifications.

An intact sialoadhesin (Sn/SIGLEC1/CD169) is not required for attachment/internalization of the porcine reproductive and respiratory syndrome virus.

Surface expression of SIGLEC1, also known as sialoadhesin or CD169, is considered a primary determinant of the permissiveness of porcine alveolar macrophages for infection by porcine reproductive and respiratory syndrome virus (PRRSV). In vitro, the attachment and internalization of PRRSV are dependent on the interaction between sialic acid on the virion surface and the sialic acid binding domain of the SIGLEC1 gene. To test the role of SIGLEC1 in PRRSV infection, a SIGLEC1 gene knockout pig was created by removing part of exon 1 and all of exons 2 and 3 of the SIGLEC1 gene. The resulting knockout ablated SIGLEC1 expression on the surface of alveolar macrophages but had no effect on the expression of CD163, a coreceptor for PRRSV. After infection, PRRSV viremia in SIGLEC1(-/-) pigs followed the same course as in SIGLEC1(-/+) and SIGLEC1(+/+) littermates. The absence of SIGLEC1 had no measurable effect on other aspects of PRRSV infection, including clinical disease course and histopathology. The results demonstrate that the expression of the SIGLEC1 gene is not required for infection of pigs with PRRSV and that the absence of SIGLEC1 does not contribute to the pathogenesis of acute disease.

Induced Pluripotent Stem Cells in the Era of Precise Genome Editing.

Genome editing has enhanced our ability to understand the role of genetics in a number of diseases by facilitating the development of more precise cellular and animal models to study pathophysiological processes. These advances have shown extraordinary promise in a multitude of areas, from basic research to applied bioengineering and biomedical research. Induced pluripotent stem cells (iPSCs) are known for their high replicative capacity and are excellent targets for genetic manipulation as they can be clonally expanded from a single cell without compromising their pluripotency. Clustered, regularly interspaced short palindromic repeats (CRISPR) and CRISPR/Cas RNA-guided nucleases have rapidly become the method of choice for gene editing due to their high specificity, simplicity, low cost, and versatility. Coupling the cellular versatility of iPSCs differentiation with CRISPR/Cas9-mediated genome editing technology can be an effective experimental technique for providing new insights into the therapeutic use of this technology. However, before using these techniques for gene therapy, their therapeutic safety and efficacy following models need to be assessed. In this review, we cover the remarkable progress that has been made in the use of genome editing tools in iPSCs, their applications in disease research and gene therapy as well as the hurdles that remain in the actual implementation of CRISPR/Cas systems.

Pigs: Large Animal Preclinical Cancer Models.

Pigs are playing an increasingly vital role as translational biomedical models for studying human pathophysiology. The annotation of the pig genome was a huge step forward in translatability of pigs as a biomedical model for various human diseases. Similarities between humans and pigs in terms of anatomy, physiology, genetics, and immunology have allowed pigs to become a comprehensive preclinical model for human diseases. With a diverse range, from craniofacial and ophthalmology to reproduction, wound healing, musculoskeletal, and cancer, pigs have provided a seminal understanding of human pathophysiology. This review focuses on the current research using pigs as preclinical models for cancer research and highlights the strengths and opportunities for studying various human cancers.

Gene editing of pigs to control influenza A virus infections.

Proteolytic activation of the hemagglutinin (HA) glycoprotein by host cellular proteases is pivotal for influenza A virus (IAV) infectivity. Highly pathogenic avian influenza viruses possess the multibasic cleavage site of the HA which is cleaved by ubiquitous proteases, such as furin; in contrast, the monobasic HA motif is recognized and activated by trypsin-like proteases, such as the transmembrane serine protease 2 (TMPRSS2). Here, we aimed to determine the effects of TMPRSS2 on the replication of pandemic H1N1 and H3N2 subtype IAVs in the natural host, the pig. The use of the CRISPR/Cas 9 system led to the establishment of homozygous gene edited (GE) TMPRSS2 knockout (KO) pigs. Delayed IAV replication was demonstrated in primary respiratory cells of KO pigs in vitro. IAV infection in vivo resulted in significant reduction of virus shedding in the upper respiratory tract, and lower virus titers and pathological lesions in the lower respiratory tract of TMPRSS2 KO pigs as compared to WT pigs. Our findings could support the commercial use of GE pigs to minimize (i) the economic losses caused by IAV infection in pigs, and (ii) the emergence of novel IAVs with pandemic potential through genetic reassortment in the "mixing vessel", the pig.