Genotyping the mouse severe combined immunodeficiency mutation using the polymerase chain reaction with confronting two-pair primers (PCR-CTPP)

TYK2 signaling promotes the development of autoreactive CD8+ cytotoxic T lymphocytes and type 1 diabetes

Tyrosine kinase 2 (TYK2), a member of the JAK family, has attracted attention as a potential therapeutic target for autoimmune diseases. However, the role of TYK2 in CD8+ T cells and autoimmune type 1 diabetes (T1D) is poorly understood. In this study, we generate Tyk2 gene knockout non-obese diabetes (NOD) mice and demonstrate that the loss of Tyk2 inhibits the development of autoreactive CD8+ T-BET+ cytotoxic T lymphocytes (CTLs) by impairing IL-12 signaling in CD8+ T cells and the CD8+ resident dendritic cell-driven cross-priming of CTLs in the pancreatic lymph node (PLN). Tyk2-deficient CTLs display reduced cytotoxicity. Increased inflammatory responses in β-cells with aging are dampened by Tyk2 deficiency. Furthermore, treatment with BMS-986165, a selective TYK2 inhibitor, inhibits the expansion of T-BET+ CTLs, inflammation in β-cells and the onset of autoimmune T1D in NOD mice. Thus, our study reveals the diverse roles of TYK2 in driving the pathogenesis of T1D.

Potassium and glutamate transport is impaired in scar-forming tumor-associated astrocytes

Unprovoked recurrent seizures are a serious comorbidity affecting most patients who suffer from glioma, a primary brain tumor composed of malignant glial cells. Cellular mechanisms contributing to the development of recurrent spontaneous seizures include the release of the excitatory neurotransmitter glutamate from glioma into extracellular space. Under physiological conditions, astrocytes express two high affinity glutamate transporters, Glt-1 and Glast, which are responsible for the removal of excess extracellular glutamate. In the context of neurological disease or brain injury, astrocytes become reactive which can negatively affect neuronal function, causing hyperexcitability and/or death. Using electrophysiology, immunohistochemistry, fluorescent in situ hybridization, and Western blot analysis in different orthotopic xenograft and allograft models of human and mouse gliomas, we find that peritumoral astrocytes exhibit astrocyte scar formation characterized by proliferation, cellular hypertrophy, process elongation, and increased GFAP and pSTAT3. Overall, peritumoral reactive astrocytes show a significant reduction in glutamate and potassium uptake, as well as decreased glutamine synthetase activity. A subset of peritumoral astrocytes displayed a depolarized resting membrane potential, further contributing to reduced potassium and glutamate homeostasis. These changes may contribute to the propagation of peritumoral neuronal hyperexcitability and excitotoxic death.

Natural Flavonol, Myricetin, Enhances the Function and Survival of Cryopreserved Hepatocytes In Vitro and In Vivo

To improve the therapeutic potential of hepatocyte transplantation, the effects of the mitogen-activated protein kinase kinase 4 (MKK4) inhibitor, myricetin (3,3′,4′,5,5′,7-hexahydroxylflavone) were examined using porcine and human hepatocytes in vitro and in vivo. Hepatocytes were cultured, showing the typical morphology of hepatic parenchymal cell under 1–10 µmol/L of myricetin, keeping hepatocyte specific gene expression, and ammonia removal activity. After injecting the hepatocytes into neonatal Severe combined immunodeficiency (SCID) mouse livers, cell colony formation was found at 10–15 weeks after transplantation. The human albumin levels in the sera of engrafted mice were significantly higher in the recipients of myricetin-treated cells than non-treated cells, corresponding to the size of the colonies. In terms of therapeutic efficacy, the injection of myricetin-treated hepatocytes significantly prolonged the survival of ornithine transcarbamylase-deficient SCID mice from 32 days (non-transplant control) to 54 days. Biochemically, the phosphorylation of MKK4 was inhibited in the myricetin-treated hepatocytes. These findings suggest that myricetin has a potentially therapeutic benefit that regulates hepatocyte function and survival, thereby treating liver failure.

Confronting two biomolecular techniques to detect NRF2 gene polymorphism biomarkers

Aim:

Gene polymorphism biomarkers identify individual susceptibility to environmental and occupational hazards. The conventional approach considers polymerase chain reaction (PCR) followed by restriction fragment length polymorphism analysis (RFLP), a reliable but expensive and time-consuming two-step procedure. Therefore we evaluated the simpler method confronting two-pair primers (CTPP)–PCR for its robustness and applicability to epidemiologic studies.

Materials & methods:

We compared CTPP–PCR and PCR–RFLP techniques to detect two NRF2 polymorphisms in a set of biological samples.

Results:

CTPP–PCR produced contradictory results and required the orthogonal technique for confirming the data.

Conclusion:

In contrast to PCR-RFLP, CTPP–PCR of NRF2 polymorphisms resulted in ambiguous genotyping which strongly jeopardized heterozygosis classification. The necessity of long optimization and control procedures nullified the potential advantages of CTPP–PCR in terms of costs and time.

Confronting two-pair primers-polymerase chain reaction (CTPP–PCR) is potentially a fast, simple and cost-efficient method for the detection of gene polymorphism biomarkers. This technique was used to genotype two SNPs of NRF2 gene in a set of biological samples but resulted in ambiguous results. Therefore, it was necessary to validate the CTPP–PCR genotyping data with the orthogonal technique PCR-RFLP. Since reproducibility is a critical issue in both biomedical research and diagnostics, we advise pairing CTPP–PCR with control methods and evaluating whether the overall package is still convenient for massive genetic screening.

Microglia are effector cells of CD47-SIRPα antiphagocytic axis disruption against glioblastoma

Glioblastoma multiforme (GBM) is a highly aggressive malignant brain tumor with fatal outcome. Tumor-associated macrophages and microglia (TAMs) have been found to be major tumor-promoting immune cells in the tumor microenvironment. Hence, modulation and reeducation of tumor-associated macrophages and microglia in GBM is considered a promising antitumor strategy. Resident microglia and invading macrophages have been shown to have distinct origin and function. Whereas yolk sac-derived microglia reside in the brain, blood-derived monocytes invade the central nervous system only under pathological conditions like tumor formation. We recently showed that disruption of the SIRPα-CD47 signaling axis is efficacious against various brain tumors including GBM primarily by inducing tumor phagocytosis. However, most effects are attributed to macrophages recruited from the periphery but the role of the brain resident microglia is unknown. Here, we sought to utilize a model to distinguish resident microglia and peripheral macrophages within the GBM-TAM pool, using orthotopically xenografted, immunodeficient, and syngeneic mouse models with genetically color-coded macrophages (Ccr2RFP) and microglia (Cx3cr1GFP). We show that even in the absence of phagocytizing macrophages (Ccr2RFP/RFP), microglia are effector cells of tumor cell phagocytosis in response to anti-CD47 blockade. Additionally, macrophages and microglia show distinct morphological and transcriptional changes. Importantly, the transcriptional profile of microglia shows less of an inflammatory response which makes them a promising target for clinical applications.

Endothelial-to-Osteoblast Conversion Generates Osteoblastic Metastasis of Prostate Cancer

Prostate cancer (PCa) bone metastasis is frequently associated with bone-forming lesions, but the source of the osteoblastic lesions remains unclear. We show that the tumor-induced bone derives partly from tumor-associated endothelial cells that have undergone endothelial-to-osteoblast (EC-to-OSB) conversion. The tumor-associated osteoblasts in PCa bone metastasis specimens and patient-derived xenografts (PDXs) were found to co-express endothelial marker Tie-2. BMP4, identified in PDX-conditioned medium, promoted EC-to-OSB conversion of 2H11 endothelial cells. BMP4 overexpression in non-osteogenic C4-2b PCa cells led to ectopic bone formation under subcutaneous implantation. Tumor-induced bone was reduced in trigenic mice (Tie2^cre/Osx^f/f/SCID) with endothelial-specific deletion of osteoblast cell-fate determinant OSX compared with bigenic mice (Osx^f/f/SCID). Thus, tumor-induced EC-to-OSB conversion is one mechanism that leads to osteoblastic bone metastasis of PCa.

PD-1 expression by tumour-associated macrophages inhibits phagocytosis and tumour immunity

Programmed cell death protein 1 (PD-1) is an immune checkpoint receptor that is upregulated on activated T cells for the induction of immune tolerance. Tumour cells frequently overexpress the ligand for PD-1, programmed cell death ligand 1 (PD-L1), facilitating their escape from the immune system. Monoclonal antibodies that block the interaction between PD-1 and PD-L1, by binding to either the ligand or receptor, have shown notable clinical efficacy in patients with a variety of cancers, including melanoma, colorectal cancer, non-small-cell lung cancer and Hodgkin's lymphoma. Although it is well established that PD-1-PD-L1 blockade activates T cells, little is known about the role that this pathway may have in tumour-associated macrophages (TAMs). Here we show that both mouse and human TAMs express PD-1. TAM PD-1 expression increases over time in mouse models of cancer and with increasing disease stage in primary human cancers. TAM PD-1 expression correlates negatively with phagocytic potency against tumour cells, and blockade of PD-1-PD-L1 in vivo increases macrophage phagocytosis, reduces tumour growth and lengthens the survival of mice in mouse models of cancer in a macrophage-dependent fashion. This suggests that PD-1-PD-L1 therapies may also function through a direct effect on macrophages, with substantial implications for the treatment of cancer with these agents.

A novel immunodeficient NOD.SCID-rd1 mouse model of retinitis pigmentosa to investigate potential therapeutics and pathogenesis of retinal degeneration

Retinitis pigmentosa (RP) is a common retinal degeneration disease caused by mutation in any gene of the photo transduction cascade and results in photoreceptor dystrophy. Over decades, several animal models have been used to address the need for the elucidation of effective therapeutics and factors regulating retinal degeneration to prohibit or renew the damaged retina. However, controversies over the immune privilege of retina during cell transplantation and the role of immune modulation during RP still remain largely uninvestigated because of the lack of suitable animal models. Here, we have developed an immunocompromised mouse model, NOD.SCID-rd1, for retinitis pigmentosa (RP) by crossing CBA/J and NOD SCID mice and selecting homozygous double mutant animals for further breeding. Characterization of the newly developed RP model indicates a similar retinal degeneration pattern as CBA/J, with a decreased apoptosis rate and rhodopsin loss. It also exhibits loss of T cells, B cells and NK cells. The NOD.SCID-rd1 model is extremely useful for allogenic and xenogenic cell-based therapeutics, as indicated by the higher cell integration capacity post transplantation. We dissect the underlying role of the immune system in the progression of RP and the effect of immune deficiency on immune privilege of the eye using comparative qPCR studies of this model and the immune-competent RP model.

Summary: NOD.SCID-rd1 is an immune compromised mouse model of retinitis pigmentosa (RP) to investigate cell-based therapeutics for retinal rescue during RP and to study immunological aspects of its pathogenesis and progression.

Simple and reliable genotyping protocol for mouse Prkdc(SCID) mutation

Mutant mouse models, genetically-engineered or spontaneous-mutations, serve as valuable tools for biomedical research. Genotyping of mutant mice is a critical requirement for maintaining the colony, to breed with other mutants and to match the phenotypic observations. The SCID (Severe Combine Immuno Deficiency) mouse model has been extensively used as a common background-strain in many immunology and transplantation studies. Many different types of assays, including Restriction Fragment Length Polymorphism (RFLP), confronting two primer pairs PCR and end-point methods have been attempted for establishing a genotyping protocol for the SCID mutation. However, the best method that is thought to be reliable is sequencing, which requires additional time and resources to perform on a routine basis. In this report, we describe a novel RFLP assay that is simple and reliable. The method is validated by sequencing analysis, and this novel method can be adapted for routine genotyping of SCID model.

PCR-CTPP design for enzyme-free SNP genotyping using memetic algorithm

In recent years, many single nucleotide polymorphisms (SNPs) have been successfully genotyped by polymerase chain reaction with confronting two-pair primers (PCR-CTPP). However, computation experiments of feasible CTPP primers are still challenging. The melting temperatures between four primers must be within a very narrow range, and many primer constraints need to be conformed to. PCR-CTPP is a simple, time- and cost-effective SNP genotyping method applied in molecular biology and biomedical fields. In this study, an MA (memetic algorithm)-based method is proposed to enable the design of feasible CTPP primer sets. Overall, 288 SNPs which exclude the deletion/insertion polymorphisms (DIPs) and multi-nucleotide polymorphisms (MNPs) in the SLC6A4 gene were tested in silico. The results were compared with a GA (genetic algorithm)-based method and indicate that the proposed method provides more feasible CTPP primers than the GA-based method. The MA-based CTPP primer design method provides critical melting temperatures and all kinds of evaluation of the common primer constraints. It could conceivably assist biologists and other researchers in obtaining feasible CTTP primer sets. The MA-CTPP algorithm is implemented in JAVA and a user-friendly input interface is freely available at http://bio.kuas.edu.tw/ma-ctpp/.

Disruption of astrocyte-vascular coupling and the blood-brain barrier by invading glioma cells

Astrocytic endfeet cover the entire cerebral vasculature and serve as exchange sites for ions, metabolites, and energy substrates from the blood to the brain. They maintain endothelial tight junctions that form the blood-brain barrier (BBB) and release vasoactive molecules that regulate vascular tone. Malignant gliomas are highly invasive tumors that use the perivascular space for invasion and co-opt existing vessels as satellite tumors form. Here we use a clinically relevant mouse model of glioma and find that glioma cells, as they populate the perivascular space of pre-existing vessels, displace astrocytic endfeet from endothelial or vascular smooth muscle cells. This causes a focal breach in the BBB. Furthermore, astrocyte-mediated gliovascular coupling is lost, and glioma cells seize control over regulation of vascular tone through Ca²⁺-dependent release of K⁺. These findings have important clinical implications regarding blood flow in the tumor-associated brain and the ability to locally deliver chemotherapeutic drugs in disease.

The Bcl-2 homology domain 3 (BH3)-only proteins Bim and bid are functionally active and restrained by anti-apoptotic Bcl-2 family proteins in healthy liver

An intrinsic pathway of apoptosis is regulated by the B-cell lymphoma-2 (Bcl-2) family proteins. We previously reported that a fine rheostatic balance between the anti- and pro-apoptotic multidomain Bcl-2 family proteins controls hepatocyte apoptosis in the healthy liver. The Bcl-2 homology domain 3 (BH3)-only proteins set this rheostatic balance toward apoptosis upon activation in the diseased liver. However, their involvement in healthy Bcl-2 rheostasis remains unknown. In the present study, we focused on two BH3-only proteins, Bim and Bid, and we clarified the Bcl-2 network that governs hepatocyte life and death in the healthy liver. We generated hepatocyte-specific Bcl-xL- or Mcl-1-knock-out mice, with or without disrupting Bim and/or Bid, and we examined hepatocyte apoptosis under physiological conditions. We also examined the effect of both Bid and Bim disruption on the hepatocyte apoptosis caused by the inhibition of Bcl-xL and Mcl-1. Spontaneous hepatocyte apoptosis in Bcl-xL- or Mcl-1-knock-out mice was significantly ameliorated by Bim deletion. The disruption of both Bim and Bid completely prevented hepatocyte apoptosis in Bcl-xL-knock-out mice and weakened massive hepatocyte apoptosis via the additional in vivo knockdown of mcl-1 in these mice. Finally, the hepatocyte apoptosis caused by ABT-737, which is a Bcl-xL/Bcl-2/Bcl-w inhibitor, was completely prevented in Bim/Bid double knock-out mice. The BH3-only proteins Bim and Bid are functionally active but are restrained by the anti-apoptotic Bcl-2 family proteins under physiological conditions. Hepatocyte integrity is maintained by the dynamic and well orchestrated Bcl-2 network in the healthy liver.

Establishment of a novel dsRed NOD/Scid mouse strain to investigate the host and tumor cell compartments

Here we describe a NOD/Scid mouse strain expressing the dsRed transgene. The strain is maintained by inbreeding of homozygous dsRed NOD/Scid siblings, and expresses red fluorescence from various organs. The model allows engraftment of human tumor tissue, and engrafted tumors were separated into stromal and malignant cell compartments. Furthermore, we compared tumor-associated and normal fibroblast for expression of fibroblast-associated markers, and identified a marker panel that was upregulated in the tumor-associated fibroblasts. In conclusion, we propose that this model may be used in a variety of studies of tumor progression and to elucidate the role of the tumor microenvironment.

Confronting two-pair primer design for enzyme-free SNP genotyping based on a genetic algorithm

Background

Polymerase chain reaction with confronting two-pair primers (PCR-CTPP) method produces allele-specific DNA bands of different lengths by adding four designed primers and it achieves the single nucleotide polymorphism (SNP) genotyping by electrophoresis without further steps. It is a time- and cost-effective SNP genotyping method that has the advantage of simplicity. However, computation of feasible CTPP primers is still challenging.

Results

In this study, we propose a GA (genetic algorithm)-based method to design a feasible CTPP primer set to perform a reliable PCR experiment. The SLC6A4 gene was tested with 288 SNPs for dry dock experiments which indicated that the proposed algorithm provides CTPP primers satisfied most primer constraints. One SNP rs12449783 in the SLC6A4 gene was taken as an example for the genotyping experiments using electrophoresis which validated the GA-based design method as providing reliable CTPP primer sets for SNP genotyping.

Conclusions

The GA-based CTPP primer design method provides all forms of estimation for the common primer constraints of PCR-CTPP. The GA-CTPP program is implemented in JAVA and a user-friendly input interface is freely available at http://bio.kuas.edu.tw/ga-ctpp/.

DNA-PK promotes the survival of young neurons in the embryonic mouse retina

Programmed cell death is a crucial process in neural development that affects mature neurons and glial cells, as well as proliferating precursors and recently born neurons at earlier stages. However, the regulation of the early phase of neural cell death and its function remain relatively poorly understood. In mouse models defective in homologous recombination or nonhomologous end-joining (NHEJ), which are both DNA double-strand break (DSB) repair pathways, there is massive cell death during neural development, even leading to embryonic lethality. These observations suggest that natural DSBs occur frequently in the developing nervous system. In this study, we have found that several components of DSB repair pathways are activated in the developing mouse retina at stages that coincide with the onset of neurogenesis. In short-term organotypic retinal cultures, we confirmed that the repair pathways can be modulated pharmacologically. Indeed, inhibiting the DNA-dependent protein kinase (DNA-PK) catalytic subunit, which is involved in NHEJ, with NU7026 increased caspase-dependent cell death and selectively reduced the neuron population. This observation concurs with an increase in the number of apoptotic neurons found after NU7026 treatment, as also observed in the embryonic scid mouse retina, a mutant that lacks DNA-PK catalytic subunit activity. Therefore, our results implicate the generation of DSB and DNA-PK-mediated repair in neurogenesis in the developing retina.

Establishment of a humanized model of liver using NOD/Shi-scid IL2Rgnull mice

Severely immunodeficient NOD/Shi-scid IL2Rg(null) (NOG) mice are used as recipients for human tissue transplantation, which produces chimeric mice with various types of human tissue. NOG mice expressing transgenic urokinase-type plasminogen activator in the liver (uPA-NOG) were produced. Human hepatocytes injected into uPA-NOG mice repopulated the recipient livers with human cells. The uPA-NOG model has several advantages over previously produced chimeric mouse models of human liver: (1) the severely immunodeficient NOG background enables higher xenogeneic cell engraftment; (2) the absence of neonatal lethality enables mating of homozygotes, which increased the efficacy of homozygote production; and (3) donor xenogeneic human hepatocytes could be readily transplanted into young uPA-NOG mice, which provide easier surgical manipulation and improved recipient survival.

The catalytic subunit of DNA-protein kinase (DNA-PKcs) is not required for Ig class-switch recombination

The joining of DNA ends during Ig class-switch recombination (CSR) is thought to involve the same nonhomologous end-joining pathway as used in V(D)J recombination. However, we reported earlier that CSR can readily occur in Ig transgenic SCID mice lacking DNA-dependent protein kinase (DNA-PK) activity, a critical enzymatic activity for V(D)J recombination. We were thus led to question whether the catalytic subunit of DNA-PK (DNA-PKcs) is essential for CSR. To address this issue, we asked whether class switching to different Ig isotypes could occur in a line of Ig transgenic mice lacking detectable DNA-PKcs protein. The answer was affirmative. We conclude that joining of DNA ends during CSR does not require DNA-PKcs and can occur by an alternative repair pathway to that used for V(D)J recombination.