Corrigendum: Entire CD3ε, δ, and γ humanized mouse to evaluate human CD3-mediated therapeutics.

This corrects the article DOI: 10.1038/srep45839.

Effect of Npt2b deletion on intestinal and renal inorganic phosphate (Pi) handling.

BACKGROUND: Hyperphosphatemia is common in chronic kidney disease and is associated with morbidity and mortality. The intestinal Na+-dependent phosphate transporter Npt2b is thought to be an important molecular target for the prevention of hyperphosphatemia. The role of Npt2b in the net absorption of inorganic phosphate (Pi), however, is controversial. METHODS: In the present study, we made tamoxifen-inducible Npt2b conditional knockout (CKO) mice to analyze systemic Pi metabolism, including intestinal Pi absorption. RESULTS: Although the Na+-dependent Pi transport in brush-border membrane vesicle uptake levels was significantly decreased in the distal intestine of Npt2b CKO mice compared with control mice, plasma Pi and fecal Pi excretion levels were not significantly different. Data obtained using the intestinal loop technique showed that Pi uptake in Npt2b CKO mice was not affected at a Pi concentration of 4 mM, which is considered the typical luminal Pi concentration after meals in mice. Claudin, which may be involved in paracellular pathways, as well as claudin-2, 12, and 15 protein levels were significantly decreased in the Npt2b CKO mice. Thus, Npt2b deficiency did not affect Pi absorption within the range of Pi concentrations that normally occurs after meals. CONCLUSION: These findings indicate that abnormal Pi metabolism may also be involved in tight junction molecules such as Cldns that are affected by Npt2b deficiency.

Entire CD3ε, δ, and γ humanized mouse to evaluate human CD3-mediated therapeutics.

T cell-mediated immunotherapy is an attractive strategy for treatment in various disease areas. In this therapeutic approach, the CD3 complex is one of the key molecules to modulate T cell functions; however, in many cases, we cannot evaluate the drug candidates in animal experiments because the therapeutics, usually monoclonal antibodies specific to human CD3, cannot react to mouse endogenous Cd3. Although immunodeficient mice transfused with human hematopoietic stem or precursor cells, known as humanized mice, are available for these studies, mice humanized in this manner are not completely immune competent. In this study we have succeeded in establishing a novel mouse strain in which all the three components of the Cd3 complex - Cd3ε, Cd3δ, and Cd3γ - are replaced by their human counterparts, CD3E, CD3D, and CD3G. Basic immunological assessments have confirmed that this strain of human CD3 EDG-replaced mice are entirely immune competent, and we have also demonstrated that a bispecific antibody that simultaneously binds to human CD3 and a tumor-associated antigen (e.g. ERBB2 or GPC3) can be evaluated in human CD3 EDG-replaced mice engrafted with tumors. Our mouse model provides a novel means to evaluate the in vivo efficacy of human CD3-mediated therapy.

Generation of Novel Chimeric Mice with Humanized Livers by Using Hemizygous cDNA-uPA/SCID Mice.

We have used homozygous albumin enhancer/promoter-driven urokinase-type plasminogen activator/severe combined immunodeficient (uPA/SCID) mice as hosts for chimeric mice with humanized livers. However, uPA/SCID mice show four disadvantages: the human hepatocytes (h-heps) replacement index in mouse liver is decreased due to deletion of uPA transgene by homologous recombination, kidney disorders are likely to develop, body size is small, and hemizygotes cannot be used as hosts as more frequent homologous recombination than homozygotes. To solve these disadvantages, we have established a novel host strain that has a transgene containing albumin promoter/enhancer and urokinase-type plasminogen activator cDNA and has a SCID background (cDNA-uPA/SCID). We applied the embryonic stem cell technique to simultaneously generate a number of transgenic lines, and found the line with the most appropriate levels of uPA expression-not detrimental but with a sufficiently damaged liver. We transplanted h-heps into homozygous and hemizygous cDNA-uPA/SCID mice via the spleen, and monitored their human albumin (h-alb) levels and body weight. Blood h-alb levels and body weight gradually increased in the hemizygous cDNA-uPA/SCID mice and were maintained until they were approximately 30 weeks old. By contrast, blood h-alb levels and body weight in uPA/SCID chimeric mice decreased from 16 weeks of age onwards. A similar decrease in body weight was observed in the homozygous cDNA-uPA/SCID genotype, but h-alb levels were maintained until they were approximately 30 weeks old. Microarray analyses revealed identical h-heps gene expression profiles in homozygous and hemizygous cDNA-uPA/SCID mice were identical to that observed in the uPA/SCID mice. Furthermore, like uPA/SCID chimeric mice, homozygous and hemizygous cDNA-uPA/SCID chimeric mice were successfully infected with hepatitis B virus and C virus. These results indicate that hemizygous cDNA-uPA/SCID mice may be novel and useful hosts for producing chimeric mice for use in future long-term studies, including hepatitis virus infection analysis or drug toxicity studies.

In vivo evidence that DNA polymerase kappa is responsible for error-free bypass across DNA cross-links induced by mitomycin C.

Translesion DNA synthesis (TLS) is an important pathway that avoids genotoxicity induced by endogenous and exogenous agents. DNA polymerase kappa (Polk) is a specialized DNA polymerase involved in TLS but its protective roles against DNA damage in vivo are still unclear. To better understand these roles, we have established knock-in mice that express catalytically-inactive Polk and crossbred them with gpt delta mice, which possess reporter genes for mutations. The resulting mice (inactivated Polk KI mice) were exposed to mitomycin C (MMC), and the frequency of point mutations, micronucleus formation in peripheral erythrocytes, and γH2AX induction in the bone marrow was determined. The inactivated Polk KI mice exhibited significantly higher frequency of mutations at CpG and GpG sites, micronucleated cells, and γH2AX foci-positive cells than did the Polk wild-type (Polk(+)) mice. Recovery from MMC-induced DNA damage, which was evaluated by γH2AX induction, was retarded in embryonic fibroblasts from the knock-in mice when compared to those from the Polk(+) mice. These results suggest that Polk mediates TLS, which suppresses point mutations and DNA double-strand breaks caused by intra- and interstrand cross-links induced by MMC treatment. The established knock-in mice are extremely useful to elucidate the in vivo roles of the catalytic activity of Polk in suppressing DNA damage that was induced by a variety of genotoxic stresses.

Novel genetically-humanized mouse model established to evaluate efficacy of therapeutic agents to human interleukin-6 receptor.

For clinical trials of therapeutic monoclonal antibodies (mAbs) to be successful, their efficacy needs to be adequately evaluated in preclinical experiments. However, in many cases it is difficult to evaluate the candidate mAbs using animal disease models because of lower cross-reactivity to the orthologous target molecules. In this study we have established a novel humanized Castleman's disease mouse model, in which the endogenous interleukin-6 receptor gene is successfully replaced by human IL6R, and human IL6 is overexpressed. We have also demonstrated the therapeutic effects of an antibody that neutralizes human IL6R, tocilizumab, on the symptoms in this mouse model. Plasma levels of human soluble IL6R and human IL6 were elevated after 4-week treatment of tocilizumab in this mouse model similarly to the result previously reported in patients treated with tocilizumab. Our mouse model provides us with a novel means of evaluating the in vivo efficacy of human IL6R-specific therapeutic agents.

Inorganic phosphate homeostasis in sodium-dependent phosphate cotransporter Npt2b⁺/⁻ mice.

An inorganic phosphate (P(i))-restricted diet is important for patients with chronic kidney disease and patients on hemodialysis. Phosphate binders are essential for preventing hyperphosphatemia and ectopic calcification. The sodium-dependent P(i) (Na/P(i)) transport system is involved in intestinal P(i) absorption and is regulated by several factors. The type II sodium-dependent P(i) transporter Npt2b is expressed in the brush-border membrane in intestinal epithelial cells and transports P(i). In the present study, we analyzed the phenotype of Npt2b(-/-) and hetero(+/-) mice. Npt2b(-/-) mice died in utero soon after implantation, indicating that Npt2b is essential for early embryonic development. At 4 wk of age, Npt2b(+/-) mice showed hypophosphatemia and low urinary P(i) excretion. Plasma fibroblast growth factor 23 levels were significantly decreased and 1,25(OH)(2)D(3) levels were significantly increased in Npt2b(+/-) mice compared with Npt2b(+/+) mice. Npt2b mRNA levels were reduced to 50% that in Npt2b(+/+) mice. In contrast, renal Npt2a and Npt2c transporter protein levels were significantly increased in Npt2b(+/-) mice. At 20 wk of age, Npt2b(+/-) mice showed hypophosphaturia and reduced Na/P(i) cotransport activity in the distal intestine. Npt2b(+/+) mice with adenine-induced renal failure had hyperphosphatemia and high plasma creatinine levels. Npt2b(+/-) mice treated with adenine had significantly reduced plasma P(i) levels compared with Npt2b(+/+) mice. Intestinal Npt2b protein and Na(+)/P(i) transport activity levels were significantly lower in Npt2b(+/-) mice than in the Npt2b(+/+) mice. The findings of the present studies suggest that Npt2b is an important target for the prevention of hyperphosphatemia.

Effect of zona incision by piezo-micromanipulator (ZIP) on in vitro fertilization in 21 transgenic mice lines.

Zona incision using a piezo-micromanipulator (ZIP) has been demonstrated to be effective for in vitro fertilization (IVF) using cryopreserved C57BL/6 spermatozoa. In this study, ZIP oocytes inseminated with frozen-thawed genetically modified C57BL/6J or FVB mice spermatozoa (21 lines) showed fertilization rates of 22-75% and live fetus rates of 8-49%. In 6 of the lines, the fertilization rates for oocytes compared with ZIP (42-75%) were significantly higher than that of nontreated oocytes (0-50%). Using only 90 oocytes for IVF with ZIP, 5 breeding pairs were produced from cryopreserved genetically modified mice spermatozoa. Our results indicate that application of the ZIP technique is effective for IVF using cryopreserved genetically modified mouse spermatozoa.