Development and Characterization of a Novel FVB-PrkdcR2140C Mouse Model for Adriamycin-Induced Nephropathy

The Adriamycin (ADR) nephropathy model, which induces podocyte injury, is limited to certain mouse strains due to genetic susceptibilities, such as the PrkdcR2140C polymorphism. The FVB/N strain without the R2140C mutation resists ADR nephropathy. Meanwhile, a detailed analysis of the progression of ADR nephropathy in the FVB/N strain has yet to be conducted. Our research aimed to create a novel mouse model, the FVB-PrkdcR2140C, by introducing PrkdcR2140C into the FVB/NJcl (FVB) strain. Our study showed that FVB-PrkdcR2140C mice developed severe renal damage when exposed to ADR, as evidenced by significant albuminuria and tubular injury, exceeding the levels observed in C57BL/6J (B6)-PrkdcR2140C. This indicates that the FVB/N genetic background, in combination with the R2140C mutation, strongly predisposes mice to ADR nephropathy, highlighting the influence of genetic background on disease susceptibility. Using RNA sequencing and subsequent analysis, we identified several genes whose expression is altered in response to ADR nephropathy. In particular, Mmp7, Mmp10, and Mmp12 were highlighted for their differential expression between strains and their potential role in influencing the severity of kidney damage. Further genetic analysis should lead to identifying ADR nephropathy modifier gene(s), aiding in early diagnosis and providing novel approaches to kidney disease treatment and prevention.

Characterization of novel, severely immunodeficient PrkdcΔex57/Δex57 mice

Severely immunodeficient mice are useful for understanding the pathogenesis of certain tumors and for developing therapeutic agents for such tumors. In addition, engraftment of these mice with human hematopoietic cells can yield information that helps us understand the in vivo molecular mechanisms underlying actual human viral infections. In our present research, we discovered a novel, severely immunodeficient strain of mice having a mutation in exon 57 of the Prkdc gene (PrkdcΔex57/Δex57) in an inbred colony of B10.S/SgSlc mice. Those PrkdcΔex57/Δex57 mice showed thymic hypoplasia and lack of mature T cells and B cells in peripheral lymphoid tissues, resulting in very low levels of production of serum immunoglobulins. In addition, those mice were highly susceptible to influenza viruses due to the lack of acquired immune cells. On the other hand, since they had sufficient numbers of NK cells, they rejected tumor transplants, similarly to Prkdc+/+ mice. Next, we generated Foxn1nu/nuPrkdcΔex57/Δex57Il2rg-/- (NPG) mice on the BALB/cSlc background, which lack all lymphocytes such as T cells, B cells and innate lymphoid cells, including NK cells. As expected, these mice were able to undergo engraftment of human tumor cell lines. These findings suggest that PrkdcΔex57/Δex57 mice will be useful as a novel model of immunodeficiency, while NPG mice will be useful for xenografting of various malignancies.

Essential role of DNA-PKcs and plasminogen for the development of doxorubicin-induced glomerular injury in mice

Susceptibility to doxorubicin-induced nephropathy (DIN), a toxic model for the induction of proteinuria in mice, is related to the single-nucleotide polymorphism (SNP) C6418T of the Prkdc gene encoding for the DNA-repair enzyme DNA-PKcs. In addition, plasminogen (Plg) has been reported to play a role in glomerular damage. Here, we investigated the interdependence of both factors for the development of DIN. Genotyping confirmed the SNP of the Prkdc gene in C57BL/6 (Prkdc^C6418/C6418) and 129S1/SvImJ (Prkdc^T6418/T6418) mice. Intercross of heterozygous 129SB6F1 mice led to 129SB6F2 hybrids with Mendelian inheritance of the SNP. After doxorubicin injection, only homozygous F2 mice with Prkdc^T6418/T6418 developed proteinuria. Genetic deficiency of Plg (Plg^−/−) in otherwise susceptible 129S1/SvImJ mice led to resistance to DIN. Immunohistochemistry revealed glomerular binding of Plg in Plg^+/+ mice after doxorubicin injection involving histone H2B as Plg receptor. In doxorubicin-resistant C57BL/6 mice, Plg binding was absent. In conclusion, susceptibility to DIN in 129S1/SvImJ mice is determined by a hierarchical two-hit process requiring the C6418T SNP in the Prkdc gene and subsequent glomerular binding of Plg.

This article has an associated First Person interview with the first author of the paper.

Summary: Susceptibility to doxorubicin-induced nephropathy in 129S1/SvImJ mice is determined by a hierarchical two-hit process requiring the C6418T single-nucleotide polymorphism in the Prkdc gene and subsequent glomerular binding of plasminogen.

A single amino acid substitution in PRKDC is a determinant of sensitivity to Adriamycin-induced renal injury in mouse

Adriamycin (ADR)-induced nephropathy is frequently utilized in rodent models of podocytopathy. However, the application of this model in mice is limited to a few strains, such as BALB/c mice. The most commonly used mouse strain, C57BL/6 (B6), is resistant to ADR-induced nephropathy, as are all mouse strains with a B6 genetic background. Reportedly, the R2140C variant of the Prkdc gene is the cause of susceptibility to ADR-induced nephropathy in mice. To verify this hypothesis, we produced Prkdc mutant B6 mice, termed B6-Prkdc^R2140C, that possess the R2140C mutation. After administration of ADR, B6-Prkdc^R2140C mice exhibited massive proteinuria and glomerular and renal tubular injuries. In addition, there was no significant difference in the severity between B6-Prkdc^R2140C and BALB/c. These findings demonstrated that B6-Prkdc^R2140C show ADR-induced nephropathy susceptibility at a similar level to BALB/c, and that the PRKDC R2140C variant causes susceptibility to ADR-induced nephropathy. In future studies, ADR-induced nephropathy may become applicable to various kinds of genetically modified mice with a B6 background by mating with B6-Prkdc^R2140C.

Differences between immunodeficient mice generated by classical gene targeting and CRISPR/Cas9-mediated gene knockout

Immunodeficient mice are widely used for pre-clinical studies to understand various human diseases. Here, we report the generation of four immunodeficient mouse models using CRISPR/Cas9 system without inserting any foreign gene sequences such as Neo^R cassettes and their characterization. By eliminating any possible effects of adding a Neo^R cassette, our mouse models may allow us to better elucidate the in vivo functions of each gene. Our FVB-Rag2^−/−, B6-Rag2^−/−, and BALB/c-Prkdc^−/− mice showed phenotypes similar to those of the earlier immunodeficient mouse models, including a lack of mature B cells and T cells and an increase in the number of CD45⁺DX-5⁺ natural killer cells. However, B6-Il2rg^−/− mice had a unique phenotype, with a lack of mature B cells, increased number of T cells, and decreased number of natural killer cells. Additionally, serum immunoglobulin levels in all four immunodeficient mouse models were significantly reduced when compared to those in wild-type mice with the exception of IgM in B6-Il2rg^−/− mice. These results indicate that our immunodeficient mouse models are a robust tool for in vivo studies of the immune system and will provide new insights into the variation in phenotypic outcomes resulting from different gene-targeting methodologies.