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Phenotypic differences among substrains of laboratory mice due to spontaneous mutations or pre-existing genetic variation confound the interpretation of targeted mutagenesis experiments and contribute to challenges with reproducibility across institutions. Notably, C57BL/6 Hsd mice and gene-targeted mice that have been backcrossed to this substrain have been reported to harbor a duplication in exons 28 and 29 of Dock2. In this study, we demonstrate the presence of this Dock2 variant in the widely used Nod2−/− mice. Nucleotide-binding oligomerization domain-containing protein 2 (NOD2) is a cytosolic innate immune receptor associated with inflammatory bowel disease susceptibility. Consistent with a role of NOD2 in an immunological disorder, Nod2−/− mice bred at our institution displayed multiple B cell defects including deficiencies in recirculating B cells, marginal zone B cells, and B1a cells in vivo, as well as defects in class switch recombination in vitro. However, we found that these effects are due to the Dock2 variant and are independent of Nod2 deletion. Despite originating from the same gene-targeted founder mice, Nod2−/− mice from another source did not harbor the Dock2 variant or B cell defects. Finally, we show that Dock2−/− mice display the same B cell defects as mice harboring the Dock2 variant, confirming that the variant is a loss-of-function mutation and is sufficient to explain the alterations to the B cell compartment observed in Nod2−/− mice. Our findings highlight the effects of confounding mutations from widely used inbred strains on gene-targeted mice and reveal new functions of DOCK2 in B cells.

Th17 cells are a proinflammatory subset of effector T cells that have been implicated in the pathogenesis of asthma. Their production of the cytokine IL-17 is known to induce local recruitment of neutrophils, but the direct impact of IL-17 on the lung epithelium is poorly understood. In this study, we describe a novel mouse model of spontaneous IL-17–driven lung inflammation that exhibits many similarities to asthma in humans. We have found that STAT3 hyperactivity in T lymphocytes causes an expansion of Th17 cells, which home preferentially to the lungs. IL-17 secretion then leads to neutrophil infiltration and lung epithelial changes, in turn leading to a chronic inflammatory state with increased mucus production and decreased lung function. We used this model to investigate the effects of IL-17 activity on airway epithelium and identified CXCL5 and MIP-2 as important factors in neutrophil recruitment. The neutralization of IL-17 greatly reduces pulmonary neutrophilia, underscoring a key role for IL-17 in promoting chronic airway inflammation. These findings emphasize the role of IL-17 in mediating neutrophil-driven pulmonary inflammation and highlight a new mouse model that may be used for the development of novel therapies targeting Th17 cells in asthma and other chronic pulmonary diseases.

The differential expression of miRNAs throughout B cell development suggests that these ncRNAs contribute to stage-specific regulation of the intricate transcriptional program during B cell development. Conditional ablation of Dicer or deletion of the miR-17~92 cluster in early pro-B cells, revealed a critical role of miRNAs in B cell differentiation. In the present study we compare the phenotypes of mice in which enzymes critical for miRNA biogenesis, Dicer, Drosha and DGCR8 are conditionally ablated in B lymphocytes, allowing us to definitively explore the role of miRNAs in B cell development and function. Global ablation of miRNAs in B lymphocytes lead to an early block in B cell development. Rescue of B cell surviva by overexpression of the anti-apopotic factor Bcl2 revealed that in the absence of miRNAs, B cells in the periphery expressed low levels of Ig heavy chain without expressing light chain. We demonstrate that miRNA-deficient B cells fail to regulate recombination machinery in the periphery, resulting in ongoing Ig light chain gene rearrangement. In addition to the upregulation of RAG1/2 in peripheral B cells, we demonstrated ongoing DNA double strand breaks at Ig light chain loci and upregulation of surrogate light chain components. We show that these events occur downstream of deregulated PI3K signaling and we recapitulate many of these defects in wild-type B lymphocytes by targeting individual components of PI3K signaling network. Furthermore, we achieve complete rescue of miRNA deficient B cells when we introduce a pro-survival Bcl2 transgene along with an Ig transgene resistant to light chain editing. Our data highlight an important and novel role for miRNAs in the maintenance of a mature phenotype in peripheral B cells.

Fogli, L. K., M. S. Sundrud, S. Goel, S. Bajwa, K. Jensen, E. Derudder, A. Sun, M. Coffre, C. Uyttenhove, J. Van Snick, M. Schmidt-Supprian, A. Rao, G. Grunig, J. Durbin, S. S. Casola, K. Rajewsky, and S. B. Koralov. 2013. T cell–derived IL-17 mediates epithelial changes in the airway and drives