Axon regeneration in the adult CNS is prevented by inhibitors in myelin. These inhibitors seem to modulate RhoA activity by binding to a receptor complex comprising a ligand-binding subunit (the Nogo-66 receptor NgR1) and a signal transducing subunit (the neurotrophin receptor p75). However, in reconstituted non-neuronal systems, NgR1 and p75 together are unable to activate RhoA, suggesting that additional components of the receptor may exist. Here we describe LINGO-1, a nervous system-specific transmembrane protein that binds NgR1 and p75 and that is an additional functional component of the NgR1/p75 signaling complex. In non-neuronal cells, coexpression of human NgR1, p75 and LINGO-1 conferred responsiveness to oligodendrocyte myelin glycoprotein, as measured by RhoA activation. A dominant-negative human LINGO-1 construct attenuated myelin inhibition in transfected primary neuronal cultures. This effect on neurons was mimicked using an exogenously added human LINGO-1-Fc fusion protein. Together these observations suggest that LINGO-1 has an important role in CNS biology.

The lymphotoxin axis is important for the maintenance of several specialized lymphoid microenvironments in secondary lymphoid tissue. Lymphoid-tissue architecture is highly plastic and requires continual homeostatic signaling to maintain its basal functional state. The cellularity of lymph nodes in adult mice was reduced by systemic blockade of lymphotoxin-beta receptor (LTbeta R) signaling with a soluble decoy receptor both in resting and reactive settings. This reduction in cellularity resulted from greatly impaired lymphocyte entry into lymph nodes due to decreased levels of peripheral lymph node addressing (PNAd) and MAdCAM on high endothelial venules (HEV). LTbeta R signaling was required to maintain normal levels of RNA expression of MAdCAM, and also of PNAd by regulating the expression of key enzymes and scaffold proteins required for its assembly. Thus, the homeostatic maintenance of functional HEV status in adult mice relies largely on LTbeta R signaling.

Partial inhibition of TGF-beta using alpha(v)beta6 integrin antibodies is effective in blocking murine pulmonary fibrosis without exacerbating inflammation. In addition, the elevated expression of alpha(v)beta6, an activator of the fibrogenic cytokine, TGF-beta, in human pulmonary fibrosis suggests that alpha(v)beta6 monoclonal antibodies could represent a promising new therapeutic strategy for treating pulmonary fibrosis.

Myelin-associated inhibitory factors (MAIFs) are inhibitors of CNS axonal regeneration following injury. The Nogo receptor complex, composed of the Nogo-66 receptor 1 (NgR1), neurotrophin p75 receptor (p75), and LINGO-1, represses axon regeneration upon binding to these myelin components. The limited expression of p75 to certain types of neurons and its temporal expression during development prompted speculation that other receptors are involved in the NgR1 complex. Here, we show that an orphan receptor in the TNF family called TAJ, broadly expressed in postnatal and adult neurons, binds to NgR1 and can replace p75 in the p75/NgR1/LINGO-1 complex to activate RhoA in the presence of myelin inhibitors. In vitro exogenously added TAJ reversed neurite outgrowth caused by MAIFs. Neurons from Taj-deficient mice were more resistant to the suppressive action of the myelin inhibitors. Given the limited expression of p75, the discovery of TAJ function is an important step for understanding the regulation of axonal regeneration.

Inflammation participates in tissue repair through multiple mechanisms including directly regulating the cell fate of resident progenitor cells critical for successful regeneration. Upon surveying target cell types of the TNF ligand TWEAK, we observed that TWEAK binds to all progenitor cells of the mesenchymal lineage and induces NF-jB activation and the expression of pro-survival, pro-proliferative and homing receptor genes in the mesenchymal stem cells, suggesting that this pro-inflammatory cytokine may play an important role in controlling progenitor cell biology. We explored this potential using both the established C2C12 cell line and primary mouse muscle myoblasts, and demonstrated that TWEAK promoted their proliferation and inhibited their terminal differentiation. By generating mice deficient in the TWEAK receptor Fn14, we further showed that Fn14-deficient primary myoblasts displayed significantly reduced proliferative capacity and altered myotube formation. Following cardiotoxin injection, a known trigger for satellite cell-driven skeletal muscle regeneration, Fn14-deficient mice exhibited reduced inflammatory response and delayed muscle fiber regeneration compared with wild-type mice. These results indicate that the TWEAK/Fn14 pathway is a novel regulator of skeletal muscle precursor cells and illustrate an important mechanism by which inflammatory cytokines influence tissue regeneration and repair. Coupled with our recent demonstration that TWEAK potentiates liver progenitor cell proliferation, the expression of Fn14 on all mesenchymal lineage progenitor cells supports a broad involvement of this pathway in other tissue injury and disease settings.

Progressive multifocal leukoencephalopathy (PML) is a rare but frequently fatal disease caused by the uncontrolled replication of JC virus (JCV), a polyomavirus, in the brains of some immunocompromised individuals. Currently, no effective antiviral treatment for this disease has been identified. As a first step in the identification of such therapy, we screened the Spectrum collection of 2,000 approved drugs and biologically active molecules for their anti-JCV activities in an in vitro infection assay. We identified a number of different drugs and compounds that had significant anti-JCV activities at micromolar concentrations and lacked cellular toxicity. Of the compounds with anti-JCV activities, only mefloquine, an antimalarial agent, has been reported to show sufficiently high penetration into the central nervous system such that it would be predicted to achieve

The transforming growth factor (TGF)-␤-inducible integrin ␣v␤6 is preferentially expressed at sites of epithelial remodeling and has been shown to bind and activate latent precursor TGF-␤. Herein , we show that ␣v␤6 is overexpressed in human kidney epithelium in membranous glomerulonephritis , diabetes mellitus , IgA nephropathy , Goodpasture's syndrome , and Alport syndrome renal epithelium. To assess the potential regulatory role of ␣v␤6 in renal disease , we studied the effects of functionblocking ␣v␤6 monoclonal antibodies (mAbs) and genetic ablation of the ␤6 subunit on kidney fibrosis in Col4A3 ؊/؊ mice , a mouse model of Alport syndrome. Expression of ␣v␤6 in Alport mouse kidneys was observed primarily in cortical tubular epithelial cells and in correlation with the progression of fibrosis. Treatment with ␣v␤6-blocking mAbs inhibited accumulation of activated fibroblasts and deposition of interstitial collagen matrix. Similar inhibition of renal fibrosis was observed in ␤6-deficient Alport mice. Transcript profiling of kidney tissues showed that ␣v␤6-blocking mAbs significantly inhibited disease-associated changes in expression of fibrotic and inflammatory mediators. Similar patterns of transcript modulation were produced with recombinant soluble TGF-␤ RII treatment , suggesting shared regulatory functions of ␣v␤6 and TGF-␤. These findings demonstrate that ␣v␤6 can contribute to the regulation of renal fibrosis and suggest this integrin as a potential therapeutic target.

Background: Assessment of approved drugs and developmental drug candidates for rare cystic fibrosis (CF)-causing variants of the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) requires abundant material from relevant models. Methods: Isogenic cell lines harboring CFTR variants in the native genomic context were created through the development and utilization of a footprint-less, CRISPR/Cas9 gene editing pipeline in 16HBE14o-immortalized bronchial epithelial cells. Results: Isogenic, homozygous cell lines for three CFTR variants (F508del and the two most common CF-causing nonsense variants, G542X and W1282X) were established and characterized. The F508del model recapitulates the known molecular pathology and pharmacology. The two models of nonsense variants (G542X and W1282X) are sensitive to Nonsense Mediated mRNA Decay (NMD) and responsive to reference compounds that inhibit NMD and promote ribosomal readthrough. Conclusions: We present a versatile, efficient gene editing pipeline that can be used to create CFTR variants in the native genomic context and the utilization of this pipeline to create homozygous cell models for the CF-causing variants F508del, G542X, and W1282X. The resulting cell lines provide a virtually unlimited source of material with specific pathogenic mutations that can be used in a variety of assays, including functional assays.