Copy number polymorphism in Fcgr3 predisposes to glomerulonephritis in rats and humans.

Identification of the genes underlying complex phenotypes and the definition of the evolutionary forces that have shaped eukaryotic genomes are among the current challenges in molecular genetics. Variation in gene copy number is increasingly recognized as a source of inter-individual differences in genome sequence and has been proposed as a driving force for genome evolution and phenotypic variation. Here we show that copy number variation of the orthologous rat and human Fcgr3 genes is a determinant of susceptibility to immunologically mediated glomerulonephritis. Positional cloning identified loss of the newly described, rat-specific Fcgr3 paralogue, Fcgr3-related sequence (Fcgr3-rs), as a determinant of macrophage overactivity and glomerulonephritis in Wistar Kyoto rats. In humans, low copy number of FCGR3B, an orthologue of rat Fcgr3, was associated with glomerulonephritis in the autoimmune disease systemic lupus erythematosus. The finding that gene copy number polymorphism predisposes to immunologically mediated renal disease in two mammalian species provides direct evidence for the importance of genome plasticity in the evolution of genetically complex phenotypes, including susceptibility to common human disease.

Revisiting Hunter Perceptions toward Chronic Wasting Disease: Changes in Behavior over Time.

Hunter behavior varies in relation to perceived risk of Chronic Wasting Disease (CWD) and changes in perceptions of CWD will lead to changes in behavior over time. During 2018, we surveyed deer (Odocoileus virginianus or Cervus nippon) hunters from Maryland, USA, regarding behavioral changes due to CWD. We matched 477 respondents to their harvest record and created two geographical groups based on harvest history in counties closest to disease presence. We compared the proportion of hunters who claimed to have changed their behavior in each group and estimated the effects of CWD on harvest rate for the 4 years immediately after the discovery of CWD and the following 4-year period. We found no difference between the groups in the proportion of hunters who changed their behavior due to CWD. We found a significant decline in harvest rate for hunters who claimed to change their behavior in the group closest to CWD presence during the period immediately after the discovery of CWD; however, these same hunters increased their harvest rates in the next time period to pre-CWD levels. Overall, we found that time alleviates some perceived risk of CWD and that this is reflected in hunting behavior.

Strain susceptibility to active induction and passive transfer of experimental autoimmune glomerulonephritis in the rat.

BACKGROUND: Previous studies have shown that different inbred rat strains vary in their susceptibility to experimental autoimmune glomerulonephritis (EAG). The Wistar Kyoto (WKY) rat is highly susceptible and develops crescentic glomerulonephritis, while the Lewis (LEW) rat is resistant. When immunized with collagenase-solubilized rat glomerular basement membrane (GBM), both strains produce circulating autoantibodies reactive with rat GBM by enzyme-linked immunosorbent assay, but only the WKY rat shows strong linear deposits of IgG on the GBM. METHODS: We investigated the hypothesis that differences in the characteristics of the anti-GBM antibodies produced, or in the inflammatory response to antibody deposition, could account for susceptibility. RESULTS: We found that circulating anti-GBM antibodies from WKY rats immunized with GBM were present at a higher concentration than those from LEW rats. Antibodies from WKY rats also recognized the rat alpha3 chain of type IV collagen [alpha3(IV)NC1], whereas those from LEW rats did not. Antibody eluted from the kidneys of WKY rats with EAG induced by GBM showed a higher affinity for GBM and recombinant rat alpha3(IV)NC1 than circulating antibody. This eluted antibody bound strongly to normal kidney sections from both WKY and LEW rats. Passive transfer of eluted anti-GBM antibodies from WKY rats with EAG resulted in similar binding of IgG to the GBM of WKY and LEW rats at 24 h. However, only the WKY recipients went on to develop crescentic glomerulonephritis by 28 days. CONCLUSIONS: This study demonstrates that the characteristics of the anti-GBM antibodies induced in WKY rats contribute to their susceptibility to EAG. However, the passive transfer experiments reveal that factors related to the inflammatory response to antibody deposition are also important in determining susceptibility. A combination of these genetic influences could explain the variation in severity of human anti-GBM disease.

The evolution of crescentic nephritis and alveolar haemorrhage following induction of autoimmunity to glomerular basement membrane in an experimental model of Goodpasture's disease.

Goodpasture's, or anti-glomerular basement membrane (GBM), disease presents with rapidly progressive glomerulonephritis and lung haemorrhage, and is caused by autoimmunity to the NC1 domain of the alpha3 chain of type IV collagen (alpha3(IV)NC1). This study examines the development of crescentic nephritis and alveolar haemorrhage in a model of Goodpasture's disease, experimental autoimmune glomerulonephritis (EAG), induced in WKY rats by immunization with rat GBM in adjuvant. An increase in circulating anti-GBM antibodies and albuminuria was observed by week 2, which increased further by weeks 3 and 4, while a decrease in creatinine clearance was observed by week 2, which decreased further by weeks 3 and 4. The kidneys of animals with EAG showed linear deposits of IgG on the GBM and a transient glomerular infiltration by CD4+ T cells at week 2. By week 3 there were large deposits of fibrin in Bowman's space, and glomerular infiltration by CD8+ T cells and macrophages, accompanied by focal necrotizing glomerulonephritis with crescent formation. Ultrastructural studies showed glomerular endothelial cell swelling and epithelial cell foot process effacement at week 2. As the lesion progressed, capillary loops became occluded and the mesangium became expanded by mononuclear cells. By week 3 there was detachment of the endothelium from the GBM, and accumulation of fibrin beneath the disrupted endothelial cells and in Bowman's space. Occasional breaks were observed in the continuity of the basement membrane, and cytoplasmic projections from infiltrating mononuclear cells could be seen crossing the capillary wall between the lumen and the crescent. The lungs of animals with EAG showed patchy binding of IgG to the alveolar basement membrane (ABM) at week 2, and infiltration of the interstitium by CD8+ T cells and macrophages by weeks 3 and 4, accompanied by both interstitial and alveolar haemorrhage. Ultrastructural studies showed focal mononuclear cell infiltrates in alveolar walls at week 2. Occasional breaks were observed in the basement membrane and adjacent endothelium by weeks 3 and 4, together with accumulation of surfactant and erythrocytes within the alveolar spaces. This study defines for the first time the relationship between the immunological and pathological events during the evolution of EAG, and provides the basis for further work on the pathogenesis of Goodpasture's disease.

Segregation of experimental autoimmune glomerulonephritis as a complex genetic trait and exclusion of Col4a3 as a candidate gene.

Experimental autoimmune glomerulonephritis (EAG), an animal model of Goodpasture's disease, can be induced in Wistar-Kyoto (WKY) rats (RT1-l) by immunization with rat glomerular basement membrane (GBM) in adjuvant. The model in this rat strain is characterized by anti-GBM antibody production accompanied by focal necrotizing glomerulonephritis with crescent formation. The main autoantigen in humans and rats has been identified as the non-collagenous domain of the alpha3 chain of type IV collagen (alpha3(IV)NC1). By contrast, Lewis (LEW) rats with the same MHC background (RT1-l), immunized with the same antigen, develop similar levels of circulating anti-GBM antibodies, but no histological evidence of nephritis. In order to investigate the genetic basis of susceptibility to EAG, we examined the response of both F1 (WKY x LEW) and backcross (BC1; WKY x F1) rats to immunization with rat GBM. F1 animals were completely resistant to the development of EAG, while BC1 animals showed a range of responses from severe crescentic glomerulonephritis to no histological evidence of disease. The results indicate that EAG is inherited as a complex trait under the control of WKY genes unlinked to the MHC. cDNA sequence analysis of alpha3(IV)NC1 in the two parental strains was identical, indicating no predicted amino acid sequence variation in the alpha3(IV)NC1 domain between these strains. Radiation hybrid mapping, using two separate PCR amplicons from rat alpha3(IV)NC1, localized rat Col4a3 to a region of chromosome 9. Since Col4a3 (encoding the autoantigen) is a candidate for susceptibility to EAG, we screened the region of rat chromosome 9 where Col4a3 is localized, using polymorphic microsatellite markers in segregating BC1 progeny. No significant linkage was detected. These results exclude Col4a3 as a recessive susceptibility gene for EAG in the BC1 progeny.