title: Unbiased modifier screen reveals that signal strength determines the regulatory role murine TLR9 plays in autoantibody production.
abstract: The autoimmune disease systemic lupus erythematosus has a complex environmental and multifactorial genetic basis. Genome-wide association studies have recently identified numerous disease-associated polymorphisms, but it remains unclear in which cells and during which step of pathogenesis specific polymorphisms interact to cause disease. Using a mouse model in which the same activating mutation (CD45E613R) causes distinct genetic background-dependent disease phenotypes, we performed a screen for genetic modifiers of autoreactivity between anti-nuclear Ab (ANA)-resistant CD45E613R.B6 and ANA-permissive CD45E613R.BALB/c mice. Within a novel autoreactivity-associated locus on chromosome 9, we identify a putative modifier, TLR9. Validating a role for TLR9 in modifying autoreactivity in the context of the CD45E613R mutation, manipulation of TLR9 gene dosage eliminates ANA in CD45E613R.BALB/c mice, but confoundingly permits ANA in CD45E613R.B6 mice. We demonstrate that sensitivity to ANA is modulated by strength of TLR9 signal, because stronger TLR9(B6) signals, but not weaker TLR9(BALB/c) signals, negatively regulate CD45E613R B cell development during competitive reconstitution at the central tolerance checkpoint. Our results identify a novel autoreactivity-associated locus and validate Tlr9 as a candidate gene within the locus. We further demonstrate a novel role for TLR9 signal strength in central tolerance, providing insight into the interplay of disease-associated polymorphisms at a discrete step of systemic lupus erythematosus pathogenesis.
authors.affiliation: Department of Pediatrics, University of California San Francisco, San Francisco, CA 94143; Biomedical Sciences Graduate Program, University of California San Francisco, San Francisco, CA 94143;
authors.forename: Robyn E
authors.initials: RE
authors.lastname: Mills
authors.affiliation: Department of Pediatrics, University of California San Francisco, San Francisco, CA 94143;
authors.forename: Viola C
authors.initials: VC
authors.lastname: Lam
authors.affiliation: Department of Pediatrics, University of California San Francisco, San Francisco, CA 94143; Howard Hughes Medical Institute, University of California San Francisco, San Francisco, CA 94143;
authors.forename: Allison
authors.initials: A
authors.lastname: Tan
authors.affiliation: Department of Pediatrics, University of California San Francisco, San Francisco, CA 94143;
authors.forename: Nicole
authors.initials: N
authors.lastname: Cresalia
authors.affiliation: Department of Pediatrics, University of California San Francisco, San Francisco, CA 94143;
authors.forename: Nir
authors.initials: N
authors.lastname: Oksenberg
authors.affiliation: Department of Medicine, University of California San Francisco, San Francisco, CA 94143; and.
authors.forename: Julie
authors.initials: J
authors.lastname: Zikherman
authors.affiliation: Department of Medicine, University of California San Francisco, San Francisco, CA 94143; and Diabetes Center, University of California San Francisco, San Francisco, CA 94143.
authors.forename: Mark
authors.initials: M
authors.lastname: Anderson
authors.affiliation: Howard Hughes Medical Institute, University of California San Francisco, San Francisco, CA 94143; Department of Medicine, University of California San Francisco, San Francisco, CA 94143; and.
authors.forename: Arthur
authors.initials: A
authors.lastname: Weiss
authors.affiliation: Department of Pediatrics, University of California San Francisco, San Francisco, CA 94143; Michelle.Hermiston@ucsf.edu.
authors.forename: Michelle L
authors.initials: ML
authors.lastname: Hermiston
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D000974:Antibodies, Antinuclear / Q000235:genetics / Q000276:immunology*; D000917:Antibody Formation / Q000235:genetics*; D001402:B-Lymphocytes / Q000276:immunology*; D033481:Chromosomes, Mammalian; D056426:Genetic Loci / Q000276:immunology; D055106:Genome-Wide Association Study; D007108:Immune Tolerance / Q000235:genetics; D017493:Leukocyte Common Antigens / Q000235:genetics / Q000276:immunology; D008180:Lupus Erythematosus, Systemic / Q000235:genetics / Q000276:immunology / Q000473:pathology; D051379:Mice; D008807:Mice, Inbred BALB C; D018345:Mice, Knockout; D020125:Mutation, Missense; D011110:Polymorphism, Genetic; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology; D051217:Toll-Like Receptor 9 / Q000235:genetics / Q000276:immunology
chemical_list: D000974:Antibodies, Antinuclear; C495370:Tlr9 protein, mouse; D051217:Toll-Like Receptor 9; D017493:Leukocyte Common Antigens; C516770:Ptprc protein, mouse