1. ¿Qué sigue después de la identificación de los genes candidatos para las enfermedades autoinmunes? Christopher J. Lessard, B.Sc., PhD Investigador Asociado, Departamento de Artritis e Inmunología Clínica, Fundación para la Investigación Médica de Oklahoma, Oklahoma City, OK, E.U.
2. What's Next After Candidate Gene and Genome-wide Association Studies in Autoimmunity Christopher J. Lessard, Ph.D., B.Sc. Associate Research Scientist Oklahoma Medical Research Foundation 2nd Colombian Autoimmune Symposium 3 March 2011
3. Outline Identification of susceptibility loci systemic lupus erythematosus (SLE) Question of missing heritability Identification of causal variants Functional studies Epistasis Future of genetics
4. Candidate Gene Studies in SLE History of SLE genetics began in 1970s C2, C4, C1q very rare but potent risk loci Human genome sequence 99.9% complete IRF5 most replicated SLE locus First genome-wide association study 2006
5. Impact of Genome Wide Association Studies on Gene Discovery Psor SLE MS CD RA T1D 1996 INS 2001 Very few confirmed associations prior to 2006 IBD5 SH2D2A CARD15 2003 CTLA4 2004 PAD14 PTPN22 PTPN22 2005 IRF5 IL2Ra IL7R PTPN22 2006 IL23R IFIH1 ICAM-1 FCRL3 PHOX2B ATG16L1 1st GWAS 2007 2008 2009 2010
8. Association between a SNP and disease status For “D” = disease risk allele: Affecteds Controls DD 10/20 = .50 Dd 6/20 = .30 dd 4/20 = .20 DD 2/20 = .10 Dd 4/20 = .20 dd 14/20 = .70 Test distributions for a statistically significant difference
9. MN GWAS Results Summary 431 SLE cases; 2155 controls MHC IRF5 TNFAIP3 P=5x10-8 (genome-wide significant) Significance level P=9x10-7 (suggestive) SNP Location (by chromosome then base pair) Genome-wide - P=5x10-8 Suggestive - P=9x10-7 Graham et al. Nat Genet 2008
10. STAT4 IRAK1 IRF5 TNFAIP3 HLA-DR PTPN22 BLK BANK1 FcγR3A FcγR2B C4A C2 FcγR3B C4B IRAK1 TNFSF4 PXK XKR6 ICA1 ATG5 NMNAT2 MECP2 ITGAM PDCD1 SCUBE1 UBE2L3 KIAA1542 CRP STAT4 C1q TNFAIP3 SPP1 HLA-DR ITGAM STAT4 LYN TREX1 CD44 T Cell signaling DNA methylation TLR/IFN signaling TNF/NFκB signaling B Cell signaling Phagocytosis Complement Apoptosis Ubiquitination Unknown Cellular adhesion Many Genes, Fewer Genetic Pathways in SLE Association of ~35 genes robustly confirmed, more on the way b((Modified from Moser et al, Gene & Immunity SLE Genetics Special Issue, 2009) Pathways Cells Genes Innate Immune Response Dendritic cells Macrophages Autoreactive T cells Autoreactive B cells Lymphocyte Activation/Function Immune Complex Clearance Macrophages Neutrophils Other
11. More Loci Identified in 2009-present Continued replication in European cohorts GWAS replication limited to top few hits CD44 ranked ~2000 Ranking of SNPs by p-value not optimal Common or rare variants hard to detect in small sample sizes
12. Asian GWAS completed in 2009 First SLE GWAS in non-European population Evidence for susceptibility loci unique to Asians Some regions not evaluated in Europeans
13. Question of Missing Heritability Many risk loci, but marginal risk odds ratios (OR) typically < 2.0 HLA and TNFAIP3 OR ≈ 2.5 HLA and IRF5 account for ~1% of heritable risk for Europeans With all loci identified (~35), it is estimated that only 8-12% of heritable risk for Europeans has been identified Why?
14. GWAS to Date Limited Many of the causal variants yet to be identified Functional consequences remain elusive No subphenotype GWAS Limited resequencing to find rare variants Methylation not comprehensively studied No whole transcriptome sequencing No Amerindian and African-American GWAS
15. Causal Variants Bottleneck Linkage Disequilibrium (LD) Correlation between variants Aids identification of association during GWAS(lowers cost) Makes causal variant localization difficult
41. Association of TNFAIP3 Europeans Identified a broad region of association No association in African-Americans Imputation and resequencing reveal putative causal variant Asians Koreans
42. Imputation and Resequencing Imputation found a novel SNP in the 1000 Genomes dataset Resequencing identified a deletion/insertion polymorphism Together form TT>A putative causal polymorphism Conditional analysis
43. Transcription Factors Sites Identified Chromatin immunopreciptitation followed by sequencing by ENCODE project Used this data to begin functional studies
44. Risk Variants Affect Biology Found difference in binding using electrophoretic mobility shift assays mRNA expression altered Protein expression altered
45. Epistasis Gene-gene interactions Usually done statistically No evidence for epistasis in regions found in SLE work TNFAIP3 and TNIP1 both associated with SLE and do interact biologically
46. Future of Autoimmune Genetics Essential to recruit more subjects Much larger GWAS: >50,000 subjects More variants (>5 million) Makes subphenotype studies possible Whole genome sequencing Whole transcriptome sequencing eQTL analysis with GWAS data Epigenetic studies
47. Power to Detect Association Power influenced by: Allele freqency Odds ratio Sample size Need large sample size for rare variants and recessive effects
48. Connecticut Mark Mamula Yale University New York Michigan Andras Perl SUNY Jane Salmon Hospital for Special Surgery Nicholas Chiarazzi Charles Chu Peter Gregerson North Shore University Hospital Joseph McCune University of Michigan Ohio Illinois John B. Harley Cincinnati Children’s Hospital MC Jane Olson Case Western University Washington Michael Schneider Southern Illinois U Timothy Niewold Tammy Utset UChicago J. Lee Nelson F. Hutchinson Cancer Res Ctr Gerald Nopom Virginia Mason Research Ctr Oklahoma Morris Foster OU Kathleen O’Neil OUHSC Pennsylvania Mark Shriver Penn State U Kathleen Sullivan Children’s Hospital of Philadelphia North Carolina Missouri Bart Haynes Duke University Andrey Shaw WashingtonU California OMRF Marta E. Alarcón-Riquelme Darise Farris Bart Frank Judith James Ken Kaufman Biji Kurien Joan Merrill Courtney Montgomery Kathy Moser Patrick Gaffney Swapan Nath Amr Sawalha Hal Scofield Minnesota Steve Bindor Bio-Rad Labs Lisa Barcellos UC Berkeley Evan Hermel Touro University Lindsey Criswell UCSF Betty Tsao UCLA Anshu Agrawal Univ California Mariana Israeli Dan Wallace Michael Weisman CSMC Chaim Jacob USC South Carolina Timothy Behrens University of Minnesota Gary Gilkeson Diane Kamen MUSC Kentucky Jonathan Chaires James Brown Cancer Center Bart Haynes Dukes University Dama Laxminarayana Wake Forest University Alabama Robert Kimberley UAB Massachusetts Harold Chapman Harvard Medical School Brigette Huber Tufts University Patricia Fraser Brigham & Women’s Hospital Texas Edward Wakeland David Karp UT Southwestern MC USA LFRR Collaborators & Approved Users
49. Sweden Marta Alarcon Uppsala University Rose Goldstein University of Ottawa Andrew Paterson University of Toronto United Kingdom Timothy Vyse Imperial College of Science, Technology & Medicine Grant Gallagher University of Glasgow Norway Finland Roland Jonsson University of Bergen Markus Perola National Public Health Institute Ana Quintero OMRF Denmark Runa Nolsoe Steno Diabetes Center Juan-Manuel Anaya Adriana Rojas University del Rosario Japan Sachiko Hirosa Juntonda U School of Medicine Sumida Takayuki University of Tsukuba Ontario Manual Ramos-Casals Barcelona Hospital South Korea Colombia Spain Bao Sang-Cheol University of Seoul Australia Puerto Rico Carola Vinuesa Australian National University International LFRR Collaborators & Approved Users
50. SGENE: The Sjogren’sGenetics Network International group interested in contributing DNA samples and clinical data for genetic studies Currently: 15 contributing sites (plus subsites) >2000 SS cases (AECG criteria), 2000 controls Developing consistent clinical dataset Goal: Continue to expand sites Overall: 15,000+ cases Primary cohort for Replication Studies
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52. The Lupus Family Registry & Repository The LFRR always needs more participants lupus-recruiters@lupus.omrf.org lupus.omrf.org More Sjögren’s syndrome Patients Needed lessardc@omrf.org