Genetic Analysis in Human Disease

1. Genetic Analysis in Human Disease Kim R. Simpfendorfer, PhD Robert S.Boas Center for Genomics & Human Genetics The Feinstein Institute for Medical Research

2. Learning Objectives • Describe the differences between a linkage analysis and an association analysis • Identify potentially confounding factors in a genetic study • Describe why a disease associated single-nucleotide polymorphism is not necessarily the causal disease variant

3. Question: • 1) You have a grant to do a genetics study of the disease of your choice. What are 3 aspects you need to consider when recruiting subjects? • A) Phenotype, gender and age • B) Phenotype, gender and income • C) Gender, age and income • D) Age, income and education

4. Question: • 2) You’ve analyzed 1,000 cases and 1,000 controls for an association study but found nothing significant. What went wrong? • A) Recruited too many subjects • B) Population was too homogeneous • C) Not enough subjects • D) Genotyped using only one platform

5. Question: • 3) You’ve made it to the big time. From your GWAS analysis you have significant hits in known genes. What’s the next step? • A) End of story, move on to the next study • B) Develop new drugs • C) Replication/validation • D) Patent the SNPs

6. Aims of Genetic Analysis in Human Disease McCarthy Nature Genetics Reviews

7. The contributions of genetic and environmental factors to human diseases Rare Genetics simple Unifactorial High recurrence rate Common Genetics complex Multifactorial Low recurrence rate

8. Twin concordance to estimate heritability

9. Heritable and non-heritable factors Heritable factors Shared environmental factors Nonshared environmental factors Castillo-Fernandez, Genome Medicine2014 6:60

10. The spectrum of genetic effects in complex diseases Bush WS and Moore JH - Bush WS, Moore JH (2012) Chapter 11: Genome-Wide Association Studies. PLoSComputBiol 8(12)

11. Getting StartedQuestion to be answered Which gene(s) are responsible for genetic susceptibility for Disease A? • What is the measurable difference • Clinical phenotype • biomarkers, drug response, outcome • Who is affected • Demographics • male/female, ethnic/racial background, age

12. Genome Wide Study Design • Linkage (single gene diseases: cystic fibrosis, Huntington’s disease, Duchene's Muscular Dystrophy) • Families • Association (complex diseases: RA, SLE, breast cancer, autism, allopecia, AMD, Alzheimer’s) • Families • Case - control

13. Linkage vs. Association Analysis Ott Nat Rev Gen 2011

14. Linkage Studies- all in the family Family based method to map location of disease causing loci Sib pairs Trios Multiplex families Abo BMC Bioinformatics 2010

15. Genome-wide linkage analysis of an autosomal recessive hypotrichosis identifies a novel P2RY5 mutation Petukhova Genomics 92 2008

16. Genome-wide linkage analysis of an autosomal recessive hypotrichosis identifies a novel P2RY5 mutation Petukhova Genomics 92 2008

17. Genome-wide linkage analysis of an autosomal recessive hypotrichosis identifies a novel P2RY5 mutation Petukhova Genomics 92 2008

18. Genome-wide linkage analysis of an autosomal recessive hypotrichosis identifies a novel P2RY5 mutation Petukhova Genomics 92 2008

19. GWAS Lasse Folkersen

20. Genome wide association study & meta-analysis Case-control SLE Meta-analysis RA

21. GWASSo you have a hit: p< 5 x10-7 • Validation/ replication • Dense mapping/Sequencing • Functional Analysis

22. Validation • Independent replication set • Same inclusion/exclusion subject criteria • Sample size • Genotyping platform • Same polymorphism • Analysis • Different ethnic group (added bonus)

23. Dense Mapping/Sequencing • Identifies the boundaries of your signal • close in on the target gene/ causal variant • find other (common or rare) variants

24. Imputation and haplotype analysis • Identifies the boundaries of your signal • close in on the target gene/ causal variant • find other (common or rare) variants

25. RA association in Europeans in BLK regulatory region BLK  MTMR9 TDH LINC00208 FAM167A SLC35G5 C8orf12 P values from Stage 1 meta GWAS Genetics of rheumatoid arthritis contributes to biology and drug discovery. Okada et al. 2013.

26. Association of the BLK risk haplotype with autoimmune disease across ancestral groups Controls n=2,134 RA cases n=2,526 European / Caucasian Systemic Lupus Erythematosus Chinese-Han Rheumatoid Arthritis Japanese Dermatomyositis African American Sjögren’s Syndrome Systemic Sclerosis Hispanic Anti-phospholipid Syndrome Simpfendorfer et al. Arthritis & Rheumatology 2015. Asian Kawasaki Disease Korean

27. Candidate causal alleles in the BLK autoimmune disease-risk haplotype Histone mark peaks from B lymphocytes 1bp insertion 1bp deletion Simpfendorfer et al. Arthritis & Rheumatology 2015.

28. Functional Analysis • Does your gene make sense? • pathway • function • cell type • expression • animal models PTPN22: first non-MHC gene associated with RA (TCR signaling)

29. Autoimmunity risk genes/loci from GWAS NHGRI GWAS catalog Sharing of risk genes between autoimmune diseases indicates involvement in a shared autoimmune disease development mechanism

30. Perfect vs Imperfect Worlds • Perfect world • Linkage and/or GWAS – identify causative gene polymorphism for your disease Publish • Imperfect world • nothing significant • identify genes that have no apparent influence in your disease of interest • Now what?

31. What Happened? • Disease has no genetic component. • Viral, bacterial, environmental • Genetic effect is small and your sample size wasn’t big enough to detect it. • CDCV vs CDRV • Phenotype /or demographics too heterogeneous • Too many outliers • Wrong controls. • Population stratification; admixture • Genotyping platform does not detect CNVs • Not asking the right question. • wrong statistics, wrong model

32. Influence of Admixture • Not all Subjects are the same

33. Meta-Analysis – Bigger is better • Meta-analysis - combines genetic data from multiple studies; allows identification of new loci • Rheumatoid Arthritis • Lupus • Crohn’s disease • Alzheimer’s • Schizophrenia • Autism

34. Candidate gene association success story: PCSK9 Cohen NEJM 2006

35. Genome-Wide Association Studies • The promise • Better understanding of biological processes leading to disease pathogenesis • Development of new treatments • Identify non-genetic influences of disease • Better predictive models of risk

36. Genome-Wide Association Studies • The reality • Few causal variants have been identified • Clinical heterogeneity and complexity of disease • Genetic results don’t account for all of disease risk

37. Question: • 1) You have a grant to do a genetics study of the disease of your choice. What are 3 aspects you need to consider when recruiting subjects? • A) Phenotype, gender and age • B) Phenotype, gender and income • C) Gender, age and income • D) Age, income and education

38. Answer: • 1) You have a grant to do a genetics study of the disease of your choice. What are 3 aspects you need to consider when recruiting subjects? • A) Phenotype, gender and age

39. Question: • 2) You’ve analyzed 1,000 cases and 1,000 controls for an association study but found nothing significant. What went wrong? • A) Recruited too many subjects • B) Population was too homogeneous • C) Not enough subjects • D) Genotyped using only one platform

40. Answer: • 2) You’ve analyzed 1,000 cases and 1,000 controls for an association study but found nothing significant. What went wrong? • C) Not enough subjects

41. Question: • 3) You’ve made it to the big time. From your GWAS analysis you have significant hits in known genes. What’s the next step? • A) End of story, move on to the next study • B) Develop new drugs • C) Replication/validation • D) Patent the SNPs

42. Answer: • 3) You’ve made it to the big time. From your GWAS analysis you have significant hits in known genes. What’s the next step? • C) Replication/validation