GWAS of longitudinal amyloid accumulation on 18F-florbetapir PET in Alzheimer's disease implicates microglial activation gene IL1RAP

Brain

Volumn 138, Issue 10, 2015, Pages 3076-3088

  Ramanan, Vijay K ^a   Risacher, Shannon L ^a   Nho, Kwangsik ^a,b   Kim, Sungeun ^a,b   Shen, Li ^a,b   McDonald, Brenna C ^a,b   Yoder, Karmen K ^a   Hutchins, Gary D ^a   West, John D ^a   Tallman, Eileen F ^a   Gao, Sujuan ^a   Foroud, Tatiana M ^a,b   Farlow, Martin R ^a,b   De Jager, Philip L ^c,d,e   Bennett, David A ^f   Aisen, Paul S ^g   Petersen, Ronald C ^h   Jack, Clifford R ^h   Toga, Arthur W ^g   Green, Robert C ^c   Jagust, William J ⁱ   Weiner, Michael W ^j,k   Saykin, Andrew J ^a,b   more..

^a INDIANA UNIVERSITY   (United States)

^b INDIANA UNIVERSITY SCHOOL OF MEDICINE   (United States)

^c BRIGHAM AND WOMEN S HOSPITAL   (United States)

^d HARVARD MEDICAL SCHOOL   (United States)

^e BROAD INSTITUTE OF MIT AND HARVARD   (United States)

^f RUSH UNIVERSITY MEDICAL CENTER   (United States)

^g UNIVERSITY OF SOUTHERN CALIFORNIA   (United States)

^h MAYO CLINIC   (United States)

ⁱ UNIVERSITY OF CALIFORNIA   (United States)

^j UNIVERSITY OF CALIFORNIA   (United States)

^k VETERANS AFFAIRS MEDICAL CENTER   (United States)

more..

Author keywords

Alzheimer's disease; amyloid; genetics; interleukin 1; microglia

Indexed keywords

AMYLOID BETA PROTEIN; APOLIPOPROTEIN E; FLORBETAPIR F 18; INTERLEUKIN 1 RECEPTOR ACCESSORY PROTEIN; RADIOLIGAND; ACETAMIDE DERIVATIVE; AMYLOID; ANILINE DERIVATIVE; APOLIPOPROTEIN E4; ETHYLENE GLYCOL DERIVATIVE; FLORBETAPIR; IL1RAP PROTEIN, HUMAN; N-(2-METHOXYBENZYL)-N-(4-PHENOXYPYRIDIN-3-YL)ACETAMIDE; PYRIDINE DERIVATIVE;

AGED; ALZHEIMER DISEASE; ARTICLE; BRAIN ATROPHY; COGNITIVE DEFECT; DISEASE COURSE; FEMALE; GENE ACTIVATION; GENE SEQUENCE; HETEROZYGOTE; HUMAN; IL1RAP GENE; MAJOR CLINICAL STUDY; MALE; MICROGLIA; MILD COGNITIVE IMPAIRMENT; NEUROMODULATION; NUCLEAR MAGNETIC RESONANCE IMAGING; PATHOGENESIS; POSITRON EMISSION TOMOGRAPHY; PRIORITY JOURNAL; PROTEIN TARGETING; SEQUENCE ANALYSIS; TEMPORAL CORTEX; BRAIN CORTEX; GENETIC ASSOCIATION STUDY; GENETICS; GENOTYPE; LONGITUDINAL STUDY; METABOLISM; PATHOLOGY; SCINTISCANNING; SINGLE NUCLEOTIDE POLYMORPHISM; VERY ELDERLY;

ACETAMIDES; AGED; AGED, 80 AND OVER; ALZHEIMER DISEASE; AMYLOID; ANILINE COMPOUNDS; APOLIPOPROTEIN E4; CEREBRAL CORTEX; ETHYLENE GLYCOLS; FEMALE; GENETIC ASSOCIATION STUDIES; GENOTYPE; HUMANS; INTERLEUKIN-1 RECEPTOR ACCESSORY PROTEIN; LONGITUDINAL STUDIES; MALE; POLYMORPHISM, SINGLE NUCLEOTIDE; POSITRON-EMISSION TOMOGRAPHY; PYRIDINES;

EID: 84952902285     PISSN: 00068950     EISSN: 14602156     Source Type: Journal    
DOI: 10.1093/brain/awv231     Document Type: Article

References (92)

1. Andrews S FastQC: a quality-control tool for high-throughput sequence data. http://wwwbioinformaticsbabrahamacuk/projects/ fastqc. 2010.
2. Askmyr M, Agerstam H, Hansen N, Gordon S, Arvanitakis A, Rissler M, et al. Selective killing of candidate AML stem cells by antibody targeting of IL1RAP. Blood 2013; 121: 3709-13.
3. Ballard C, Gauthier S, Corbett A, Brayne C, Aarsland D, Jones E. Alzheimers disease. Lancet 2011; 377: 1019-31.
4. Barreyro L, Will B, Bartholdy B, Zhou L, Todorova TI, Stanley RF, et al. Overexpression of IL-1 receptor accessory protein in stem and progenitor cells and outcome correlation in AML and MDS. Blood 2012; 120: 1290-8.
5. Bennett DA, Schneider JA, Arvanitakis Z, Wilson RS. Overview and findings from the religious orders study. Curr Alzheimer Res 2012a; 9: 628-45.
6. Bennett DA, Schneider JA, Buchman AS, Barnes LL, Boyle PA, Wilson RS. Overview and findings from the rush memory and aging project. Curr Alzheimer Res 2012b; 9: 646-63.
7. Bettens K, Sleegers K, Van Broeckhoven C. Genetic insights in Alzheimers disease. Lancet Neurol 2013; 12: 92-104.
8. Borenstein M. Introduction to meta-analysis. Chichester, UK: John Wiley & Sons; 2009.
9. Bradshaw EM, Chibnik LB, Keenan BT, Ottoboni L, Raj T, Tang A, et al. CD33 Alzheimers disease locus: altered monocyte function and amyloid biology. Nat Neurosci 2013; 16: 848-50.
10. Brown AK, Fujita M, Fujimura Y, Liow JS, Stabin M, Ryu YH, et al. Radiation dosimetry and biodistribution in monkey and man of 11C-PBR28: a PET radioligand to image inflammation. J Nucl Med 2007; 48: 2072-9.
11. Chakrabarty P, Li A, Ceballos-Diaz C, Eddy JA, Funk CC, Moore B, et al. IL-10 Alters immunoproteostasis in APP mice, increasing plaque burden and worsening cognitive behavior. Neuron 2015; 85: 519-33.
12. Chetelat G, Villemagne VL, Bourgeat P, Pike KE, Jones G, Ames D, et al. Relationship between atrophy and beta-amyloid deposition in Alzheimer disease. Ann Neurol 2010; 67: 317-24.
13. Chibnik LB, Shulman JM, Leurgans SE, Schneider JA, Wilson RS, Tran D, et al. CR1 is associated with amyloid plaque burden and age-related cognitive decline. Ann Neurol 2011; 69: 560-9.
14. Clark CM, Pontecorvo MJ, Beach TG, Bedell BJ, Coleman RE, Doraiswamy PM, et al. Cerebral PET with florbetapir compared with neuropathology at autopsy for detection of neuritic amyloidb plaques: a prospective cohort study. Lancet Neurol 2012; 11: 669-78.
15. Condello C, Yuan P, Schain A, Grutzendler J. Microglia constitute a barrier that prevents neurotoxic protofibrillar Abeta42 hotspots around plaques. Nat Commun 2015; 6: 6176.
16. Consortium EP. An integrated encyclopedia of DNA elements in the human genome. Nature 2012; 489: 57-74.
17. Corder EH, Saunders AM, Strittmatter WJ, Schmechel DE, Gaskell PC, Small GW, et al. Gene dose of apolipoprotein E type 4 allele and the risk of Alzheimers disease in late onset families. Science 1993; 261: 921-3.
18. Cruchaga C, Kauwe JS, Harari O, Jin SC, Cai Y, Karch CM, et al. GWAS of cerebrospinal fluid tau levels identifies risk variants for Alzheimers disease. Neuron 2013; 78: 256-68.
19. De Jager PL, Srivastava G, Lunnon K, Burgess J, Schalkwyk LC, Yu L, et al. Alzheimers disease: early alterations in brain DNA methylation at ANK1, BIN1, RHBDF2 and other loci. Nat Neurosci 2014; 17: 1156-63.
20. DePristo MA, Banks E, Poplin R, Garimella KV, Maguire JR, Hartl C, et al. A framework for variation discovery and genotyping using next-generation DNA sequencing data. Nat Genet 2011; 43: 491-8.
21. Dinarello CA. Interleukin-1 in the pathogenesis and treatment of inflammatory diseases. Blood 2011; 117: 3720-32.
22. Doens D, Fernandez PL. Microglia receptors and their implications in the response to amyloid beta for Alzheimers disease pathogenesis. J Neuroinflam 2014; 11: 48.
23. Doraiswamy PM, Sperling RA, Johnson K, Reiman EM, Wong TZ, Sabbagh MN, et al. Florbetapir F 18 amyloid PET and 36-month cognitive decline: a prospective multicenter study. Mol Psychiatry 2014; 19: 1044-51.
24. Dore V, Villemagne VL, Bourgeat P, Fripp J, Acosta O, Chetelat G, et al. Cross-sectional and longitudinal analysis of the relationship between abeta deposition, cortical thickness, and memory in cognitively unimpaired individuals and in Alzheimer disease. JAMA Neurol 2013: 1-9.
25. Feng S, Wang S, Chen CC, Lan L. GWAPower: a statistical power calculation software for genome-wide association studies with quantitative traits. BMC Genet 2011; 12: 12.
26. Gabay C, Lamacchia C, Palmer G. IL-1 pathways in inflammation and human diseases. Nat Rev Rheumatol 2010; 6: 232-41.
27. Ghosh S, Wu MD, Shaftel SS, Kyrkanides S, LaFerla FM, Olschowka JA, et al. Sustained interleukin-1beta overexpression exacerbates tau pathology despite reduced amyloid burden in an Alzheimers mouse model. J Neurosci 2013; 33: 5053-64.
28. Green EK, Harris JM, Lemmon H, Lambert JC, Chartier-Harlin MC, St Clair D, et al. Are interleukin-1 gene polymorphisms risk factors or disease modifiers in AD?. Neurology 2002; 58: 1566-8.
29. Guerreiro R, Wojtas A, Bras J, Carrasquillo M, Rogaeva E, Majounie E, et al. TREM2 variants in Alzheimers disease. N Engl J Med 2013; 368: 117-27.
30. Harold D, Abraham R, Hollingworth P, Sims R, Gerrish A, Hamshere ML, et al. Genome-wide association study identifies variants at CLU and PICALM associated with Alzheimers disease. Nat Genet 2009; 41: 1088-93.
31. Higgins JP, Thompson SG, Deeks JJ, Altman DG. Measuring inconsistency in meta-analyses. BMJ 2003; 327: 557-60.
32. Hollingworth P, Harold D, Sims R, Gerrish A, Lambert JC, Carrasquillo MM, et al. Common variants at ABCA7, MS4A6A/ MS4A4E, EPHA1, CD33 and CD2AP are associated with Alzheimers disease. Nat Genet 2011; 43: 429-35.
33. Howie B, Fuchsberger C, Stephens M, Marchini J, Abecasis GR. Fast and accurate genotype imputation in genome-wide association studies through pre-phasing. Nat Genet 2012; 44: 955-9.
34. Huijbers W, Mormino EC, Schultz AP, Wigman S, Ward AM, Larvie M, et al. Amyloid-beta deposition in mild cognitive impairment is associated with increased hippocampal activity, atrophy and clinical progression. Brain 2015; 138: 1023-35.
35. Ionita-Laza I, Lee S, Makarov V, Buxbaum JD, Lin X. Sequence kernel association tests for the combined effect of rare and common variants. Am J Hum Genet 2013; 92: 841-53.
36. Jack CR, Jr, Knopman DS, Jagust WJ, Petersen RC, Weiner MW, Aisen PS, et al. Tracking pathophysiological processes in Alzheimers disease: an updated hypothetical model of dynamic biomarkers. Lancet Neurol 2013a; 12: 207-16.
37. Jack CR, Jr, Wiste HJ, Lesnick TG, Weigand SD, Knopman DS, Vemuri P, et al. Brain beta-amyloid load approaches a plateau. Neurology 2013b; 80: 890-6.
38. Jagust WJ, Bandy D, Chen K, Foster NL, Landau SM, Mathis CA, et al. The Alzheimers Disease Neuroimaging Initiative positron emission tomography core. Alzheimers Dement 2010; 6: 221-9.
39. Johansson JU, Woodling NS, Wang Q, Panchal M, Liang X, Trueba- Saiz A, et al. Prostaglandin signaling suppresses beneficial microglial function in Alzheimers disease models. J Clin Invest 2015; 125: 350-64.
40. Jones L, Holmans PA, Hamshere ML, Harold D, Moskvina V, Ivanov D, et al. Genetic evidence implicates the immune system and cholesterol metabolism in the aetiology of Alzheimers disease. PLoS One 2010; 5: e13950.
41. Jonsson T, Atwal JK, Steinberg S, Snaedal J, Jonsson PV, Bjornsson S, et al. A mutation in APP protects against Alzheimers disease and age-related cognitive decline. Nature 2012; 488: 96-9.
42. Jonsson T, Stefansson H, Steinberg S, Jonsdottir I, Jonsson PV, Snaedal J, et al. Variant of TREM2 associated with the risk of Alzheimers disease. N Engl J Med 2013; 368: 107-16.
43. Kang HJ, Kawasawa YI, Cheng F, Zhu Y, Xu X, Li M, et al. Spatiotemporal transcriptome of the human brain. Nature 2011; 478: 483-9.
44. Kapranov P, Willingham AT, Gingeras TR. Genome-wide transcription and the implications for genomic organization. Nat Rev Genet 2007; 8: 413-23.
45. Karran E, Mercken M, De Strooper B. The amyloid cascade hypothesis for Alzheimers disease: an appraisal for the development of therapeutics. Nat Rev Drug Discov 2011; 10: 698-712.
46. Kendler KS, Neale MC. Endophenotype: a conceptual analysis. Mol Psychiatry 2010; 15: 789-97.
47. Kim J, Basak JM, Holtzman DM. The role of apolipoprotein E in Alzheimers disease. Neuron 2009; 63: 287-303.
48. Kreisl WC, Jenko KJ, Hines CS, Lyoo CH, Corona W, Morse CL, et al. A genetic polymorphism for translocator protein 18 kDa affects both in vitro and in vivo radioligand binding in human brain to this putative biomarker of neuroinflammation. J Cereb Blood Flow Metab 2013; 33: 53-8.
49. Lambert JC, Ibrahim-Verbaas CA, Harold D, Naj AC, Sims R, Bellenguez C, et al. Meta-analysis of 74,046 individuals identifies 11 new susceptibility loci for Alzheimers disease. Nat Genet 2013; 45: 1452-8.
50. Latz E, Xiao TS, Stutz A. Activation and regulation of the inflammasomes. Nat Rev Immunol 2013; 13: 397-411.
51. Li H, Durbin R. Fast and accurate short read alignment with Burrows- Wheeler transform. Bioinformatics 2009; 25: 1754-60.
52. Li MX, Gui HS, Kwan JSH, Sham PC. GATES: a rapid and powerful gene-based association test using extended simes procedure. Am J Hum Genet 2011; 88: 283-93.
53. Li Y, Willer CJ, Ding J, Scheet P, Abecasis GR. MaCH: using sequence and genotype data to estimate haplotypes and unobserved genotypes. Genet Epidemiol 2010; 34: 816-34.
54. Lim YY, Villemagne VL, Laws SM, Pietrzak RH, Snyder PJ, Ames D, et al. APOE and BDNF polymorphisms moderate amyloid betarelated cognitive decline in preclinical Alzheimers disease. Mol Psychiatry 2014. doi: 10.1038/mp.2014.123
55. Lourdusamy A, Newhouse S, Lunnon K, Proitsi P, Powell J, Hodges A, et al. Identification of cis-regulatory variation influencing protein abundance levels in human plasma. Hum Mol Genet 2012; 21: 3719-26.
56. Mattson MP. Neurobiology: Ballads of a protein quartet. Nature 2003; 422: 385-7.
57. Naj AC, Jun G, Beecham GW, Wang L-S, Vardarajan BN, Buros J, et al. Common variants at MS4A4/MS4A6E, CD2AP, CD33 and EPHA1 are associated with late-onset al.zheimers disease. Nat Genet 2011; 43: 436-41.
58. Nam D, Kim J, Kim SY, Kim S. GSA-SNP: a general approach for gene set analysis of polymorphisms. Nucleic Acids Res 2010; 38: W749-54.
59. Nho K, Corneveaux JJ, Kim S, Lin H, Risacher SL, Shen L, et al. Whole-exome sequencing and imaging genetics identify functional variants for rate of change in hippocampal volume in mild cognitive impairment. Mol Psychiatry 2013; 18: 781-7.
60. Peer I, Yelensky R, Altshuler D, Daly MJ. Estimation of the multiple testing burden for genomewide association studies of nearly all common variants. Genet Epidemiol 2008; 32: 381-5.
61. Potkin SG, Turner JA, Guffanti G, Lakatos A, Torri F, Keator DB, et al. Genome-wide strategies for discovering genetic influences on cognition and cognitive disorders: methodological considerations. Cogn Neuropsychiatry 2009; 14: 391-418.
62. Primiani CT, Ryan VH, Rao JS, Cam MC, Ahn K, Modi HR, et al. Coordinated gene expression of neuroinflammatory and cell signaling markers in dorsolateral prefrontal cortex during human brain development and aging. PLoS One 2014; 9: e110972.
63. Prinz M, Priller J, Sisodia SS, Ransohoff RM. Heterogeneity of CNS myeloid cells and their roles in neurodegeneration. Nat Neurosci 2011; 14: 1227-35.
64. Ramanan VK, Kim S, Holohan K, Shen L, Nho K, Risacher SL, et al. Genome-wide pathway analysis of memory impairment in the Alzheimers Disease Neuroimaging Initiative (ADNI) cohort implicates gene candidates, canonical pathways, and networks. Brain Imaging Behav 2012a; 6: 634-48.
65. Ramanan VK, Nho K, Shen L, Risacher SL, Kim S, McDonald BC, et al. FASTKD2 is associated with memory and hippocampal structure in older adults. Mol Psychiatry 2014a. doi: 10.1038/ mp.2014.142
66. Ramanan VK, Risacher SL, Nho K, Kim S, Swaminathan S, Shen L, et al. APOE and BCHE as modulators of cerebral amyloid deposition: a florbetapir PET genome-wide association study. Mol Psychiatry 2014b; 19: 351-7.
67. Ramanan VK, Saykin AJ. Pathways to neurodegeneration: mechanistic insights from GWAS in Alzheimers disease, Parkinsons disease, and related disorders. Am J Neurodegener Dis 2013; 2: 145-75.
68. Ramanan VK, Shen L, Moore JH, Saykin AJ. Pathway analysis of genomic data: concepts, methods, and prospects for future development. Trends Genet 2012b; 28: 323-32.
69. Rhinn H, Fujita R, Qiang L, Cheng R, Lee JH, Abeliovich A. Integrative genomics identifies APOE epsilon4 effectors in Alzheimers disease. Nature 2013; 500: 45-50.
70. Risacher SL, Kim S, Nho K, Foroud T, Shen L, Petersen RC, et al. APOE effect on Alzheimers disease biomarkers in older adults with significant memory concern. Alzheimers Dement 2015. doi: 10.1016/ j.jalz.2015.03.003
71. Risacher SL, Shen L, West JD, Kim S, McDonald BC, Beckett LA, et al. Longitudinal MRI atrophy biomarkers: relationship to conversion in the ADNI cohort. Neurobiol Aging 2010; 31: 1401-18.
72. Saykin AJ, Shen L, Foroud TM, Potkin SG, Swaminathan S, Kim S, et al. Alzheimers Disease Neuroimaging Initiative biomarkers as quantitative phenotypes: genetics core aims, progress, and plans. Alzheimers Dement 2010; 6: 265-73.
73. Saykin AJ, Shen L, Xiaohui Y, Kim S, Nho K, Risacher SL, et al. Genetic studies of quantitative MCI and AD phenotypes in ADNI: progress, opportunities, and plan. Alzheimers Dement 2015; 11: 792-814.
74. Schmidt ME, Chiao P, Klein G, Matthews D, Thurfjell L, Cole PE, et al. The influence of biological and technical factors on quantitative analysis of amyloid PET: points to consider and recommendations for controlling variability in longitudinal data. Alzheimers Dement 2014. doi: 10.1016/j.jalz.2014.09.004
75. Shulman JM, Chen K, Keenan BT, Chibnik LB, Fleisher A, Thiyyagura P, et al. Genetic susceptibility for Alzheimer disease neuritic plaque pathology. JAMA Neurol 2013; 70: 1150-7.
76. Smith DE, Lipsky BP, Russell C, Ketchem RR, Kirchner J, Hensley K, et al. A central nervous system-restricted isoform of the interleukin-1 receptor accessory protein modulates neuronal responses to interleukin- 1. Immunity 2009; 30: 817-31.
77. Sperling RA, Johnson KA, Doraiswamy PM, Reiman EM, Fleisher AS, Sabbagh MN, et al. Amyloid deposition detected with florbetapir F 18 ((18)F-AV-45) is related to lower episodic memory performance in clinically normal older individuals. Neurobiol Aging 2013; 34: 822-31.
78. Storandt M, Mintun MA, Head D, Morris JC. Cognitive decline and brain volume loss as signatures of cerebral amyloid-beta peptide deposition identified with Pittsburgh compound B: cognitive decline associated with Abeta deposition. Arch Neurol 2009; 66: 1476-81.
79. Swaminathan S, Shen L, Risacher SL, Yoder KK, West JD, Kim S, et al. Amyloid pathway-based candidate gene analysis of [(11)C]PiB-PET in the Alzheimers Disease Neuroimaging Initiative (ADNI) cohort. Brain Imaging Behav 2012; 6: 1-15.
80. Tsai S-J, Hong C-J, Liu M-E, Hou S-J, Yen F-C, Hsieh C-H, et al. Interleukin-1 beta (C-511T) genetic polymorphism is associated with cognitive performance in elderly males without dementia. Neurobiol Aging 2010; 31: 1950-5.
81. Van der Auwera GA, Carneiro MO, Hartl C, Poplin R, Del Angel G, Levy-Moonshine A, et al. From FastQ data to high confidence variant calls: the Genome Analysis Toolkit best practices pipeline. Curr Protoc Bioinform 2013; 11: 11.10.1-33.
82. Villemagne VL, Burnham S, Bourgeat P, Brown B, Ellis KA, Salvado O, et al. Amyloid beta deposition, neurodegeneration, and cognitive decline in sporadic Alzheimers disease: a prospective cohort study. Lancet Neurol 2013; 12: 357-67.
83. Villemagne VL, Fodero-Tavoletti MT, Masters CL, Rowe CC. Tau imaging: early progress and future directions. Lancet Neurol 2015; 14: 114-24.
84. Wang DL, Zhang SY, Li LA, Liu X, Mei KR, Wang XQ. Structural insights into the assembly and activation of IL-1 beta with its receptors. Nat Immunol 2010a; 11: 905-952.
85. Wang K, Li M, Hakonarson H. ANNOVAR: functional annotation of genetic variants from high-throughput sequencing data. Nucleic Acids Res 2010b; 38: e164.
86. Wang WF, Liao YC, Wu SL, Tsai FJ, Lee CC, Hua CS. Association of interleukin-I beta and receptor antagonist gene polymorphisms with late onset al.zheimers disease in Taiwan Chinese. Eur J Neurol 2005; 12: 609-13.
87. Weiner MW, Aisen PS, Jack CR, Jr, Jagust WJ, Trojanowski JQ, Shaw L, et al. The Alzheimers disease neuroimaging initiative: progress report and future plans. Alzheimers Dement 2010; 6: 202-11 e7.
88. Willer CJ, Li Y, Abecasis GR. METAL: fast and efficient meta-analysis of genomewide association scans. Bioinformatics 2010; 26: 2190-1.
89. Yang J, Lee SH, Goddard ME, Visscher PM. GCTA: a tool for genome-wide complex trait analysis. Am J Hum Genet 2011; 88: 76-82.
90. Yoder KK, Nho K, Risacher SL, Kim S, Shen L, Saykin AJ. Influence of TSPO genotype on 11C-PBR28 standardized uptake values. J Nucl Med 2013; 54: 1320-2.
91. Zhang B, Gaiteri C, Bodea LG, Wang Z, McElwee J, Podtelezhnikov AA, et al. Integrated systems approach identifies genetic nodes and networks in late-onset al.zheimers disease. Cell 2013; 153: 707-20.
92. Zuk O, Schaffner SF, Samocha K, Do R, Hechter E, Kathiresan S, et al. Searching for missing heritability: designing rare variant association studies. Proc Natl Acad Sci USA 2014; 111: E455-64.