title: Inferring rare disease risk variants based on exact probabilities of sharing by multiple affected relatives.
abstract: BACKGROUND
  Family-based designs are regaining popularity for genomic sequencing studies because they provide a way to test cosegregation with disease of variants that are too rare in the population to be tested individually in a conventional case-control study.
  
  
  RESULTS
  Where only a few affected subjects per family are sequenced, the probability that any variant would be shared by all affected relatives-given it occurred in any one family member-provides evidence against the null hypothesis of a complete absence of linkage and association. A P-value can be obtained as the sum of the probabilities of sharing events as (or more) extreme in one or more families. We generalize an existing closed-form expression for exact sharing probabilities to more than two relatives per family. When pedigree founders are related, we show that an approximation of sharing probabilities based on empirical estimates of kinship among founders obtained from genome-wide marker data is accurate for low levels of kinship. We also propose a more generally applicable approach based on Monte Carlo simulations. We applied this method to a study of 55 multiplex families with apparent non-syndromic forms of oral clefts from four distinct populations, with whole exome sequences available for two or three affected members per family. The rare single nucleotide variant rs149253049 in ADAMTS9 shared by affected relatives in three Indian families achieved significance after correcting for multiple comparisons ([Formula: see text]).
  
  
  METHODS
  Source code and binaries of the R package RVsharing are freely available for download at http://cran.r-project.org/web/packages/RVsharing/index.html.
  
  
  BACKGROUND
  alexandre.bureau@msp.ulaval.ca or ingo@jhu.edu
  
  
  BACKGROUND
  Supplementary data are available at Bioinformatics online.
authors.affiliation: Centre de Recherche de l'Institut Universitaire en Santé Mentale de Québec, G1J 2G3, Département de Médecine Sociale et Préventive, Université Laval, Québec, G1V 0A6 Canada, Department of Biostatistics, Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, Inherited Disease Research Branch, National Human Genome Research Institute, National Institutes of Health, Baltimore, MD 21224, Department of Oral Biology, Center for Craniofacial and Dental Genetics, School of Dental Medicine, University of Pittsburgh, PA 15219, Department of Pediatrics, School of Medicine, University of Iowa, IA 52242, USA, Institute of Human Genetics, University of Bonn, Bonn D-53127, Germany and Dr. Hejazi Clinic, P.O. Box 2519, Riyadh 11461, Saudi ArabiaCentre de Recherche de l'Institut Universitaire en Santé Mentale de Québec, G1J 2G3, Département de Médecine Sociale et Préventive, Université Laval, Québec, G1V 0A6 Canada, Department of Biostatistics, Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, Inherited Disease Research Branch, National Human Genome Research Institute, National Institutes of Health, Baltimore, MD 21224, Department of Oral Biology, Center for Craniofacial and Dental Genetics, School of Dental Medicine, University of Pittsburgh, PA 15219, Department of Pediatrics, School of Medicine, University of Iowa, IA 52242, USA, Institute of Human Genetics, University of Bonn, Bonn D-53127, Germany and Dr. Hejazi Clinic, P.O. Box 2519, Riyadh 11461, Saudi Arabia.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Bureau
authors.affiliation: Centre de Recherche de l'Institut Universitaire en Santé Mentale de Québec, G1J 2G3, Département de Médecine Sociale et Préventive, Université Laval, Québec, G1V 0A6 Canada, Department of Biostatistics, Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, Inherited Disease Research Branch, National Human Genome Research Institute, National Institutes of Health, Baltimore, MD 21224, Department of Oral Biology, Center for Craniofacial and Dental Genetics, School of Dental Medicine, University of Pittsburgh, PA 15219, Department of Pediatrics, School of Medicine, University of Iowa, IA 52242, USA, Institute of Human Genetics, University of Bonn, Bonn D-53127, Germany and Dr. Hejazi Clinic, P.O. Box 2519, Riyadh 11461, Saudi Arabia.
authors.forename: Samuel G
authors.initials: SG
authors.lastname: Younkin
authors.affiliation: Centre de Recherche de l'Institut Universitaire en Santé Mentale de Québec, G1J 2G3, Département de Médecine Sociale et Préventive, Université Laval, Québec, G1V 0A6 Canada, Department of Biostatistics, Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, Inherited Disease Research Branch, National Human Genome Research Institute, National Institutes of Health, Baltimore, MD 21224, Department of Oral Biology, Center for Craniofacial and Dental Genetics, School of Dental Medicine, University of Pittsburgh, PA 15219, Department of Pediatrics, School of Medicine, University of Iowa, IA 52242, USA, Institute of Human Genetics, University of Bonn, Bonn D-53127, Germany and Dr. Hejazi Clinic, P.O. Box 2519, Riyadh 11461, Saudi Arabia.
authors.forename: Margaret M
authors.initials: MM
authors.lastname: Parker
authors.affiliation: Centre de Recherche de l'Institut Universitaire en Santé Mentale de Québec, G1J 2G3, Département de Médecine Sociale et Préventive, Université Laval, Québec, G1V 0A6 Canada, Department of Biostatistics, Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, Inherited Disease Research Branch, National Human Genome Research Institute, National Institutes of Health, Baltimore, MD 21224, Department of Oral Biology, Center for Craniofacial and Dental Genetics, School of Dental Medicine, University of Pittsburgh, PA 15219, Department of Pediatrics, School of Medicine, University of Iowa, IA 52242, USA, Institute of Human Genetics, University of Bonn, Bonn D-53127, Germany and Dr. Hejazi Clinic, P.O. Box 2519, Riyadh 11461, Saudi Arabia.
authors.forename: Joan E
authors.initials: JE
authors.lastname: Bailey-Wilson
authors.affiliation: Centre de Recherche de l'Institut Universitaire en Santé Mentale de Québec, G1J 2G3, Département de Médecine Sociale et Préventive, Université Laval, Québec, G1V 0A6 Canada, Department of Biostatistics, Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, Inherited Disease Research Branch, National Human Genome Research Institute, National Institutes of Health, Baltimore, MD 21224, Department of Oral Biology, Center for Craniofacial and Dental Genetics, School of Dental Medicine, University of Pittsburgh, PA 15219, Department of Pediatrics, School of Medicine, University of Iowa, IA 52242, USA, Institute of Human Genetics, University of Bonn, Bonn D-53127, Germany and Dr. Hejazi Clinic, P.O. Box 2519, Riyadh 11461, Saudi Arabia.
authors.forename: Mary L
authors.initials: ML
authors.lastname: Marazita
authors.affiliation: Centre de Recherche de l'Institut Universitaire en Santé Mentale de Québec, G1J 2G3, Département de Médecine Sociale et Préventive, Université Laval, Québec, G1V 0A6 Canada, Department of Biostatistics, Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, Inherited Disease Research Branch, National Human Genome Research Institute, National Institutes of Health, Baltimore, MD 21224, Department of Oral Biology, Center for Craniofacial and Dental Genetics, School of Dental Medicine, University of Pittsburgh, PA 15219, Department of Pediatrics, School of Medicine, University of Iowa, IA 52242, USA, Institute of Human Genetics, University of Bonn, Bonn D-53127, Germany and Dr. Hejazi Clinic, P.O. Box 2519, Riyadh 11461, Saudi Arabia.
authors.forename: Jeffrey C
authors.initials: JC
authors.lastname: Murray
authors.affiliation: Centre de Recherche de l'Institut Universitaire en Santé Mentale de Québec, G1J 2G3, Département de Médecine Sociale et Préventive, Université Laval, Québec, G1V 0A6 Canada, Department of Biostatistics, Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, Inherited Disease Research Branch, National Human Genome Research Institute, National Institutes of Health, Baltimore, MD 21224, Department of Oral Biology, Center for Craniofacial and Dental Genetics, School of Dental Medicine, University of Pittsburgh, PA 15219, Department of Pediatrics, School of Medicine, University of Iowa, IA 52242, USA, Institute of Human Genetics, University of Bonn, Bonn D-53127, Germany and Dr. Hejazi Clinic, P.O. Box 2519, Riyadh 11461, Saudi Arabia.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Mangold
authors.affiliation: Centre de Recherche de l'Institut Universitaire en Santé Mentale de Québec, G1J 2G3, Département de Médecine Sociale et Préventive, Université Laval, Québec, G1V 0A6 Canada, Department of Biostatistics, Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, Inherited Disease Research Branch, National Human Genome Research Institute, National Institutes of Health, Baltimore, MD 21224, Department of Oral Biology, Center for Craniofacial and Dental Genetics, School of Dental Medicine, University of Pittsburgh, PA 15219, Department of Pediatrics, School of Medicine, University of Iowa, IA 52242, USA, Institute of Human Genetics, University of Bonn, Bonn D-53127, Germany and Dr. Hejazi Clinic, P.O. Box 2519, Riyadh 11461, Saudi Arabia.
authors.forename: Hasan
authors.initials: H
authors.lastname: Albacha-Hejazi
authors.affiliation: Centre de Recherche de l'Institut Universitaire en Santé Mentale de Québec, G1J 2G3, Département de Médecine Sociale et Préventive, Université Laval, Québec, G1V 0A6 Canada, Department of Biostatistics, Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, Inherited Disease Research Branch, National Human Genome Research Institute, National Institutes of Health, Baltimore, MD 21224, Department of Oral Biology, Center for Craniofacial and Dental Genetics, School of Dental Medicine, University of Pittsburgh, PA 15219, Department of Pediatrics, School of Medicine, University of Iowa, IA 52242, USA, Institute of Human Genetics, University of Bonn, Bonn D-53127, Germany and Dr. Hejazi Clinic, P.O. Box 2519, Riyadh 11461, Saudi Arabia.
authors.forename: Terri H
authors.initials: TH
authors.lastname: Beaty
authors.affiliation: Centre de Recherche de l'Institut Universitaire en Santé Mentale de Québec, G1J 2G3, Département de Médecine Sociale et Préventive, Université Laval, Québec, G1V 0A6 Canada, Department of Biostatistics, Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, Inherited Disease Research Branch, National Human Genome Research Institute, National Institutes of Health, Baltimore, MD 21224, Department of Oral Biology, Center for Craniofacial and Dental Genetics, School of Dental Medicine, University of Pittsburgh, PA 15219, Department of Pediatrics, School of Medicine, University of Iowa, IA 52242, USA, Institute of Human Genetics, University of Bonn, Bonn D-53127, Germany and Dr. Hejazi Clinic, P.O. Box 2519, Riyadh 11461, Saudi Arabia.
authors.forename: Ingo
authors.initials: I
authors.lastname: Ruczinski
mesh_terms: D016022:Case-Control Studies; D059472:Exome / Q000235:genetics; D005260:Female; D008040:Genetic Linkage; D020022:Genetic Predisposition to Disease / Q000235:genetics; D014644:Genetic Variation; D055106:Genome-Wide Association Study; D023281:Genomics / Q000379:methods*; D006801:Humans; D008297:Male; D009010:Monte Carlo Method; D010375:Pedigree; D011336:Probability; D035583:Rare Diseases / Q000235:genetics*
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