title: Robust physical methods that enrich genomic regions identical by descent for linkage studies: confirmation of a locus for osteogenesis imperfecta.
abstract: BACKGROUND
  The monogenic disease osteogenesis imperfecta (OI) is due to single mutations in either of the collagen genes ColA1 or ColA2, but within the same family a given mutation is accompanied by a wide range of disease severity. Although this phenotypic variability implies the existence of modifier gene variants, genome wide scanning of DNA from OI patients has not been reported. Promising genome wide marker-independent physical methods for identifying disease-related loci have lacked robustness for widespread applicability. Therefore we sought to improve these methods and demonstrate their performance to identify known and novel loci relevant to OI.
  
  
  RESULTS
  We have improved methods for enriching regions of identity-by-descent (IBD) shared between related, afflicted individuals. The extent of enrichment exceeds 10- to 50-fold for some loci. The efficiency of the new process is shown by confirmation of the identification of the Col1A2 locus in osteogenesis imperfecta patients from Amish families. Moreover the analysis revealed additional candidate linkage loci that may harbour modifier genes for OI; a locus on chromosome 1q includes COX-2, a gene implicated in osteogenesis.
  
  
  CONCLUSIONS
  Technology for physical enrichment of IBD loci is now robust and applicable for finding genes for monogenic diseases and genes for complex diseases. The data support the further investigation of genetic loci other than collagen gene loci to identify genes affecting the clinical expression of osteogenesis imperfecta. The discrimination of IBD mapping will be enhanced when the IBD enrichment procedure is coupled with deep resequencing.
authors.affiliation: IntegraGen SA, Evry, France. peter.brooks@parisbc.com
authors.forename: Peter
authors.initials: P
authors.lastname: Brooks
authors.forename: Charles
authors.initials: C
authors.lastname: Marcaillou
authors.forename: Maud
authors.initials: M
authors.lastname: Vanpeene
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Saraiva
authors.forename: Daniel
authors.initials: D
authors.lastname: Stockholm
authors.forename: Stephan
authors.initials: S
authors.lastname: Francke
authors.forename: Reyna
authors.initials: R
authors.lastname: Favis
authors.forename: Nadine
authors.initials: N
authors.lastname: Cohen
authors.forename: Francis
authors.initials: F
authors.lastname: Rousseau
authors.forename: Frédéric
authors.initials: F
authors.lastname: Tores
authors.forename: Pierre
authors.initials: P
authors.lastname: Lindenbaum
authors.forename: Jörg
authors.initials: J
authors.lastname: Hager
authors.forename: Anne
authors.initials: A
authors.lastname: Philippi