title: Congenital cataracts: de novo gene conversion event in CRYBB2.
abstract: OBJECTIVE
  To identify the cause of congenital cataracts in a consanguineous family of Ashkenazi Jewish ancestry.
  
  
  METHODS
  We performed genome-wide linkage analysis and whole-exome sequencing for the initial discovery of variants, and we confirmed the variants using gene-specific primers and Sanger sequencing.
  
  
  RESULTS
  We found significant evidence of linkage to chromosome 22, under an autosomal dominant inheritance model, with a maximum logarithm of the odds (LOD) score of 3.91 (16.918 to 25.641 Mb). Exome sequencing identified three nonsynonymous changes in the CRYBB2 exon 5 coding sequence that are consistent with the sequence of the corresponding region of the pseudogene CRYBB2P1. The identification of these changes was complicated by possible mismapping of some mutated CRYBB2 sequences to CRYBB2P1. Sequencing with gene-specific primers confirmed that the changes--rs2330991, c.433 C>T (p.R145W); rs2330992, c.440A>G (p.Q147R); and rs4049504, c.449C>T (p.T150M)--present in all ten affected family members are located in CRYBB2 and are not artifacts of cross-reaction with CRYBB2P1. We did not find these changes in six unaffected family members, including the unaffected grandfather who contributed the affected haplotype, nor did we find them in the 100 Ashkenazi Jewish controls.
  
  
  CONCLUSIONS
  Our data are consistent with a de novo gene conversion event, transferring 270 base pairs at most from CRYBB2P1 to exon 5 of CRYBB2. This study highlights how linkage mapping can be complicated by de novo mutation events, as well as how sequence-analysis pipeline mapping of short reads from next-generation sequencing can be complicated by the existence of pseudogenes or other highly homologous sequences.
authors.affiliation: Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, MI.
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Garnai
authors.affiliation: Department of Biostatistics, University of Michigan, Ann Arbor, MI.
authors.forename: Jeroen R
authors.initials: JR
authors.lastname: Huyghe
authors.affiliation: Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, MI.
authors.forename: David M
authors.initials: DM
authors.lastname: Reed
authors.affiliation: Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, MI.
authors.forename: Kathleen M
authors.initials: KM
authors.lastname: Scott
authors.affiliation: Einhorn Clinical Research Center, New York Eye and Ear Infirmary at Mount Sinai School of Medicine, New York, NY ; New York University School of Medicine, New York, NY.
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Liebmann
authors.affiliation: Department of Biostatistics, University of Michigan, Ann Arbor, MI.
authors.forename: Michael
authors.initials: M
authors.lastname: Boehnke
authors.affiliation: Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, MI ; Department of Epidemiology, University of Michigan, Ann Arbor, MI.
authors.forename: Julia E
authors.initials: JE
authors.lastname: Richards
authors.affiliation: Einhorn Clinical Research Center, New York Eye and Ear Infirmary at Mount Sinai School of Medicine, New York, NY.
authors.forename: Robert
authors.initials: R
authors.lastname: Ritch
authors.affiliation: Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, MI.
authors.forename: Hemant
authors.initials: H
authors.lastname: Pawar
mesh_terms: D000328:Adult; D000368:Aged; D001483:Base Sequence; D016022:Case-Control Studies; D002386:Cataract / Q000151:congenital / Q000208:ethnology / Q000235:genetics* / Q000473:pathology; D002648:Child; D002892:Chromosomes, Human, Pair 22; D003241:Consanguinity; D059472:Exome; D005091:Exons; D005260:Female; D005785:Gene Conversion; D005799:Genes, Dominant; D008040:Genetic Linkage; D006801:Humans; D007585:Jews; D007908:Lens, Crystalline / Q000378:metabolism / Q000473:pathology; D008297:Male; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010375:Pedigree; D017422:Sequence Analysis, DNA; D038206:beta-Crystallin B Chain / Q000235:genetics*
chemical_list: D038206:beta-Crystallin B Chain; C113634:beta-crystallin B2