title: Fine-scale survey of X chromosome copy number variants and indels underlying intellectual disability.
abstract: Copy number variants and indels in 251 families with evidence of X-linked intellectual disability (XLID) were investigated by array comparative genomic hybridization on a high-density oligonucleotide X chromosome array platform. We identified pathogenic copy number variants in 10% of families, with mutations ranging from 2 kb to 11 Mb in size. The challenge of assessing causality was facilitated by prior knowledge of XLID-associated genes and the ability to test for cosegregation of variants with disease through extended pedigrees. Fine-scale analysis of rare variants in XLID families leads us to propose four additional genes, PTCHD1, WDR13, FAAH2, and GSPT2, as candidates for XLID causation and the identification of further deletions and duplications affecting X chromosome genes but without apparent disease consequences. Breakpoints of pathogenic variants were characterized to provide insight into the underlying mutational mechanisms and indicated a predominance of mitotic rather than meiotic events. By effectively bridging the gap between karyotype-level investigations and X chromosome exon resequencing, this study informs discussion of alternative mutational mechanisms, such as noncoding variants and non-X-linked disease, which might explain the shortfall of mutation yield in the well-characterized International Genetics of Learning Disability (IGOLD) cohort, where currently disease remains unexplained in two-thirds of families.
authors.affiliation: Department of Medical Genetics, Cambridge Institute for Medical Research, Cambridge CB2 0XY, UK.
authors.forename: Annabel C
authors.initials: AC
authors.lastname: Whibley
authors.forename: Vincent
authors.initials: V
authors.lastname: Plagnol
authors.forename: Patrick S
authors.initials: PS
authors.lastname: Tarpey
authors.forename: Fatima
authors.initials: F
authors.lastname: Abidi
authors.forename: Tod
authors.initials: T
authors.lastname: Fullston
authors.forename: Maja K
authors.initials: MK
authors.lastname: Choma
authors.forename: Catherine A
authors.initials: CA
authors.lastname: Boucher
authors.forename: Lorraine
authors.initials: L
authors.lastname: Shepherd
authors.forename: Lionel
authors.initials: L
authors.lastname: Willatt
authors.forename: Georgina
authors.initials: G
authors.lastname: Parkin
authors.forename: Raffaella
authors.initials: R
authors.lastname: Smith
authors.forename: P Andrew
authors.initials: PA
authors.lastname: Futreal
authors.forename: Marie
authors.initials: M
authors.lastname: Shaw
authors.forename: Jackie
authors.initials: J
authors.lastname: Boyle
authors.forename: Andrea
authors.initials: A
authors.lastname: Licata
authors.forename: Cindy
authors.initials: C
authors.lastname: Skinner
authors.forename: Roger E
authors.initials: RE
authors.lastname: Stevenson
authors.forename: Gillian
authors.initials: G
authors.lastname: Turner
authors.forename: Michael
authors.initials: M
authors.lastname: Field
authors.forename: Anna
authors.initials: A
authors.lastname: Hackett
authors.forename: Charles E
authors.initials: CE
authors.lastname: Schwartz
authors.forename: Jozef
authors.initials: J
authors.lastname: Gecz
authors.forename: Michael R
authors.initials: MR
authors.lastname: Stratton
authors.forename: F Lucy
authors.initials: FL
authors.lastname: Raymond
mesh_terms: D019457:Chromosome Breakage; D020090:Chromosome Segregation / Q000235:genetics; D041321:Chromosomes, Human, X / Q000235:genetics*; D015331:Cohort Studies; D056915:DNA Copy Number Variations / Q000235:genetics*; D004194:Disease / Q000235:genetics; D005260:Female; D015321:Gene Rearrangement / Q000235:genetics; D050172:Genes, X-Linked / Q000235:genetics; D006801:Humans; D054643:INDEL Mutation / Q000235:genetics*; D008607:Intellectual Disability / Q000235:genetics*; D008297:Male; D020411:Oligonucleotide Array Sequence Analysis; D010375:Pedigree; D015203:Reproducibility of Results; D018626:Retroelements / Q000235:genetics; D017384:Sequence Deletion / Q000235:genetics
chemical_list: D018626:Retroelements