title: Independent mutational events are rare in the ATM gene: haplotype prescreening enhances mutation detection rate.
abstract: Mutations in the ATM gene are responsible for the autosomal recessive disorder ataxia-telangiectasia (A-T). Many different mutations have been identified using various techniques, with detection efficiencies ranging from 57 to 85%. In this study, we employed short tandem repeat (STR) haplotypes to enhance mutation identification in 55 unrelated A-T families of Iberian origin (20 Spanish, 17 Brazilian, and 18 Hispanic-American); we were able to identify 95% of the expected mutations. Allelic sizes were standardized based on a reference sample (CEPH 1347-2). Subsequent mutation screening was performed by PTT, SSCP, and DHPLC, and abnormal regions were sequenced. Many STR haplotypes were found within each population and six haplotypes were observed across several of these populations. Single nucleotide polymorphism (SNP) haplotypes further suggested that most of these common mutations are ancestrally related, and not hot spots. However, two mutations (8977C>T and 8264_8268delATAAG) may indeed be recurring mutational events. Common haplotypes were present in 13 of 20 Spanish A-T families (65%), in 11 of 17 Brazilian A-T families (65%), and, in contrast, in only eight of 18 Hispanic-American families (44%). Three mutations were identified that would be missed by conventional screening strategies. In all, 62 different mutations (28 not previously reported) were identified and their associated haplotypes defined, thereby establishing a new database for Iberian A-T families, and extending the spectrum of worldwide ATM mutations.
authors.affiliation: Department of Pathology and Laboratory Medicine, The David Geffen School of Medicine, Los Angeles, California 90095-1732, USA.
authors.forename: Midori
authors.initials: M
authors.lastname: Mitui
authors.forename: Catarina
authors.initials: C
authors.lastname: Campbell
authors.forename: Gabriela
authors.initials: G
authors.lastname: Coutinho
authors.forename: Xia
authors.initials: X
authors.lastname: Sun
authors.forename: Chih-Hung
authors.initials: CH
authors.lastname: Lai
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Thorstenson
authors.forename: Sergi
authors.initials: S
authors.lastname: Castellvi-Bel
authors.forename: Luis
authors.initials: L
authors.lastname: Fernandez
authors.forename: Eugenia
authors.initials: E
authors.lastname: Monros
authors.forename: Beatriz Tavares Costa
authors.initials: BT
authors.lastname: Carvalho
authors.forename: Oscar
authors.initials: O
authors.lastname: Porras
authors.forename: Gumersindo
authors.initials: G
authors.lastname: Fontan
authors.forename: Richard A
authors.initials: RA
authors.lastname: Gatti
mesh_terms: D001260:Ataxia Telangiectasia / Q000453:epidemiology / Q000208:ethnology / Q000235:genetics; D064007:Ataxia Telangiectasia Mutated Proteins; D001938:Brazil / Q000453:epidemiology; D018797:Cell Cycle Proteins; D003364:Costa Rica / Q000453:epidemiology; D004268:DNA-Binding Proteins; D030541:Databases, Genetic; D018703:Founder Effect; D005820:Genetic Testing / Q000379:methods*; D006239:Haplotypes / Q000235:genetics*; D006630:Hispanic or Latino / Q000235:genetics; D006801:Humans; D020407:Internet; D016296:Mutagenesis / Q000235:genetics*; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D011174:Portugal / Q000453:epidemiology; D017346:Protein Serine-Threonine Kinases / Q000235:genetics*; D013030:Spain / Q000453:epidemiology; D020080:Tandem Repeat Sequences / Q000235:genetics; D025521:Tumor Suppressor Proteins; D014481:United States / Q000453:epidemiology
chemical_list: D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D025521:Tumor Suppressor Proteins; C576324:ATM protein, human